Correction: Phenothiazine-based dyes for efficient dye-sensitized solar cells

Correction for ‘Phenothiazine-based dyes for efficient dye-sensitized solar cells’ by Zu-Sheng Huang et al., J. Mater. Chem. C, 2016, 4, 2404–2426.

Photokinetic examination of (Z,E,E)-4,4′-distyrylazobenzene

Abstract 4,4′-Distyrylazobenzenes demonstrate a photokinetic equilibrium and a superimposed thermal backward reaction in which the absorption coefficient of one of the partners in the equilibrium is principally unknown. Using the dependence of the photostationary state on the irradiation intensity, the photochemical quantum yields ϕ 1 A and ϕ 2 B were determined, as well as the thermal rate constant k , as a function of the irradiation and observation wavelengths. Experimental difficulties and the wavelength dependence of ϕ 1 A and ϕ 2 B are discussed.

A new synthesis of soluble poly(1,4-phenylenevinylene)s and poly(2,5-pyrimidinylenevinylene)s

Abstract Alkoxy-substituted 4-methylbenzylideneanilines 2a-f and their pyrimidine analogues 2g,h show an efficient selfcondensation in the alkaline medium KOC(CH 3 ) 3 /DMF. The totally stereoselective reaction yields 3a-h which are transformed by acidic work-up to 4a-h . A narrow distribution of the molecular weight can be achieved.

Star-Shaped Compounds Having 1,3,5-Triazine Cores

The 1,3,5-triazine derivatives 1−4 having styryl or higher oligo(phenylenevinylene) chains in the 2-, 4-, and 6-positions represent star-shaped push-pull compounds. Alkoxy or dimethylamino groups on the peripheral benzene rings, which act as electron donors, and the central 1,3,5-triazine ring, which acts as an electron acceptor, cause intramolecular charge transfer (ICT) to occur in the absorption S0⇄S1. Protonation of the 1,3,5-triazine core enhances the effect, as demonstrated by a bathochromic shift; a secondary protonation on the dimethylamino groups, however, leads to the breakdown of the ICT. Thus, the yellow compound 1d first becomes violet and then colorless upon the addition of tr…

Triphenanthro‐anellierte [18]Annulene mit Alkoxy‐Seitenketten — Eine neue Klasse discotischer Flüssigkristalle

Triphenanthro-Anellated [18]Annulenes with Alkoxy Side Chains - A Novel Class of Discotic Liquid Crystals Two different types 6 and 16 of [18]annulenes condensed with phenanthrene systems were prepared by cyclocondensation reactions (Schemes 2 and 3). The central 18-membered rings do not show a macrocyclic diamagnetic ring current. Conformational analyses and X-ray analyses in the solid state reveal non-planar structures in which aromatic “islands” are connected by (E)-configurated olefinic bridges. The introduction of long alkoxy side chains yields a new class of discotic liquid crystals; either ND or hexagonal columnar phases are generated, which were characterized by DSC, microscopy with…

Hohe elektrische Leitfähigkeit einzelner Moleküle - eine Herausforderung in der Reihe der konjugierten Oligomere

Auf dem Weg zu molekularer Elektronik: Ausgedehnte konjugierte Oligomere sind wunschenswert fur die molekulare Elektronik, ihre elektrische Leitfahigkeit sollte hierfur jedoch einen niedrigen Abklingfaktor aufweisen. Nun wurden die abgebildeten Zink-komplexierten Oligo(ethinylenporphyrindiylethinylene) entwickelt, die sich durch ultraniedrige Abklingfaktoren der Einzelmolekul-Leitfahigkeit auszeichnen.

ChemInform Abstract: Bis(stilbenyl)squaraines. Novel Pigments with Extended Conjugation.

Abstract We report on the synthesis of a novel type of squaraines ( 11a-f, 17c ) in which the conjugation of the chromophore is extended by stilbene units. These pigments exhibit absorption bands which have their maxima at the end on the Vis region and reach partly into the NIR.

Selective precipitation of alkyl dihalides using a newly synthesized water-soluble bisphosphorylpillar[5]arene

Bisphosphorylpillar[5]arenes ( and ) were synthesized and used to study the host-guest complexation in organic solvents and water. The interactions between the guests and the phosphate of the hosts lead to strong binding towards alkyl dihalides and alkyldiammonium ions. may be used to detect or separate alkyl dihalides in water due to the rapid precipitation of the complex.

Alkoxy-Substituted Hexastyrylbenzenes

Star-shaped compounds 2a–e with a central benzene ring and six p-substituted, (E)-configured styryl groups have been prepared by a sequence of three-fold Heck and three-fold Wittig–Horner reactions. Alkoxy chains (OC3H7, OC6H13, OC10H21, OC12H25) on all six arms guarantee a good solubility of 2a–d, whereas the alternating hexyloxy and cyano substitution in 2e leads to an almost insoluble push-pull system. Irradiation into the long-wavelength absorption of 2a–d (with λmax values of 341–342 nm) results in a statistical photocross-linking, which is characterized by the complete degradation of all stilbene chromophores.

Impact of hydroxy and octyloxy substituents of phenothiazine based dyes on the photovoltaic performance

Two novel organic dyes containing hydroxy and octyloxy substituents onto a phenothiazine skeleton were synthesized and their effects on the photovoltaic performance were studied. Hydroxy acts as an ancillary anchoring unit along with the carboxylic group, while the phenothiazine modified moiety acts as an electron donor. The photophysical and electrochemical studies revealed that maximum absorbance of the dye with the hydroxy group in the solution was blue shifted and its band gap increased, indicating that donor acceptor strength was reduced as compared to the octyloxy substituted dye. Furthermore, electron lifetime of the organic dye with the hydroxy moiety was shorter due to smaller resi…

ChemInform Abstract: Synthesis of Pyrido(2,3-d)pyrimidinones by the Reaction of Aminopyrimidin-4-ones with Benzylidene Meldrum′s Acid Derivatives.

A series of pyrido[2,3-d]pyrimidine-4,7-diones 5a-h were prepared from 6-amino-4-pyrimidones 1 and benzylidene Meldrum's acid derivatives 2 by cyclization reactions in boiling nitrobenzene. The structure of 5, determined by nmr measurements, reveals a selective orientation of 1 and 2 in the addition step.

ChemInform Abstract: 3,6-Bis(2-arylethenyl)-1,2,4,5-tetrazines - Synthesis, LC Properties, and Photochemistry.

Preparation and reactivity of macrocyclic dienynes

Abstract (1 E ,5 E )-Cyclopentadeca-1,5-dien-3-yne ( 1c ), which represents the first macrocyclic 1,5-dien-3-yne, can be obtained by thermal- or butyllithium-induced fragmentation of the corresponding 1,2,3-selenadiazole 8 . The ( E , E )-dienyne functionality causes a geometrical strain E g , which enhances the reactivity in addition ( 1c → 12 , 13 ) and cycloaddition ( 1c → 10 ) reactions and lowers the isomerization barrier to the unstrained ( E , Z )-configuration 1d ( E g  = 0). A slow process 1c → 1d occurs even at ambient temperatures within several weeks.

Preparation of 5‐bromo‐6‐phenylimidazo[2,1‐b][1,3,4]thiadiazol‐2‐ylamines

The reaction of primary or secondary amines with 2,5-dibromo-6-phenylimidazo[2,1-b][1,3,4]-thiadiazole (5) leads to a chemoselective replacement of the 2-Br substituent. The process represents a convenient route to the corresponding 2-ylamines 7a-d. Hydrazine reacts in an analogous fashion (5 → 7e). The structure determinations are based on an X-ray crystal structure analysis and on one- and two-dimensional NMR measurements.

Effect of structural engineering of π-spacers on anti-aggregation of D–A–π–A dyes

In this paper, the encapsulated insulated molecular wire (EIMW) and 2′,7′-bis(hexyloxy)spiro[cyclopenta[2,1-b:3,4-b′]dithiophene-4,9′-fluorene] (SPDF) were specifically designed as efficient anti-aggregation π-bridges for two novel D–A–π–A metal-free sensitizers (IBT1 and IBT2). Compared with the reference dye IBT3 with 3,3′-dihexyl-2,2′-bithiophene (DHBT) as an anti-aggregation π-bridge, both the dyes IBT1 with EIMW and IBT2 with SPDF as π-bridges can suppress intermolecular aggregation more efficiently. The π-bridge of SPDF shows the strongest anti-aggregation ability due to the rigid ‘T’ configuration among these dyes. Meanwhile, the π-bridge of EIMW shows better anti-aggregation ability…

Performance of dye-sensitized solar cells based on novel sensitizers bearing asymmetric double D−π−A chains with arylamines as donors

Abstract Three novel, metal-free organic sensitizers bearing two asymmetric double donor-π-acceptor (D-π-A) chains ( DC1 - 3 ), each, and a reference dye containing single D-π-A chain ( SC ) with cyanoacrylic acid as electron acceptor are synthesized. Their photophysical, electrochemical properties and the performances of the corresponding dye-sensitized solar cells (DSSCs) are further investigated. The dyes, DC1, DC2 and DC3 contain one chain with diphenylamine and another chain with carbazole or phenothiazine as electron donor, while diphenylamine is only employed as electron donor in SC . Compared to the inferior solar energy to electricity conversion efficiency ( η ) of 2.82%, 4.66% and…

Preparation and nonlinear optics of monodisperse oligo(1,4-phenyleneethynylene)s

Oligo(1,4-phenyleneethynylene)s 1a−e, with solubilizing propoxy side chains, were prepared by use of Hagihara−Sonogashira coupling reactions. The synthetic strategy was based on a building block system and on the use of trimethylsilyl and triisopropylsilyl protecting groups that could be cleaved selectively. The extension of the conjugation with an increasing number of repeat units provokes a bathochromic shift of the long wavelength absorption and a superlinear increase of the second hyperpolarizability |γ|. The corresponding third harmonic generation (THG) measurements were performed using polystyrene matrices and variable laser wavelengths. We conclude that the conjugation length is much…

Bicyclo[6.1.0]nonine

MNDO-Rechnungen zeigen, das fur die drei konstitutionsisomeren cis-Bicyclo[6.1.0]nonine (1–3) jeweils zwei energiearme, zueinander diastereomere Konformere a und b existieren. Zur experimentellen Uberprufung werden die mit der Selenadiazol-Methode oder durch Dehydrobromierung hergestellten, hoch gespannten Bicyclen mit Hilfe von 1H- und 13C-NMR-Messungen auf die Population der Konformeren und auf deren wechselseitige Umwandlung durch Inversion der Achtringe untersucht. Bicyclo[6.1.0]nonine MNDO calculations reveal that two diastereomeric conformations a and b of low energy exist for each of the three isomeric cis-bicyclo[6.1.0]nonynes (1–3). For the experimental proof, the highly strained b…

Untersuchungen zur Konformation von 2‐Diazo‐1,3‐diketonen

Mit Hilfe von 1H- und 13C-NMR-Messungen in Losung (und im Festkorper) werden die Konformationen von 2-Diazo-1,3-diketonen (2a–f) mit sperrigen Resten untersucht. Investigation on the Conformation of 2-Diazo-1,3-diketones Conformational analyses of 2-diazo-1,3-diketones (2a–f) with bulky substituents are performed by applying 1H- and 13C-NMR measurements in solution (and in solid state).

Dithienopyrrolobenzothiadiazole-based organic dyes for efficient dye-sensitized solar cells

Four novel D–π–A metal-free organic dyes DTP1–4 containing a dithienopyrrolobenzothiadiazole (DTPBT) unit were synthesized and applied in dye-sensitized solar cells, where DTPBT was employed as a π-spacer for the first time. The photophysical, electrochemical and photovoltaic properties of the dyes were systematically investigated. The dyes DTP1–4 showed broad absorption spectra and high molar extinction coefficient, resulting in high light harvesting efficiency. In addition, the impacts of donors and the thiophene unit as an additional π-spacer were also studied. The results showed that the dye DTP4 with triphenylamine as the donor exhibited better photovoltaic performance than DTP1–3 with…

ChemInform Abstract: Synthesis of Pillar[6]arenes and Their Host-Guest Complexes

Pillar[n]arenes are a fast-growing research topic in supramolecular chemistry. Originally the focus was predominantly on pillar[5]arenes; however, now more and more studies on pillar[6]arenes are being performed. The ability and selectivity of host–guest complexations depend strongly on the size of the inner cavities of these macrocycles. New results have stimulated us to compile the synthetic entries and the complexations of pillar[6]arenes with large cylindric cavities that offer space for many different guest molecules. 1 Introduction 2 Preparation of Pillar[6]arenes 2.1 Pillar[6]arenes by Macrocyclization Reactions 2.2 Hydroxypillar[6]arenes through Ether Cleavage 2.3 Hydroxypillar[6]ar…

Liquid crystals in the series of 2,4,6-tristyryl-1,3,5-triazines

Abstract Alkaline condensation reactions of 2,4,6-trimethyl-1,3,5-triazine ( 1 ) and substituted benzaldehydes ( 2a – n ) yield 2,4,6-tristyryl-1,3,5-triazines ( 3a – n ). A sufficient number and length of the alkoxy chains at the benzene rings provide liquid crystalline phases Col hd . A special structure was found for compound 3i with 9 hexyloxy chains; it exists in the solid state in a helical columnar arrangement, which is transformed by heating to a hexagonal columnar mesophase. Irradiation of the mesophases of 3i – 3m leads to partial cyclodimerization reactions, which cause different textures and lower the clearing points. The border line between the irradiated and the unirradiated z…

Intramolecular photocycloaddition of anthracene and benzene ring systems

Abstract The anthracenes 3a – c , substituted in the 9-position with 3,5-dialkoxybenzyloxymethyl groups exhibit, in diluted solutions, intramolecular [4π+4π] photocycloaddition reactions to the polycyclic compounds 4a – c . The quantitative processes are completely reversible by heating, unless acid-catalyzed cleavages lead to thermally stable mono- and diketones: 4a – c → 5a – c → 6 .

Cycloaddition Reactions of 2H-Benzo[b]thiete and Thiocarbonyl Compounds

2H-Benzo[b]thiete (1) reacts in the o-quinoid form 1′ with the cyclic trithiocarbonates 4 and 6a, b and with the thioketones 8, 10 and 12 in [8π + 2π] cycloaddition reactions to the spiro compounds 5, 7a, b, 9, 11a, b. Irrespective of the presence of CC double bonds, chemoselective and regioselective addition processes at the CS double bonds take place that lead to 4H-1,3-benzodithianes.

ChemInform Abstract: Two Strained Hexahelicenophanes.

The crystal structures of the [6]­helicenes 4,13-(1,10-deca­methyl­ene­dioxy)­hexahelicene, C36H34O2, (I), and 4,13-(1,8-octa­methyl­ene­dioxy)­hexahelicene, C34H30O2, (II), show strong steric interactions between the terminal benzene rings and the poly­methyl­ene­dioxy chains. The shortest ring A and F distances amount to 2.941 (3) and 2.902 (3) A, respectively. The increased steric energy of the ground state is responsible for a significantly lower racemization barrier of (I) and (II) in comparison to the unsubstituted [6]­helicene.

Methylium Ions with OPV Chains − New NIR Dyes

Carbinols, which contain three OPV chains, were generated in convergent syntheses. The extension of the conjugation leads to a bathochromic effect that shifts the absorption from the UV into the visible region. The carbinol series has a convergence limit of the absorption at λmax = 415 nm. The corresponding carbenium ions exhibit a stronger bathochromic shift with the increasing number of repeating units in each chain. Thus, NIR dyes were obtained which show a convergence limit at λmax = 879 nm. The charge distribution in the ground state of the carbocations is discussed on the basis of 13C NMR spectroscopic data.

ChemInform Abstract: Bathochromic or Hypsochromic Effects via the Extension of Conjugation: A Study Stilbenoid Squaraines.

Tris[oligo(1,4-phenylenevinylene)]methylium Dyes

The tris[oligo(1,4-phenylenevinylene)]carbinols 2a–f (n =1–4) and the tris(4-styrylphenyl)methanes 7a,b have been prepared by Wittig–Horner (3 + 4a–f 2a–f) and Siegristreactions (5 + 6a,b 7a,b). The Wittig–Horner reactions in these examples are accompanied by an autoxidation, whereas a reduction occurs in the Siegrist reactions. Compound 2a, the lowest member (n = 1) of the series 2a–d with terminal dialkylamino groups, generates first, on treatment with acids, the methylium dye 2′a, which absorbs far into the NIR region (λmax = 1100 nm). The higher members 2b,c (n = 2,3) of the carbinol series yield by acidic treatment only N-protonated methylium dyes 2″′b,c. The different behavior is due …

1-Cycloundecen-3-in

Es wird ein Syntheseweg fur (E)-1-Cycloundecen-3-in (E-5) beschrieben (Schema 2). Die extrem gespannte Verbindung isomerisiert sich bei Raumtemperatur mit einer Halbwertszeit von 2.2 h (ΔG≠ = 76 kJ/mol). Durch Rotation um die CC-Doppelbindung entsteht dabei (Z)-1-Cycloundecen-3-in (Z-5), das keine geometrische Ringspannung Eg mehr besitzt.

Synthesis of novel 1,2,5,6-tetrahydro-4H-pyrrolo[3,2,1-ij]quinolines via benzotriazole methodology

Abstract Pyrroloquinolines have been synthesized reacting 1-(benzotriazol-1(2)-ylmethyl)indolines with unactivated and electron-rich alkenes in the presence of p-toluenesulfonic acid catalyst. Mixtures of the expected diastereomers were obtained and some of them separated in their respective components. X-Ray diffraction along with two-dimensional NMR experiments was needed to assist the determination for both the structures of the precursors and products.

Preparation and Photochemistry of Dendrimers with Isolated Stilbene Chromophores

In addition to the model compounds 4a and 4b, the dendrimers 11 and 14 with trans-stilbene chromophores in the core and on the periphery of the dendrons were prepared and their photochemistry was studied in solution and in neat films. Due to the flexibility of the arms, intramolecular and intermolecular CC bonds are formed on irradiation. Thus, the generation of nanoparticles, which represent small oligomers, is much more likely than for the cross-linking of rigid, cross-conjugated stilbenoid dendrimers. The photoreactions in solution were studied by UV and NMR spectroscopy, the transformation of the films was studied by AFM. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 200…

ChemInform Abstract: Synthesis of Thiacycloocteno-1,2,3-selenadiazoles.

Efficient synthesis of copillar[5]arenes and their host–guest properties with dibromoalkanes

An efficient method for the synthesis of copillar[5]arenes was developed with FeCl(3) as catalyst and different 1,4-dialkoxybenzenes and paraformaldehyde as reactants (yields: 50-85%). The host-guest property of (co)pillar[5]arenes and terminal dibromoalkanes was investigated by (1)H NMR measurements and an X-ray study. The complexation behavior of the copillar[5]arenes can be tuned by changing the substituents on the host. A complete complexation selectivity was found between pillar[5]- and pillar[6]arenes, which is an interesting aspect for sensor techniques.

ChemInform Abstract: Preparation and Nonlinear Optics of Monodisperse Oligo(1,4-phenyleneethynylene)s.

Oligo(1,4-phenyleneethynylene)s 1a−e, with solubilizing propoxy side chains, were prepared by use of Hagihara−Sonogashira coupling reactions. The synthetic strategy was based on a building block system and on the use of trimethylsilyl and triisopropylsilyl protecting groups that could be cleaved selectively. The extension of the conjugation with an increasing number of repeat units provokes a bathochromic shift of the long wavelength absorption and a superlinear increase of the second hyperpolarizability |γ|. The corresponding third harmonic generation (THG) measurements were performed using polystyrene matrices and variable laser wavelengths. We conclude that the conjugation length is much…

Dehydrotriphenylene zum Aufbau gewinkelter molekularer Bandstrukturen

Dehydrotriphenylenes for the Generation of Bent Molecular Ribbons The synthetic sequences 1 11 and 17 23a lead to highly reactive mono- and bisdienophiles whose cycloaddition processes with in situ generated isobenzofuran 13 were studied: 11 + 13 15 and 23a + 2×13 24a.

Oligo(phenylenevinylene)s with Terminal Donor–Acceptor Substitution This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie.

ChemInform Abstract: 1,4-Epoxyarenes for the Generation of Molecular Ribbons

Structure Determination of Photoproducts of Anthracenes with (Arylmethoxymethyl) Sidechains

Irradiation of 9-(arylmethoxymethyl)anthracenes 3 leads either to a cyclomer and cyclodimer mixture (3a  4a,5a), to selectively formed dimers (3b  5b), or a selectively formed cyclomer (3c  4c). The [4π+4π]cyclodimerization is under the conditions used a regioselective head-to-tail process. In the crystals of the dimers 5a,b, the sidechains are attached in an antiperiplanar position related to the CC bonds generated in the dimerization. In solutions, however, the structures consist of three rotamers the equilibration of which was studied by temperature-dependent NMR spectra. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Oligomere aus gleichsinnig angeordneten Chalkon-Bausteinen

The cross-conjugated oligomers 1a–d, which contain up to eight alternately arranged chalcone building blocks, were prepared by stereoselective condensation reactions of formyl and acetyl components. The synthetic sequence started with 1,4-dibromo-2,5-dipropoxybenzene (2). Bouveault reactions with DMF and DMA yielded the aldehydes 3 and 6 and the ketones 7 and 10. After the protection of the carbonyl group (3 4 and 7 8), a further Bouveault reaction led to monoprotected dialdehyd 5 and diketone 9, respectively. Repetitive condensation reactions starting with the acetophenone derivative 11 and 5 furnished the aldehyde 12, the ketone 13 and the aldehyde 14. In the final step the target compoun…

( E )‐ und ( Z )‐Enole von β‐Ketocarbonsäureamiden

(E)- and (Z)-Enols of β-Ketocarboxylic Acid Amides Reaction of dimesitoyldiazomethane (1) with ammonia (3a), primary and secondary amines (3b – o and 3p – v, respectively) leads to the completely enolized amides 4a – v. Besides the chelated Z configuration the unusual E isomer exists in the most cases, too. The Z/E distribution in the equilibrium depends on the steric and electronic effects present in the amide group CONR2R3 and on the solvent.

Reaction of 4,5-diamino-1,6-dihydropyrimidin-6-ones with two equivalents of chalcones

The reaction of 4,5-diamino-1,6-dihydropyrimidin-6-ones 1 with two equivalents of the chalcones 2 leads in an acidic medium to the formation of the 2,3,6,7-tetrahydro-1H-pyrimido[4,5-b][1,4]diazepin-6-one derivatives 3a-d. The structure elucidation of the products is based on nmr measurements and an X-ray diffraction.

ChemInform Abstract: Cycloaddition Reactions of 2H-1-Benzothietes and 1,3,5,7-Tetrathio-s-indacene-2,6-dithiones.

Reaktionen von Benzothiet mit Iminen

Reactions of Benzothiete with Imines A great variety of compounds 3a–w containing CN double bonds was studied in the reaction with benzothiete (1). H, alkyl, aryl, OR, SR and NR groups can be attached to the imino function. The azomethines 3a–f, the thiazolines 3g–i, the lactim 3n, the oximes 3r–t, the isoxazolinone 3u and the azine 3v show [8π + 2π] cycloaddition reactions yielding derivatives of 1,3-benzothiazine (4a–i, n, r–v). In the case of 4n, s, t secondary reactions occur, initiated by elimination processes. [8π + 2π] Cycloadditions account also for the reactions 3e 10, 11, 3o 18(I), and 3q 19; however, CC double bonds are representing the 2π component in these examples. The thiazol…

Crystal structure analysis of a star-shaped triazine compound: a combination of single-crystal three-dimensional electron diffraction and powder X-ray diffraction.

The solid-state structure of star-shaped 2,4,6-tris{(E)-2-[4-(dimethylamino)-phenyl]ethenyl}-1,3,5-triazine is determined from a powder sample by exploiting the respective strengths of single-crystal three-dimensional electron diffraction and powder X-ray diffraction data. The unit-cell parameters were determined from single crystal electron diffraction data. Using this information, the powder X-ray diffraction data were indexed, and the crystal structure was determined from the powder diffraction profile. The compound crystallizes in a noncentrosymmetric space group,P212121. The molecular conformation in the crystal structure was used to calculate the molecular dipole moment of 3.22 Debye,…

Dithienopyrrolobenzotriazole-based organic dyes with high molar extinction coefficient for efficient dye-sensitized solar cells

Abstract Four novel organic dyes DT1-DT4 containing a dithienopyrrolobenzotriazole unit were synthesized and applied in dye sensitized solar cells, where dithienopyrrolobenzotriazole moiety was introduced as a π-spacer for the first time. The four dyes exhibited good light harvesting efficiency with high molar extinction coefficients and broad spectral response. The influence of the different electron donor on the photovoltaic performance was evaluated. The effects of the linear and branched alkyl chains in the π-bridge on the photophysical, electrochemical and photovoltaic performance were systemically investigated. The results show that branched alkyl chains are better than linear alkyl c…

Formation and Reactivity of 2-Styryl-1,4-benzoquinones

Untersuchungen zur Photoleitf�higkeit von alkoxysubstituierten Oligo- und Poly(1,4-phenylenethenylen)en

Investigations on the Photoconductivity of Alkoxy Substituted Oligo- and Poly(1,4-phenyleneethenylene)s The photoreactivity and the photoconductivity of the mono- and dialkoxy substituted oligo- and poly(1,4-phenyleneethenylene)s 1/1′a-n were investigated in order to optimize the photoconducting properties of these materials. Increasing the length of the side chains enhances the average length of the main chain during the polycondensation and decreases the band gap till the limit of convergence is reached. The highest photoconductivity was observed for the 2,5-dipropyloxy system 1/1′j. Longer side chains render the charge transfer from chain to chain more difficult. The measurements were pe…

Metal-free organic dyes with di(1-benzothieno)[3,2-b:2′,3′-d]pyrrole as a donor for efficient dye-sensitized solar cells: Effect of mono- and bi-anchors on photovoltaic performance

Abstract Four novel metal-free organic dyes WL1a-b and WL2a-b containing di(1-benzothieno)[3,2-b:2′,3′-d]pyrrole (DBTP) as electron donor were synthesized and applied for dye-sensitized solar cells (DSSCs), where DBTP was firstly employed as a donor in the organic dyes. It has been demonstrated that the dyes WL with DBTP as a donor show better photovoltaic performance than the reference dye PTZ with phenothiazine as a donor. In comparison with WL1a-b with one cyanoacrylic acid as mono-anchor, WL2a-b with two cyanoacrylic acids as bi-anchors show a broader light absorption on the TiO2 film and higher molar extinction coefficients in solution, resulting in higher power conversion efficiency. …

Anti-recombination organic dyes containing dendritic triphenylamine moieties for high open-circuit voltage of DSSCs

Abstract Three novel sensitizers with dendritic triphenylamine moieties were synthesized and used for dye-sensitized solar cells (DSSCs). Their absorption spectra, electrochemical and photovoltaic properties were extensively investigated. All three DSSCs exhibit high open-circuit voltage over 0.8 V. The photovoltaic results indicate that the dendritic triphenylamine units improve the open-circuit voltage, which is attributed to the retardation of charge recombination, demonstrating that non-planar and larger molecules exert better blocking function. Under standard global AM 1.5 solar conditions, the best performance of the DSSCs exhibits a short-circuit current density of 10.35 mA cm−2, an …

Kinetische Untersuchungen zu Diels‐Alder‐Reaktionen des Cyclooctins mit anschließender Aromatisierung

Aus Cyclooctin (1) und den cyclischen Dienen 2a – g entstehen die Tricyclen 3a – g, die ganz unterschiedliche Stabilitat aufweisen. 3a, b, f und g zerfallen spontan. Unter Abspaltung von CO2, SO2, CO und N2 entstehen die aromatischen Verbindungen 4a – c. 3c eliminiert beim Erhitzen C2H4. 3e wird thermisch kaum mehr gespalten, aber ganz effizient bei der Photolyse, und 3d ist schlieslich gegenuber einer Aromatisierung stabil. Die thermische Ethylenabspaltung und die doppelte Photodecarbonylierung werden kinetisch untersucht. Kinetic Investigations of Diels-Alder-Reactions of Cyclooctyne with Consecutive Aromatization The tricyclic compounds 3a – g, generated from cyclooctyne (1) and the cycl…

Single-Crystal Structures of Model Compounds for Poly(2,5-dialkoxy-1,4-phenylenevinylene)

ChemInform Abstract: Extended Conjugation in Stilbenylsquaraines.

Cycloaddition reactions of 2H-benzo[b]thiete and conjugated cyclic dienes

2H-Benzo[b]thiete 1 reacts with cyclopentadiene 3 in consecutive [8π + 2π]cycloadditions yielding the condensed heterocycles 6–8. Tetracyclone 9 on the other hand gives only the monoadduct 10. An [8π + 8π]cycloaddition can be observed for 1 and diphenylisobenzofuran 11. The related π system 13 shows again consecutive [477π + 27π]processes (1 + 13 ← 14, 15).

Synthesis and Conformational Properties of Nonsymmetric Pillar[5]arenes and Their Acetonitrile Inclusion Compounds

The catalytic cyclocondensation of 1-butoxy-4-methoxy-2,5-bis(methoxymethyl)benzene (1d) affords a statistical mixture of the regioisomeric pillar[5]arenes 3a–d in high yield. The alkoxy groups are arranged stereoselectively in a mode so that they avoid steric interactions. The rotation of the benzene rings is, at room temperature, fast in terms of the NMR timescale and leads to a de facto Cs symmetry for 3a–c and a C5h symmetry for 3d. All four structural isomers can encapsulate two CH3CN guest molecules. The structure determinations are based on four crystal structure analyses (constitutions) and NMR spectroscopic measurements (conformations).

1,2-Methyl shift in the reaction of 4,7-dihydro-4,5-dimethyl-7-phenyl-(1,2,4)-triazolo[1,5-a]pyrimidine with tosyl azide

The reaction of the heterocyclic enamine 1 with tosyl azide (2) leads to the tosylimino derivative 4 of 1,2,4-triazolo[1,5-a]pyrimidine. The extrusion of nitrogen from the primary adduct 3 is followed by a 1,2-shift of a methyl group. The structure determination of 4 is based on 1H and 13C nmr spectra including NOE measurements.

ChemInform Abstract: Methylium Ions with OPV Chains - New NIR Dyes.

Carbinols, which contain three OPV chains, were generated in convergent syntheses. The extension of the conjugation leads to a bathochromic effect that shifts the absorption from the UV into the visible region. The carbinol series has a convergence limit of the absorption at λmax = 415 nm. The corresponding carbenium ions exhibit a stronger bathochromic shift with the increasing number of repeating units in each chain. Thus, NIR dyes were obtained which show a convergence limit at λmax = 879 nm. The charge distribution in the ground state of the carbocations is discussed on the basis of 13C NMR spectroscopic data.

Relationship between structure and electroluminescence of oligo(p-phenylenevinylene)s

The preparation of LEDs with poly(p-phenylenevinylene) (PPV) as emitting material is well established, However, due to the presence of a distribution of conjugated chain lengths in the polymer, systematic investigations of the electroluminescence with polymeric materials are difficult, as far as the optical emission is concerned. We are studying the relationship between structural variation of substituted oligo(p-phenylenevinylene)s and their electroluminescent behaviour using a series of distyrylbenzenes with a variety of substituents in order to investigate their influence on the electroluminescence (EL). Furthermore, we synthesized a homologous series of monodisperse oligo(2,5-dipropoxy-…

ChemInform Abstract: 1H-Naphtho(2,1-b)thiete and 2H-Naphtho(2,3-b)thiete - Synthesis and Reactivity.

Abstract The title compounds 4 and 8 are obtained by flash vacuum pyrolysis of the corresponding hydroxymethylthionaphthols 3 and 7. Whereas 4 shows a smooth ring opening on heating, 8 is thermally stable but reacts photochemically. The different behavior is explained on the basis of an MNDO calculation. The valence isomers 4′ and 8′ represent thioquinonemethides, which are highly reactive components in [12π + 2π]cycloaddition processes (4 → 9, 10, 11; 8 → 12).

Equilibrium between Hydroxycycloalkanones and Oxabicycloalkanols

Guido Kramer, Annette Oehlhof, and Herbert Meier Institute of Organic Chemistry, University of Mainz, Duesbergweg 10 – 14, 55099 Mainz, Germany Reprint requests to Prof. Dr. H. Meier. Fax: +49-(0)6131-3925396. E-mail: hmeier@mail.uni-mainz.de Z. Naturforsch. 2009, 64b, 847 – 850; received April 8, 2009 Hydroxycycloalkanones 1 of medium ring size (8 – 10) exist in a transannular tautomeric equilibrium with the corresponding oxabicycloalkan-1-ols 2, which represent hemiacetals. Normally, the bicyclic structures 2 predominate in solution although their portion decreases with increasing solvent polarity. A correlation of the Gibbs reaction enthalpies ∆G (1→2) with the solvent parameters ET (30)…

Synthesis of pyrido[2,3-d]pyrimidines in the reaction of 6-amino-2,3-dihydro-2-thioxo-4(1H)-pyrimidinone with chalcones

6-Amino-2,3-dihydro-2-thioxo-4(1H)-pyrimidinone (1) reacts in boiling DMF with α,/β-unsaturated ketones 2 yielding the pyrido[2,3-d]pyrimidine systems 5 and 6, respectively. The orientation in the addition process can be determined by nmr measurements, especially by NOE difference spectroscopy. The products do not correspond to a normal Skraup or Doebner-v. Miller synthesis.

Diketopyrrolopyrrole based D-π-A-π-D type small organic molecules as hole transporting materials for perovskite solar cells

Abstract Three novel diketopyrrolopyrrole (DPP) based small organic molecules were synthesized as hole transporting materials for perovskite solar cells. The effects of different donors and π bridges on the performance of perovskite solar cells (PSCs) were discussed. The efficiency of TPADPP-1, TPADPP-2, PTZDPP-2 was 5.10%, 9.85% and 8.16% respectively. Compared to TPADPP-2, the voltage of PTZDPP-2 was higher. Because the electron-donating ability of phenothiazine based donor was larger than that of triphenylamine based donor, the HOMO level of PTZDPP-2 was lower than that of TPADPP-2. The results indicated that the diketopyrrolopyrrole based D-π-A-π-D type small organic molecule might be a…

Untersuchungen über das Benzothiiren

Thermolyse und Photolyse von 1,2,3-Benzothiadiazol 10c, liefern die Produkte 11c – 15c. Mit Hilfe der 13C-Markierungstechnik wird gezeigt, das dabei kein intermediares Benzothiiren 1c gebildet wird. Isotopomere Reaktionsprodukte gehen auf H-Verschiebungen zuruck. Durch elektronenziehende Estergruppen in 6-Position wird der Ringschlus zu den substituierten Benzothiirenen 1d, e zwar nicht bei der Thermolyse, wohl aber bei der photochemischen Reaktionsfuhrung ermoglicht. Zum Nachweis dient eine eingehende Untersuchung der bei Thermolyse, Photolyse und auf einem unabhangigen Weg erhaltenen Disulfide 14d, e, bzw. 14d′, e′ und 14d˝, e˝. Die vorliegenden Ergebnisse basieren auf 13C- und 1H-NMR-Mes…

Ein neuer Syntheseweg zu Offenkettigen und cyclischen Oligoetherketonen

A Novel Synthetic Route to Open-Chained and Cyclic Oligoetherketones Oligoetherketones of the structure 2a,b can be generated by repetitive insertion reactions of terminal biscarbenoids 4a,b, into the OH bonds of diols like 5. The formation of the corresponding ring systems 7a and the involved carbene dimerization leading to 8b are processes which compete with the linear polyinsertion. A related one-component reaction can be performed with ω-hydroxy-1-diazo-2-alkanones (13a–c 14a–c).

Gekreuzt konjugierte oligomere aus pyrrol-, benzol- und carbonyl-Bausteinen

Abstract Chalcones can serve as C 2 or C 3 components for the formation of 1 H -pyrroles. In particular the reaction with tosylisocyanid could be applied to the oligochalcones 2d - g with up to 6 enone units. A series of cross-conjugated oligomers 8d - g was obtained; these compounds consist of a chain of 1,4-phenylene, carbonyl and 1 H -pyrrole-3,4-diyl building blocks. The benzene rings bear two propoxy sidechains in order to enhance the solubility.

Cyclooctadienine — hoch gespannte C 8 H 8 ‐Kohlenwasserstoffe

Mit Hilfe der MNDO-Methode werden die energiearmsten Konformationen der vier strukturisomeren Cyclooctadienine 1–4 berechnet. Aus ihren Bildungswarmen ΔHf konnen durch Bezug zu den Cyclooctatrienen 5 und 6 die geometrischen Ringspannungen Eg abgeschatzt werden. Als experimentelle Sonde fur die Ringspannung dienen die UV-, IR (Raman)- und 13C-NMR-Spektren. Cyclooctadienynes — Highly Strained C8H8-Hydrocarbons Applying the MNDO-method the conformations with lowest energy of the isomeric cyclooctadienynes 1–4 are calculated. The geometrical ring strains Eg can be evaluated from the enthalpies of formation ΔHf in relation to the cyclooctatrienes 5 and 6. UV, IR (Raman) and 13C NMR spectra serve…

The Unusual Photochemistry of Dendrimers with an Anthracene Core

Cycloaddition of benzothiete and electron-deficient nitriles

The o-quinoid 8π electron system 2, generated by thermal ring opening of benzothiete (1), enters regio-specific [8π + 2π] cycloaddition reactions with electron-deficient nitriles 3a-d, yielding the 4H-1,3-benzothiazines 4a-d. A competitive dimerization of 1 leads to 1,5-dibenzo[b,f]dithiocin (5). Depending on the nitrile further competitive or subsequent reactions (2 + 3b 7b, 2 + 3d 4d 8d) can occur. The cycloadducts 10e and 11e gained from 3e anticipate a primary cleavage of 3e to methylisothiocyanate 9e which reacts at the CN double bond as well as at the CS double bond.

Conjugated Compounds Based on Vinylthiazole Units

Conjugated oligomers attract increasing attention because of their interesting properties in materials science [1]. Moreover, they are model compounds for conjugated polymers. Molecules polarized by electronic effects, in particular push-pull systems having terminal donor-acceptor substitution represent a special class of such oligomers [2]. Their major applications are in the field of nonlinear optics (NLO), twophoton absorption (TPA), two-photon induced fluorescence (TPIF), and photorefractive materials (PR). Fig. 1 illustrates known 2,5-thienylenevinylenes with zwitterionic resonance structures 1 (D = NR2; A = NO2, CHO, SO2R; n = 1, 2) [3, 4]. The corresponding compounds 2 with thiazole …

Synthesis and photodimerisation of tetrabenzo[ab,f,jk,o][18]annulenes

Abstract The tetrabenzo[ab,f,jk,o][18]annulenes 7a,b, generated in a 5-step synthesis, show photodimerisation and -oligomerisation reactions in the solid state and in solution. The state of aggregation determines the reaction route. Whereas the cyclodimer 8a has a simple cyclobutane structure, the dimer 8b is a highly symmetrical cyclophane.

ChemInform Abstract: Reaction of 4,5-Diamino-1,6-dihydropyrimidin-6-ones with Two Equivalents of Chalcones.

The reaction of 4,5-diamino-1,6-dihydropyrimidin-6-ones 1 with two equivalents of the chalcones 2 leads in an acidic medium to the formation of the 2,3,6,7-tetrahydro-1H-pyrimido[4,5-b][1,4]diazepin-6-one derivatives 3a-d. The structure elucidation of the products is based on nmr measurements and an X-ray diffraction.

ChemInform Abstract: Transformation of Hydroxycycloalkanones to Oxabicycloalkenes.

ChemInform Abstract: A New Synthetic Route to Tribenzo[a,e,i][12]annulenes.

Abstract The tribenzo[a,e,i][12]annulene 10 and the corresponding twofold annulene 14 were prepared on synthetic routes which first led from suitably functionalised starting compounds (2, 11) to the 1,2-distyryl- and 1,2,3,4-tetrastyrylbenzene derivatives 9 and 13 with two and four formyl groups, respectively. The cyclisation to 10 and 14 was achieved by applying the McMurry reaction. The extended ring system of compound 14 represents a discotic mesogen. The generation of liquid crystals was obtained with eight hexyloxy chains on the periphery.

ChemInform Abstract: Synthesis and Photodimerization of Tetrabenzo[ab,f,jk,o][18]annulenes.

4-Alkenyl-1,2,3-thiadiazole

Die Titelverbindungen 5 werden aus entsprechenden Alkylderivaten durch Bromierung/Dehydrobromierung (Weg A) oder durch Wittig-Reaktion (Weg B) dargestellt. Mit 4-Phenyl-4H-1,2,4-triazol-3,5-dion entstehen unter Erhaltung des Thiadiazolrings die Monoaddukte 12. 4-Alkenyl-1,2,3-thiadiazoles The title compounds 5 are prepared from the corresponding alkyl derivatives by bromination/dehydrobromination (route A) or by Wittig reaction (route B). 4-Phenyl-4H-1,2,4-triazole-3,5-dione yields the monoadducts 12 by maintenance of the thiadiazole ring.

Preparation of 2-amino-5-methyl-7H-1,3,4-thiadiazolo[3,2-α]pyrimidin-7-ones

2-Amino substituted 7H-1,3,4-thiadiazolo[3,2-α]pyrimidin-7-ones 11a-e were prepared by the reaction of 2-bromo-5-amino-1,3,4-thiadiazole (1b) and diketene (8), subsequent cyclocondensation (9b 3b) and displacement of the bromo substituents by the reaction with primary or secondary amines (3b 11a-e). The hydrogen atom 6-H in the heterobicycle 3b is replaced by a Cl or Br atom in the transformation of 3b 14a,b. The 2-bromo-6-chloro compound 14a reacts chemoselectively in the 2-position with dimethylamine (14a 15). The structure elucidations are based on one- and two-dimensional NMR techniques including a heteronuclear NOE measurement.

ChemInform Abstract: Preparation of Dithiacycloalkynes by Cyclization Reactions Applying the Cesium Effect.

Abstract The strained dithiacycloalkynes 3a,b and the larger heterocyclic alkynes 3c and 4 are obtained by cesium assisted cyclization reactions of the dithiols 1a–c and 1,4-dibromo-2-butyne (2). The reactivity of 3a–c was studied in cycloaddition and complexation reactions generating the adducts 5a,b and 6 and the silver and cobalt complexes 7 and 8.

Erweiterte Konjugation in unsymmetrischen Stilbenylsquarainen

Extended Conjugation in Stilbenylsquaraines Unsymmetrical 1-aryl-3-stilbenylsquaraines 2a–e and 1,3-bis(stilbenyl)squaraines 3a–c were prepared by CC coupling reactions of the corresponding substituted arenes with derivatives of squaric acid (Schemes 2 and 3). Dialkylamino and alkoxy groups enhance the solubility of these dyes and enlarge the intramolecular charge transfer of these donor–acceptor–donor systems. The extended conjugation of the stilbene units – in comparison with arene building blocks – leads to significant bathochromic shifts in the Vis/NIR absorption spectra.

Cycloadditionen von Benzothiet und aromatischen Nitroso‐Verbindungen

Cycloaddition Reactions of Benzothiete and Aromatic Nitroso Compounds The new heterocyclic ring systems 4H-3,1,2-benzoxathiazines 4 and 2,3-dihydro-1,2-benzothiazol 1-oxides 6 can be synthesized by cycloaddition of benzothiete (1) and aromatic nitroso compounds 3. The regioselectivity of the primary step and the secondary thermal or acid-catalyzed rearrangements are discussed.

ChemInform Abstract: Optical Switches with Biplanemers Obtained by Intramolecular Photocycloaddition Reactions of Tethered Arenes

The dimerization of anthracene by a [4π + 4π] cycloaddition is one of the oldest and best known reactions in photochemistry. In the series of tethered bichromophoric arenes, this reaction type could be extended to anthracene–naphthalene, naphthalene–naphthalene and recently even to anthracene–benzene and naphthalene–benzene systems. Cyclophanes, which can be regarded as twofold or multiple tethered systems, are not discussed here. The cycloisomerizations are performed by irradiation at the long-wavelength absorption (λ > 270 nm), whereas shorter wavelengths (λ < 270 nm) lead to cycloreversions, which can be also achieved by a thermal route. The systems represent therefore a P- and T-type ph…

Impact of the position isomer of the linkage in the double D–A branch-based organic dyes on the photovoltaic performance

Abstract Three organic dyes with double D–A system were synthesized and applied in the dye-sensitized solar cells. These dyes contain phenothiazine as an electron donor and cyanoacetic acid as an acceptor/anchor. Linkages were incorporated at the ortho-, meta- and para-positions and their impact on the performance of photovoltaic was observed. Among them, the dye with a para-position linkage exhibited the highest short-circuit photocurrent density (12.26 mA cm−2) and open-circuit photovoltage (756 mV), leading to the best overall efficiency (6.14%) due to better light harvesting capacity under standard global 1.5 AM conditions. Under similar measuring conditions the dyes with ortho and meta…

A new synthetic route to tribenzo[a,e,i][12]annulenes

Abstract The tribenzo[a,e,i][12]annulene 10 and the corresponding twofold annulene 14 were prepared on synthetic routes which first led from suitably functionalised starting compounds (2, 11) to the 1,2-distyryl- and 1,2,3,4-tetrastyrylbenzene derivatives 9 and 13 with two and four formyl groups, respectively. The cyclisation to 10 and 14 was achieved by applying the McMurry reaction. The extended ring system of compound 14 represents a discotic mesogen. The generation of liquid crystals was obtained with eight hexyloxy chains on the periphery.

Eine leichte und effiziente Herstellung von Pillararenen und einem Pillarchinon

Introduction of unsaturated segments in the bridge of metacyclophanes

Abstract The cyclophanes 2a,b, which contain a triple bond in the meta-bridge, were transformed to the allenes 3a,b by the action of bases or acids. A further isomerization yielded the dienes 4a,b with ( E,Z )- or ( Z,Z )-configuration.

ChemInform Abstract: Synthesis of Benzo(b)thioxanthenes.

Synthese und Eigenschaften von 1-Thia-2-cyclooctin

Aus 6-Bromhexansaure (1) wird uber das Keton 9 mit der Selenadiazol-Methode die Titelverbindung 14 hergestellt. 14 besitzt eine gespannte und polarisierte Dreifachbindung, was sich in einer ungewohnlich hohen Reaktivitat bemerkbar macht. Auser der Addition von Wasser und Ethanol zu 9 bzw. 29 werden die Cycloadditionen mit Tetraphenylcyclopentadienon zu 16, mit Diazomethan zu 32 und 33 und mit Schwefelkohlenstoff zu 35 und 36 besprochen. 35 und 36 bilden mit TCNQ die tiefschwarzen Komplexe 37, 38. Als Nebenprodukte werden bei der thermischen Selenadiazol-Fragmentierung die 1,4-Diselenine 21, 22, die Selenophene 23–25 und die 1,3-Diselenole 27, 28 erhalten.

Pillar[n]arenes-a Novel, Highly Promising Class of Macrocyclic Host Molecules

Since 2008 a new field of supramolecular chemistry has developed rapidly: the chemistry of pillar[n]arenes. These “younger brothers and sisters” of calixarenes are conveniently accessible and extremely guest-friendly. Guests from many different classes of organic compounds are welcome. Nevertheless, a high selectivity for the threading of guest molecules in the macrocyclic cavities can be achieved. The complex stability is characterized by association constants Ka between 10 and 1×108 M−1. The rate constants of the threading vary over several orders of magnitude. The focus of this article lies on the preparation (sections 2 and 3) and the structures (section 4) of pillar[n]arenes (n=5–10) i…

Fluorescent-Cavity Host: An Efficient Probe to Study Supramolecular Recognition Mechanisms

Using fluorometry to study the interactions between guests and host cavities is often challenging, especially for hosts with small cavities because the fluorophore may not be close to the binding site. Therefore, it is critical to overcome this hurdle to broaden the applicability of fluorometry in supramolecular chemistry. Herein, we designed a fluorescent-cavity host (H1) by conjugating the binding site of a pillar[5]arene cavity and studied its host-guest recognition mechanism in the cavity. Distinct fluorescent responses of H1 were observed for cyano homologues: the fluorescence was enhanced for succinonitrile but quenched for malononitrile. Such an unusual phenomenon with such subtle di…

Generation of hexahydroazulenes

(Z)-Cyclodec-1-en-6-yne (3) generates three conjugated hexahydroazulenes 3→1k→1c, 1l under FVP conditions, whereas flash vacuum pyrolysis (FVP) of cyclodecyne (2) leads to 1,2,9-decatriene (9). We attribute the different thermal behavior of 2 (ring opening) and 3 (ring closure) to different transannular interactions. Altogether 22 constitutional isomers of hexahydroazulene should exist; three new isomers (1k, 1l, and 1m) are presented here, ten were described earlier, but the reinvestigation of the dehydration route of bicyclic alcohol 11 showed that one of the ten structures has to be revised.

Isomerisierung der Dihydropentalene und Umsetzung mit Tetracyanethylen

Zwischen den sechs isomeren Dihydropentalenen 1–6 existieren eine Reihe von H-Verschiebungen (Schema 1), die in Gasphasenpyrolysen untersucht werden. Der thermodynamisch kontrollierte irreversible Ausgang aus den Gleichgewichten von 1–6 fuhrt uber 1-Vinylfulven (14) zu Styrol (15). Praparativ nutzlich ist besonders die katalytische Isomerisierung zwischen 1,5-DHP (4) und 1,2-DHP (1) bei Raumtemperatur. Die Umsetzung der Dihydropentalene mit Tetracyanethylen liefert bei 1 das [2+2]-Addukt 24, bei 3 und 5 die [4+2]-Addukte 25 bzw. 26 und bei 4 das doppelte [4+2]-Addukt 22.2 und 6 lassen sich unter Blitzpyrolyse-Bedingungen mit TCNE nicht abfangen. Isomerization of Dihydropentalenes and Reacti…

Thermal rearrangements of 1,2-dialkoxybenzenes by flash vacuum pyrolysis

Flash vacuum pyrolysis of 1,2-dialkoxybenzenes 1a-c leads to the liberation of alkanes from the interacting side chains. A rearrangement of the skeleton yields the o-hydroxy carbonyl compounds 2 and 4. The generation of phenol 3 can be rationalized by a decarbonylation. The latter reaction is the sole process which can be observed for the bicyclic starting compound 9.

ChemInform Abstract: Synthesis of Highly Substituted Hexahelicenes

C2-Symmetric hexahelicenes 3a–3g, which bear four or six alkoxy chains, were prepared in eight-to-nine reaction steps in high overall yields. The final step consisted of a twofold oxidative photocyclization of the corresponding 2,7-bis(2-phenylethenyl)naphthalenes. Long (and branched) chains provide a good solubility and processability, which is a prerequisite for applications in organic synthesis and materials science.

Protonation and rearrangement of the tricyclo[4.2.2.22,5]dodeca-3,7,9,11-tetraene scaffold

The biplanemers 2a,b contain enol ether substructures, which permit facile protonations of the π electron system. The subsequent ether cleavage is characterized by rearrangements of the polycyclic scaffold of the carbenium ions or the electroneutral primary products. Apart from the expected products 3a and 5a, a series of unexpected ketones and diketones (4a′, 9b, 10b, 11b, and 12b) were obtained.

ChemInform Abstract: An Efficient Synthesis of Rubin′s Aldehyde and Its Precursor 1,3,5-Tribromo-2,4,6-tris(dichloromethyl)benzene.

The title compound (IV) serves as precursor of hexaethynylbenzenes and other [6]star compounds.

Crystal structure of a dimeric 1-benzothiepin

AbstractThe crystal structure of the 1-benzothiepin derivativemeso-5is presented. Compound5is the first dimeric 1-benzothiepin system.

Addition von Phosphor‐Nucleophilen an Benzothiet

Addition Reactions of Phosphorus Nucleophiles to Benzothiete Trialkyl phosphites 4 add to the o-quinoid form 2 of benzothiete (1) to yield the phosphonates 6. An intermolecular migration of an alkyl group from oxygen to sulfur is the most important feature of this transformation. The rearrangement – related to the Arbuzov reaction – can be avoided in a two-step process by the subsequent action of PCl3 and alcohol; thus the phosphonates 10 are generated. Analogous to 2 6, dimethyl phenylphosphinate (11) furnishes 13. In contrast, the cyclic esters 14a–d form 2:1 adducts, namely the 12- to 15-membered heterocyclic compounds 17a – d. An intramolecular rearrangement in a 1:1 adduct is only obse…

Synthesis and photovoltaic performance of asymmetric di-anchoring organic dyes

Abstract Two novel metal-free organic dyes bearing two asymmetric double donor–acceptor segments were synthesized. Their physical, optical, electrochemical properties and photovoltaic performances were investigated. Compared with the mono-anchoring dye containing single donor–acceptor chain, these new dyes exhibited a broader and much stronger absorption in the light wavelength ranging from 400 to 600 nm, showed higher IPCE values and short-circuit current density, which led to more efficient photovoltaic performance. The dye with triphenylamine and phenothiazine as two electron donors and two cyanoacrylic acids as two electron acceptors exhibited an impressive power conversion efficiency o…

ChemInform Abstract: Benzothiete, a Versatile Reagent in Heterocyclic Syntheses

Reactions of benzothiete with phosphorus nucleophiles - a novel type of arbuzov rearrangement

The reaction of trialkylphosphites or related P-nucleophiles with benzothiete (1) leads to zwitter ionic species, which show an Arbuzov - like rearrangement to the products 4 and 7, respectively. New heterocyclic ring systems are generated in the case of cyclic esters. The normal SN2 reaction leads to the 1:2 adducts 9, whereas in an SN1 process the 1:1 adduct 13 is formed.

The formation of pyrazolo[1,5-a]pyrimidines by the reaction of 3-(4-chlorophenyl)pyrazol-5-amine with chalcones

Cyclocondensation reactions of the pyrazol-5-amine 1 and the 1-aryl-3-phenyl-2-propen-1-ones 2a-d yield the 6,7-dihydropyrazolo[1,5-a]pyrimidines 7a-d. Whereas 7a-c can be isolated in pure state, 7d is subjected to a spontaneous oxidation.

Phenothiazine-based dyes for efficient dye-sensitized solar cells

As an emerging photovoltaic technology, dye-sensitized solar cells (DSSCs) have attracted a great deal of academic and industrial interest due to their reasonably high power conversion efficiency, low material cost and facile fabrication process. Metal-free organic dyes, as one of the key components of DSSCs, play a pivotal role in light harvesting and electron injection. Among the various species of organic dyes, easily tunable 10H-phenothiazine-based dyes hold a large proportion. The electron-rich nitrogen and sulfur atoms render 10H-phenothiazine a stronger donor character than other amines, even better than triphenylamine, tetrahydroquinoline, carbazole and iminodibenzyl. On the other h…

Synthesis and Stereochemistry of Diepoxynaphthacenes and Tetraepoxyheptacenes

Cycloaddition reactions of 1,4-dihydro-1,4-epoxynaphthalenes (2) and benzo[c]furans (4), generated in situ from the tetracyclone adducts of 2, yield the diepoxynaphthacenes 5 (Schemes 1, 2). Out of 4 possible stereoisomers an exo-exo and an exo-endo geometry (A and C in Scheme 3) can be realized. The ratio A:C varies from pure A to pure C depending on the substituents of 2 and 4. Stereoisomeric heptacenes 7 can be obtained by a twofold cycloaddition of the same type (Scheme 4). Only one π bond of reactive alkynes such as cyclooctyne or acetylenedicarboxylate is capable of an addition to 4 (Schemes 5, 6).

4,4′‐Distyrylazobenzol als Mesogen

4,4′-Distyrylazobenzene as Mesogen From 3,4-dihydroxybenzaldehyde (1) the tetraalkoxy-substituted 4,4′-distyrylazobenzenes (E,E,E)-5a – c are synthesized. A similar reaction sequence leads from ethyl 3,4,5-trihydroxy-benzoate (6) to the hexaalkoxy-substituted 4,4′-distyrylazobenzenes (E,E,E)-11 b, c. With the exception of 5a all products show thermotropic LC properties. Smectic phases have been characterized by polarizing microscopy and by differential scanning calorimetry.

Blue Fluorescent Exciplexes Consisting oftrans-Stilbene and Antibodies

β‐Ketocarbonsäureester mit trans ‐Enolisierung

Durch die Einfuhrung von Mesitylsubstituenten gelingt es, offenkettige β-Ketocarbonsaureester 10/11 herzustellen, die bevorzugt in der E-Konfiguration 2 der Enolform vorliegen. Der Energiegewinn der intramolekularen Wasserstoffbrucke in der Z-Konfiguration 1 wird durch die sterische Energie kompensiert. Sterische und elektronische Effekte bewirken, das die Ketoformen 10/11 energetisch so hoch liegen, das sie im Gleichgewicht keine Rolle spielen. Auser den Substituenteneinflussen von R1, R2 und R3 werden die Solvensabhangigkeit und die basekatalysierte Einstellung der Gleichgewichte 1⇄2 untersucht. Die hohe Energiebarriere fur die E,Z-Isomerisierung gestattet die Reindarstellung und Lagerung…

ChemInform Abstract: High Electrical Conductance of Single Molecules: A Challenge in the Series of Conjugated Oligomers

En route to molecular electronics: As extended, conjugated oligomers are desirable for molecular electronics, their electrical conductance should display a low attenuation factor. Zinc-complexed oligo(ethynyleneporphyrindiylethynylene)s have been prepared that are distinguished by ultralow attenuation factors in single-molecule conductance.

Multiple 1,2,3-thiadiazoles

A series of compounds 3a-d,i-n with two or three 1,2,3-thiadiazole rings, useful for photocrosslinking processes, was prepared from the di- or triketones 1a-d,i-n via the corresponding hydrazones 2a-d,i-n by applying the Hurd-Mori method. A special synthetic sequence, 1e, 2e, 3e, 3f/3g, was elaborated for the olefinic system 3h.

Stereoselective Synthesis of Polycyclic Thiopyrans

The reaction of benzothiete (1) and the bicyclic alkenes 5, 7, 9, or 12 shows a very high π side selectivity (de > 95%) in the formation of the polycyclic thiopyrans 6, 8, 10, 11, 13, and 14.

Influence of spatial arrangements of π-spacer and acceptor of phenothiazine based dyes on the performance of dye-sensitized solar cells

Abstract Three phenothiazine based organic dyes PTA , PDTA and PTDA with D– π –A, π –D– π –A and A– π –D– π –A frameworks were designed and synthesized for the dye sensitized solar cells (DSSCs). Phenothiazine with octyloxyphenyl moiety acts as donor while thiophene and cyanoacetic acid units act as a π -spacer and an acceptor, respectively. The effects of the molecular structures of the dyes on the performance of the DSSCs were investigated systematically along with their photophysical and photoelectrochemical properties. The dye PTDA with A– π –D– π –A framework exhibited a better light harvesting capacity and an effective electron extraction pathway from the electron donor to the TiO 2 s…

(Z)- und (E)-Enole von diarylsubstituierten β-Ketocarbonsäurederivativen

(Z) and (E) Enols of Diaryl-Substituted β-Ketocarboxylic Acid Derivatives Thermolysis of the 1,3-diaryl-2-diazo-1,3-propanediones 4 in the presence of alcohols or amines yielded the compounds 7–11 which exist as chelated (Z) enols or as tautomeric ketones. Contrary to the steric interaction of two mesityl groups the steric interaction between two naphthyl or two anthryl groups or between naphthyl and mesityl is not sufficient to stabilize the corresponding (E) enols. The latter isomers were generated in irradiation processes of some (Z) enols. Detailed NMR studies were performed in order to characterize the enols and their molecular dynamics.

ChemInform Abstract: The Reaction of 2,4,5,6-Tetraaminopyrimidine with Chalcones.

The reaction of the tetraaminopyrimidine 1 with the chalcones 2a-f yields, in the presence of catalytic amounts of acetic acid, the 1H-pyrimido[4,5-b][1,4]diazepine derivatives 3a-f. The cyclization process consists of a condensation reaction and a Michael type addition.

Unexpected Behavior of Enaminones: Interesting New Routes to 1,6-Naphthyridines, 2-Oxopyrrolidines and Pyrano[4,3,2-de][1,6]naphthyridines

Reaction of enaminones 1a&amp;#8211;d with 2-aminoprop-1-ene-1,1,3-tricarbonitrile (2) in the presence of AcOH/NH4OAc afforded 7-amino-5-oxo-5,6-dihydro-1,6-naphthyridine-8-carbonitrile derivatives 9a&amp;#8211;d. On the other hand, 2-aminopyrano[4,3,2-de] [1,6]naphthyridine-3-carbonitriles 20a&amp;#8211;c,e were the only obtained products from the reactions of 1a&amp;#8211;d with 2 in the presence of AcOH/NaOAc, while 1d afforded [3,5-bis-(4-chloro-benzoyl)-phenyl]-(4-chloro-phenyl)-methanone 21 under the same condition. The reaction of 2 with diethyl acetylenedicarboxylate in the presence of AcOH/NH4OAc afforded (4-cyano-5-dicyanomethylene-2-oxo-2,5-dihydro-1H-pyrrol-3-yl)-acetic acid eth…

Monodisperse Oligo(2,5-dipropoxy-1,4-phenyleneethynylene)s

Oligo(phenyleneethynylene)s 1 are rod-like compounds with undisturbed conjugation. In supplementation of the previously described members of this series 1a−e, with repeating units of up to n = 5, this work contains the preparation of higher oligomers 1f−i (n = 6, 7, 8, 10) through the use of the Sonogashira−Hagihara reaction. Both the absorption and the fluorescence bands showed convergence for increasing values of n, reaching limiting values at the effective conjugation length of nECL = 10. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

ChemInform Abstract: Areno-Condensed Annulenes - Extended Discotic Mesogens.

[n]Annulenes (n ≥12) condensed with 2-4 aromatic ring systems (benzenes, naphthalenes, anthracenes, phenanthrenes, chrysenes, pyrenes) can be prepared by cyclocondensation reactions or ring transformations. Due to the local arene aromaticity, the molecules can be regarded as aromatic islands, which are connected by olefinic bridges. The compounds are non-planar, but the majority of the systems shows a fast inversion of the central macrocyclic ring, so that the molecules appear on average as large planar discs, which consist of extended π systems. The aggregation tendency (π stacking) of the compounds can be strengthened by the attachment of flexible saturated chains on the periphery. The di…

Band-Shaped Structures by Repetitive Cycloaddition Reactions of Benzo[1,2-b:4,5-b′]bisthiete

Benzo[1,2-b:4,5-b′]bisthiete (1) undergoes stepwise thermal opening of the 4-membered rings, thereby generating two highly reactive 8π systems (Scheme 1). In the presence of 1,4-dihydro-1,4-epoxynaphthalenes 2, the dithiaheptacene derivatives 3 are formed, dehydration of which leads to the compounds 4 and 5 (Scheme 2). Repetitive cycloaddition reactions of 1 with the twofold 2π component 11 (Scheme 3) yield the oligomers 15 with statistically bent (and possibly cyclic) structures (Schemes 4 and 5). While 15 and the related oligomers 14 are freely soluble in many organic solvents, the dehydrated systems 16 (Scheme 6) are totally insoluble.

The reaction of amino-imidazoles, -pyrazoles and -triazoles with α,β-unsaturated nitriles

The reactions of α,β-unsaturated nitriles (1, 9, 12) as bielectrophiles with aminoazoles (2, 4, 6) as binu-cleophiles were investigated. Acrylonitrile (1) reacts almost exclusively in a chemoselective Michael-type addition yielding the substituted azoles 3, 5 and 7, respectively. Cinnamonitriles 9a,b behave in a similar way, but the free CN group adds a second molecule 4 yielding 10a,b and its cyclocondensation product 11a,b as minor component. The attempted formation of azolopyrimidines is best achieved by the reaction of the benzylidenemalononitriles 12a - f with 2 or 4. The process is chemo- and regioselective. The structure determinations were based on NMR measurements including DEFT, C…

ChemInform Abstract: Synthesis of Areno-Condensed [24]Annulenes.

[24]Annulenes condensed with three phenanthrene units (11a−d) or with three chrysene ring systems (22) were prepared by multi-step syntheses. The cyclic condensation reaction in the final step led to highly symmetrical compounds. Long flexible alkoxy groups attached to the periphery enhance the solubility and give rise to a strong aggregation of the molecules which was observed in solution by NMR and fluorescence excitation spectroscopy, and in the pure state by the detection of liquid crystalline phases in differential scanning calorimetry and polarization microscopy.

ChemInform Abstract: Cycloaddition of Benzothiete and Electron-Deficient Nitriles.

The o-quinoid 8π electron system 2, generated by thermal ring opening of benzothiete (1), enters regio-specific [8π + 2π] cycloaddition reactions with electron-deficient nitriles 3a-d, yielding the 4H-1,3-benzothiazines 4a-d. A competitive dimerization of 1 leads to 1,5-dibenzo[b,f]dithiocin (5). Depending on the nitrile further competitive or subsequent reactions (2 + 3b 7b, 2 + 3d 4d 8d) can occur. The cycloadducts 10e and 11e gained from 3e anticipate a primary cleavage of 3e to methylisothiocyanate 9e which reacts at the CN double bond as well as at the CS double bond.

Star-Shaped Push-Pull Compounds Having 1,3,5-Triazine Cores

The 1,3,5-triazines 9–11 having OPV chains in the 2-, 4- and 6-position represent star-shaped compounds which exhibit strong push-pull effects. Their long-wavelength absorption S0 S1 is characterized by an intramolecular charge transfer (ICT) from the dialkylamino group as electron donor D via the conjugated chain to the 1,3,5-triazine core as electron acceptor A. Protonation of the dialkylamino group removes the donor capability, whereas protonation of the 1,3,5-triazine ring enhances the acceptor strength. Thus, the prevailing protonation site has a crucial influence on the push-pull effect and the ICT. The transition energies ΔE (S0 S1) pass through a minimum for the second generation 10…

Phenothiazine dye featuring encapsulated insulated molecular wire as auxiliary donor for high photovoltage of dye-sensitized solar cells by suppression of aggregation

Abstract Two efficient dye-sensitized solar cells have been fabricated by two novel D–D–π–A phenothiazine-based organic dyes (PH2 and PH3) with an encapsulated insulated molecular wire (EIMW) as an auxiliary donor. The cell sensitized by PH2 with EIMW as an auxiliary donor shows a much higher photovoltage (Voc) relative to the reference dye PH1 without EIMW, because the former dye can inhibit dye aggregation and suppress the charge recombination effectively. The results show that the cell sensitized by PH2 with co-adsorption of chenodeoxycholic acid obtains a high power conversion efficiency, even higher than that of the cell based on N719. Thus, an effective way to increase the photovoltag…

Synthesis and Tautomerization of 6,7-Dihydro-(1,2,3)-triazolo[1,5-a]pyrimidines.

The condensation of 5-amino-4-phenyl-1,2,3-triazole (1) with chalcones 2a-e or 3-dimethylamino-propiophenone (4f) leads to the 6,7-dihydro-(1,2,3)-triazolo[1,5-a]pyrimidines 3a-f. The equilibrium of 3 and the tautomeric 4,7-dihydro-(1,2,3)-triazolo[1,5-a]pyrimidines 3′ is described.

ChemInform Abstract: Multiple 1,2,3-Thiadiazoles.

A series of compounds 3a-d,i-n with two or three 1,2,3-thiadiazole rings, useful for photocrosslinking processes, was prepared from the di- or triketones 1a-d,i-n via the corresponding hydrazones 2a-d,i-n by applying the Hurd-Mori method. A special synthetic sequence, 1e, 2e, 3e, 3f/3g, was elaborated for the olefinic system 3h.

Naphthalenophane durch doppelte Photocyclodimerisierung von Distyrylnaphthalinen

Bei der Belichtung von Distyrylnaphthalinen entstehen in regiospezifischen Kopf-Kopf-Cycloadditionen Naphthalenophane. Je nach Stellung der Styryl-Gruppen beobachtet man vollkommen stereospezifische Prozesse (1d 2, 1g 3, 1h 4) und Dimerisierungen mit partiellen Stereoselektivitaten (1b 5–8, 1i 9, 10). Masgeblich sind die Rotamerenpopulation im Ausgangsprodukt 1 und die elektronischen und sterischen Effekte in den Excimeren. Prinzipiell sind Excimere mit paralleler Anordnung moglichst vieler π-Zentren bevorzugt — ein experimenteller Befund, der durch HMO-Rechnungen untermauert wird. Naphthalenophanes by Twofold Photocyclodimerizatio Reactions of Distyrylanaphthalenes Regiospecific head-to-he…

Star-shaped conjugated compounds forming nematic discotic systems

Abstract Star-shaped compounds, having a benzene ( 9a,b ) or a 1,3,5-triazine ( 11a,b ) core and stilbenoid arms were prepared. Hexyloxy chains, attached in the middle of the arms, provide nematic discotic phases ND, which are unusual for such systems. The position of the sidechains prevents the micro-segregation, which is valid for star-shaped discs of columnar phases. The stilbenoid character of 9a,b and 11a,b guarantees a high light sensitivity. Apart from the statistical CC bond formation by irradiation in solution or in the LC phases, a topochemically controlled chemo-, regio- and stereoselective photocyclodimerization 11a → 12 was found in the crystalline state. The structure determin…

ChemInform Abstract: Synthesis of Tripyreno[2,3,4,-abc:2,3,4-ghi:2,3,4-mno][18]annulenes.

The title compounds were prepared in a multi-step synthesis in which primarily the pyrene building blocks were formed (1,2 11a,b). The final reaction step 11a,b 12a,b consisted of a threefold trans selective cyclocondensation process that generated the central 18-membered ring. Hexyloxy or dodecyloxy sidechains attached on the periphery led to the formation of liquid crystalline phases.

ChemInform Abstract: Conjugated Compounds Based on Vinylthiazole Units.

Conjugated oligomers attract increasing attention because of their interesting properties in materials science [1]. Moreover, they are model compounds for conjugated polymers. Molecules polarized by electronic effects, in particular push-pull systems having terminal donor-acceptor substitution represent a special class of such oligomers [2]. Their major applications are in the field of nonlinear optics (NLO), twophoton absorption (TPA), two-photon induced fluorescence (TPIF), and photorefractive materials (PR). Fig. 1 illustrates known 2,5-thienylenevinylenes with zwitterionic resonance structures 1 (D = NR2; A = NO2, CHO, SO2R; n = 1, 2) [3, 4]. The corresponding compounds 2 with thiazole …

Synthese von 2-alkoxysubstituierten Oligo- und Poly(1,4-phenylenethenylen)en und 2-Arylbenzo[b]furanen mit Hilfe der Siegrist-Reaktion

Synthesis of 2-Alkoxy Substituted Oligo- and Poly(1,4-phenyleneethylene)s and 2-Arylbenzo[b]furanes by Applying the Siegrist Reaction Alkylation of 2-hydroxy-4-methylbenzaldehyde (1) yields the 2-alkoxy-4-methylbenzaldehydes (2a-l) which can be easily transformed to the Schiff bases 3a-l. The intermolecular self-condensation in a strongly alkaline medium leads to the oligo- and poly(1,4-phenyleneethenylene)s (4a-i) with an outstanding regular constitution and overall (E)-configuration. The terminal N-arylamino group can be cleaved by hydrolysis generating the compounds 5a-i. An intramolecular condensation forming the benzo[b]furanes 6j,k is observed for 3j,k – due to the activated OCH2 grou…

Photoreactive Liquid Crystals in the Series of Dendritic and Cyclic Stilbenoid Compounds

The dendrimers 1 and 2 and the areno-condensed annulenes 3 and 4 represent new mesogens for the generation of discotic mesophases. The stilbenoid building blocks of these compounds provide the molecular basis for interesting photochemical and photophysical effects like dimerisation, oligomerisation or the formation of charge carriers.

Preparation of dithiacycloalkynes by cyclization reactions applying the cesium effect

Abstract The strained dithiacycloalkynes 3a,b and the larger heterocyclic alkynes 3c and 4 are obtained by cesium assisted cyclization reactions of the dithiols 1a–c and 1,4-dibromo-2-butyne (2). The reactivity of 3a–c was studied in cycloaddition and complexation reactions generating the adducts 5a,b and 6 and the silver and cobalt complexes 7 and 8.

ChemInform Abstract: Synthesis of a Tetraazido-Substituted 2-Tetrazene from 1,5- Cyclooctadiene and Iodine Azide.

In contrast to the addition of iodine azide to cyclooctene (1) or 1,3-cyclooctadiene (5), its reaction with 1,5-cyclooctadiene (12) leads mainly to the surprisingly stable tetraazido-substituted 2-tetrazene 14 The structure of this was established by 15N-NMR studies and an X-ray structural analysis. Treatment of 14 with hydrochloric acid yields the diazido-substituted 9-azabicyclo[3.3.1]nonane 20.

Thermische Cycloadditionen von 1,2‐Dihydropentalen

1,2-Dihydropentalen (1) ist ein gekreuzt konjugiertes 6π-Elektronensystem, das in thermischen Cycloadditionen als 2π-, 4π- oder 6π-Komponente fungieren kann. Es werden die Additionen an Tetraphenylcyclopentadienon (1+23), N-Phenylmaleinimid (1+45) und Tropon (1+68 bzw. 10) beschrieben. Auf der Basis von MNDO-Rechnungen werden Peri-, Regio- und Stereoselektivitat anhand von primaren und sekundaren Orbitalwechselwirkungen diskutiert. Thermal Cycloaddition of 1,2-Dihydropentalene 1,2-Dihydropentalene (1) is a cross-conjugated 6π-electron system, that can act in thermal cycloaddition processes as a 2π, 4π, or 6π component. The addition reactions with tetraphenylcyclopentadienone (1+23), N-pheny…

Monoester copillar[5]arenes: synthesis, unusual self-inclusion behavior, and molecular recognition.

The self-inclusion behavior of monoester copillar[5]arenes depends on the position of the ester group, which causes different guest selectivities. Monoester copillar[5]arenes bearing an acetate chain can form stable self-inclusion complexes in low- and high-concentration solution and exhibit high guest selectivity. However, a monoester copillar[5]arene bearing a butyrate chain can not form a self-inclusion complex and exhibits low guest selectivity. Thus, a new class of stable self-inclusion complexes of copillar[5]arenes was explored to improve the selectivity of molecular recognition.

Ring-expansion of 5-methylene-thiazolidine-2-thione with hydrazine

Synthesis of a Tetraazido-Substituted 2-Tetrazene from 1,5-Cyclooctadiene and Iodine Azide

In contrast to the addition of iodine azide to cyclooctene (1) or 1,3-cyclooctadiene (5), its reaction with 1,5-cyclooctadiene (12) leads mainly to the surprisingly stable tetraazido-substituted 2-tetrazene 14 The structure of this was established by 15N-NMR studies and an X-ray structural analysis. Treatment of 14 with hydrochloric acid yields the diazido-substituted 9-azabicyclo[3.3.1]nonane 20.

Die symmetrischen Cyclooctadienine: 1,5‐Cyclooctadien‐3‐in und 1,3‐Cyclooctadien‐6‐in

Die Titelverbindungen 16 und 17, hoch gespannte Kohlenwasserstoffe aus der C8H8-Reihe, konnen auf sechs- bzw. siebenstufigen Synthesewegen aus 1,5-Cyclooctadien (1) bzw. Cyclooctatetraen (2) hergestellt und in reiner Form isoliert werden. Ihre Stabilitat und ihr chemisches Verhalten werden diskutiert. Dabei stehen Di- und Oligomerisierungen einerseits und Diels-Alder-Reaktionen andererseits im Vordergrund. 16 und 17 sind sehr reaktive Dienophile; 17 ist daruber hinaus auch als Dien einzusetzen. The Symmetrical Cyclooctadienynes: 1,5-Cyclooctadien-3-yne and 1,3-Cyclooctadien-6-yne Starting with 1,5-cyclooctadiene (1) and cyclooctatetraene (2), respectively, the title compounds 16 and 17, hig…

Complexation Selectivities of Pillar[5]arenes with Primary Ammonium Salts

The complexation of alkyl-substituted pillar[5]arenes with primary ammonium salts is investigated. 1,4-Bis(methoxy)pillar[5]arene (MeP5) can form strong complexes with the primary ammonium salts in CDCl3. However, 1,4-bis(ethoxy)pillar[5]arene (EtP5) shows weak interaction with these guests, and 1,4-bis(butoxy)pillar[5]arene (BuP5) can not form such a complex at all. These results indicate that the modified alkyl chains of pillar[5]arene play an important role in the complexation selectivity.

Photochemical formation of [4.4.4](1,3,5)cyclophanes from 1,3,5-tris(3-phenylpropenoyl)benzenes

Abstract Irradiation of 1,3,5-tris(3-phenylpropenoyl)benzene ( 1a ) yields in solution a dimer 2a by a threefold head-to-head/anti [2π+2π]cycloaddition. The stereochemistry of this [4.4.4](1,3,5)cyclophane was determined by 1H and 13C NMR studies including NOE measurements and a calculation of the AA′MM′ spin pattern of the methine protons. In contrast to the solution photochemistry, which is presumably controlled by the arrangement of an excimer, the irradiation in the crystalline state leads by a topochemical control to a dimer 3a , which contains a single four-membered ring.

ChemInform Abstract: Multi-Arm 1,2,3-Thiadiazole Systems.

Benzene derivatives 2a–c with 6, 4, and 3 side chains bearing terminal 1,2,3-thiadiazole rings, respectively, have been prepared. Alkaline cleavage of 2a–c led to the corresponding alkynethiolates 6a–c, which were trapped by electrophiles such as benzyl bromide or iodomethane. The method provides an alternative to the thermal or photochemical cleavage of 1,2,3-thiadiazoles to thioketenes, which react further with nucleophiles.

A Dendrimer Chiroptical Switch Based on the Reversible Intramolecular Photoreaction of Anthracene and Benzene Rings

A series of Fréchet-type dendrimers with 9-benzyloxymethylanthracene cores were synthesized and characterized. The chiral source for the dendrimers was an (S)-2-methyl-1-butoxy group in the 3-position of the benzene ring. Irradiation at 366 nm of a dilute benzene solution led to the formation of two diastereomers (1:1) through a quantitative intramolecular [4pi+4pi] cycloaddition between the central anthracene ring and the neighboring benzene ring. The process can be reversed with 254 nm UV light or heat. The benzene rings in the dendrons work as a light-harvesting system. The optical rotation values measured for the reversible process showed fatigue resistance. Thus, a promising new type o…

ChemInform Abstract: 1-Alkyl- and Azeto[1,2-a][1,5]benzodiazepine Derivatives in the Reaction of o-Phenylenediamine with 3-(Dimethylamino)propiophenones.

The reaction of o-phenylenediamine (4) with one, two or three equivalents of p-substituted 3-dimethylaminopropiophenone hydrochlorides 5a−e was studied. 4-Aryl-2,3-dihydro-1H-1,5-benzodiazepine derivatives 6a−e were obtained in good yields, along with the 1:2-adducts 7c−e and the unexpected 1:3-adducts rac-8c−e. The type of adduct formed is determined by the molar ratio of the reactants 4 and 5 and by the nature of the substituent in the para position of the propiophenone 5.

Cycloaddition von benzothiet an oxime, oximether und oximester

Benzothiete 1 generates by thermal ring opening an 8π electron system 2 which undergoes [8π + 2π] cycloaddition reactions with the oxime systems 3a-g. In accordance with the FMO theory the 1,3-thiazine derivatives 4a-g are formed in a regiospecific and 4f additionally in a stereospecific manner. The O-acylated adducts 4h-j enter the same cycloaddition; however, an elimination reaction 4 5, 6 can provoke the addition of a second benzothiete, yielding the tetracyclic compounds 7j, and 8i,j.

Synthesis of Areno-Condensed [24]Annulenes

[24]Annulenes condensed with three phenanthrene units (11a−d) or with three chrysene ring systems (22) were prepared by multi-step syntheses. The cyclic condensation reaction in the final step led to highly symmetrical compounds. Long flexible alkoxy groups attached to the periphery enhance the solubility and give rise to a strong aggregation of the molecules which was observed in solution by NMR and fluorescence excitation spectroscopy, and in the pure state by the detection of liquid crystalline phases in differential scanning calorimetry and polarization microscopy.

ChemInform Abstract: Synthesis of Hexastyrylbenzenes.

Synthese von 9‐Oxabicyclo[6.1.0]non‐3‐in

Ausgehend von 1,5-Cyclooctadien (1) wird in einer siebenstufigen Synthese die Titelverbindung 9 gewonnen. Sie liegt in zwei Konformationen 9a und 9b vor, wobei in 9a eine starke sterische Wechselwirkung zwischen dem Sauerstoffatom und der gespannten Dreifachbindung auftritt. Zur Einfuhrung der Dreifachbindung dient die thermische Fragmentierung des 1,2,3-Selenadiazols 7. Der Strukturnachweis fur die regiospezifische Bildung von 7 wird mit 2D-NMR-Spektroskopie gefuhrt. Starting with 1,5-cyclooctadiene (1), the title compound 9 is gained in a synthesis of seven steps. 9 exists in two conformations 9a and 9b, of which 9a shows a strong interaction between the oxygen atom and the strained tripl…

Einführung einer Dreifachbindung in das Bicyclo[6.1.0]nonan-Gerüst

Ausgehend von den auf verschiedenen Wegen zuganglichen Ketonen 1a–c wird die Einfuhrung einer Dreifachbindung in das Bicyclo[6.1.0]nonan-Gerust mit Hilfe der Selenadiazol-Methode untersucht. Dabei Konnen die hochgespannten Bicyclo-[6.1.0]nonine 2a und 2b in reiner Form isoliert werden. Masgeblich fur die Position der Dreifachbindung ist die Regioselektivitat der Ringschlusreaktion bei der Selenadiazolbildung. Introduction of a Triple Bond into the Bicyclo[6.1.0]nonane Skeleton The introduction of a triple bond into the bicyclo[6.1.0]nonane skeleton is investigated by applying the selenadiazole method to the ketones 1a–c, accessible on different pathways. The highly strained bicyclo[6.1.0]no…

Extension of Conjugation Leading to Bathochromic or Hypsochromic Effects in OPV Series

Four OPV series 1-4 (a-d) with a terminal dialkylamino group as electron donor were prepared by Wittig-Horner reactions. To study the influence of the push-pull effect on the long-wavelength absorption, three of the four series contained terminal acceptor groups (CN, CHO, NO(2)). The length of the chromophores strongly affects the intramolecular charge transfer (ICT)-an effect which superimposes upon the extension of the conjugation. Increasing numbers n of repeat units cause an overall bathochromic shift for the purely donor-substituted series 1 a-4 a and the series 1 b-4 b with CN as weak acceptor. The two effects annihilate each other in the series 1 c-4 c with terminal CHO groups, so th…

Die ungewöhnliche Photochemie von Dendrimeren mit Anthracen als Kern

Red- and Blue-Shifts in Oligo(1,4-phenyleneethynylene)s Having Terminal Donor−Acceptor Substitutions

Four series of oligo(1,4-phenyleneethynylene)s (OPEs), 1−4 (a−d), each having a terminal dialkylamino group as their electron donor, were prepared by applying Sonogashira−Hagihara reactions and a protecting group strategy. To study the influence that the push−pull effect has on the long-wavelength absorption, three of the four series of OPEs contain terminal acceptor groups (CN, CHO, NO2). Extending the conjugation (increasing the number of repeat units, n) lowers the energy E(n) of the electron transition in the purely donor-substituted series 1a−4a (bathochromic shift). This effect is superimposed in the push−pull series 1−4 (b−d) by the effect of the intramolecular charge transfer (ICT),…

Reaction of 2H-1-benzothiete with diazo compounds in the presence of rhodium(II) acetate

2,3-Dihydrobenzo[b]thiophenes (7a-e) were prepared by the Rh2+ catalyzed reaction of 2H-1-benzothiete (1) and diazo compounds (3a-e). α,β-Unsaturated diazo esters (3b,e) and diazo ketones (3d,e) yielded additionally 4,5-dihydro-1-benzothiepins (11b,c) and 5H-4,1-benzoxathiepins (12d,e), respectively.

Comparison of Alkoxy-substituted 4,4´-Distyrylbiphenyls and the Corresponding 4,4´-Distyrylbenzenes

Abstract Configurationally highly pure (E,E)-4,4´-bis(styryl)biphenyls 2a - e were obtained by Siegrist reactions of 4,4´-dimethylbiphenyl 3 and alkoxy-substituted benzaldimines (4a - e). DSC measurements have indicated different crystalline modifications of these conjugated compounds. The stilbenoid chromophores of 2a - e are compared to the stilbenoid chromophores in the OPV series, which have a similar length of conjugation. The intense fluorescence and the high transparency in the visible region are promising properties for an application of the donor-substituted compounds 2a - e in twophoton absorption (TPA) techniques.

Tautomerism of Diazepines Fused with Pyrimidine Rings.

The tautomerism of 1,4-diazepines fused with pyrimidine rings was studied by means of nmr spec-troscopy, X-ray analysis and quantum chemical calculations. It was found that in the case of 6,8-diphenyl-pyrimido[4,5-b][1,4]diazepin-4-ols (7a - e) the enamine form is more stable than the diimine form. This result is rationalized with the electron-withdrawing effect of the 4-hydroxypyrimidine ring and with the formation of intermolecular hydrogen bonds. In contrast to 7a - e, the 6,8-diaryl-2,3,4,7-tetrahydro-1,3-dimethyl-1H-pyrimido[4,5-b][1,4]diazepine-2,4-diones (9a, c, f) exist in the diimine form.

Generation of 6,7-Dihydro-5H-1,3,4-thiadiazolo[3,2-a]pyridines — Unexpected Products in the Reaction of 5-Ethylthio-1,3,4-thiadiazole-2-amine and 3-(Dimethylamino)propiophenones

ChemInform Abstract: Synthesis of Pyrido(2,3-d)pyrimidines in the Reaction of 6-Amino-2,3- dihydro-2-thioxo-4(1H)-pyrimidinone with Chalcones.

6-Amino-2,3-dihydro-2-thioxo-4(1H)-pyrimidinone (1) reacts in boiling DMF with α,/β-unsaturated ketones 2 yielding the pyrido[2,3-d]pyrimidine systems 5 and 6, respectively. The orientation in the addition process can be determined by nmr measurements, especially by NOE difference spectroscopy. The products do not correspond to a normal Skraup or Doebner-v. Miller synthesis.

Herstellung von 1,5‐Cyclooctadiin und 1,3,5,7‐Cyclooctatetraen aus 1,5‐Cyclooctadien

Preparation of 1,5-Cyclooctadiyne and 1,3,5,7-Cyclooctatetraene from 1,5-Cyclooctadiene Bromination of 1,5-cyclooctadiene (1) and stepwise dehydro-bromination first with KOtBu and then with KOtBu/18-crown-6 yields 1,5-cyclooctadiyne (5). A prolonged interaction of the base causes a complete transformation to cyclooc-tatetraene (6). Diyne 5 and even more the intermediate enyne 4 are highly reactive dienophiles. The cycloadducts 10–14 formed with 1,3-cyclohexadiene, carbon disulfide, and tetraphenylcyclopentadienone were isolated and characterized. Treatment of 5 with titanium tetrachloride induces a vigorous polymerization.

ChemInform Abstract: Benzothietes. Versatile Synthons for the Preparation of Heterocycles

Abstract Thermal or photochemical ring opening transforms benzo[b]thiete to o-thiobenzoquinonemethide, a highly reactive 8π electron system. Cycloaddition reactions or linear additions with subsequent cyclizations lead to larger heterocyclic rings. A variety of compounds containing sulfur and possibly further heteroatoms like nitrogen, oxygen or phosphorus in normal, medium and large ring systems can be synthesized on this route.

Photochemie des 1,3‐Distyrylbenzols — Ein neuer Weg zu syn ‐[2.2](1,3)Cyclophanen

Conjugated Oligomers with Terminal Donor–Acceptor Substitution

Conjugated oligomers represent a prominent class of compounds from a viewpoint of their theory, synthesis, and applications in materials science. Push-pull substitution with an electron donor D at one end of the conjugation and an electron acceptor A at the other end results in them having outstanding optical and electronical properties. This Review highlights fundamental synthetic strategies for the preparation of such oligomers with n repeat units (n=1, 2, 3, 4, ..) and the rules that govern their linear and nonlinear optical properties (absorption, frequency doubling and tripling). The unification of chemical, physical, and theoretical aspects with an interdisciplinary image of this clas…

Towards highly luminescent phenylene vinylene films

Abstract Fluorescence and electronic absorption spectra, fluorescence decay curves and fluorescence quantum yields of a series of oligo (p-phenylene vinylenes) are investigated in solution, nanoaggregates and vapour-deposited or cast ultrathin films. The film constituting molecules are varied in chain length and modified by electron donating and withdrawing substituents and bulky alkyl spacers. PPP-MO calculations serve to rationalize the resulting spectral changes. In dilute solutions, fluorescence yields of the short oligomers with alkyl or oxyalkyl substituents approach the region of unity. The yields decrease with chain length, reaching a long-chain limit of ΦF=0.4–0.7. Introduction of …

Defined-length Carbon-rich Conjugated Oligomers

Extension of the Squaraine Chromophore in Symmetrical Bis(stilbenyl)squaraines

The bis(stilbenyl)squaraines 6d−j,d‘,j‘ represent a novel class of NIR pigments. Their synthesis was performed by the regioselective 2-fold condensation of highly nucleophilic 3,5-dihydroxystilbene...

Benzoxetes and Benzothietes ¾ Heterocyclic Analogues of Benzocyclobutene

Benzo-condensed four-ring heterocycles, such as benzoxetes 1 and benzothietes 3 represent multi-purpose starting compounds for the preparation of various higher heterocyclic ring systems. The thermal or photochemical valence isomerizations between the benzenoid forms 1,3 and the higher reactive o-quinoid structures 2,4 provide the basis for the synthetic applications. On the other hand, this valence isomerization impedes in particular the generation and storage of 1 because the thermal equilibrium 1 ⇆ 2 is completely on the side of 2. Thus, the number of erroneous or questionable benzoxete structures published to date is surprisingly high. On the contrary, the thermal equilibrium 3 ⇆ 4 is o…

Konjugierte Oligomere mit terminaler Donor-Acceptor-Substitution

Konjugierte Oligomere sind in theoretischer, praparativer und materialwissenschaftlicher Hinsicht eine prominente Substanzklasse. Die Push-pull-Substitution durch einen Elektronendonor an einem Ende und einen Elektronenacceptor am anderen Ende verleiht den Verbindungen D-π-A besondere optische und elektronische Eigenschaften. Der vorliegende Aufsatz schildert die grundsatzlichen Strategien zur Synthese solcher Oligomerenreihen mit n Wiederholungseinheiten (n=1, 2, 3, 4, …) und die fur ihre linearen und nichtlinearen optischen Eigenschaften (Absorption, Frequenzverdoppelung und -verdreifachung) geltenden Gesetzmasigkeiten. Aus den chemischen, physikalischen und theoretischen Aspekten der pus…

Dithiametacyclophane mit Dreifachbindungen

Dithiametacyclophanes with Triple Bonds Schemes 1 and 2 show the syntheses of dithia[8]metacyclo-phanes 4a-d and tetrathia[m.n]metacyclophanes 9, 10 by cyclization reactions applying the cesium effect. All these cyclophanes contain C—C triple bonds which influence the molecular dynamics; especially the halogen substituents in 4b-d obstruct the topomerization.

1-Alkyl- and azeto[1,2-a][1,5]benzodiazepine derivatives in the reaction of o-phenylenediamine with 3-(dimethylamino)propiophenones

The reaction of o-phenylenediamine (4) with one, two or three equivalents of p-substituted 3-dimethylaminopropiophenone hydrochlorides 5a−e was studied. 4-Aryl-2,3-dihydro-1H-1,5-benzodiazepine derivatives 6a−e were obtained in good yields, along with the 1:2-adducts 7c−e and the unexpected 1:3-adducts rac-8c−e. The type of adduct formed is determined by the molar ratio of the reactants 4 and 5 and by the nature of the substituent in the para position of the propiophenone 5.

Near infrared dyes by combination of squaraine and ferrocene chromophores

Abstract Squaraines represent a class of compounds which attracts a lot of attention in materials science. A synthetic sequence for the preparation of the symmetrical squaraines 12a , b , which contain ferrocene units as electron donors, is described. The compounds exhibit, in dichloromethane or chloroform, two intense absorption bands. One of them is located at 641/650 nm—a normal region for squaraines; however, the other band is strongly shifted to long wavelengths and has its maximum at 921/961 nm. Alkyl sidechains enhance the solubility of 12a , b , which represent a new type of NIR dyes.

ChemInform Abstract: Crown Ether Substituted 1,4-Distyrylbenzenes and Their Complexation with Alkali Picrates.

Photochemical generation of benzene–naphthalene biplanemers

Abstract A direct biplanemer synthesis could be achieved by a quantitative [4π+4π]photocycloaddition of benzyloxy substituted benzene and naphthalene rings ( 3d , e  ⇄  4d , e ). Since the products do not show a thermal Cope rearrangement—in contrast to the related longicyclic conjugated 9,10-benzotricyclo[4.2.2.2 2,5 ]dodeca-3,7,9-trienes—but a quantitative reverse reaction, they are interesting systems for an optical switching.

ChemInform Abstract: Pillar[n]arenes - A Novel, Highly Promising Class of Macrocyclic Host Molecules

Review: [preparation, structure in solution and in the solid state and complexation; 100 refs.

ChemInform Abstract: Phenylethynyl- and Phenylethenylmetacyclophanes.

The cyclophanes 6,8,10 and 13–15 were synthesized by cesium assisted ring closure reactions. The main interest in these systems concerns the interaction of the unsaturated bridge with the tolan and the stilbene chromophores, respectively.

Bis(stilbenyl)squaraines — Novel pigments with extended conjugation

Abstract We report on the synthesis of a novel type of squaraines ( 11a-f, 17c ) in which the conjugation of the chromophore is extended by stilbene units. These pigments exhibit absorption bands which have their maxima at the end on the Vis region and reach partly into the NIR.

Cycloaddition reactions of benzothiete with azomethines

Obtention de diaryl-2,3 dihydro-3,4 benzothiazines-1,3 (70%) via la cycloaddition de la thiobenzoquinone methode-1,2 (obtenue par scission thermique du benzothiete) et d'arylimines de benzaldehydes. Obtention egalement de 10% du dimere (dibenzo [b, f] dithiocinne-1,5)

Push-Pull Oligomers with 2,2-Dicyanovinyl Groups as Electron Acceptors

Three conjugated oligomer series with terminal donor–acceptor substitution were studied: oligo(1,4-phenylenevinylene)s DAOPVs 4a–d (n = 1–4), oligo(1,4-phenyleneethynylene)s DAOPEs 6a–d (n = 1–4) and oligo(2,5-thienyleneethynylene)s DAOTEs 8a–e (n = 1–5). Dialkylamino or methoxy groups served as electron donors and 2,2-dicyanovinyl groups as strong electron acceptors. The push-pull effect polarizes the molecular chains – an effect which is documented by the splitting of the 13C chemical shifts of two carbon atoms of the double or triple bonds in the chain. For higher oligomers (n ≥ 3), the effect is mainly localized at the chain ends. The long-wavelength absorption results in a charge-trans…

ChemInform Abstract: A Novel Synthetic Route to Open-Chained and Cyclic Oligoetherketones.

2,3-Dipentyldithieno[3,2-f:2′,3′-h]quinoxaline-Based Organic Dyes for Efficient Dye-Sensitized Solar Cells: Effect of π-Bridges and Electron Donors on Solar Cell Performance

Five novel metal-free organic dyes DQ1-5 containing a dipentyldithieno[3,2-f:2',3'-h]quinoxaline (DPQ) unit were synthesized and applied in dye-sensitized solar cells (DSSCs), where DPQ was employed as a π-spacer for the first time. Their photophysical, electrochemical, and theoretical calculations and photovoltaic properties were systematically investigated. All the five dyes show broad photoresponse. Especially the absorption edges of DQ3-5 extend to 800 nm on the TiO2 films. The inserted electron-rich unit 3,4-ethylenedioxythiophene or electron-withdrawing group benzothiadiazole (BTD) in DPQ-based dyes can greatly influence the optoelectronic properties of the dyes. In addition, the diff…

ChemInform Abstract: Blue Fluorescent Exciplexes Consisting of trans-Stilbene and Antibodies.

Mesomorphic Donor-Acceptor-substituted 1,4-Distyrylbenzenes

Conjugated oligomers with terminal donor-acceptor substitution attract increasing attention in organic chemistry because of their outstanding and not seldom unexpected properties in materials science [1 – 4]. Although a variety of oligo(1,4-phenylene-vinylene)s with terminal donor-acceptor substitution (DAOPVs 1, Scheme 1) are known [5 – 22], the number of thermotropic liquid crystals among them is very low and is confined to monomers (n = 1), that means to certain push-pull substituted (E)-stilbenes [23 – 31]. The behavior of conjugatedmolecules, which are highly polar and form mesophases by self-organization, is very interesting for various applications of liquid crystals [3]. A big disad…

The effect of 2,2-dicyanovinyl groups as electron acceptors in push–pull substituted oligo(1,4-phenylenevinylene)s

Abstract The newly synthesized oligo(1,4-phenylenevinylene) series 2a–d with bis(2-hexyloctyl)amino groups as electron donors and 2,2-dicyanovinyl groups as electron acceptors represents conjugated oligomers with strong push–pull effects. Due to the decrease of the intramolecular charge transfer with increasing numbers of repeat units (n=1–4), the long-wavelength transition shows a particularly great hypsochromic shift for the extension of the chromophore.

Supramolecular order of stilbenoid dendrons: importance of weak interactions

Stilbenoid dendrons with various donor and acceptor groups on the focal unit were synthesised by a Wittig–Horner reaction, starting from an aldehyde functionalised dendron and various substituted phosphonic acid esters. The target molecules are composed of meta-branched arms, two of them with extended conjugation (distyrylbenzene) and three flexible dodecyloxy chains; the focal group consists of a donor or acceptor substituted styryl unit. The cross-conjugation of the arms prevents the strong electronic influence of substituents on the two extended oligophenylenevinylene chromophores. However, intermolecular interactions mediated by the focal unit allow control of the supramolecular stackin…

1,4-Benzoquinones with Styryl Substituents

2-Styryl-1,4-benzoquinone (1) and compounds 2 and 3 containing 1 as a substructure all proved to be highly reactive towards thermal or photochemical [4π + 2π] cyclodimerization reactions. Chemo-, regio- and stereoselective processes lead to dimers (compounds 1−10), which can undergo secondary reactions consisting of the addition of nucleophiles combined with a twofold keto-enol tautomerism (10 ⇄ 12). An alternative process is dehydrogenation/oxidation followed by an intramolecular [4π + 2π] cycloaddition (10 ⇄ 11). The same selective [4π + 2π] cyclodimerization can be observed in solution upon irradiation (e.g., 1a ⇄ 10a), in contrast to irradiation in the crystalline state which yields a […

Pillar[5]arene-Diketopyrrolopyrrole Fluorescent Copolymer: A Promising Recognition and Adsorption Material for Adiponitrile by Selective Formation of a Conjugated Polypseudorotaxane

Conjugated pillar[5]arene-diketopyrrolopyrrole copolymer (P1) is synthesized by the copolymerization of a difunctionalized pillar[5]arene and a diketopyrrolopyrrole-based monomer, which shows large extinction coefficients (1.1 × 104 m-1 cm-1 ) at 519 nm and strong emission at 587 nm. P1 exhibits very strong host-guest binding affinity towards adiponitrile but low binding affinity towards 1,4-dihalobutane and 1,4-bis(imidazol-1-yl)butane. Such an enhanced selectivity is first found in the polypseudorotaxane between pillararene and neutral guests in organic solution and is successfully used for the recognition and adsorption of adiponitrile by the formation of a P1-adiponitrile polypseudorota…

Vergleichende Untersuchung zur Diastereoselektivität derO-Methylierung von sterisch behinderten β-Ketocarbonsäureestern und ihren Enolen

Diastereoselectivity of the O-Methylation of Sterically Hindered β-Ketocarboxylates and Their Enols The enols 1a, b, and 1c, which exists almost completely in the keto form, have been methylated at the oxygen atom with diazomethane. The regioselective reaction can be catalyzed by methanol, but may loose in that case the diastereoselectivity. A comparison with the methylation of the enolates by iodomethane is discussed.

Configuration of Enolates of β-Ketocarboxylic Acid Esters — Carbocation-Carbanion Salts

Deprotonation of (Z)- or (E)-3-hydroxy-2,3-dimesitylpropenoic acid methyl ester (1a) with tetrakis(dimethylamino)-methane (3) led to stable salt (E)-2a, which belongs to a very rare species of salts that consist of a heteroatom-stabilized carbocation and a heteroatom-stabilized carbanion. An analogous guanidinium salt (E)-2b was formed in the reaction of 3-oxo-2,3-diphenylpropanoic acid methyl ester (1b) and 3. The molecular structures of these enolates were studied by NMR spectroscopy and an X-ray analysis of (E)-2a {MC[N(CH3)2]3} and compared with those of the corresponding alkali enolates.

ChemInform Abstract: Cyclocondensation of 6-Acetyl-4,7-dihydro-5-methyl-7-phenyl[1,2,4]triazolo[1,5-a]pyrimidine with Hydroxylamine and Hydrazine.

The cyclocondensation of 6-acetyl-4,7-dihydro-5-methyl-7-phenyl[1,2,4]triazolo[1,5-a]pyrimidine (3) with hydroxylamine or hydrazine leads to 3a,4,9,9a-tetrahydro-3,9a-dimethyl-4-phenylisoxazolo-[5,4-d][1,2,4]triazolo[1,5-a]pyrimidine (4a) and 3a,4,9,9a-tetrahydro-3,9a-dimethyl-4-phenyl-1H-pyrazolo[3,4-d][1,2,4]triazolo[1,5-a]pyrimidine (4b), respectively. In the presence of methanolic hydrogen chloride, 4b undergoes a cleavage of the pyrimidine ring to yield (5-amino-1,2,4-triazol-1-yl)(3,5-dimethylpyrazol-4-yl)phenylmethane (5). The structure determination of the compounds obtained is based on 1H and 13C nmr spectra including NOE measurements.

Synthesis of Tripyreno[2,3,4-abc: 2,3,4-ghi: 2,3,4-mno][18]annulenes

The title compounds were prepared in a multi-step synthesis in which primarily the pyrene building blocks were formed (1,2 11a,b). The final reaction step 11a,b 12a,b consisted of a threefold trans selective cyclocondensation process that generated the central 18-membered ring. Hexyloxy or dodecyloxy sidechains attached on the periphery led to the formation of liquid crystalline phases.

Impact of π-conjugation configurations on the photovoltaic performance of the quinoxaline-based organic dyes

Abstract Three novel quinoxaline-based donor-π-acceptor type organic dyes were synthesized and explored as sensitizers in dye-sensitized solar cells (DSSCs). The impacts of various π-conjugation configurations which contain different quinoxaline derivatives on the absorption properties, electrochemical properties and photovoltaic performances, as well as theoretical calculations have been investigated systematically. The photovoltaic performances of these dyes were found to be highly relevant to the π-conjugated configurations. In particular, the DSSC based on the dye with 2,3-dioctylquinoxaline as the spacer exhibited the highest efficiency of 8.20% with a short-circuit photocurrent densit…

Untersuchungen zur Konformation und elektronischen Struktur von Cyclooctadieninen

Die mit semiempirischer Quantenmechanik vorhergesagten Konformationen und elektronischen Strukturen der Cyclooctadienine 1 und 2 werden experimentell an Hand von 1H-NMR- und PE-Spektren verifiziert. Dabei wird Bezug genommen auf eine Reihe von anderen, verwandten Cycloalkinen 3–5 und Cycloalkenen 6–11. Wahrend die hohe geometrische Ringspannung entscheidenden Einflus auf 1 und 2 hat, ist eine Homoaromatizitat, die auf sechs nahezu eben angeordneten π-Elektronen-Zentren beruht, nicht signifikant. Investigations on the Conformation and the Electronic Structure of Cyclooctadienynes Conformations and electronic structures of the cyclooctadienynes 1 and 2, predicted by semi-empirical quantum mec…

ChemInform Abstract: Stereoselective Synthesis of Polycyclic Thiopyrans.

Reactions of benzothiete (I) with bicyclic alkenes exhibit very high π-side selectivity in the formation of polycyclic thiopyrans.

Pillararene-based fluorescent sensors for the tracking of organic compounds

Abstract Fluorescent chemosensors based on pillararene complexes represent a new, promising branch in sensor technology. Because of CH⋅⋅⋅π interactions, aliphatic chains are well suited for the columnar cavities of pillararenes and bulky or sheet-like (sub)structures can be arranged on the portals. Thus, pillararenes form versatile receptors and an alteration of the fluorescence behavior upon complexation ensures the function of these chemosensors as the reporter. Although this field of research exists only since a few years, remarkable chemosensors were developed for substances as diverse as medical drugs, biochemicals, herbicides and explosives.

ChemInform Abstract: 1,2-Methyl Shift in the Reaction of 4,7-Dihydro-4,5-dimethyl-7-phenyl-(1,2,4)-triazolo[1,5-a]pyrimidine with Tosyl Azide.

The reaction of the heterocyclic enamine 1 with tosyl azide (2) leads to the tosylimino derivative 4 of 1,2,4-triazolo[1,5-a]pyrimidine. The extrusion of nitrogen from the primary adduct 3 is followed by a 1,2-shift of a methyl group. The structure determination of 4 is based on 1H and 13C nmr spectra including NOE measurements.

Kronenethersubstituierte 1,4-Distyrylbenzole und ihre Komplexierung mit Alkalipikraten

Crown Ether Substituted 1,4-Distyrylbenzenes and their Complexation with Alkali Picrates The 1,4-distyrylbenzenes 8 and 9, which contain two crown ether units, each, were prepared by Wittig—Horner reactions. Their complexation tendencies with alkali picrates (Li—Cs) in water/dichloromethane were investigated. Potas sium ions give the strongest complexes. Generally monomo-lecular 1:1-complexes are formed; however, [K-8] + [Pik]—, [K-9]+ [Pik]— and [Rb-8] + [Pik]— generate aggregates, for which a stairway structure is proposed.

ChemInform Abstract: Benzoxetes and Benzothietes - Heterocyclic Analogues of Benzocyclobutene

Benzo-condensed four-ring heterocycles, such as benzoxetes 1 and benzothietes 3 represent multi-purpose starting compounds for the preparation of various higher heterocyclic ring systems. The thermal or photochemical valence isomerizations between the benzenoid forms 1,3 and the higher reactive o-quinoid structures 2,4 provide the basis for the synthetic applications. On the other hand, this valence isomerization impedes in particular the generation and storage of 1 because the thermal equilibrium 1 2 is completely on the side of 2. Thus, the number of erroneous or questionable benzoxete structures published to date is surprisingly high. On the contrary, the thermal equilibrium 3 4 is on th…

ChemInform Abstract: A Versatile Synthesis of 4,5-Dihydropyrrolo[1,2-a]quinoxalines.

The reaction of 1-(2-aminophenyl)pyrrole with aromatic or heteroaromatic aldehydes in ethanol and catalytic amounts of acetic acid leads to 4,5-dihydropyrrolo[1,2-a]quinoxalines in high yields. When aliphatic aldehydes were used under the same conditions, a slow oxidation to the corresponding pyrrolo[1,2-a]quinoxalines can occur; the oxidation can be avoided by preparing in situ the 5-acetyl derivatives of the 4,5-dihydropyrrolo[1,2-a]quinoxalines.

4 H ‐3,1‐Benzoxathiine aus Benzothiet und Carbonylverbindungen

4H-3,1-Benzoxathiines from Benzothiete and Carbonyl Compounds The o-quinoid 8-π electron system 2, generated by thermal ring opening of benzothiete (1) undergoes [8π + 2π] cycloaddition reactions with electron-deficient carbonyl compounds 3. In accordance with the frontier orbital theory, 4H-3,1-benzoxathiines (4) are obtained in a regioselective manner.

ChemInform Abstract: An Alternative Route to 2H-Naphtho[1,2-b]thiete and Its Cycloaddition Products.

Dimerization control in the self-assembly behavior of copillar[5]arenes bearing ω-hydroxyalkoxy groups.

Two novel copillar[5]arenes bearing ω-hydroxyalkoxy groups are synthesized and their self-assembly properties are studied by (1)H NMR spectroscopy, specific viscosity, and X-ray measurements. The copillar[5]arene 2b bearing a 6-hydroxyhexyloxy group exhibits a reversible self-assembly behavior, leading to the formation of the self-inclusion monomer and hugging dimers. The reversible self-assembly behavior can be controlled by tuning solvent, temperature, guest, and H-bond interaction. However, the copillar[5]arene 2a bearing a short 4-hydroxybutyloxy group does not show such a self-assembly behavior to the formation of the self-inclusion monomer and hugging dimers.

ChemInform Abstract: Synthesis of Novel 1,2,5,6-Tetrahydro-4H-pyrrolo[3,2,1-ij]quinolines via Benzotriazole Methodology.

Abstract Pyrroloquinolines have been synthesized reacting 1-(benzotriazol-1(2)-ylmethyl)indolines with unactivated and electron-rich alkenes in the presence of p-toluenesulfonic acid catalyst. Mixtures of the expected diastereomers were obtained and some of them separated in their respective components. X-Ray diffraction along with two-dimensional NMR experiments was needed to assist the determination for both the structures of the precursors and products.

ChemInform Abstract: Cyclocondensation Reaction of 1,2-Diamino-4-methylbenzene and p- Substituted Acetophenones.

1,2-Diamino-4-methylbenzene 1 reacts in the presence of sulphuric acid with 4-substituted acetophenones 2a-e yielding 2,4-diaryl-2,3-dihydro-2,8-dimethyl-1H-1,5-benzodiazepines 3a-e and as minor component 2,4-diaryl-2,3-dihydro-2,7-dimethyl-1H-1,5-benzodiazepines 4a-e. The ratio 3:4 is in the range of 7:3. The structure determination of the regioisomers was performed by NOE measurements.

Benzothiete, a Versatile Reagent in Heterocyclic Syntheses

ChemInform Abstract: Reactions of Benzothiete with Phosphorus Nucleophiles. A Novel Type of Arbuzov Rearrangement.

The reaction of trialkylphosphites or related P-nucleophiles with benzothiete (1) leads to zwitter ionic species, which show an Arbuzov - like rearrangement to the products 4 and 7, respectively. New heterocyclic ring systems are generated in the case of cyclic esters. The normal SN2 reaction leads to the 1:2 adducts 9, whereas in an SN1 process the 1:1 adduct 13 is formed.

Reactions of 4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidines with α,β-unsaturated carbonyl compounds

The reaction of 5,7-diphenyl-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine (1) with α,β-unsaturated carbonyl compounds 2a-f led to the formation of the alkylated heterocycles 3a-f (Figure 1). However, the reaction of 5-methyl-7-phenyl-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine (5) with 2a-c yielded under the same conditions the triazolo[5,1-b]quinazolines 6a-c (Figure 3). In this case, the alkylation is followed by a cyclocondensation. The structure elucidation of the products is based on ir, ms, 1H and 13C nmr measurements and on an X-ray diffraction study.

3,6-Bis(2-arylethenyl)-1,2,4,5-tetrazine - Synthese, Fl�ssigkristallinit�t und Photochemie

3,6-Bis(2-arylethenyl)-1,2,4,5-tetrazines - Synthesis, LC Properties and Photochemistry The (E,E)-3,6-Bis(2-arylethenyl)-1,2,4,5-tetrazines 8 were prepared in a synthetic sequence starting with aromatic aldehydes 1 and cinnamic acids 2, respectively (Scheme 1). The rod-like conjugated molecules represent calamitic mesogens as well as extended chromophores. Hence, we investigated the formation of liquid crystals, achieved by the introduction of long flexible side chains, and the photochemical behaviour that is characterized by the fragmentation of the central ring (Scheme 3).

Fluoreszenz‐Untersuchungen an styrylsubstituierten Benzolen

Die Fluoreszenz-Abklingzeiten der stilbenartigen Verbindungen 1 – 4 zeigen, das die mittleren Lebensdauern dieser Molekule im elektronisch angeregten Singulettzustand um rund zwei Zehnerpotenzen hoher sind als bei trans-Stilben selbst. Anhand von UV-Absorptions-und Anregungsspektren wird das auf einen neu gefundenen S1-Zustand zuruckgefuhrt, der einem verbotenen Ubergang S0 S1 auf der langwelligen Seite der intensiven Absorption entspricht. Investigations on the Fluorescence of Styryl-substituted Benzenes Fluorescence decay measurements of the stilbene-like compounds 1 – 4 demonstrate that the average lifetimes of these molecules in the electronically excited singlet state are about 102 tim…

Photochemistry of 3,6-bis(styryl)pyridazines in solution and in neat liquid crystalline phase—optical switching and imaging techniques

Abstract 3,6-Bis(styryl)pyridazines 1a – f with 2–6 alkoxy groups show on irradiation in solution a stereoisomerization which leads to a photostationary state of ( E , E )- and ( E , Z )-isomer. Sensitizing and quenching experiments reveal that the ( E , E )→( E , Z ) route is a pure triplet process, whereas the ( E , Z )→( E , E ) route can have a minor singlet by-reaction. Hexyloxy or dodecyloxy chains on the terminal benzene rings convey the ( E , E )-isomers of compounds 1a , b , d – f thermotropic liquid crystalline properties. In particular S A , S C , and S F/I phases were studied with regard to their photochemical behavior. Depending on the system, photodegradation of the smectic ph…

Novel dithieno[3,2-b:2′,3′-d]pyrrole-based organic dyes with high molar extinction coefficient for dye-sensitized solar cells

Abstract Three new metal-free organic dyes FD1 – 3 with a planar dithieno[3,2- b :2′,3′- d ]pyrrole unit as linker were synthesized and used for dye-sensitized solar cells with high molar extinction coefficients. In this work, dithieno[3,2- b :2′,3′- d ]pyrrole was employed as π-conjugated bridge to construct A–π– d –π–A organic dyes, where 9,9-dihexyl-9 H -fluorene was used as a donor, and cyanoacrylic acid as an electron acceptor. For a typical device, a solar energy conversion efficiency ( η ) of 6.36% based on FD2 was achieved under simulated AM 1.5 solar irradiation (100 mW cm −2 ) with a short-circuit photocurrent density ( J sc ) of 13.76 mA cm −2 , an open-circuit voltage ( V oc ) o…

Effect of the linkage location in double branched organic dyes on the photovoltaic performance of DSSCs

Two novel double branched D–π–A organic dyes (DB dyes) are synthesized to investigate the influence of the linkage location in DB dyes on the performance of dye-sensitized solar cells (DSSCs), where phenothiazine is introduced as a donor, thiophene–benzotriazole unit as the π-bridge and cyanoacrylic acid as the electron-acceptor. The photophysical, electrochemical and photovoltaic properties of the dyes are systematically investigated. The results show that the location of the linkage unit has a small effect on the physical and electrochemical properties of the dyes. However, when the dyes are applied in DSSCs, an obvious decline of short-circuit current (Jsc) and open-circuit voltage (Voc)…

2-(Benzotriazol-1-ylmethyl)-1-phenyl-3-pyrazolidinone: two weak hydrogen bonds combine to form molecular ladders

In the supramolecular structure of C16H15N5O, weak C—H⋯O and C—H⋯N bonds combine to form molecular ladders, the former bonds acting as the rungs and the latter as the uprights.

ChemInform Abstract: Cycloaddition Reactions of Benzothiete with Azomethines.

Obtention de diaryl-2,3 dihydro-3,4 benzothiazines-1,3 (70%) via la cycloaddition de la thiobenzoquinone methode-1,2 (obtenue par scission thermique du benzothiete) et d'arylimines de benzaldehydes. Obtention egalement de 10% du dimere (dibenzo [b, f] dithiocinne-1,5)

An efficient probe for sensing different concentration ranges of glutathione based on AIE-active Schiff base nanoaggregates with distinct reaction mechanism

Abstract A novel tetraphenylethene-diketopyrrolopyrrole Schiff base (TPE-DPP) was synthesized by one-pot protocol. Based on thiol group and acid-base property of glutathione, nanoaggregates of TPE-DPP for sensitive and selective detection of diff ;erent concentration ranges of glutathione by two distinct reaction mechanisms was reported. It showed a turn-on mode of fluorescence signals towards low concentration of GSH by hydrolysis of TPE-DPP, but a ratiometric mode of fluorescence signal was elicited towards high concentration of GSH by addition reaction of thiol with TPE-DPP. What’s more, the probe was successfully utilized for monitoring GSH in living cells.

A conjugated polymer with ethyl 2-(2-(pyridin-2-yl)-1H-benzo[d]imidazol-1-yl) acetate units as a novel fluorescent chemosensor for silver(I) detection

Abstract A novel conjugated polymer ( P1 ) containing fluorene and ethyl 2-(2-(pyridin-2-yl)-1 H -benzo[ d ]imidazol-1-yl)acetate (PBMA) was designed and successfully synthesized through the Sonogashira coupling reaction. P1 shows high sensitivity and selectivity for Ag + detection in comparison to other metal cations. Upon addition of Ag + , the fluorescent emission of the polymer solution in THF was quenched dramatically, accompanying the color changed from blue to green. The detection limit for Ag + was 5 × 10 −8  mol L −1 . However, the similar copolymers P2 and P3 containing 2-(pyridin-2-yl)-1 H -benzo[ d ]imidazole and 2-(thiophen-2-yl)-1 H -benzo[ d ]imidazole, respectively, did not …

Synthesis and photovoltaic performance of dihydrodibenzoazepine-based sensitizers with additional lateral anchor

Three novel metal-free organic dyes with dihydro-5H-dibenzo[b,f]azepine as a donor and cyanoacrylic acid as an anchoring unit were designed as an innovative linear skeleton of D-D-pi-A type of organic dyes. The conversion efficiency of the derived dye-sensitized solar cells is moderate. Among them, the dye with a hydroxy group as an additional anchoring moiety exhibited the highest UV-Vis absorption with a maximum molar extinction coefficient of 24,136 M-1 cm(-1) at lambda(max) = 458 nm and the best photovoltaic performance with an overall power conversion efficiency of 4.88%, while the dye with a carboxy group as an additional anchoring moiety exhibited the lowest conversion efficiency (4.…

Synthesis of Pillar[6]arenes and Their Host–Guest Complexes

Pillar[n]arenes are a fast-growing research topic in supramolecular chemistry. Originally the focus was predominantly on pillar[5]arenes; however, now more and more studies on pillar[6]arenes are being performed. The ability and selectivity of host–guest complexations depend strongly on the size of the inner cavities of these macrocycles. New results have stimulated us to compile the synthetic entries and the complexations of pillar[6]arenes with large cylindric cavities that offer space for many different guest molecules. 1 Introduction 2 Preparation of Pillar[6]arenes 2.1 Pillar[6]arenes by Macrocyclization Reactions 2.2 Hydroxypillar[6]arenes through Ether Cleavage 2.3 Hydroxypillar[6]ar…

Generation and transformation of the [3.3.1]propellane skeleton by thermal rearrangements

Abstract In a sequence of unexpected thermal rearrangements the strained monocyclic alkyne 4 is transformed into the tricyclic system 5 which yields in a flash vacuum pyrolysis again a monocyclic compound 10 .

Dodecyloxy-substituted 2,4,6-tris(styryl)pyridines

(E,E,E)-2,4,6-Tris(styryl)pyridines 2a-c with 3, 6 or 9 dodecyloxy substituents were prepared by the highly stereoselective condensation reaction of collidine (8) and the corresponding phenyl-(1-phenyl-methylidene)amines 7a-c (Siegrist reaction). In contrast to the corresponding compounds with a benzene or a 1,3,5-triazine core, 2a-c do not show any hints for the formation of thermotropic liquid crystals. The major application of such star-shaped systems is in the field of nonlinear optics.

Chemical and Spectroscopical Properties of Medium Sizedtrans- andcis-Bicyclo[n.1.0]alk-2-ynes

Chemical and spectroscopical properties of cis- and trans-cyclopropano-anellated cycloalkynes of medium ring size are investigated and compared with results from force field calculations. IR and 13C-NMR data of the alkynes reflect the deformation of the triple bond due to ring strain. Parallel to bending the reactivity increases with decreasing ring size, the trans fused alkynes prove to be nearly as reactive as the cis fused with a two carbon smaller ring size. The bicycloalkynes are complexed with silver triflate. 13C NMR reveals that the triple bond as well as the cyclopropane serve as ligands.

Cyclocondensation reaction of 1,2-diamino-4-methylbenzene andp-substituted acetophenones

1,2-Diamino-4-methylbenzene 1 reacts in the presence of sulphuric acid with 4-substituted acetophenones 2a-e yielding 2,4-diaryl-2,3-dihydro-2,8-dimethyl-1H-1,5-benzodiazepines 3a-e and as minor component 2,4-diaryl-2,3-dihydro-2,7-dimethyl-1H-1,5-benzodiazepines 4a-e. The ratio 3:4 is in the range of 7:3. The structure determination of the regioisomers was performed by NOE measurements.

Photoconductivity of Poly(Arylenevinylene)S and Poly(Hetarylenevinylene)S

Abstract The intramolecular condensation of aromatic Schiff bases leads under strong alkaline conditions to the poly(arylenevinylene)s and poly(hetarylenevi-nylene)s A - H. Due to the extreme stereoselectivity the resulting products are rigid, (E)-configurated polymers. The broad band gap of the unsubstituted intrinsic insulators is decreased by alkoxy substituents. Investigations of the photoconductivity and the photoreactivity, as well as of the AC-conductivity of some undoped, doped and quaternized systems are performed.

syn ‐[2.2](1,3)Cyclophane durch doppelte Photocyclodimerisierung

Durch doppelte Cyclodimerisierung wird in einer Photolyse in Losung aus dem 1,3-disubstituierten Benzol 3 das syn[2.2](1,3)Cyclophan 4 erhalten. Eine kombinierte Belichtung Festkorper/Losung ergibt bei 5 das analoge System 6 mit Estergruppen. Beide Reaktionen erfolgen streng regiospezifisch durch Kopf-Kopf-Verknupfung und stereospezifisch bezuglich der syn-Geometrie im Cyclophan und der trans-Konfiguration der Vierringsubstituenten. Die einzige stereochemische Freiheit besteht in der Anordnung der Vierringe, wobei die Isomeren 4/6a,b,c, den drei moglichen Rotameren in 3 und 5 entsprechen. Wahrend das Gerust von 4 starr ist, zeigt 6 bei Raumtemp. eine langsame Inversion des zentralen 10-Ring…

ChemInform Abstract: Dehydrotriphenylenes for the Generation of Bent Molecular Ribbons.

Cyclocondensation of 6-acetyl-4,7-dihydro-5-methyl-7-phenyl[1,2,4]triazolo[1,5-a]pyrimidine with hydroxylamine and hydrazine

The cyclocondensation of 6-acetyl-4,7-dihydro-5-methyl-7-phenyl[1,2,4]triazolo[1,5-a]pyrimidine (3) with hydroxylamine or hydrazine leads to 3a,4,9,9a-tetrahydro-3,9a-dimethyl-4-phenylisoxazolo-[5,4-d][1,2,4]triazolo[1,5-a]pyrimidine (4a) and 3a,4,9,9a-tetrahydro-3,9a-dimethyl-4-phenyl-1H-pyrazolo[3,4-d][1,2,4]triazolo[1,5-a]pyrimidine (4b), respectively. In the presence of methanolic hydrogen chloride, 4b undergoes a cleavage of the pyrimidine ring to yield (5-amino-1,2,4-triazol-1-yl)(3,5-dimethylpyrazol-4-yl)phenylmethane (5). The structure determination of the compounds obtained is based on 1H and 13C nmr spectra including NOE measurements.

Untersuchungen zur Konfigurationsstabilität von Enolaten aus β‐Ketocarbonsäureestern

Z- und E-Enole von β-Ketocarbonsaurederivaten 1a–c werden vollstandig und irreversibel deprotoniert, wobei unter Konfigurationserhalt (kinetische Kontrolle) die Enolate 2a–c entstehen. Abhangig von Gegenionen (Li, Na, K), Medium (THF, HMPT) und Temperatur kann anschliesend eine Z/E-Aquilibrierung eintreten. Auf dieser Basis last sich die Synthese von Enolethern und Enolestern auf die gewunschte Konfiguration hinsteuern. Investigations on the Stability of the Configuration of Enolates from β-ketocarboxylic Acid Esters Z- and E-enoles of β-ketocarboxylic acid esters 1a–c are completely and irreversibly deprotonated yielding the enolates 2a–c under retention of the configuration (kinetic contr…

Synthesis of pillar[7]arene

Abstract The first synthesis of pillar[7]arene is reported with two methods. Method A: the FeCl 3 -catalyzed condensation reaction of 1,4-dimethoxybenzene ( 1 ) with paraformaldehyde in CHCl 3 gave dimethoxypillar[7]arene ( 3 ). Method B: the p -toluenesulfonic acid catalyzed condensation reaction of 2,5-bis(benzyloxymethyl)-1,4-dimethoxybenzene ( 2 ) in CH 2 Cl 2 gave compound 3 . Demethylation of 3 with BBr 3 gave pillar[7]arene ( 4 ). The pillar[7]arene might be a perspective macrocyclic host in host–guest chemistry.

ChemInform Abstract: Bis-, Tris-, and Tetrakis(squaraines) Linked by Stilbenoid Scaffolds.

The oligosquaraines 1−5, with stilbenoid scaffolds, were prepared by multistep syntheses in which the final steps consisted of condensation reactions between the semisquaric acid 21 and multiple resorcinols 12b−15b and 17b. The target compounds exhibit intense (ϵ > 250000 L·mol−1·cm−1) and sharp absorption bands with maxima between 687 to 778 nm, depending on the conjugation in the stilbenoid scaffold. Comparison with the monosquaraine 6 as a model compound reveals intramolecular interactions between different donor−acceptor−donor moieties, which give rise to increased absorption intensities.

Die unsymmetrischen Cyclooctadienine: 1,3‐Cyclooctadien‐5‐in und 1,6‐Cyclooctadien‐3‐in

Verschiedene Varianten des synthetischen Zugangs zu den beiden Titelverbindungen 15 und 45 werden diskutiert. 15 und 45 konnen in situ umgesetzt werden. Fur die Isolierung in reiner Form ist ihre mittlere Lebensdauer zu gering. Sie isomerisieren sich auf der C8H8-Energiehyperflache zu Styrol (47) und/oder Benzocyclobuten (22).

ChemInform Abstract: Ring-Expansion of 5-Methylene-thiazolidine-2-thione with Hydrazine.

Cycloalkin-vinylidencycloalkan-umlagerungen

Abstract Flash pyrolysis of the strained cyclic alkynes 1 leads to ring systems 2 with an exocyclic allene group and in a further isomerization step to the conjugated vinyl compounds 3 .

Guest-Host Systems of 1,3,5-Tristyrylbenzenes

(E,E,E)-1,3,5-Tris(3,4,5-trimethoxystyryl)benzene (1a) forms monoclinic crystals of the space group P21/c. Incorporation of three transoid diacetyl guest molecules between the three arms leads to triclinic crystals of the space group P1. The styryl groups, originally present in a nonsymmetrical conformation, are simultaneously transformed to a C3 arrangement. (E,E,E)-1,3,5-Tris- (3,4,5-tripropoxystyryl)benzene (1b) forms monoclinic crystals of the space group P21/c. The C3 arrangement of the styryl groups is present in the first, the unsymmetrical arrangement in the second modification. Incorporation of two acetone guests in the largest and the middle-sized angle space between the styryl ar…

An alternative route to 2H-naphtho[1,2-b]thiete and its cycloaddition products

2-(1H-Benzotriazol-1-ylmethyl)-1-naphthalenol (1) can be transformed in high yields to the corresponding thiol 4. Flash vacuum pyrolysis of 4 leads to 2H-naphtho[1,2-b]thiete (5). The benzotriazolyl group proved to be a good leaving group; however, a subsequent nitrogen extrusion takes place under flash vacuum pyrolysis conditions and cyclopentadienecarbonitriles 6a,b are formed by a ring contraction (Scheme 1). Cycloaddition reactions of 5 and dienophiles or heterodienophiles yield the naphtho-condensed sulfur heterocycles 8, 10, 12 and 14 (Scheme 2).

ChemInform Abstract: Formation and Reactivity of 2-Styryl-1,4-benzoquinones.

Organic Dye Bearing Asymmetric Double Donor-π-Acceptor Chains for Dye-Sensitized Solar Cells

A novel efficient metal free sensitizer containing asymmetric double donor-π-acceptor chains (DC) was synthesized for dye-sensitized solar cells (DSSCs). Comparing to 3.80%, 4.40% and 4.64% for the DSSCs based on the dyes with single chain (SC1, SC2) and cosensitizers (SC1 + SC2), the overall conversion efficiency reaches 6.06% for DC-sensitized solar cells as a result of its longer electron lifetime and higher incident monochromatic photon-to-current conversion efficiency.

Alkoxy substituted (E,E)-3,6-bis(styryl)pyridazine—a photosensitive mesogen for liquid crystals

Abstract (E,E)-3,6-Bis(styryl)pyridazines (3a–t) bearing 2, 4 or 6 alkoxy chains were prepared by applying the Siegrist reaction of 3,6-dimethylpyridazine (13) and the corresponding azomethines 10a–t. The transversal dipole moment of these calamitic compounds effects an extremely high tendency for self-organization in thermotropic LC phases (N, SA, SB, SC, SE, SI/F, and Cub). The conjugated core structure represents moreover a chromophore with a high photosensitivity for (E,E)⇄(E,Z) isomerization reactions: this property makes the compounds interesting for optical imaging and switching techniques.

On the basis of an extended series of monodisperse oligomers of the dialkoxy-substituted phenyleneethenylenes 1a–i the Eqs. (3) and (4) were conceived in order to determine the limiting values of the energies Ei and the wavelengths λi of the UV/vis absorption. The convergence of the Ei, and λi values with a growing number n of repeating units permits a precise prediction of the Ei,∞ and λi,∞ values of the corresponding polymer 1j as well as a statement about the overall effect of conjugation ΔEi and the effective conjugation length ECL. A great variety of different conjugated oligomers 2–14 can be evaluated by the same algorithm.

Synthesis and photovoltaic performance of the porphyrin based sensitizers with 2H-[1,2,3]triazolo[4,5-c]pyridine and benzotriazole as auxiliary acceptors

Abstract Two novel zinc porphyrin dyes containing either benzotriazole or 2 H -[1,2,3]triazolo[4,5- c ]pyridine as auxiliary acceptors, respectively, were synthesized for dye-sensitized solar cells. These two auxiliary acceptors were firstly applied into porphyrin based dyes. The photophysical and electrochemical properties of the dyes were investigated. These two dyes show the whole visible light absorption when they are adsorbed on the TiO 2 film, which means that they are promising sensitizers for dye-sensitized solar cells. The absorption intensity of the triazolopyridine containing dye is higher than that of the benzotriazole containing dye, resulting in a better light harvesting. Thus…

ChemInform Abstract: 6-Fluoro-7-(1-piperazinyl)quinoxaline-1,4-dioxides. Part 1. 2-(N-2- hydroxyalkylcarbamoyl) Derivatives.

Oligo(phenylenvinylene) mit terminaler Donor-Acceptor-Substitution

Conjugating pillararene dye in dye-sensitized solar cells

Summary The improvement of open-circuit voltage (VOC) is a crucial goal to develop efficient dye-sensitized solar cells (DSSCs). Here, conjugating pillar[5]arene dyes (PPI and PPII) are designed, synthesized, and applied in DSSCs. The presence of pillar[5]arene moiety in the dyes inhibits the dye aggregation and charge recombination in the DSSCs, leading to the enhancement of VOC. PPI with a single D-π-A backbone and a pillar[5]arene moiety achieves a VOC of 715 mV, which is much higher than the reference dye (VOC of 674 mV) with the same D-π-A backbone but no pillar[5]arene moiety. PPII with 2 D-π-A backbones also achieves a VOC of 746 mV and a much higher short-circuit photocurrent (JSC) …

Preparation of 5-methyl-2-sulfanyl-7h-1,3,4-thiadiazolo[3,2-a]-pyrimidin-7-ones

7H-1,3,4-Thiadiazolo[3,2-a]pyrimidin-7-ones can be prepared by the acylation of 5-amino-1,3,4-thiadiazoles with diketene and subsequent ring closure (dehydration). Whereas arylthio substituents (SC6H5) can be introduced in 2-position by the replacement of Br, alkylthio groups (SC2H5) have to be already presentin the starting 5-amino-1,3,4-thiadiazole. The ambident nucleophile 2-thiazolidinethione reacts in the Br substitution reaction on the N atom.

Dendrimers consisting of stilbene or distyrylbenzene building blocks synthesis and stability

Abstract On the basis of Wittig-Horner reactions and protection group techniques compound 7 for the core and the components 9a-c and 11a-c for the dendrons were prepared and linked in the final step. The convergent synthesis yielded constitutionally and configurationally pure dendrimers ( 2a-c, 2a'-c' ) which consist of distyrylbenzene units. Their thermo-oxidative stability in the presence of air was studied by chemiluminescence and compared to the dendrimers 1 consisting of stilbene units.

Phenothiazine-based dyes with bilateral extension of π-conjugation for efficient dye-sensitized solar cells

Four novel organic photo-sensitizers based on phenothiazine were designed, synthesized and characterized for efficient dye-sensitized solar cells. Anisole, octyloxybenzene and dodecyloxybenzene were incorporated into the phenothiazine by an Ullmann reaction. An additional octyloxybenzene was incorporated into one dye unit through a Suzuki coupling reaction. The modified phenothiazine moiety acts as an electron donor and cyanoacrylic acid acts as an electron acceptor and anchoring unit. The photophysical, electrochemical and sensitizing characteristics of the new dyes were evaluated. The bis(octyloxybenzene) substituted dye delivered the best performance with its sensitized solar cell displa…

Poly(propylene imine) dendrimers functionalized with stilbene or 1,4-distyrylbenzene chromophores

Abstract Two generations of dendritic nanoparticles were prepared, which contain ( E )-stilbene or ( E , E )-1,4-distyrylbenzene chromophores in the 4 or 8 terminal positions of the propylene imine dendrons. The compounds show a highly efficient photoreactivity. On prolonged irradiation all stilbenoid chromophores were destroyed by oligomerization (crosslinking) and the typical absorption and fluorescence of the chromophores disappeared completely.

(E,E,E)-4,4′-Distyrylstilbenes – Synthesis, Photophysics, Photochemistry and Phase Behavior

The fluorescence quantum yields F(n) of oligo[2,5-bis(propyloxy)-1,4-phenylenevinylene]s (1b) reach for the trimer (n = 3) in solution a maximum of 86 %, which is almost twice as high as for the monomer (n = 1) and the octamer or undecamer (n = 8, 11). The latter represent the convergence limit of 46 %. 4-Mono-, 3,4-di- or 3,4,5-trisubstituted terminal phenyl rings in the trimers 6a–f do not lead to calamitic or phasmidic liquid crystals; however, 2,3,4-trisubstitution with hexyloxy groups (6h) and even with OCH3 groups (6g) effects LC formation. Irradiation with energy-rich UV light provokes a crosslinking of the originally conjugated chains. In the case of 6c, a chemo- and stereoselective…

Pentadecamer 2,5-Dipropoxy-1,4-phenylenevinylene

The conjugated, all-(E)-configured pentadecamer 2,5-dipropoxy-1,4-phenylenevinylene 1j was prepared by a multistep synthesis on the basis of hydroquinone. The procedure consists of a general method for the repetitive extension of oligo(phenylenvinylene) chains by two styryl units (7a ⇄ 10 ⇄ 12 ⇄ 14). The relatively rigid oligomer 1j represents a molecular wire of about 100 A. The absorption of 1j provides a proof for the convergence theory for electronic properties of conjugated oligomers with increasing number of repeat units. The corresponding conjugated polymer 1p with the same substitution matches the values which were extrapolated from the oligomer series 1a−1j. (© Wiley-VCH Verlag Gmb…

Monodisperse Dialkoxy-Substituted Oligo(phenyleneethenylene)s

Individual but connected synthetic routes for the preparation of the all-E-configured 2,5-dipropoxy-substituted oligo(1,4-phenyleneethenylene)s 1a–g were developed. An increasing number of conjugated stilbene units from n = 1 to n = 11 led to a convergent bathochromic shift (Δλ = λ∞ − λ1 = 127 nm) in the UV/Vis absorption. An exponential function for the convergence of the absorption energies (wavelengths) in conjugated systems is proposed. By a simple extrapolation of this function the effective chain length may be determined.

A monophosphoryl copillar[5]arene: synthesis and host–guest complexation with alkanols

A monophosphoryl copillar[5]arene 1 was prepared. The introduction of the phosphoryl group remarkably promoted the binding affinity of 1 with alkanols and alkanediols in comparison with 1,4-dimethoxypillar[5]arene. Thus 1 can form a stable 1 : 1 host–guest complex with alkanols in CDCl3.

An Efficient Synthesis of Rubin’s Aldehyde and its Precursor 1,3,5-Tribromo-2,4,6-tris(dichloromethyl)benzene

2,4,6-Tribromobenzene-1,3,5-tricarboxaldehyde (4) can be efficiently prepared in two reaction steps from 1,3,5-tribromobenzene. The intermediate 1,3,5-tribromo-2,4,6-tris(dichloromethyl)benzene (3) crystallizes from petroleum ether in its C3h structure. However, in CDCl3 solution it exists at room temperature in two isomeric forms: 3a (C3h) and 3b (Cs) (1:1.15).The intramolecular Br・・・Cldistances are much smaller than the sum of the van der Waals radii. Therefore, the exocyclic C-C bonds show a hindered rotation.

trans- andcis-Bicyclo[n.1.0]alk-2-ynes of Medium Ring Size

Starting from cycloalkenes, the cis- or trans-cyclopropano anellated cycloalkynes 2–7 of medium ring size were synthesized. The triple bonds were introduced in the final reaction step either by the fragmentation of the corresponding 1,2,3-selenadiazoles or by direct dehydration of a ketone (Scheme 2). The cis-fused bicycles 2 and 3 and the trans-fused bicycles 5, 6 and 7 could be isolated in a pure state. The intermediary existence of the most strained system trans-bicyclo[7.1.0]dec-2-yne (4) was proven by trapping reactions.

Crystal Structure and Host-Guest Binding Ability of Three Types of Pillar[5]arenes

A systematic research of the structural characterization and the host-guest binding abilities between three types of pillar[5]arenes 3–5 (3 for Structure Type I, 4 for Structure Type II and 5 for Structure Type III) is carried out by 1H NMR measurements and X-ray study. The results show that the configurations or symmetry of their cavities not only have large difference in these three types of pillar[5]arenes, but also have more or less variations even in the same structure type or the same host locked different guests such as crystals of 3a–3b, 4a–4d. On the other hand, the complexation behavior of pillar[5]arenes with 1,4-dibromobutane (DBB) is affected by the different symmetrical struct…

Two strained hexahelicenophanes

The crystal structures of the [6]­helicenes 4,13-(1,10-deca­methyl­ene­dioxy)­hexahelicene, C36H34O2, (I), and 4,13-(1,8-octa­methyl­ene­dioxy)­hexahelicene, C34H30O2, (II), show strong steric interactions between the terminal benzene rings and the poly­methyl­ene­dioxy chains. The shortest ring A and F distances amount to 2.941 (3) and 2.902 (3) A, respectively. The increased steric energy of the ground state is responsible for a significantly lower racemization barrier of (I) and (II) in comparison to the unsubstituted [6]­helicene.

Phenylethynyl- and Phenylethenylmetacyclophanes with π,π Interactions

Metal-free organic dyes with di(1-benzothieno)[3,2-b:2′,3′-d]pyrrole as an auxiliary donor for efficient dye-sensitized solar cells: Effect of the molecular engineering on the photovoltaic performance

Abstract A series of novel di(1-benzothieno)[3,2-b:2′,3′-d]pyrrole (DBTP)-based organic dyes (WL5-10) with D-D-π-A or D-D-A-π-A configurations are designed and the relationship between the properties and molecular configurations of these organic dyes are studied systematically. WL5,7–8 with D-D-π-A configuration incorporating triphenylamine or phenothiazine as donor and DBTP as auxiliary donor and WL9-10 with D-D-A-π-A configuration incorporating benzothiadiazole as an auxiliary acceptor are synthesized to study the effect of the molecular engineering on the photovoltaic performance. WL5,7–8 exhibit similar absorption spectra and high molar extinction coefficient. Especially, the dye WL5 wi…

1H-naphtho[2,1-b]thiete and 2H-naphtho[2,3-b]thiete- synthesis and reactivity

Abstract The title compounds 4 and 8 are obtained by flash vacuum pyrolysis of the corresponding hydroxymethylthionaphthols 3 and 7. Whereas 4 shows a smooth ring opening on heating, 8 is thermally stable but reacts photochemically. The different behavior is explained on the basis of an MNDO calculation. The valence isomers 4′ and 8′ represent thioquinonemethides, which are highly reactive components in [12π + 2π]cycloaddition processes (4 → 9, 10, 11; 8 → 12).

ChemInform Abstract: The Formation of Pyrazolo(1,5-a)pyrimidines by the Reaction of 3-(4- Chlorophenyl)pyrazol-5-amine with Chalcones.

Cyclocondensation reactions of the pyrazol-5-amine 1 and the 1-aryl-3-phenyl-2-propen-1-ones 2a-d yield the 6,7-dihydropyrazolo[1,5-a]pyrimidines 7a-d. Whereas 7a-c can be isolated in pure state, 7d is subjected to a spontaneous oxidation.

Untersuchungen zur Diastereoselektivität beim O ‐Angriff von Elektrophilen auf β‐Ketocarbonsäureester‐Enolate

Aus den in reiner Form eingesetzten Z- oder E-Enolen 2a–c werden uber die Enolatstufe 3a–c die O-alkylierten, -silylierten oder -acylierten Produkte 4aa–ae, 4ba, bf und 4ca, cc, cf hergestellt. Im Gegensatz zu der vollstandigen Regioselektivitat hangt die Z/E-Diastereoselektivitat dabei von den Substituenten in 2/3, dem verwendeten Elektrophil und den Reaktionsbedingungen ab. Insbesondere bei weichen Elektrophilen kann sich das Z/E-Verhaltnis bei der Umsetzung 34 stark andern. On the Diastereoselectivity of the O-Attack of Electrophiles on Enolates from β-Ketocarboxylates The O-alkylated, -silylated or -acylated derivatives 4aa–ae, 4ba, bf, 4ca, cc, cf of the pure Z or E enoles 2a–c are gen…

5-Alkenyl-1,2,3-thiadiazole

Es wird die Herstellung der Titelverbindungen 5 durch Bromierung-Dehydrobromierung entsprechender 5-Alkyl-1,2,3-thiadiazole 3, ihre spektroskopische Charakterisierung und ihre Umsetzung mit 4-Phenyl-4H-1,2,4-triazol-3,5-dion (6) zu 7, 8 beschrieben. 5-Alkenyl-1,2,3-thiadiazoles A method of preparation for the title compounds 5, by bromination-dehydrobromination of the corresponding 5-alkyl-1,2,3-thiadiazoles 3, their spectroscopical characterization, and the reaction of 5 with 4-phenyl-4H-1,2,4-triazole-3,5-dione (6) with formation of 7, 8 is described.

Photochemical Generation of Cyclophanes from 1,3,5-Trisubstituted Benzenes with Chalcone Chromophores

(E,E,E)-1,3,5-Tricinnamoylbenzene (7a) photodimerizes in solution to the [4.4.4](1,3,5)cyclophane 8a. The process consists of three consecutive steps in which cisoid enone conformations of 7a react in regio- and stereoselective anti-head-to-head cycloadditions. (E,E,E)-1,3,5-Tris(3-oxo-3-phenylpropenyl)benzene (13a), an isomer of 7 with reversed enone units, shows a single [2π+2π] cycloaddition of the same type. Due to steric reasons, it is afterwards not capable of intramolecular processes and oligomerizes by intermolecular photocycloadditions. Photolyses in the crystalline state yield dimers by topochemically controlled syn-head-to-tail processes (7a → 10a, 13a → 15a). An efficient dimeri…

Multi-Arm 1,2,3-Thiadiazole Systems

Benzene derivatives 2a–c with 6, 4, and 3 side chains bearing terminal 1,2,3-thiadiazole rings, respectively, have been prepared. Alkaline cleavage of 2a–c led to the corresponding alkynethiolates 6a–c, which were trapped by electrophiles such as benzyl bromide or iodomethane. The method provides an alternative to the thermal or photochemical cleavage of 1,2,3-thiadiazoles to thioketenes, which react further with nucleophiles.

Selectivity in the direction of photoisomerization reactions in liquid-crystalline guest-host systems

E ⇄ Z photoisomerization reactions of stilbenes la-c were studied in liquid-crystalline (LC) phases and in the corresponding isotropic melts. Whereas viscosity has a moderate influence on the photostationary states, a strong effect caused by the regular incorporation of the stilbene molecules in the LC phases was observed. The direction of the isomerization can be reversed, up to the case of a one-way isomerization Z E for the tailored guest-host system 1b/BS. Such an LC-matrix effect is of typical highly ordered (smectic) phases with free volumina which are strictly limited by hydrophobic interactions; it could not be detected in a much more mobile nematic phase. Textures based on the bire…

Trilateral π-conjugation extensions of phenothiazine-based dyes enhance the photovoltaic performance of the dye-sensitized solar cells

Abstract Two novel organic dyes TLEP-1 and TLEP-2 based on phenothiazine with trilateral π-conjugation extensions were designed and synthesized for dye-sensitized solar cells, where phenothiazine ring was linked with two phenyl moieties at 7- and 10-positions as the first and second π-conjugation extensions, and with furan or thiophene ring at 3-position as the third π-conjugation extension for TLEP-1 and TLEP-2, respectively. The influence of the π-conjugation extensions on the photovoltaic performance was evaluated. The cell based on TLEP-2 exhibits an impressive short-circuit photocurrent density of 14.87 mA cm−2, which is much higher than the cell based on the reference dye without π-co…

Cycloaddition reactions of 2H-1-benzothietes and 1,3,5,7-tetrathio-s-indacene-2,6-dithiones

Abstract 2H-1-benzothiete (1) and 2H,5H-benzo[1,2-b:4,5-b′]bisthiete (3) react in form of their open valence isomers with the trithiocarbonic acid esters 2a–c. The one- or twofold cycloaddition reactions yield 1,3-dithiin rings, in which C-2 is a spiro-C atom, that bears four sulfur groups. The bifunctional reactant 3 gives additionally band-shaped, hardly soluble oligomers.

Untersuchungen zur Konformerenvielfalt von mono- und 2,5-dialkoxysubstituierten Poly(1,4-phenylenethenylen)en

Investigations on the Conformational Variety of Mono- and 2,5-Dialkoxy Substituted Poly(1,4-phenyleneethenylene)s The alkoxy substituted poly(1,4-phenyleneethenylene)s 1 and 2 can principally exist in an enormous variety of conformers (table 1). However, force field calculations (MMX) reveal a far-reaching restriction to a relatively small number of non planar conformers with minimized steric energy. The decisive criterion is due to the interaction between the oxygen atoms and the olefinic hydrogens. An increasing steric hindrance should lead to higher twist angles θ in the main chain and hence to a shorter effective conjugation length. Such an effect could play a minor role between the uns…

ChemInform Abstract: The Reaction of Aromatic α,β-Unsaturated Ketones with 4,5- Diamino-1,6-dihydropyrimidin-6-ones.

The reaction of 4,5-diamino-1,6-dihydropyrimidin-6-ones 1 with one equivalent of the chalcones 2 leads in an acidic medium to the formation of the 2,4-diaryl-2,3,6,7-tetrahydro-1H-pyrimido[4,5-b][1,4]diazepin-6-ones 3a-m. The structure elucidation of the products is based on detailed nmr investigations including selective 13C[1H] decoupling experiments.

Dendrimers with peripheral stilbene chromophores

Abstract Two types of dendritic nanoparticles were prepared, which contain ( E )-stilbene chromophores in the terminal positions of the dendrons. The compounds showed a highly efficient photoreactivity in the course of which statistical CC bond formations led to a crosslinking of the particles. Finally, all stilbene chromophores reacted and the typical ( E )-stilbene absorption and fluorescence disappeared completely.

ChemInform Abstract: Preparation of 5-Bromo-6-phenylimidazo[2,1-b][1,3,4]thiadiazol-2-ylamines.

The reaction of primary or secondary amines with 2,5-dibromo-6-phenylimidazo[2,1-b][1,3,4]-thiadiazole (5) leads to a chemoselective replacement of the 2-Br substituent. The process represents a convenient route to the corresponding 2-ylamines 7a-d. Hydrazine reacts in an analogous fashion (5 → 7e). The structure determinations are based on an X-ray crystal structure analysis and on one- and two-dimensional NMR measurements.

ChemInform Abstract: Chemical and Spectroscopical Properties of Medium Sized trans- and cis- Bicyclo(n.1.0)alk-2-ynes.

Chemical and spectroscopical properties of cis- and trans-cyclopropano-anellated cycloalkynes of medium ring size are investigated and compared with results from force field calculations. IR and 13C-NMR data of the alkynes reflect the deformation of the triple bond due to ring strain. Parallel to bending the reactivity increases with decreasing ring size, the trans fused alkynes prove to be nearly as reactive as the cis fused with a two carbon smaller ring size. The bicycloalkynes are complexed with silver triflate. 13C NMR reveals that the triple bond as well as the cyclopropane serve as ligands.

9‐Oxabicyclo[6.1.0]nonine

Semiempirische quantenmechanische Rechnungen (MNDO) und Kraftfeldrechnungen (MM2) zeigen, das fur die drei konstitutionsisomeren cis-9-Oxabicyclo[6.1.0]nonine 1–3 jeweils zwei energiearme, zueinander diastereomere Konformere a und b existieren. Der synthetische Zugang zu den hoch gespannten Verbindungen 1–3 gelingt mit der Selenadiazolmethode oder durch Dehydrobromierung (Schemata 3, 4 und 6). Die NMR-spektroskopische Konformationsanalyse bestatigt bei 2 das vorhergesagte Konformerengleichgewicht; bei 1 gehen selbst bei –60°C die beiden Konformeren durch Umklappen des Achtrings schnell ineinander uber, und bei 3 ist praktisch nur eine Konformation populiert. 9-Oxabicyclo[6.1.0]nonynes Semie…

Organoselenum chemistry I. Functional Group Transformations. Von A. Krief und L. Hevesi. Springer, Berlin 1988. XI, 221 S., geb. DM 186.00. – ISBN 3-540-18629-8

ChemInform Abstract: Cycloaddition Reactions of Benzothiete and Hetero Dienophiles for the Synthesis of Heterocyclic Systems.

Abstract Benzothiete ( 1 ) undergoes cycloaddition reactions with hetero dienophiles with NN-, NO- or CO- double bonds, leading to six-membered heterocyclic ring systems of 2H-3,4-dihydro-1,2,3-benzothiadiazine ( 3 ), 4H-3,1,2-benzoxathiazine ( 4 ) and 4H-3,1-benzoxathiin.

Star-Shaped Conjugated Systems

The present review deals with the preparation and the properties of star-shaped conjugated compounds. Three, four or six conjugated arms are attached to cross-conjugated cores, which consist of single atoms (B, C+, N), benzene or azine rings or polycyclic ring systems, as for example triphenylene or tristriazolotriazine. Many of these shape-persistent [n]star compounds tend to π-stacking and self-organization, and exhibit interesting properties in materials science: Linear and non-linear optics, electrical conductivity, electroluminescence, formation of liquid crystalline phases, etc.

4,4′‐Distyrylazobenzol als Chromophor

4,4′-Distyrylazobenzene as Chromophore 4,4′-Distyrylazobenzenes are prepared from 4,4′-dimethylazobenzene. Whereas the Siegrist method furnishes stereoselectively the (E,E,E) configuration, a Wittig olefination leads to a mixture of (Z,E,Z), (Z,E,E) and (E,E,E) isomers which can be easily separated. Irradiation of the intense absorption at λ ≈ 400 nm causes a selective (E) (Z) isomerization of the N = N bond of all three isomers. The reverse reaction takes part in the photochemical equilibration, moreover, it is a thermal process with a relatively low activation barrier.

Kinetische Untersuchungen zur Bildung der E ‐ und Z ‐Enole bei der Thermolyse von 2‐Diazo‐1,3‐dimesityl‐1,3‐propandion in Nucleophilen

Bei der Thermolyse der Diazoverbindung 1 in Ethanol bzw. Piperidin oder Morpholin entstehen die Enole 3a–c von β-Ketocarbonsaurederivaten. Z- und E-Konfigurationen stehen miteinander im Gleichgewicht. Die Bestimmung der Geschwindigkeits-konstanten zeigt, das sich zunachst bevorzugt die Z-Formen bilden; im Gleichgewicht dominieren jedoch schlieslich in den Thermolysemedien die E-Isomeren. In aprotischen, apolaren oder masig polaren Medien uberwiegen dagegen die Z-Isomeren mit einer intramolekularen Wasserstoffbrucke. Investigation on the Kinetics of the Formation of E- and Z-Enols in the Thermolysis of 2-Diazo-1,3-propanedione in Nucleophiles Thermolysis of the diazo compound 1 in ethanol an…

Oligo(1,4-phenylenepyrazole-3,5-diyl)s

The bifunctional nucleophile methylhydrazine reacts in an alkaline medium in a regioselective mode with chalcones to yield 2-pyrazolines, which can be oxidized by DDQ to the corresponding 1H-pyrazoles. From oligo(chalcone)s this reaction yields cross-conjugated compounds with an alternating sequence of 1,4-disubstituted benzene rings and 3,5-disubstituted 1H-pyrazole rings. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Synthesis of pyrido[2,3-d]pyrimidinones by the reaction of aminopyrimidin-4-ones with benzylidene meldrum's acid derivatives

A series of pyrido[2,3-d]pyrimidine-4,7-diones 5a-h were prepared from 6-amino-4-pyrimidones 1 and benzylidene Meldrum's acid derivatives 2 by cyclization reactions in boiling nitrobenzene. The structure of 5, determined by nmr measurements, reveals a selective orientation of 1 and 2 in the addition step.

Synthesis of phenothiazine-based di-anchoring dyes containing fluorene linker and their photovoltaic performance

Abstract A new di-anchoring organic dye based on phenothiazine featuring A-D-π-D-A (acceptor-donor-π-linker-donor-acceptor) configuration with fluorene as the π linker was designed and successfully synthesized. Compared to the corresponding mono-anchoring D-A congener, this new dye exhibited a broader and stronger absorption in the light wavelength ranging from 400 nm to 600 nm and thus showed a more efficient photovoltaic performance for dye-sensitized solar cells (DSSCs). The overall power conversion efficiency (η) of this new dye in a sensitized solar cell amounted to 5.70%, which is 17% higher than that of the equivalent based counterpart (4.87%). On the other hand, the introduction of …

Cyclecondensation of 3-amino-1,2,4-triazole with substituted methyl cinnamates

The reaction of 3-amino-1,2,4-triazole (1) with substituted methyl cinnamates 2a-h leads selectively to the formation of 7-aryl-6,7-dihydro[1,2,4]triazolo[1,5-a]pyrimidin-5(4H)-ones 3a-h. The structure eluci dation of the products is based on ir, 1H and 13C nmr measurements and X-ray diffraction.

2,5-Dialkoxysubstituierte Oligo- und Poly(1,4-phenylenethenylen)e

2,5-Dialkoxy Substituted Oligo- and Poly(1,4-phenyleneethenylene)s O-Alkylation and regioselective Rieche formylation of 2-methylhydroquinone (1) yields the 2,5-dialkoxy-4-methylbenzaldehydes 4a–j. The corresponding azomethines 5a–j enter in a strongly alkaline medium a selfcondensation reaction leading to the title compounds 6/7a–j. These conjugated oligomers and polymers possess highly regular structures with exclusively (E)-configurated double bonds. GPC, IR, 1H-, 13C-NMR and MS-FD measurements were used for their characterization. Somewhat different results were obtained for the similarly prepared Schiff base 5l which contains chlorine substituents in the side chains. Cleavage of hydrog…

The reaction of 2,4,5,6-tetraaminopyrimidine with chalcones

The reaction of the tetraaminopyrimidine 1 with the chalcones 2a-f yields, in the presence of catalytic amounts of acetic acid, the 1H-pyrimido[4,5-b][1,4]diazepine derivatives 3a-f. The cyclization process consists of a condensation reaction and a Michael type addition.

Extended conjugation in stilbenoid squaraines

Abstract Squaraines, two-fold condensation products in 1,3-position of squaric acid, represent dyes or pigments of high actuality. After their first boom in electrophotography diverse applications are presently studied in a wide area of research, which reaches from electrooptical materials to biosensors and compounds used in photodynamic therapy. Absorption and/or emission ranges in the NIR are mandatory for many of these techniques. The present article deals with stilbenoid squaraines, which feature an extended conjugation in their biradicaloid D-π-A-π-D structure. Due to the charge-transfer character of the excitation, boundaries are set for the optimal length of the conjugation. The abso…

Durch sterische effekte stabilisierte ß-ketocarbonsäuren

Abstract Increasing steric hindrance in β-keto carboxylic acids leads to an increasing kinetic stability towards decarboxylation, till systems are reached which are completely stable at room temperature. Simultaneously the tautomeric equilibrium is changed in favour of the (Z)-enol, and finally in favour of the (E)-configurated enol.

ChemInform Abstract: Poly(propylene imine) Dendrimers Functionalized with Stilbene or 1,4-Distyrylbenzene Chromophores.

Abstract Two generations of dendritic nanoparticles were prepared, which contain ( E )-stilbene or ( E , E )-1,4-distyrylbenzene chromophores in the 4 or 8 terminal positions of the propylene imine dendrons. The compounds show a highly efficient photoreactivity. On prolonged irradiation all stilbenoid chromophores were destroyed by oligomerization (crosslinking) and the typical absorption and fluorescence of the chromophores disappeared completely.

1‐Oxa‐3‐cyclooctin

1-Oxa-3-cyclooctyne According to an MNDO calculation, 1-oxa-cyclooctyne (13) and 1-oxa-3-cyclooctyne (14) are 8-membered heterocyclic ring systems with high steric energy (ring strain). On the basis of THF (1) and acetoacetic ester (4), a multi-step synthesis is described for 14. The triple bond is introduced in the last step by a thermal fragmentation of the 1,2,3-selenadiazole 12.

Naphthothiete und ihre Anwendung in der Heterocyclen-Synthese

Naphtothietes and Their Application to the Synthesis of Heterocycles The three isomeric naphthothietes 5, 11, and 16 were prepared according to the reaction sequences shown in Schemes 1–3. The final step was in each case a flash vacuum pyrolysis (FVP) of the corresponding mercaptonaphthalenemethanol 4, 9, and 15, respectively. The thiete rings in 5 and 11 can be opened by gentle heating; the ring opening of the isomer 16 possesses a much higher activation barrier. A MNDO calculation of the ΔHf values of 5, 11, and 16 and the open isomers 5′, 11′, and 16′ provides an explanation for the different behavior. Photochemical ring opening represents a useful alternative. The reaction Schemes 4, 6,…

The reaction of aromatic α,β-unsaturated ketones with 4,5-diamino-1,6- dihydropyrimidin-6-ones

The reaction of 4,5-diamino-1,6-dihydropyrimidin-6-ones 1 with one equivalent of the chalcones 2 leads in an acidic medium to the formation of the 2,4-diaryl-2,3,6,7-tetrahydro-1H-pyrimido[4,5-b][1,4]diazepin-6-ones 3a-m. The structure elucidation of the products is based on detailed nmr investigations including selective 13C[1H] decoupling experiments.

Synthesis of Tetrastilbenylmethanes by Wittig−Horner Reactions

The all-(E)-configured tetrastilbenylmethanes 3a−e and 5a,b can be obtained by fourfold Wittig−Horner reactions. The tetrahedral arrangement of these compounds guarantees independent stilbenoid chromophores with a high chromophore density. Apart from (E)/(Z) isomerization reactions, irradiation leads to a three-dimensional network with isolated unchanged stilbene units. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Double D–π–A branched dyes – a new class of metal-free organic dyes for efficient dye-sensitized solar cells

Double branched donor acceptor compounds (D–π–A)2L, whose separate branches are linked by saturated chains or ring systems, are highly promising sensitizers for dye-sensitized solar cells (DSSCs). Their photovoltaic performance η (power conversion efficiency PCE) is higher than the η value of the corresponding single branched sensitizers D–π–A. This advantage can be attributed to the lower aggregation tendency and to the higher loading density of the chromophores on the semi-conductor surface (TiO2). Moreover, the intramolecular transfer of the excitation energy can enhance the contact time of the adsorbed dye molecules in the excited state S1 and thus reduce the unwanted charge recombinati…

High electrical conductance of single molecules: a challenge in the series of conjugated oligomers.

En route to molecular electronics: As extended, conjugated oligomers are desirable for molecular electronics, their electrical conductance should display a low attenuation factor. Zinc-complexed oligo(ethynyleneporphyrindiylethynylene)s have been prepared that are distinguished by ultralow attenuation factors in single-molecule conductance.

Cycloaddition reactions of benzothiete and hetero dienophiles for the synthesis of heterocyclic systems

Abstract Benzothiete ( 1 ) undergoes cycloaddition reactions with hetero dienophiles with NN-, NO- or CO- double bonds, leading to six-membered heterocyclic ring systems of 2H-3,4-dihydro-1,2,3-benzothiadiazine ( 3 ), 4H-3,1,2-benzoxathiazine ( 4 ) and 4H-3,1-benzoxathiin.

A pillar[5]arene-containing cross-linked polymer: synthesis, characterization and adsorption of dihaloalkanes and n-alkylene dinitriles

A pillar[5]arene-containing cross-linked polymer was synthesized via Williamson reaction involving monohydroxy pillar[5]arene with chloromethylated polystyrene. Its adsorption behavior towards guests was investigated. It was found that the pillar[5]arene-containing polymer exhibited good adsorption capacities towards dihaloalkanes and dinitriles by host-guest complexation.

Die Cycloaddition von 4‐Phenyl‐1,2,4‐triazolin‐3,5‐dion an 9,10‐Diallylidenbicyclo[6.2.0]deca‐1(8),2,6‐trien

Das Dimere 2 von 1,5-Cyclooctadien-3-in (1) bildet mit 4-Phenyl-1,2,4-triazolin-3,5-dion (PTD) ein Bisaddukt 6. Nach den spektroskopischen Daten kommt eine der symmetrischen Strukturen a–d in Frage. Die Rontgenstrukturanalyse beweist die Konstitution c. Die beiden PTD-Molekule reagieren demnach nicht nur in einer doppelten regiospezifischen [π2s + π4s]-Cycloaddition, sondern greifen auch stereospezifisch von derselben Seite an. Von den Rontgenstrukturdaten ist besonders die Konformation des Tricyclo[8.6.0.02,9]hexadeca-3,8,11,16-tetraen-Grundgerustes hervorzuheben, die aus zwei bootformigen Achtringen und einem zentralen, leicht gefalteten Vierring besteht. Cycloaddition of 4-Phenyl-1,2,4-t…

Rearrangement of the carbon skeleton in the intramolecular photoadduct of anthracene and benzene rings

Abstract The effectivity of optical switching between anthracene derivatives 3a,b and their intramolecular photocycloadducts 4a,b is impaired by traces of acid. The systematic treatment of 4a,b with an increasing excess of formic acid revealed that—apart from the normal enolether cleavage 4a,b → 6a,b → 7a,b —a cleavage with rearrangement of the carbon skeleton can occur: 5b → 6b′ . The driving force is a stability enhancement of the involved carbenium ions 5b → 5b′ . A further increased excess of formic acid leads finally to a competitive ether cleavage in the tetrahydrofuran ring 5b → 8 .

Optical Switching and Antenna Effect of Dendrimers with an Anthracene Core

Dendrimers 6G(i) (i=1-4) consisting of an anthracene core and Fréchet dendrons which are attached via a CH(2)OCH(2) chain in the 9-position undergo quantitative and completely reversible intramolecular [4pi+4pi] cycloaddition. The process can be monitored by absorption and fluorescence measurements. The Fréchet dendrons act as an energy funnel that collects and focuses the photon energy but does not change the photostationary states, which for both directions are completely on the product side when the separate chromophores are selectively irradiated. The quantum yields of anthracene fluorescence and of singlet energy transfer from the dendrons to the core were studied as a function of dend…

Cycloaddition von Benzothiet an 4‐substituierte Styrole

Durch thermische Ringoffnung entsteht aus Benzothiet (1) ein 8-π-Elektronensystem 2, das mit den 4-substituierten Styrolen 3a–j die Cycloaddukte 4/5a–j bildet. Die Erhohung der Reaktivitat durch elektronenspendende oder elektronenanziehende Reste und die Einflusse auf die Regioselektivitat werden an Hand von Grenzorbitalbetrachtungen diskutiert. Cycloaddition of Benzothiete of 4-Substituted Styrenes By thermal ring opening benzothiete (1) generates an 8-π electron system 2, which forms the cycloadducts 4/5a–j with 4-substituted styrenes 3a–j. The enhancement of the reactivity by electrondonating as well as electron-withdrawing substituents and their influence on the regioselectivity are dis…

Stronger host-guest binding does not necessarily give brighter particles: a case study on polymeric AIEE-tunable and size-tunable supraspheres.

Supraspheres were prepared from a pillar[5]arene-based linear polymer (the host) and several multitopic guests. According to host-guest binding studies in nanosystems, the optical and structural properties (fluorescence capability, density, and particle size) of the nanoparticles were correlated not with the host-guest binding affinities, but with the relative fluorescence quantum yield.

Polymerisation und Kettenverknüpfung von Alkenyl-1,2,3-thiadiazolen

4- und 5-Vinyl-1,2,3-thiadiazole 1, 2 lassen sich in radikalischen oder kationischen Kettenreaktionen polymerisieren. Die dabei vollstandig intakt bleibenden Thiadiazolringe konnen photochemisch abgebaut werden, wobei es zur Kettenvernetzung uber substanzeigene S-Brucken kommt. Das 5-Vinylsystem 2 kann mit 4,4′-(1,6-Hexandiyl)bis(4H-1,2,4-triazol-3,5-dion) unter Denitrogenierung copolymerisiert werden. Polymerization and Cross-Linking of Alkenyl-1,2,3-thiadiazoles 4- and 5-Vinyl-1,2,3-thiadiazoles 1, 2 can be polymerized in radical or cationic chain processes. The completely intact remaining thiadiazole ring systems can be photochemically cleaved yielding a cross-linking of the polymer chai…

Blau fluoreszierende Exciplexe austrans-Stilben und Antikörpern

Pillarquinones and Pillararenequinones

Optical switches with biplanemers obtained by intramolecular photocycloaddition reactions of tethered arenes.

The dimerization of anthracene by a [4π + 4π] cycloaddition is one of the oldest and best known reactions in photochemistry. In the series of tethered bichromophoric arenes, this reaction type could be extended to anthracene–naphthalene, naphthalene–naphthalene and recently even to anthracene–benzene and naphthalene–benzene systems. Cyclophanes, which can be regarded as twofold or multiple tethered systems, are not discussed here. The cycloisomerizations are performed by irradiation at the long-wavelength absorption (λ > 270 nm), whereas shorter wavelengths (λ < 270 nm) lead to cycloreversions, which can be also achieved by a thermal route. The systems represent therefore a P- and T-type ph…

ChemInform Abstract: trans- and cis-Bicyclo(n.1.0)alk-2-ynes of Medium Ring Size.

Starting from cycloalkenes, the cis- or trans-cyclopropano anellated cycloalkynes 2–7 of medium ring size were synthesized. The triple bonds were introduced in the final reaction step either by the fragmentation of the corresponding 1,2,3-selenadiazoles or by direct dehydration of a ketone (Scheme 2). The cis-fused bicycles 2 and 3 and the trans-fused bicycles 5, 6 and 7 could be isolated in a pure state. The intermediary existence of the most strained system trans-bicyclo[7.1.0]dec-2-yne (4) was proven by trapping reactions.

BENZOTHIETES—VERSATILE SYNTHONS FOR THE PREPARATION OF HETEROCYCLES

Abstract Thermal or photochemical ring opening transforms benzo[b]thiete to o-thiobenzoquinonemethide, a highly reactive 8π electron system. Cycloaddition reactions or linear additions with subsequent cyclizations lead to larger heterocyclic rings. A variety of compounds containing sulfur and possibly further heteroatoms like nitrogen, oxygen or phosphorus in normal, medium and large ring systems can be synthesized on this route.

Synthese und Kristallstrukturanalyse eines 2,4-Diaryl-2,3-dihydro-1H-1,5-benzodiazepins / Synthesis and Crystal Structure Analysis of a 2,4-Diaryl-2,3-dihydro-1H-1,5-benzodiazepine

Abstract The enone unit of chalcones is a synthetically valuable substructure for the formation of heterocycles. Whereas propoxy groups as solubilizing side chains on the phenyl groups do not much affect the generation of pyrazole and pyridine rings, they reduce significantly the yield of the diazepine ring system 4. We attribute this effect to the large twist angles between the ring planes, which are demonstrated by a crystal structure analysis.

Molecular design of the diketopyrrolopyrrole-based dyes with varied donor units for efficient dye-sensitized solar cells

Abstract Three types of novel diketopyrrolopyrrole-based organic dyes ( Type 1 – 3 ) with phenyl unit as an additional π -bridge and triphenylamine or phenothiazine as the donors are designed and synthesized for dye-sensitized solar cells (DSSCs). Type 1 dyes incorporating the donor segment directly to the diketopyrrolopyrrole core lead to a better electron communication between the donor and acceptor, allowing an efficient charge transfer process. Type 2 and Type 3 dyes with a phenyl unit between the donor and diketopyrrolopyrrole unit show lower delocalization of the excited state. Compared with Type 3 dyes, Type 1 dyes exhibit higher conjugated skeleton co planarity and shorter electron …

Areno-Condensed 1,7,13-Triaza[18]annulenes

The 1,7,13-triaza[18]annulenes 9a−c were prepared by multi-step processes in which the final step consisted of a threefold cyclic condensation reaction of the Schiff bases 8a−c. Due to the length of the nine peripheral alkoxy chains, discotic liquid crystalline phases were obtained for 9b,c. The three nitrogen atoms in the central 18-membered ring not only permit protonation, but they can also serve for the complexation of NH4+ ions. The compounds 9a−c are highly photosensitive and exhibit crosslinking reactions on irradiation.

Bis-, Tris-, and Tetrakis(squaraines) Linked by Stilbenoid Scaffolds

The oligosquaraines 1−5, with stilbenoid scaffolds, were prepared by multistep syntheses in which the final steps consisted of condensation reactions between the semisquaric acid 21 and multiple resorcinols 12b−15b and 17b. The target compounds exhibit intense (ϵ > 250000 L·mol−1·cm−1) and sharp absorption bands with maxima between 687 to 778 nm, depending on the conjugation in the stilbenoid scaffold. Comparison with the monosquaraine 6 as a model compound reveals intramolecular interactions between different donor−acceptor−donor moieties, which give rise to increased absorption intensities.

Photochemie des 1,3,5‐Tristyrylbenzols

In Abhangigkeit von den Reaktionsbedingungen erhalt man bei der Belichtung der Titelverbindung 1 das Cyclophan 5, das Pyrenderivat 6 oder das polykondensierte aromatische System 9. Fur den neuen Cyclophantyp 5, bei dem zwei Benzolringe selbst wieder durch Ringe verbruckt sind, wurde eine Rontgenstrukturanalyse durchgefuhrt. Photochemistry of 1,3,5-Tristyrylbenzene Depending on the reaction conditions the irradiation of the title compound 1 yields the cyclophane 5, the pyrene derivative 6, or the polycondensed aromatic system 9. An X-ray analysis was performed for 5, representing a new type of cyclophane in which two benzene rings are bridged again by rings.

Aggregation and Photodimerization of Areno-Condensed Annulenes

Photo-Crosslinking of Copolymeric Methacrylates Bearing Stilbene Chromophores

Radical polymerization of methyl methacrylate (2) as major component and the methacrylates 1a or 1b, which contain an (E)-stilbene unit fixed by a tether to the ester group, yield easily soluble copolymers 3a, b. Whereas the dominant photoreactions in solution are (E)⇄Z) isomerizations and intra-chain [2π +2π] cycloadditions, cast films of 3a, b give an inter-chain photo-crosslinking on irradiation. Compared to homopolymers, the copolymers are not only better soluble and more easily processible, their films show less undesired light scattering. The cross-linked material is completely insoluble in organic solvents. Thus, it represents the basis for negative photoresists and the corresponding…

Book Review: Organoselenium Chemistry I. Functional Group Transformations. By A. Krief and L. Hevesi

Synthese von Benzo[b]thioxanthenen

Synthesis of Benzo[b]thioxanthenes Benzo[b]thioxanthenes, heterocyclic compounds related to tetracenes and tetracyclines can be obtained by the reaction of 2H-benzo[b]thiete (1) and 1,4-naphthoquinones (3a–g). The primary cycloadducts 4a–g undergo an autoxidation process leading to the quinones 6a–g. The dihydroxy compound 4e shows an additional isomerization by a tetrafold H transfer (4e 5e′). Another preparative route to benzo[b]thioxanthenes makes use of the cycloadditon reaction of 1 and 1,4-epoxynaphthalenes (7a–d). The primary adducts can be transformed to the title compounds by catalytic dehydration processes (8a–d 9a-d). An alternate regioselective opening of the oxygen bridge can b…

Unambiguous structure elucidation of heterocyclic products from condensation-cyclisation reactions of enaminones by 2D INADEQUATE and 15 N NMR

The reaction of enaminones with 3-amino-2-cyanopent-2-enedinitrile can lead to an array of 12 possible products, depending on the reaction pathway and tautomerization. The use of 2D INADEQUATE and 15N NMR for the unambiguous structure elucidation of the reaction products is discussed in this manuscript. Copyright © 2012 John Wiley & Sons, Ltd.

A facile and efficient preparation of pillararenes and a pillarquinone.

Konvergenz von Absorption und Fluoreszenz bei gekreuzt konjugierten Oligomeren aus Chalkon-Bausteinen

The absorption and fluorescence spectra of two series of chalcone oligomers (1a–d) and (2a–d) are reported. Due to small or vanishing orbital coefficients (HMO calculation) within the cross-conjugated systems, the bathochromic shifts caused by the extension of the chains are modest. The effective conjugation lengths amount to 6 and 14 chalcone building blocks in the absorptions of the series 1 and 2. The convergence of the fluorescence bands is already reached in 1d and 2d with 4 and 8 enone units, respectively. Besides the uniform or alternate arrangement of the chalcone building blocks, the positions of the propoxy substituents show a considerable influence on the electronic transitions p…

ChemInform Abstract: Anti-Bredt Enol Ethers by Transannular Cyclization of Cycloalkynols.

Photochemie elektronenreicher 1,3‐Distyrylbenzole

Die 1,3-Distyrylbenzole 3 mit bis zu sieben Alkoxygruppen werden der oxidativen Photocyclisierung unterworfen. Bei der Bildung der Produkte 6, 7 und 8 konnen als Konkurrenz- bzw. Folgeprozesse die Abspaltung von Methanol (3bb 7bb, 3bf 7bf) und die Chinonoxidation (3cf 8) auftreten. Die eigensensiblisierte Erzeugung von Singulettsauerstoff kann bei 6bf zur Endoperoxidbildung fuhren (6bf 11). Photochemistry of Electron-Rich 1,3-Distyrylbenzenes The 1,3-distyrylbenzenes 3, containing up to seven alkoxy groups, are subjected to the oxidative photocyclization. Elimination of methanol (3bb 7bb, 3bf 7bf) and quinone oxidation can occur as competitive or consecutive reactons in the formation of the…

Oligo(2,5-thienyleneethynylene)s with Terminal Donor-Acceptor Substitution

Five oligo(2,5-thienyleneethynylene) series (OTE, n = 1–5), namely the push-pull substituted compounds 1b-5b and 1c-5c, the purely donor substituted compounds 1a-5a and two precursor series with protected and deprotected ethynyl end-groups, respectively, were obtained by a convergent synthetic strategy. The extension of the conjugated chromophores in the donor-acceptor OTE (DAOTE) series is superimposed by an intramolecular charge transfer (ICT), which decreases with an increasing number, n, of repeat units. The overall effect is studied by the convergence of the UV/Vis absorption maxima λmax (n) → λ∞ for n → ∞.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

A versatile synthesis of 4,5-dihydropyrrolo[1,2-a]quinoxalines

The reaction of 1-(2-aminophenyl)pyrrole with aromatic or heteroaromatic aldehydes in ethanol and catalytic amounts of acetic acid leads to 4,5-dihydropyrrolo[1,2-a]quinoxalines in high yields. When aliphatic aldehydes were used under the same conditions, a slow oxidation to the corresponding pyrrolo[1,2-a]quinoxalines can occur; the oxidation can be avoided by preparing in situ the 5-acetyl derivatives of the 4,5-dihydropyrrolo[1,2-a]quinoxalines.

Light-emitting diodes based on phenylenevinylene oligomers with defined chain lengths

Abstract We present characteristic electroluminescence data on single-layer devices based on three different oligo phenylenevinylene compounds with defined chain lengths. Light-emitting diodes (LEDs) were prepared by subsequent vacuum evaporation of the oligomer film and the A1 top electrode onto an indium—tin oxide (ITO) substrate. The LEDs show light emission in the spectral range of yellow to orange depending on the conjugation length of the compound used. We report photoluminescence and optical absorption data of the thin sublimed films, together with the wavelength dependence of the electroluminescence and with the current—voltage characteristics of the LED devices. The redox behavior …

Synthese von Oligo(p-phenylen-m-pyridindiyl)en

Cycloadditionen von 2H ‐Benzo[ b ]thiet und Verbindungen mit kumulierten Doppelbindungen

Cycloaddition Reactions of 2H-Benzo[b]thiete and Compounds with Cumulated Double Bonds o-Thiobenzoquinone methide (2), generated by thermal ring opening of 2H-benzo[b]thiete (1), reacts with allene 3, ketene imine 7, the carbodiimides 9a-c, and the N-sulfinylamines 11a-c in highly specific [8π + 2π] cycloaddition processes to form novel types of heterocyclic systems 4, 8, 10a-c, and 12a-c with exocyclic double bonds. The 1:1 adduct 4 can add a further molecule of allene to yield the spiro compounds 5 and 6.

CCDC 1811268: Experimental Crystal Structure Determination

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CCDC 861196: Experimental Crystal Structure Determination

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CCDC 882877: Experimental Crystal Structure Determination

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CCDC 902683: Experimental Crystal Structure Determination

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CCDC 838314: Experimental Crystal Structure Determination

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