Complexation of M3+Lanthanide Cations by Calix[4]arene-CMPO Ligands: A Molecular Dynamics Study in Methanol Solution and at a Water/Chloroform Interface

Abstract We report a molecular dynamics study on the 1:1 M3+ lanthanide (La3+, Eu3+ and Yb3+) inclusion complexes of an important extractant molecule L: a calix[4]arene-tetraalkyl ether substituted at the wide rim by four NH-C(O)-CH2-P(O)Ph2 arms. The M(NO3)3 and MCl3 complexes of L are compared in methanol solution and at a water / chloroform interface. In the different environments the coordination sphere of M3+ involves the four phosphoryl oxygens and three to four loosely bound carbonyl oxygens of the CMPO-like arms. Based on free energy simulations, we address the question of ion binding selectivity in pure liquid phases and at the liquid-liquid interface where L and the complexes are …

Calix[4]arene-functionalized naphthalene and perylene imide dyes.

[reaction: see text] Calix[4]arenes bearing one, two, or four 1,8-naphthyl imide groups at the wide rim and bis-calix[4]arenes connected via perylene-bisimide dye spacers have been synthesized. The low-temperature NMR spectrum of the tetranaphthylimide suggests, in agreement with a crystal structure, a C2-symmetrical pinched cone conformation stabilized via face-to-face pi-pi interactions between opposite naphthylimide groups. UV-vis and fluorescence studies have been carried out for the perylene bis-calix[4]arene dyes.

Extraction of lanthanides and actinides by a magnetically assisted chemical separation technique based on CMPO-calix[4]arenes

A novel particulate system carrying CMPO ligands pre-organised on a calixarene scaffold has been synthesised and demonstrated to extract Eu3+, Am3+ and Ce3+ at high efficiency from simulated nuclear waste streams.

Selective derivatisation of resorcarenes: 1. The regioselective formation of tetra-benzoxazine derivatives

Abstract Four 5,6-benzo-1,3-oxazine rings are formed by the condensation of resorcarenes with various aliphatic or aromatic primary amines and formaldehyde. From four possible regioisomers only the C4 symmetrical compound is isolated in yields of up to 90%. Semiempirical calculations confirm its relative stability, which is due to the possible formation of four intramolecular OH…O hydrogen bonds. The regioselectivity of the reaction is further established for two examples by single crystal X-ray analysis. A solvent molecule is included in the extended cavity.

Unexpected Conformational Behaviour of a Diphosphate Derived from a Spherand-Type Calixarene

The spherand-type calixarene 2a, which consists of three diphenol units linked by methylene bridges, was treated with phosphorus pentachloride and then with water. A C1-symmetrical conformation was found for the resulting bisphosphate 7 in the crystalline state by X-ray analysis, with an anti orientation of the phosphoryl groups. MM3 calculations lead to a nearly identical conformation for the most stable isomer (RRS-twist), while a slightly higher energy was found for an RRS-crown isomer with a syn orientation of the phosporyl groups. Surprisingly, all NMR studies (1H, 13C and 31P) of 7 are in agreement with a dynamic C2 symmetry in solution. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Wein…

Friessche Verschiebung vonortho- undpara-Methoxyphenylacetaten. Die Bildung von Ketoestern

During theFries rearrangement ofo- andp-methoxy phenyl acetates with AlCl3 in nitromethane at 20°C substitution occurs mainly in thep-position of the phenolic residue to yieldp-acylphenols. Larger quantities ofo-acylphenols are obtained only, if thisp-position is already substituted. Witho-methoxy phenyl acetates the substitution of the acid residue to yield ketoesters is observed as a side reaction. Those ketoesters are obtained as main products if TiCl4 is taken as a catalyst.

Resorcarenes in the Boat Conformation as Building Blocks for Hydrogen-Bonded Assemblies Including Two Ammonium Cations

Crystal structures are reported for various co-crystals of rccc-resorcarenes with triethylammonium chloride. Usually, two molecules of a C2v-symmetric tetraester 2 in the boat conformation are linked through four hydrogen-bonded chloride anions to give dimeric assemblies. Two of the chloride anions may be replaced by four hydrogen-bonded ethanol molecules in an otherwise similar structure. These assemblies, which consist of six or eight components, posses voluminous, negatively charged chambers in which two triethylammionium cations, 3+, are included as guests by strong electrostatic and hydrogen-bonding interactions. The host-guest N-H...Cl hydrogen bonds were clearly detected at 173 K. Th…

Das kondensationsverhalten hydroxy- und chlormethylierter phenole und anisole mit dimethylphenolen

Selective derivatisation of resorcarenes. Part 5. Acylation of tetrabenzoxazine derivatives

The reaction of the tetrabenzoxazines 2 with acetic anhydride under mild conditions leads selectively and exclusively to the tetraamides 3 in which the oxazine rings are opened; their structure was deduced from their 1H NMR spectra and confirmed for one example by an X-ray single crystal structure analysis; acylation of the hydroxy groups was not observed.

Reasons for the exclusive formation of heterodimeric capsules between tetra-tolyl and tetra-tosylurea calix[4]arenes

The selective heterodimerization of tetra-tolyl (1a) and tetra-tosylurea (1b) calixarenes, serendipitously found by Rebek et al. (R. K. Castellano, B. H. Kim and J. Rebek, Jr., J. Am. Chem. Soc., 1997, 119, 12671–12672), has been used for the construction of highly sophisticated macrocycles and well-defined supramolecular assemblies. Regrettably, hitherto, neither the exact structure of these heterodimers nor the reason for their exclusive formation is known. We present molecular dynamics simulations using the AMBER force field in explicit chloroform solvent for the two homodimers, the heterodimer and the two uncomplexed tetra-urea calixarenes. The rigid rotation about the C–S–N–C bond of t…

Discontinuous electrokinetic chromatography of parabens using different substituted resonances as pseudostationary phases

Resorcarene derivatives, negatively charged even at moderate pH, were synthesized and employed as pseudostationary phases to achieve mobilities exceeding that of the electroosmotic flow. Under these conditions, a discontinuous electrolyte system was developed which allows the separation of four uncharged homologous 4-hydroxybenzoic esters (parabens) within a zone of resorcarene electrolyte, and the detection of these UV active compounds in a resorcarene-free zone, free from the high UV background absorbance of the resorcarenes. Resorcarenes, with differently charged functionalities (carboxylate and phosphate groups) to provide the electrophoretic mobility and with alkyl residues of differen…

Bis-ferrocene derivatives of bridged calix[4]arenes: syntheis, X-ray crystal structure and electrochemical properties

The reaction of chlorocarbonylferrocene (2) with bridged calix[4]arene macrocyclic compounds, in which two opposite para-positions are connected by an additional aliphatic chain where n = 5 (1a) or n = 8 (1b) respectively, gave the corresponding new redox-active bis-ferrocene derivatives of bridged calix[4]arenes, 3a and 3b. An X-ray diffraction study of 3a shows that the caliz[4]arene has a cone conformation in which the two ferrocene substituents are located on the phenolic units connected to each other by the aliphatic chain bridge. Cyclic voltammetric and coulometric studies in dichloromethane reveal that 3a and 3b undergo reversible two electron oxidations at + 0.90 V (versus SCE), sug…

New Molecular Topologies by Fourfold Metathesis Reactions within a Hydrogen-Bonded Calix[4]arene Dimer

A calix[4]arene tetrapentyl ether in the cone conformation substituted at its wide rim by four m-(omega-octenyloxy)phenyl urea groups forms hydrogen-bonded dimeric capsules in dichloromethane/benzene (95:5). Metathesis reaction with Grubbs' catalyst under high-dilution conditions (1.1 x 10(-4) M) followed by hydrogenation leads to a covalent connection of all the urea groups within a dimer. Three topologically different products may be expected in such a reaction: a bis[2]catenane, a doubly bridged monocatenane and a tetrabridged capsule. All three possible reaction products could be isolated in an overall yield up to 60 % for the separated and purified compounds. Their identification was b…

Ein Selbstordnungsschema für Tetraharnstoffcalix[4]arene

Grose und Form sind wichtig: Eine aquimolare Mischung aus elf unterschiedlich substituierten Tetraharnstoff-Calix[4]arenen bildet in unpolaren Losungsmitteln nur 6 von 35 moglichen Homo- und Heterodimeren. Da das Calixarengerust und die vier Harnstoffreste in allen Fallen gleich sind, wird dieser Prozess der Selbstorganisation allein durch das Zusammenwirken von sterischen und stochiometrischen Randbedingungen bestimmt.

Die kristallstruktur von oligo[(2-hydroxy-1,3-phenylen)methylen]en

The crystal structure of three tetranuclear phenolic compounds – 6,6′-bis (2-hydroxy-5-methylbenzyl)-4,4′-dimethyl-2,2′-methylenediphenol (1), 6-(2-hydroxy-3,5-dimethylbenzyl)-6′-(2-hydroxy-5-methylbenzyl)-4,4′-dimethyl-2,2′-methylendiphenol (2), and 6-(3-tert-butyl-2-hydroxy-5-methylbenzyl)-6′-(2-hydroxy-5-methylbenzyl)-4,4′-dimethyl-2,2′-methylene-diphenol (3) –, was determined by single crystal X-ray analysis. Intramolecular hydrogen bonds between all hydroxyl groups of adjacent phenolic units are found for all molecules. They are directed to the opposite end of the molecule by the ortho-methyl or ortho-tert-butyl group in compounds 2 and 3, while no special orientation is found in 1. Th…

The kinetics of the electrophilic bromination of 17 oligonuclear phenolic compounds with molecular bromine in acetic acid were studied at 22°C. Some of these compounds, consisting of up to 6 phenolic units, which are linked in ortho-position by methylene bridges, and having only one (or two) reactive ortho-position(s) at the end of the molecule, were synthesized for the first time. It could be shown, even for hexanuclear compounds, that the variation of substituents at one end of the molecule leads to a change in the reactivity at the other end, that means over a distance of 22 nonconjugated covalent links. So far, this can be explained only by a chain of intramolecular hydrogen bonds betwe…

Adamantylcalixarenes with CMPO groups at the wide rim: synthesis and extraction of lanthanides and actinides

Abstract Starting from p -adamantylcalix[4]- and [6]arenes functionalized with carboxylic acid or ester groups at the adamantane nuclei, carbamoylmethylphosphine oxide (CMPO)-containing ligands of a novel type were synthesized. They were studied as extractants for a series of f-block elements including radioactive 152 Eu(III), 241 Am(III), 233 U(VI), and 239 Pu(IV). Tetrameric ligand 4b in which CMPO residues are connected to adamantane nuclei through methylene groups gave the best extraction results for lanthanides and actinides. For all the ligands the extraction efficiency does not decrease at higher nitric acid concentration. Although the discrimination between trivalent actinides and l…

2,2′-Dimethyl-2,2′-(m-phenyl­ene­dimethyl­ene)propane­dinitrile

The title compound, C16H14N4, features an aromatic ring with two 2,2´-dicyanopropyl residues in positions 1 and 3, which are located above and below the ring plane. The two residues differ in their conformation with respect to the aromatic ring: whereas one of the Cmethyl-C-Cmethylene-Caromatic torsion angles is gauche [68.93 (12)°], the other one is fully staggered [177.63 (9)°]. The crystal structure is stabilized by C-H...N hydrogen-bonding interactions. Key indicators: single-crystal X-ray study; T = 173 K; mean σ(C–C) = 0.002 Å; R factor = 0.037; wR factor = 0.101; data-to-parameter ratio = 15.0.

Tetra-urea calix[4]arenes 1,3-bridged at the narrow rim.

The synthesis of special tetra-urea calix[4]arene derivatives is described. Two propyl ether groups in 1,3-position and a 5-iodo-isophthalamide bridge connecting two aminopropylether residues in 2,4-position at the narrow rim keep the molecule fixed in the cone conformation. The aryl urea residues are substituted by decyloxy groups in p-position to increase the solubility in apolar solvents, while the iodo substituent allows further functionalization. Two single crystal X-ray structures of 3 and 4 show a strongly pinched cone conformation in which the bridged phenol units are bent outwards, while the phenol units bearing the propyl ether groups are nearly parallel. The molecules are flexibl…

Regio- and diastereoselective condensation of resorcarenes with primary amines and formaldehyde

Abstract Mannich reactions of resorcarenes 1 with chiral amines yield single diastereomeric tetrakis-(benzodihydro-1,3-oxazine) derivatives 2 in high yields (80–90%). Epimerisation of these products occurs in the presence of acid.

Multiple Catenanes Derived from Calix[4]arenes

A multicatenane is described in which two belts consisting of four annelated rings attached to the wide rims of two calix[4]arenes are interwoven in such a way that each ring of one belt penetrates two adjacent rings of the other belt and vice versa. The key step of the synthesis of this [8]catenane is the exclusive formation of preorganized heterodimers between a multimacrocyclic tetraurea calix[4]arene and an “open-chain” tetraurea calix[4]arene containing eight ω-alkenyl groups. When a tetraurea calix[4]arene containing four alkenyl groups is used, a bis-[3]catenane is formed analogously.

(o-Hydroxyphenyl)methylphosphonic Acids: Spectrophotometric determination of their pKavalues and of the deprotonation sequence

UV/VIS Absorption spectra of nitrosubsituted (o-hydroxyphenyl)methylphosphonic acids (o-(phosphonomethyl)phenols) were measured as a function of pH at 25° in 0.1M NaClo4 solutions. Computational treatment of the whole set of optical density data between 200 and 500 nm resulted in the determination of the dissociation constants of these polyacids and also of the individual electronic spectra of all the species involved in the deprotonation sequence. The spectral behavior gives information on the structure of the anions formed and consequently the order of the subsequent deprotonation steps could be deduced. For the (2-hydroxy-3-nitro(or 5-nitro)phenyl)methylphosphonic acid and the 2-hydroxy-…

Kinetik der bromierung von phenolen und phenolischen mehrkernverbindungen, 2. Die reaktionsfähigkeit isomerer zweikernverbindungen

Die Geschwindigkeit der Bromierung von 6 isomeren Zweikernverbindungen mit jeweils einer reaktionsfahigen Stelle (Hydroxydimethylbenzyl-methylphenole 1, 2 und 3) wurde in Eisessig bei 22°C UV-spektroskopisch bestimmt. Fur die Reaktion in ortho-Stellung zur phenolischen Hydroxy-Gruppe ergibt sich eine Verminderung der Geschwindigkeit um den Faktor 3–3,5 wenn zwischen den Hydroxy-Gruppen der beiden Phenolbausteine eine intramolekulare Wasserstoffbrucke sterisch moglich ist (1a). In den anderen Fallen (1b, 2a, 2b) verlauft die Bromierung ungefahr ebenso schnell wie bei 2,4-Dimethylphenol. Die schneller verlaufende Reaktion in para-Stellung (3a, 3b) wird durch eine Wasserstoffbrucke um den Fakt…

Rigidified Calixarenes Bearing Four Carbamoylmethylphosphineoxide or Carbamoylmethylphosphoryl Functions at the Wide Rim

Conformationally rigidified tetraCMPO derivatives have been prepared from calix[4]arene bis(crown ether) 4 a in which adjacent oxygens are bridged at the narrow rim by two diethylene glycol links. Acylation of the tetraamine 4 c with the CMPO-active ester 5 b gave the tetraphosphine oxide 6 a, while the tetraphosphinate 6 b and the tetraphosphonate 6 c were obtained by Arbuzov reaction of tetrabromoacetamido derivative 7 with PhP(OEt)2 or P(OEt)3. The extraction ability of these CMPO derivatives was checked for selected lanthanides and actinides and compared with the analogous compounds 1 b, 10 b and 10 d derived from calix[4]arene tetrapentyl ether. All rigidified bis(crown ether) ligands …

Double and triple calix[4]arenis connected via the oxygen functions

New macrocyclic molecules are described containing two or three p-tert-butylcalix[4]arene subunits connected via their oxygen atoms. These macrocycles are available by two general methods which are capable of producing assemblies with bridges of varying rigidity and length.

The first dissociation constant of oligonuclear phenolic compounds consisting of one nitrophenol unit besides further alkyl phenol units (10 dinuclear, 15 trinuclear, 6 tetranuclear compounds, and 4 nitrophenols as model) was determined spectroscopically in water/methanol (50/50 by vol.) at 25°C. For the ortho-linked title compounds with the nitrophenol unit at the end of the molecule a decrease of pK1 is observed which becomes stronger with increasing chain length. The introduction of bulky groups in ortho-position of the dissociating phenolic unit, as well as at the opposite end of the molecule causes a further decrease of pK1. The lowest value is found for a p-nitrophenol unit in the mid…

Structurally Uniform Oligomers

Model compounds as well as prototype reactions are frequently used to understand more complex chemical systems. In the case of phenolic resins a large number of model compounds have been synthesized. They are regarded as either components of a complex mixture of novolaks or resoles or as representative segments of the phenolic crosslinked network. These model compounds were formerly the basis for the correlation of physical properties to molecular structure. Presently the progress of analytical separations and identification methods is formidable; highly sophisticated chemical instrumentation allows the analysis of highly complex mixtures. Nevertheless, well defined compounds with definite …

Tetraurea Calix[4]arenes

Cyclic tetraureas with variable flexibility--synthesis, crystal structures and properties.

Macrocyclic molecules containing several amide or urea functions may serve as anion receptors. We describe the synthesis of 32-membered macrocycles, in which four rigid xanthene units (X) and/or diphenyl ether units (D) as flexible analogues are linked via urea groups. All six possible combinations of these units (XXXX, XXXD, XXDD, XDXD, XDDD and DDDD) were synthesized and two examples were characterised by single-crystal X-ray analyses (DDDD and two structures for XXXD). Both macrocycles showed distinct differences in their overall conformation and consequently in their hydrogen-bonding pattern. Hydrogen-bonded solvent molecules are found for both compounds and intramolecular hydrogen bond…

Mechanically interlocked calix[4]arene dimers display reversible bond breakage under force.

The physics of nanoscopic systems is strongly governed by thermal fluctuations that produce significant deviations from the behaviour of large ensembles1,2. Stretching experiments of single molecules offer a unique way to study fundamental theories of statistical mechanics, as recently shown for the unzipping of RNA hairpins3. Here, we report a molecular design based on oligo calix[4]arene catenanes—calixarene dimers held together by 16 hydrogen bridges—in which loops within the molecules limit how far the calixarene nanocapsules can be separated. This mechanically locked structure tunes the energy landscape of dimers, thus permitting the reversible rupture and rejoining of the individual n…

Self-assembled dendrimers with uniform structure

Calix[4]arenes substituted at their wide rim by four aryl urea residues (1) form hydrogen-bonded dimers in apolar solvents. Replacement of one urea residue by an acetamido moiety leads to calix[4]arene derivatives (5) which form hydrogen-bonded tetramers under the same conditions. Both self-assembly processes occur independently. Therefore, molecules have been prepared in which a tetra-urea calix[4]arene and a tri-urea mono acetamide derivative are covalently connected between their narrow rims by a long, mainly aliphatic chain [-O-(CH(2))(n)-C(O)-NH-(CH(2))(m)-O-] (7). In the presence of an equimolar amount of tetra-tosyl urea calix[4]arene () they form dendritic assemblies since the well …

Fourfold tetraurea calix[4]arenes--potential cores for the formation of self-assembled dendrimers.

Wide rim tetraurea calix[4]arenes monofunctionalized at the narrow rim by COOH or NH2 have been synthesized in five steps from t-butylcalix[4]arene tripropylether. Their covalent linkage via the narrow rim to a central calix[4]arene fixed in the 1,3-alternate conformation led to pentacalix[4]arenes 9 bearing four tetraurea derivatives in the cone conformation in a flexible tetrahedral arrangement. Their self-assembly via the formation of hydrogen bonded dimeric capsules has been studied under different conditions. A fourfold heterodimerisation of tetrakis-tetraurea derivatives of type 9 with tetratosylurea 10 has been confirmed by 1H NMR-spectroscopy and dynamic light scattering.

Orientational preferences of aromatic guests in dimeric capsules of tetraurea calix[4]arenes—MD and NMR studies

Molecular dynamics (MD) simulations have been performed for complexes of a dimeric capsule of a tetraurea calixarene with a series of twelve aromatic guests. A distinct orientational preference and a restriction of the internal mobility was found which depend on the size and electronic properties of the guests. The results are in agreement with the CIS values obtained from (1)H NMR spectroscopic measurements and with complexation selectivities obtained by competition experiments.

Synthesis of huge macrocycles using two calix[4]arenes as templates.

Macrocycles with up to 100 atoms have been synthesised using two calix[4]arenes as templates: first, (3,5-dialkenyloxy)phenyl groups are attached to the wide rim of a calix[4]arene via urea links, then the alkenyl groups are connected via a metathesis reaction using a tetratosylurea calix[4]arene for their correct prearrangement and finally the urea functions are cleaved to detach the newly formed macrocycles.

Der NMR-spektroskopische Nachweis der m-Substitution bei der Kondensation von chlormethylierten Nitrophenolen mit Methylphenolen

Die Kondensation von drei chlormethylierten Nitrophenolen mit p-Kresol und 2.4-Dimethylphenol wurde untersucht. Mit Zinkchlorid als Katalysator und bei etwa 100°C entstehen stets zwei Hauptprodukte, die in allen Fallen getrennt und in rGeiner Form erhalten wurden. Hauptsachlich anhand ihrer NMR-Spektren konnte gezeigt werden, das es sich um die isomeren 2.2′-Dihydroxy- bzw. 2.3′-Dihydroxydiphenylmethanderivate handelt. Die Substitution erfolgt demnach nicht nur in ortho-, sondern auch in meta-Stellung zur phenolischen OH-Gruppe. Das Verhaltnis, in dem beide Produkte nebeneinander gebildet werden, konnte ebenfalls NMR-spektroskopisch bestimmt werden. Der Anteil an 2.3′-Dihydroxydiphenylmetha…

Selective N-Protection of a Tetraamino Calix[4]arene Tetraether.

Stepwise synthesis and selective dimerisation of bis- and trisloop tetra-urea calix[4]arenes.

Tetra-urea calix[4]arenes substituted with four mono- or bisalkenyl residues have been converted into bis- or tetraloop compounds by intramolecular olefin metathesis, with use of a tetratosylurea calix[4]arene as template. The same strategy has now been used to synthesise trisloop compounds and bisloop compounds with adjacent loops, completing the series of the loop-containing tetra-urea derivatives. A tetra-urea calix[4]arene of the AABB type, where A stands for a bisalkenyl- and B for a monoalkenyl-substituted urea unit, was used as precursor for the three loops. It was easily synthesised from a tetraamino calix[4]arene in which two adjacent amino groups were Boc-protected. The ABCB-type …

Regioselective synthesis of calixcrowns derived from p-tert-butylcalix[5]arene

Abstract Alkylation of p-tert-butylcalix[5]arene with oligoethylene glycol-ditosylates in the presence of CsF affords the 1,3-bridged calix[5]crowns 1a–c in 51 to 72% yield. In the case of hexaethylene glycol the isomeric 1,2-bridged calix[5]crown-7 2c was obtained additionally. The calixcrowns were further modified by alkylation of the remaining hydroxyl groups.

First Protection of a Wide-Rim Tetraamino Calix[4]arene in Opposite Positions

The importance of tetraamino calix[4]arenes as starting materials is distinctly increased by the first versatile protective group for opposite amino functions. Reaction with trityl chloride leads to the 1,3-dialkylated derivative easily isolated in 34% yield; after a first acylation of the remaining amino groups, the trityl residues can be removed by TFA to introduce a second acyl group. [reaction: see text]

Heterodimeric capsules formed by tetratosyl and tetratolyl urea calix[4]arenes

Predictions made by MD simulations for size, shape and guest inclusion of a heterodimer formed by a tetratosyl and a tetratolyl urea calix[4]arene and for its hydrogen bonding system have been entirely confirmed by a single crystal X-ray structure.

Recent Developments in Calixarenes and Their Properties

The increasing number of reports, monographs and patents dealing with the hemistry of inclusion compounds shows the growing interest of organic chemists in elaborating new chemical systems presenting novel physical and chemical properties. These properties are available for fundamental as well as applied research. On the one hand, basic studies on the structure and the nature of inclusion compounds provide information on the intermolecular forces implicated in organized systems and in enzyme processes. On the other hand, applications are in progress in laboratories and industries, for instance, in catalyzing chemical reactions, in transporting and extracting metallic cations, and in modifyi…

Electrochemical response of ferrocenium filled calix[4]arene capsules in solution and immobilized on gold

Abstract Hydrogen-bonded dimers of tetra-urea calix[4]arenes are able to include ferrocenium ions as a guest. Heterodimeric capsules are exclusively formed in 1:1 mixtures of tetra-arylurea calix[4]arene 1 with tetra-tosylurea calix[4]arene 2. Sulfide groups attached via spacers on the urea rim of 1 allow their binding to metal surfaces rendering simultaneously their dissociation more difficult. Thus, the electrochemical response of encapsulated ferrocenium could be studied in a self-assembled monolayer (SAM) in addition to the solution electrochemistry with cyclic voltammetry. The stability of the electrochemically active monolayers was tested after a heat treatment (225 °C for 30 min in N…

Selective derivatisation of resorcarenes: Part 7. The reason for the diastereoselectivity of Mannich reactions with chiral amines

The formation of tetrakis(benzo-3,4-dihydro-1,3-oxazines) 2 by condensation of resorcarenes 1 with various primary amines and an excess of formaldehyde is not only regioselective but, in the case of (R)- or (S)-1-phenylethylamine and their para-substituted (Br, Me) derivatives, also completely diastereoselective. The reaction with the structurally similar (R)-1-aminoindane and (S)-1-(1-naphthyl)ethylamine, on the other hand, produced only a slight excess of one of the two possible epimers 2 and with (R)-1-cyclohexylethylamine no diastereoselectivity was found at all. The presence and the ratio of both diastereomeric structures can be clearly determined by NMR spectroscopy. Inspection of par…

Enantiomerization of an inherently chiral resorcarene derivative: determination of the interconversion barrier by computer simulation of the dynamic HPLC experiment

Abstract The inherently chiral tetrabenzoxazine resorcarene derivative 1 shows characteristic plateau-formation during enantioselective HPLC separation on the chiral stationary phase Chiralpak AD. By computer assisted peak form analysis of the elution profiles, obtained from temperature dependent dynamic HPLC (DHPLC) experiments, with ChromWin, the enantiomerization barrier Δ G # (298 K)=92±2 kJ mol −1 and the activation parameters Δ H # =53.0±1.8 kJ mol −1 and Δ S # =−131±14 J (K mol) −1 were determined.

Multiple catenanes based on tetraloop derivatives of calix[4]arenes

Abstract Four novel tetraarylurea calix[4]arenes ( 4a – d ) have been synthesized, substituted by ω-alkenyloxy residues in 3,5-positions of the arylurea residues. The eight alkenyl groups were pairwise connected by olefin metathesis and subsequent hydrogenation. The ring-closure reaction was carried out with heterodimers exclusively formed by 4 with a tetratosylurea calix[4]arene 1 , which serves as a template in this reaction step. The potential trans-cavity bridging is entirely suppressed in this way. Bis- and tetraloop calix[4]arenes cannot form dimers due to overlapping loops. However, they readily form heterodimers with open-chain tetraureas, as long as their urea residues can pass thr…

Resorcinol. Its Uses and Derivatives (Topics in Applied Chemistry). VonH. Dressler. Plenum Press, New York, 1994. 500 S., geb., 115.00 $ - ISBN 0-306-44850-5

Calix[4]arene-Based Bis[2]catenanes: Synthesis and Chiral Resolution

The exclusive formation of hydrogen-bonded dimers between tetraaryl and tetratosylurea calix[4]arenes has been used to prepare a series of ten "bisloop" tetraurea calix[4]arenes 3, in which adjacent phenylurea groups are covalently linked through alpha,omega-dioxyalkane chains. This dimerization with tetratosylurea 2 as template preorganizes the alkenyl residues of tetra(m-alkenyloxyphenyl) ureas 1 and enables their selective connection in high yield (up to 95 %) by olefin metathesis followed by hydrogenation. The "bisloop" calixarenes 3 also exclusively form heterodimers with 1. Thus, in a separated metathesis/hydrogenation sequence, a series of 14 cyclic bis[2]catenanes 4, in which two ca…

Conformationally Mobile Wide Rim Carbamoylmethylphosphine Oxide (CMPO)-Calixarenes

Six new calix[4]arene derivatives 2a–f have been synthesised, bearing CMPO-like functions (-NH–C(O)–CH2–P(O)Ph2) at their wide rim. They differ by their alkoxy groups at the narrow rim, comprising all possible combinations of methoxy and syn-propoxy groups including the conformationally mobile tetramethyl ether 2e and the tetrapropyl ether 2f fixed in the cone conformation. Their extraction behaviour for thorium(IV) and several lanthanides(III) from 1M HNO3 to dichloromethane has been studied and compared also to non cyclic calixarene analogues 6a–e. Surprisingly the best extraction results were found for the 1,2-dimethoxy-3,4-dipropoxy derivative 2c among the calixarenes and for the tetram…

Guest exchange in dimeric capsules of a tetraurea calix[4]arene in the solid state

A solid powder of hydrogen bonded dimers of a tetraurea calix[4]arene is able to exchange the encapsulated guest in contact with the vapor of a second guest. The molecules of a guest-free powder obtained from a polar solvent cannot rearrange in the solid phase to form new guest-filled capsules under these conditions.

Molecules with New Topologies Derived from Hydrogen-Bonded Dimers of Tetraurea Calix[4]arenes

Tetraurea calix[4]arenes 2 have been synthesized in which two adjacent aryl urea residues are connected to a loop by an aliphatic chain -O-(CH(2))(n)-O-. The remaining urea residues have a bulky 3,5-di-tert-butylphenyl residue and an omega-alkenyloxyphenyl residue. Since this bulky residue cannot pass through the loop, only one homodimer (22) is formed in apolar solvents, for steric reasons, in which the two alkenyl residues penetrate the two macrocyclic loops. Covalent connection of these alkenyl groups by olefin metathesis followed by hydrogenation creates compounds 3, which consist of molecules with hitherto unknown topology. Their molecular structure was confirmed by (1)H NMR spectrosco…

Narrow rim CMPO/adamantylcalix[4]arenes for the extraction of lanthanides and actinides

Abstract Six p-(1-adamantyl)calix[4]arenes 7, 8 with four differently attached diphenyl-carbamoylmethylphosphine oxide (CMPO) functions at the narrow rim were synthesized. This series was extended by adamantylcalix[4]arenes with two CMPO and two ester, acid or (diethylphosphono)acetylamino groups. Structures of new compounds were proved by NMR, mass-spectrometry and a single-crystal X-ray analysis for the intermediate di-phthalimide 103. The extraction studies towards selected lanthanides and thorium showed that the ligands 7 surpassed the corresponding p-H, p-tert-butyl and p-tert-octyl analogues 3–5 in lanthanide extraction while thorium was extracted with the same or lesser extent. For t…

Self-Sorting Dimerization of Tetraurea Calix[4]arenes

Calix[4]arenes substituted by four urea functions are self-complementary molecules that spontaneously combine in apolar solvents in the presence of an ammonium salt to form dimeric capsules held together by a belt of hydrogen bonds. In the presence of tetraethylammonium salts, the Et4N+ cation is included as a guest. The sorting between dimeric capsules formed in a mixture of calix[4]arenes directly depends on the steric crowding of the substituents grafted on the urea groups whether aromatic derivatives or aliphatic chains linking urea functions in mono-, di-, or tetraloop structures. Simple rules allow one to anticipate which capsules will be exclusively formed when calix[4]arenes are mix…

Selective derivatisations of resorcarenes - 2. Multiple regioselective ring closure reactions

Abstract The condensation of the C-pentyl resorcarene 1 with long chain aliphatic diamines 3a-d and excess formaldehyde leads under high dilution conditions to tetrabenzoxazine derivatives 4a-d in which pairs of adjacent oxazine rings are connected by an aliphatic chain. Six new rings are formed per resorcarene molecule during this reaction in a regioselective way. For one example (4a) the chiral cleft-like structure with C2 symmetry was proved by single crystal X-ray analysis. Hydrolysis of the oxazine rings gives the secondary amine derivatives 5a,b with C2v symmetry in high yield.

Hydrogen bonding in dimers of tritolyl and tritosylurea derivatives of triphenylmethanes.

The crystal structure of the homodimer formed by the tritolylurea 3a proves the existence of a belt of six bifurcated hydrogen bonds between both NH and the O=C groups of the adjacent urea residues. For the tritosylurea 3b, four additional three-center hydrogen bonds, also involving the SO2 oxygen, are found in the crystalline state. Molecular dynamics simulations in a chloroform box confirm these patterns of the hydrogen bonds and the resulting elongation of the dimer 3b. 3b in comparison to 3a x 3a. The calculated complexation energies for the three dimeric combinations are nearly identical in agreement with the simultaneous formation of heterodimer 3a x 3b in a mixture of 3a and 3b.

Vierfache [2]Rotaxane von Calix[4]arenen durch Ringschluss

Solid-state NMR and computational studies of tetratolyl urea calix[4]arene inclusion compounds.

Solid-state guest dynamics of tetratolyl tetraurea calix[4]arene tetrapentylether dimeric capsules filled with different types of aromatic guests such as benzene-d6, fluorobenzene-d5 and 1,4-difluorobenzene were studied. Upon inclusion, all guest moieties revealed complexation-induced shifts varying from 2.8 ppm to 5.1 ppm. All guest molecules were shown to undergo distinct motions, ranging from mere C6-rotations of benzene-d6 to (ill-defined) 180 degrees phenyl flips of fluorobenzene-d5. In all cases, dynamic heterogeneities were identified based on 2H lineshape deconvolution. In addition, by combination of both a computed nucleus independent chemical shift (NICS) map and explicit 19F and …

Selective dimerisation of tetraurea calix[4]arenes

The formation of hydrogen-bonded dimeric capsules from tetraurea calix[4]arenes is controlled by loops, connecting adjacent urea functions, and more or less bulky substituents. The dimerisation is only possible if loops are not overlapping and if the respective residues can pass the loops. A sorting scheme based on small and bulky residues and one to four loops allows reducing the number of possible dimers from 35 to 6 in a stoichiometric mixture of 11 ureas. With three different loop sizes (O–(CH2) n –O chains with n = 10, 14, 20 connecting adjacent phenylurea functions via their meta positions), it is possible to distinguish four urea residues of different sizes (small, medium, bulky and …

The polyamides 3–5 were synthesized from α,ω-diamino-substituted oligo(oxyethylene)s (1) and bis-chlorides of dicarboxylic acids (2). As copolymers with defined sequences they contain up to five oxyethylene units per repeating unit. Hereby properties like solubility, thermal stability and complexing ability towards alkali metal cations are influenced.

(o-Hydroxyphenyl)methylphosphonic acids: Synthesis and potentiometric determinations of their pKaValues

(o-Hydroxyphenyl)methylphosphonic acids are readily obtained from o-(bromomethyl)- or o-(hydroxymethyl)phenols and trialkyl phosphites. Subsequent hydrolysis leads to the corresponding phosphonic acids. For a series of such compounds, the pKa values have been determined by potentiometry. Their dependence on additional substituents in the aromatic ring is discussed in terms of electronic and steric effects.

Special Calixarenes by Directed Syntheses

The synthesis of special calixarenes and calixarene-like macrocyclic compounds via stepwise procedures and fragment condensation is reviewed. Among the compounds available are exo- and endo-calixarenes consisting of different phenolic units, having bridges other than methylene or showing inherent chirality (Cn-symmetry). Macrobi- and -tricyclic molecules such as bridged calixarenes, double calixarenes, bicyclocalixarenes and annelated calixarenes are also described. Single crystal X-ray structures are reported for several compounds. Some properties like conformational barriers, pKa values or the ability to complex metal ions are discussed, showing the potential of these compounds which may …

Calix[4]arenes with alkylidene bridges, synthesis and conformational properties

Abstract Calix[4]arenes with one or two alkylidene bridges were synthesized by “2+2” fragment condensation. As predicted by molecular mechanics calculations aliphatic residues at the bridging carbon atom(s) prefer the equatorial position.

Gemischte Diester von 2,2′-Methylendiphenolen mit Methacryl- und Crotonsäure und ihre Polymeren. 13C NMR-Untersuchungen zur Strukturaufklärung

The structure of mixed diesters of three 2,2′-methylenediphenols with crotonic acid and methacrylic acid was studied by 13C NMR-spectroscopy. The position of the two acyl groups, expected from the synthetic pathway, was unambiguously confirmed by comparison with the corresponding mono- and diesters containing the same acyl group. In the same way, it was shown that the crotonoyl residue is not involved in the radical polymerisation of these esters.

Die stufenweise Synthese von 4,11,18,25-Tetra-tert-butyl-[1.1.1.1]metacyclophan-7,14,21,28-tetraol und 4,11-Dimethyl-[1.1.1.1]-metacyclophan-7,14,21,28-tetraol

Two phenolic alcohols with four phenolic units in their molecules are obtained by stepwise synthesis starting from simple phenolic derivatives. The phenolic alcohols are cyclized by boiling of a diluted solution in acetic acid. A third cyclic compound is obtained by debutylation of that cyclic compound which contains two neighbouringtert-butyl groups and two methyl groupspara to the phenolic hydroxyl groups.

Selective Derivatization of Resorcarenes. 3. C2-Symmetrical and Transcavity Bridged Bis-Benzoxazines Derived from C2v-Symmetrical Tetratosylates

The regioselective condensation of resorcarene tetratosylates 3/4 with formaldehyde and various primary amines readily gives bis-benzoxazines 5/6 in 65−86% yield. The chiral, C2-symmetrical structure of these compounds has been proved by NMR-spectroscopy and single-crystal X-ray analysis. Bis-benzoxazines 5f and 5i assume in the crystalline state a boat conformation in which the two resorcinol rings bearing the oxazine fragments are nearly parallel. The tosylated resorcinol units are horizontally arranged in a propeller-like fashion, and two intramolecular hydrogen bonds are formed between the phenolic hydroxy groups and the oxygens of the neighboring sulfonyl fragments. Molecular mechanics…

Enhanced thermodynamic and kinetic stability of calix[4]arene dimers locked in the cone conformation.

Wide rim tetraurea derivatives (2a,b) have been prepared from a calix[4]arene rigidified in the cone conformation by two diethyleneglycol ether bridges between adjacent oxygens. In comparison to the analogous tetraurea derivatives (3a,b) of a tetrapentoxy calix[4]arene, 2a,b show an increased thermodynamic stability in mixtures of CDCl(3) and DMSO-d(6). Their kinetic stability as expressed by the rate of guest exchange (benzene or cyclohexane against the solvent benzene-d(6)) is also strongly increased by factors of 30-38. Noticeable differences for the inclusion of selected guests are found.

Compensation of steric demand by cation–π interactions, cobaltocenium cations as guests in tetraurea calix[4]arene dimers

The affinities of ferrocene (2) and the cobaltocenium cation (3+), which have roughly the same size and differ in their charge, towards the inner cavity of the dimeric capsule formed by tetraurea calix[4]arene (1) were studied in C2D4Cl2 solutions. While 3+, which occupies more than 75% of the internal volume of the dimer, is readily encapsulated this is not the case for 2. This is probably due to cation-pi interactions, which operate only between 3+ and the aromatic rings of the calix[4]arene dimer. We found that the affinity of the cobaltocenium cation is higher than that of the tropylium cation (4+) and is only 2-3 times less than that of the tetraethylammoniun cation (5+). From the vari…

Two chloride ions as a template in the formation of a cyclic hexaurea.

tert-Butyl-calix[4]arenes Substituted at the Narrow Rim with Cobalt Bis(dicarbollide)(1–) and CMPO Groups – New and Efficient Extractants for Lanthanides and Actinides

Calix[4]arene derivatives bearing two residues A(–) derived from cobalt bis(dicarbollide)(1–) (1) and two CMPO groups B at their narrow rim were synthesized from tBu-calix[4]arene in four steps. The first step involved the preparation of tBu-calix[4]arene diether derivatives with appropriate precursors for amino groups (mostly nitriles 3). These were O-alkylated through ring-opening reactions with the zwitterionic dioxane derivative [(8-O(CH2CH2)2O-1,2-C2B9H10)-(1′,2′-C2B9H11)-3,3′-Co]0 (10) to produce ionic nitrile derivatives 4. Reduction of the nitrile groups with BH3·SMe2 (or deprotection in the case of the corresponding phthalimido or Boc derivatives 8) led to a series of diamines 5a–f…

ChemInform Abstract: Calixarenes in Self-Assembly Phenomena

Crown ethers derived from bicyclocalix[4]arenes as chromoionophores

The synthesis of calix[4]arenes in which opposite phenolic units are connected by a poly(oxyethylene) bridge at the narrow rim and a 2,6-dimethylene-4-nitrophenol bridge at the wide rim is reported. For two derivatives with tetra- (4) and penta(oxyethylene) (5) bridges UV-Vis spectrophotometric studies were carried out in buffered solution in the presence of alkali metal ions. Their complexation was associated with changes in their UV-Vis spectra, especially with an increase of the absorption band at 450 nm. For 4 and 5 this was most intense in the presence of potassium and caesium ions, respectively, indicating that the calixarene with the shorter crown ether bridge is selective towards po…

Template synthesis of multi-macrocycles by metathesis reaction.

Selective heterodimerisation of tetraurea calix[4]arenes containing four or eight ω-alkenyl groups with a tetratosyl urea calix[4]arene has been effectively used to synthesize multi-macrocycles via metathesis reaction.

Friessche verschiebung bei acetylderivaten phenolischer mehrkernverbindungen

Die FRIES sche Verschiebung wurde an den Acetylderivaten einiger phenolischer Zweiund Dreikernverbindungen untersucht. In Nitrobenzol, mit AlCl3 als Katalysator, ist bei Temperaturen von 40-60°C eine gleichzeitige Umlagerung von mehreren Acylgruppen pro Molekul in die para-Stellung zur phenolischen Hydroxylgruppe ohne Schwierigkeiten moglich. Methoxygruppen bleiben dabei erhalten. Die bei hoheren Temperaturen verlaufende Umlagerung in die ortho-Stellung zur phenolischen Hydroxylgruppe gelang jedoch bisher nicht. Die erhaltenen Mehrkernverbindungen mit p-Hydroxyacetophenonbausteinen wurden IR-, UV- und NMR-spektroskopisch untersucht. Sie wurden ferner durch Uberfuhrung in die entsprechenden …

Eine oligomeranaloge friessche umlagerung oligomerer 2-acetoxy-1,3-phenylenmethylene

α-Hydro-ω-hydroxypoly(5-chloro-2-hydroxy-1,3-phenylenemethylene)s (1a, b), the oligomeric condensation products from 4-chloro-2,6-bis(hydroxymethyl)phenol and 4-chlorophenol with hydrochloric acid in 1,4-dioxane, could be completely dehalogenated at room temperature and atmospheric pressure with hydrogene/Raney-Ni. The resulting oligomers 2a, b were esterified with acetic anhydride, and the esters 3a, b were subjected to a oligomer analogous Fries rearrangement to form the linear α-hydro-ω-hydroxypoly(5-acetyl-2-hydroxy-1,3-phenylenemethylene)s 4a and 4b. The characterization of the products was mainly done by spectroscopic methods.

Sterically and guest-controlled self-assembly of calix[4]arene derivatives.

In solvents such as chloroform or benzene, tetraurea calix[4]arenes 1 form dimeric capsules in which one solvent molecule is usually included as guest. To explore the structural requirements for the formation of such hydrogen-bonded dimers we replaced one p-tolylurea residue by a simple acetamide function. The resulting calix[4]arene 2 a, substituted at its wide rim with one acetamide and three p-tolylurea functions, assumes a C(1)-symmetrical conformation in apolar solvents as shown by (1)H NMR, which is not compatible with the usual capsule. In the crystalline state, four molecules of 2 a, adopting a pinched cone conformation, assemble into a quasi S(4)-symmetrical tetramer stabilized by …

Conformational properties of methylene bridged resorcarenes

Abstract Conformations and conformational interconversions of resorcarene 1c have been studied by molecular mechanics calculations. As with calix[4]arenes the general stability of the four basic conformations is cone > partial cone > 1,2-alternate > 1,3-alternate. The lowest energy is calculated for a pinched cone conformer with C2v symmetry stabilised by intramolecular hydrogen bonds of the two “parallel” resorcinol units as donors. The topomerisation of the cone conformation proceeds via the partial cone and 1,2-alternate intermediates with a calculated barrier of 9.9 kcal mol−1 which is in excellent agreement with the experimental value.

Functionalized Calix[8]arenes, Synthesis and Self-assembly on Graphite

With the intention of building hollow tubular structures by self-assembly, we have designed and successfully synthesized a series of calix[8]arene derivatives. Their phenolic units were functionalized in p-position by various groups which are able to interact via hydrogen bonding or π−π stacking. Ethynyl, amide, urea, or imide links were chosen for the covalent attachment of these functional groups, to ensure the adjustment of an optimal distance for their interaction. Two different kinds of nanostructures self-assembled on a highly oriented pyrolytic graphite (HOPG) surface were found by scanning force microscopy:  parallel aligned nanorods in which the calixarene molecules are adsorbed ed…

Covalently linked multi-calixarenes

Abstract ipso-Nitration of t-butyl calix[4]arene tetraethers and subsequent hydrogenation provides an easy access to monoamino calix[4]arenes. Reaction with di- and triacid chlorides leads to various double- and triple-calix[4]arenes. With tetraacid chlorides derived from calix[4]arenes in the cone- or 1,3-alternate-conformations penta-calix[4]arenes are available as molecularly uniform species, which may be regarded as the first generation of calix[4]arene based dendrimers. The structure of the mononitro tetraester derivative, which may serve as a general building block has been confirmed by single crystal X-ray analysis.

Cobalt bis(dicarbollides)(1-) covalently attached to the calyx[4]arene platform: the first combination of organic bowl-shaped matrices and inorganic metallaborane cluster anions

Various calix[4]arene and resorc[4]arene ionic compounds substituted by cobalt bis(dicarbollide) anions (1) have been prepared for the first time. From tBu-calix[4]arene (A) the complete series of mono-, di-, tri- and tetrasubstituted derivatives bearing one to four cluster anions on the lower rim (3-6) have been obtained in the form of their alkali-metal salts by O-alkylation with the 1-dioxane derivative [8-O(CH2CH2)2O(+)-1,2-C2B9H10)-(1',2'-C2B9H11)-3,3'-Co] (2), all of which are syn or cone isomers. In contrast, disubstitution of the dipropyl ether of tBu-calix[4]arene (B) led to a mixture of the cone and 1,3-alternate conformers 7a and 7b, respectively. Starting from tetrapropoxy-calix…

The acidity of calix[5]arenes and their linear analogues

Abstract Five new calix[5]arenes containing a single p-nitrophenol unit as the most acidic phenolic unit have been synthesised by (3+2) fragment condensation of a trimer with a p-nitrophenol in the middle with various bishydroxymethylated alkanediyl diphenols. Their first acid constant (pKal) has been determined in 2-methoxyethanol/water (9:1) at 22°C by optical titration. The pKal values are distinctly lower (ΔpKa > 2) than for the trimer, while no difference has been found in comparison to structurally analogous calix[4]arenes. Rigidification of the calix[5]arene skeleton by introducing a single alkanediyl bridge opposite to the p-nitrophenol unit has no effect on pKal. All values are in …

Topologically Novel Multiple Rotaxanes and Catenanes Based on Tetraurea Calix[4]arenes

Calix[4]arenes bearing at their wide rim four urea residues easily form hydrogen bonded dimeric capsules. This has been used to preorganise alkenyl functions attached to these urea groups for their controlled connection via metathesis reaction. Multimacrocyclic tetraurea derivatives are thus obtained in excellent yields via heterodimers which are formed exclusively with tetratosylurea derivatives. Heterodimerisation of such bis- and tetraloop tetraureas leads analogously to multicatenanes, or to rotaxanes by stoppering. Huge macrocycles are detached from tetraloop derivatives by cleavage of the urea function.

Darstellung und polymerisation von diestern aus 2,2′-methylendiphenolen und acryl-, methacryl- bzw. Crotonsäure

Several mono- and diesters of four selected 2,2′-methylenediphenols with acrylic, methacrylic, and crotonic acid were synthesized for the first time. Special emphasis was paid to the preparation of diesters with two different acyl groups which could be obtained via the corresponding monoesters. The radical polymerization of these esters with AIBN (mainly in benzene) gave insoluble (crosslinked) products from dimethacrylates and soluble (linear) polymers from mixed diesters with methacrylic and crotonic acid, while the dicrotonates are not reactive.

Calix[4]arenes as Selective Extracting Agents. An NMR Dynamic and Conformational Investigation of the Lanthanide(III) and Thorium(IV) Complexes

The lanthanide and Th4+ complexes with calix[4]arene ligands substituted either on the narrow or at the wide rim by four coordinating groups behave totally differently as shown by an NMR investigation of the dia- and paramagnetic complexes. Solutions of complexes were prepared by reacting anhydrous metal perchlorate salts with the ligands in dry acetonitrile (CAUTION). Relaxation time T1 titrations of acetonitrile solutions of Gd3+ by calixarenes indicate that ligands subsituted on the narrow rim form stable 1:1 complexes whether they feature four amide groups (1) or four phosphine oxide functions. In contrast, a ligand substituted by four (carbamoylmethyl)-diphenylphosphine oxide moieties …

THET-BUTYL GROUP AS A POSSIBLE PROTECTIVE GROUP IN THE SYNTHESIS OF OLIGO [HYDROXY-1,3-PHENYLENE]METHYLENES

(1978). THE T-BUTYL GROUP AS A POSSIBLE PROTECTIVE GROUP IN THE SYNTHESIS OF OLIGO [HYDROXY-1,3-PHENYLENE]METHYLENES. Organic Preparations and Procedures International: Vol. 10, No. 3, pp. 113-121.

Kinetik der Bromierung von Phenolen und phenolischen Mehrkernverbindungen, 1. Mechanismus und meßmethode

Die Bromierung von 2-(2-Hydroxy-5-methylbenzyl)-4,6-dimethylphenol (1) und 2-[2-Hydroxy-3-(2-hydroxy-5-methylbenzyl)-5-methylbenzyl]-4,6-dimethylphenol (2a) wurde in Eisessig bei 22°C untersucht. Die Reaktion last sich fur [Br2]0 = 1,4·10−3 bis 6,0·10−3 mol dm + und Konzentrationen der phenolischen Verbindungen [P]0 zwischen 1,1·10−3 und 5,5·10−3mol dm−3 durch das folgende Geschwindigkeitsgesetz beschreiben: Wahrend die gebildete Bromverbindung keinen Einflus auf die Reaktionsgeschwindigkeit hat, verlangsamt der entstehende Bromwasserstoff die Reaktion. Die Bromierung ist trotzdem zur Bestimmung der Reaktionsfahigkeit von Phenolen und phenolischen Mehrkernverbindungen gut geeignet, da die R…

Self-Assembled Hydrogen Bonded Dimers of Calix[4]arenes

Self-assembly of suitably functionalized molecules to well defined supramolecular structures has become a topic of current interest. Various molecules have been designed which are able to mimic in part the recognition and self-organisation processes which are found as a general principle in nature.[1]

Hydrogen-Bonded Analogues of Cavitands

Chemical Modification of Calix[4]arenes and Resorcarenes

A Self-Sorting Scheme Based on Tetra-Urea Calix[4]arenes

Size and shape do matter: When dimerized in nonpolar solvents, an equimolar mixture of eleven tetra-urea calix[4]arenes with different wide-rim substituents self-sorts into only six out of 35 different homo- and heterodimers (see picture). Since the calixarene scaffold and the four urea units are the same in all cases, the self-sorting process is driven only by the cooperative action of steric requirements and stoichiometry.

Mono- and Multi-Layers

Thin films incorporating or consisting of calixarenes have been widely investigated. The capacity of such films to adsorb both ions and neutral species has engendered particular interest in their use in sensor devices. Semiconductors, non-linear optical and pyroelectric materials or switchable systems for data storage are further examples of their potential use [1]. Both monoand multi-layer films can be formed from calixarenes and resorcarenes, using a variety of techniques. This chapter deals with the fundamental basis of calixarene thin film applications, including film formation and characterisation as well as studies of selectivity in small molecule interactions. Real and potential appl…

Self-assembly of programmed building blocks into structurally uniform dendrimers.

Selective and independent dimerization of tri- and tetraurea derivatives was used to build up dendritic assemblies which are uniform in size and structure. Dendrimers with the total molecular masses of about 25 000 g/mol were obtained. The existence of uniform assemblies was proved by 1H and 1H DOSY NMR experiments and also by dynamic light scattering.

Crystal structure of t-Butylcalix[8]arene octamethyl ether

Abstract The title compound 1a crystallized with a molecule of chloroform in a triclinic lattice, space group P-1, with a=16.5215(19) A, b=17.4181(19) A, c=18.7403(18) A, α=78.328(8)°, β=64.210(8)°, γ=87.863(9)°, Z=2. The molecule assumes a not yet observed conformation with approximate (not crystallographic) C4V-symmetry with the inclusion of one molecule of chloroform in the molecular cavity. Layers of molecules are packed in alternating order in the crystal lattice.

Head-to-tail connected double calix[4]arenes

New macrotricyclic compounds consisting of two calix[4]arene substructures connected by aliphatic chains of various length (three to five carbon atoms) between two oppositep-positions and two distal phenolic oxygens have been synthesized. Starting withp-tert-butyl-calix[4]arene, two O-protected phenolic units are attachedvia ether links in 1,3-position by reaction with the corresponding tosylates. After deprotection, the new calix[4]arene is formed by fragment condensation with 2,6-bisbromomethylated 4-alkylphenols. The structure of one example (8c) has been confirmed by single crystal X-ray analysis. Both calixarene parts assume the cone conformation, a molecule of acetonitrile being inclu…

Kinetische untersuchungen zur reaktionsfähighkeit von chlormethylgruppen in methylendiphenolen

The chloromethyl derivatives of 16 differently substituted methylenediphenols were synthesized for the first time. To compare their reactivity, the solvolysis in methanol and the animolysis with an excess of p-nitroaniline in dimethyl sulfoxide were studied kinetically at 25°C. The rate constants for the methanolysis do not differ very much, beside of the fact that para-chloromethyl derivatives react about 100 times faster than ortho-chloromethyl derivatives. However, for the aminolysis a large acceleration up to 103 was found for compounds having both hydroxyl groups in ortho-position to the methylene bridge. Obviously, the cleavage of the OH bond, which occurs in the rate determining step…

Cation-π interactions between neutral calix[5]arene hosts and cationic organic guests

Abstract The binding properties of the 1,3-bridged calix[5]crowns 1–3 towards a number of quaternary ammonium, phosphonium, and iminium ions have been investigated by 1H NMR in CDCl3 solution, where the sole driving force for association is provided by cation-π interactions. We have found that the cavity of a calix[5]arene fixed in a cone-like conformation provides a fairly efficient, but rather unselective, receptor site for quaternary salts. The conformationally mobile p-tert-butylcalix[5]arene (4) is in general a much less efficient binder than the more preorganized calixcrowns, but displays a remarkable selectivity towards N-methylquinuclidinium ion that is believed to arise from a good…

Vibrational spectroscopy of a tetraureidocalix[4]arene based molecular capsuleElectronic supplementary information (ESI) available: three tables containing fully assigned IR data of tetraureido calix[4]arene 1, its complex with cyclohexane and benzene, and the corresponding model substances 2–5 as well as 1H NMR spectra of the capsules 1·C6H6·1 and 1·C6H12·1 in solution. See http://www.rsc.org/suppdata/p2/b1/b108055p/

Structural models for self-assembled dimers composed of two urea calix[4]arenes which entrap benzene or cyclohexane are developed using Fourier transform infrared (FTIR) spectroscopy. Based on the host–guest ratio determined by 1H NMR spectroscopy in solution, and confirmed for the solid state by a thermogravimetric analysis, it is possible to prove by a comparison of the FTIR data of host, guest, complex and model compounds, that the capsule is held together by a cyclic array of weak and strong hydrogen bonds between the urea units attached at the wide rim of the calixarenes. The dimerization of the two urea units leads to a loss of symmetry, and an averaged C4 symmetrical arrangement is p…

A resorcinol derived calix[5]arene with C5-symmetry

Abstract Condensation of 2,4-dihydroxy-3-hydroxymethyl benzophenone (4) in dioxane/H2SO4 gave the cyclic pentamer 5, a calix[5]arene with regular incorporation of the resorcinol units via their 2- and 6-positions. The structure follows from the 1H NMR and mass spectra and was further confirmed by single crystal X-ray analysis. Dynamic NMR in C2D2Cl4 gave a surprisingly high barrier of ΔG‡ = 17.3 kcal/mol for the cone-to-cone ring inversion.

5,11,17,23-Tetranitro-25,26,27,28-tetrapentyloxycalix[4]arene

The mol­ecule of the title compound, C48H60N4O12, is located on a crystallographic twofold rotation axis. It is found in the typical pinched cone conformation. The dihedral angles between the reference plane (defined by the C atoms of the methyl­ene bridges) and the benzene rings are 83.33 (6) and 141.61 (5)°.

Dendrimer-coated magnetic particles for radionuclide separation

Magnetic particles were synthesised for radionuclide removal from nuclear wastes by magnetic separation. Dendrimers with terminal amino groups attached to the particle surface were used to bind chelating groups for lanthanides and actinides. This led to a 50–400-fold increase of the distribution coefficients for europium and americium in comparison to the reference particles without the dendrimers. Back-extraction studies have demonstrated the possibility of multiple particle recycling.

Symmetry: Friend or foe?

While symmetry in molecules or supramolecular complexes is desirable from the design point of view and affords simpler NMR spectra, the study of symmetrical species by NMR is often subject to ambiguities resulting from signal degeneracy. In this paper we shall discuss different ways of breaking symmetry in order to obtain additional structural information by NMR.

Structure of 5,17-dimethyl-11,23-dioctylcalix[4]arene

The title compound C46O4H60 crystallizes in the triclinic space group, P¯1, witha=11.584(2),b=16.261(2),c=11.172(1) A,α=103.15(8),β=95.68(1),γ=96.85(1)°. The structure was solved by direct methods, and refined by weighted full-matrix least squares toR=0.097. This is the second calix[4]arene with two different alkyl substituents atpara positions of the phenolic rings. The macrocycle adopts the cone conformation. Interactions CH3-π are established between two calixarenes related by a center of symmetry. Comparisons are made between the conformation of this molecule and that of symmetrically substituted calix[4]arenes.

Counteranion Effect on Complexation of Quats by a Neutral Calix[5]arene Receptor

3-Oxa-6,8-diaza-1,2:4,5-dibenzocycloocta-1,4-dien-7-one: a three-dimensional network assembled by hydrogen-bonding, pi-pi and edge-to-face interactions.

The title compound, C(13)H(10)N(2)O(2), is the first structure in which the urea moiety is incorporated into an eight-membered ring. Two molecules are found in the asymmetric unit, which are almost identical in their conformation and their hydrogen-bond pattern. The carbonyl O atom acts as a double acceptor for the NH groups of two adjacent molecules. In this way, infinite tapes are formed, which are connected via pi-pi and edge-to-face interactions in the second and third dimension. This hierarchical order of interactions is confirmed by molecular mechanics calculations. Force-field and semi-empirical calculations for a single molecule did not find the envelope conformation present in the …

Macrocyclic oligoureas with xanthene and diphenyl ether units

Two cyclic oligoureas with 64- and 80-membered rings in which two sets of three or four rigid xanthene (X) units are connected via flexible diphenyl ether (D) units were synthesized by a stepwise fragment condensation. The compounds were characterized by (1)H NMR and ESI mass spectrometry. The structure of the cyclic octamer (XXXDXXXD) was additionally confirmed by single crystal X-ray analysis. The molecule assumes a strongly folded conformation with distorted C(2)-symmetry, stabilized by intramolecular hydrogen bonds. Surprisingly, intermolecular hydrogen bonds between the macrocycles were not observed. (1)H NMR spectra suggest a C(2) symmetrical conformation of the octamer in solution al…

Untersuchungen zur Reaktionsfähigkeit statistisch verteilter Estergruppierungen in Copolymeren aus Styrol und Acrylsäureestern

Die Aminolyse der ortho- und para-Nitrophenylester von Propionsaure, Isobuttersaure, 4-Phenylbuttersaure und 4-Phenylvaleriansaure sowie von Copolymeren aus Styrol und geringen Mengen Acrylsaure wurde mit Butylamin in Dioxan untersucht. Bei grosem Aminuberschus reagieren die niedermolekularen Ester streng nach erster Ordnung, wobei die Reaktionsgeschwindigkeit durch Zugabe von Polystyrol nicht beeinflust wird. Fur Copolymere, deren Reaktionsgeschwindigkeit deutlich geringer ist, erhalt man dagegen keine Beziehung erster Ordnung, obwohl die Anfangsgeschwindigkeit der Gesamtkonzentration der Estergruppen direkt proportional ist. Bei den Copolymeren erhalt man annahernd die gleichen Aktivierun…

Calix[4]arenes with resorcinol units incorporated in 2,6-position

Abstract Calix[4]arenes containing one or two resorcinol units incorporated via their 2,6-positions were prepared by fragment condensation. Due to the cyclic array of intramolecular hydrogen bonds these molecules assume the cone-conformation.

Untersuchungen zur reaktionsfähigkeit von estergruppen in polymeren, 2. Aminolyse von p-nitrophenylestergruppen

A New Type of Double Calix[4]arenes by Linkage via the Phenolic Hydroxy Groups

Self-Assembled Hydrogen-Bonded Dimeric Capsules with High Kinetic Stability

Darstellung und spektroskopische Analyse von Oligo{[4-(1,1,3,3-tetramethylbutyl) (bzw. 4-octyl)2-hydroxy-1,3-phenylen]methylen}en und ihrer Ausgangsverbindungen

4-(1,1,3,3-Tetramethylbutyl)phenol und 4-Octylphenol, erhalten durch Friessche Verschiebung der entsprechenden Phenylester und anschliesende Reduktion der Carbonylgruppe, wurden in ortho-Stellung monobromiert und mit Formaldehyd hydroxymethyliert. Aus diesen Verbindungen konnten sechs 2,2′-Methylendiphenole (2a–f) sowie sieben 2,6-Bis(2-hydroxybenzyl)phenole (3a–g) dargestellt werden, die in 4-Stellung zu den phenolischen Hydroxygruppen Methyl-, 1,1,3,3-Tetramethylbutyl- und Octyl-Substituenten in verschiedenen Verhaltnissen enthalten. Die IR- und 1H-NMR-spektroskpischen Analysen bestatigten die angegebenen Strukturen der dargestellten phenolischen Mehrkernverbindungen. 4-(1,1,3,3-Tetrameth…

Versuche zur Decarboxylierung phenolischer Mehrkernverbindungen aus 4-Hydroxybenzoesäurebausteinen

Es wurden verschiedene 2.2′-Dihydroxy-3.3′-dihalogen-5.5′-dicarboxydiphenylmethane bzw. 2.6-Di-(2-hydroxy-3-halogen-5-carboxybenzyl)-4-carboxyphenole in Gegenwart von N.N-Dimethylanilin bzw. Chinolin bei 170 bis 215°C zu den entsprechenden Phenolen decarboxyliert. Bei Verwendung von N.N-Dimethylanilin wurde neben der Decarboxylierung auch die Abspaltung von Halogen beobachtet, wahrend diese Nebenreaktion bei Verwendung von Chinolin nur in sehr geringem Umfang festgestellt wurde. Some 2.2′-Dihydroxy-3.3′-dihalogen-5.5′-dicarboxydiphenylmethanes and 2.6-Di-(2-hydroxy-3-halogen-5-carboxybenzyl)-4-carboxyphenols were decarboxylated in the presence of N.N-dimethylaniline or quinoline at temperat…

Conformational properties of cyanomethoxy calix[4]arenes.

O-Alkylation of the dinitro calix[4]arene 2, easily available by selective ipso-nitration of the di-cyanomethyl ether 1, with allylbromide (DMF/Cs2CO3) gave tetraethers 3 and 4 with anti- and syn-orientations of the two allyl ether residues. The two possible stereoisomers of 3 in the partial cone and 1,2-alternate conformation exist as an equilibrium mixture which could be quantitatively analysed by 1H NMR spectroscopy. The temperature dependence of this equilibrium leads to ΔH0 = − 7.6 to −9.7 kJ mol−1 in different solvents (tetrachloroethane, benzene, dimethylsulfoxide). Since 3(1,2-alt) could be obtained in pure form, its isomerisation to the equilibrium mixture with 3(paco) could be fol…

Crystal and molecular structure of the (1 : 1) clathrate between a calix[4]arene containing onep-nitrophenol unit and toluene

p-(Methyl,tert-butyl, nitro,tert-butyl) calix[4]arene: toluene, C37H41NO6. C7H8,Mr = 687.87, triclinic,\(P\bar 1\),a = 13.668(2),b = 12.187(2),c = 13.231(1) A,α = 106.78(8),β = 77.88(1),γ = 114.00(1)°,V = 1916.8(8) A3,Z = 2,Dx = 1.19 g cm−3,λ (CuKα) = 1.54178 A,μ = 5.90 cm−1,F(000) = 736,T = 293 K, finalR = 0.068 for 6309 observed reflections. This macrocycle, having different substituents at the positionspara to the hydroxyl groups, is the first one of its type to be studied. The general conformation of this calix[4]arene is compared to similar symmetrical ones. Thetert-butyl groups are not disordered as is usual and toluene is retained between the macrocycles. Two calixarene molecules are…

Metal ion complexation by tetraester derivatives of bridged calix [4] arenes

A series of bridged calix [4] arenes (5–10 methylene groups in the bridge) were synthesized and transformed into their tetraester derivatives by reaction with ethyl bromoacetate. The stability constants for complexes of the tetraester derivatives with sodium, potassium and silver cations, determined in methanol by spectroscopic or potentiometric techniques, show a drastic decrease (more than 105 for Na +) for the shorter methylene chains. 1H NMR studies demonstrate a conformational rearrangement of the calixarene part to fourfold symmetry to be necessary for the complexation of a cation, which is prevented by the shorter chains. This is further confirmed by the X-ray structure of a tetraest…

Special Calixarenes, Synthesis and Properties

In the previous chapter the standard one step procedures for the synthesis of calixarenes from p-tert-butyl phenol and several p-alkyl phenols have been described. However, these procedures necessarily lead to calixarenes consisting of one single type of phenolic unit. This remains true even for those compounds in which all the terf-butyl groups are removed and replaced by other functional groups. The construction of more sophisticated, special calixarenes which could serve for instance as enzyme models, requires new synthetic approaches capable of producing molecules with selected functionalization.

Asymmetrically substituted calix[4]arenes; A two-dimensional 1H NMR study of a tetraester derivative in the cone-conformation

Abstract Several new chiral calix[4]arenes with three or four different substituents in the p-position have been prepared by fragment condensation. Standard derivatization procedures always led to the formation of mixtures of various conformational isomers from which the derivative in the cone-conformation could be isolated only by preparative HPLC. For a tetraester derivative it was shown by two-dimensional 1H NMR spectroscopy, that due to the different substituents the cone-conformation is strongly distorted. The sodium complex of this tetraester, however, assumes a regular cone-conformation again.

Tetraurea calix[4]arenes with sulfur functions: synthesis, dimerization to capsules, and self-assembly on gold.

Various calix[4]arene derivatives, fixed in the cone conformation by decylether groups and functionalized at their wide rim by urea residues, were synthesized. In two compounds (4f,g) sulfur functions were attached to the urea groups via different spacers in order to allow binding to metal surfaces. While they exist as single molecules in polar solvents, tetraurea calix[4]arenes of this type (4) combine to form dimeric capsules in aprotic, apolar solvents. A solvent molecule is usually included in such a capsule, if no guest with a higher affinity is present. In the presence of an equimolar amount of the tetratosylurea 5, the exclusive formation of heterodimers, consisting of one molecule o…

Intramolekulare Wasserstoffbrückenketten in Oligo(2-hydroxy-1,3-phenylen)methylenen und ihre Bedeutung für die Dissoziationskonstante des Endbausteins

Kinetik der Bromierung von Phenolen und phenolischen Mehrkernverbindungen, 5. Mitt.

The kinetics of the bromination of six differently substituted 2,6-bis(hydroxybenzyl)phenols having only one reactivepara position at the phenolic unit in the middle of the molecule were studied in acetic acid at 22°C. The reaction rate decreases if intramolecular hydrogen bonds between one or two hydroxy groups of the adjacent phenolic units and the hydroxy group of the reacting unit become possible, and it is especially low, if these hydrogen bonds are directed to the middle by bulky substituents inortho position. This must be explained by a smaller +M-effect of the hydroxy group of the reacting unit. A kinetic isotope effect is observed in deutero acetic acid, where the reaction rate is …

Tetra-CMPO-derivatives of calix[4]arenes fixed in the 1,3-alternate conformation

Calix[4]arene derivatives fixed in the 1,3-alternate conformation and substituted at one side by four carbamoylmethylphosphine oxide (CMPO) residues were synthesised. Two CMPO groups are directly attached to the wide rim, while the second pair is bound to the narrow rim via a tri- or tetramethylene spacer. Similar compounds, in which two CMPO groups at the wide rim are combined with two picolinamide groups or two ionisable carboxylic groups at the narrow rim, were also prepared. Some of these calixarene derivatives were studied as extractants for lanthanides (La3+, Eu3+, Yb3+) and thorium (Th4+) from acidic solution into methylene chloride. For selected samples, stability constants in metha…

Hydrogen-bonded dimers of a thiacalixarene substituted by carbamoylmethylphosphineoxide groups at the wide rim.

A thiacalix[4]arene derivative bearing four carbamoylmethylphosphineoxide groups at the wide rim forms hydrogen-bonded, dimeric capsules with S8 symmetry in the crystalline state and in apolar solvents, where the inclusion of cationic guests could be proved by 1H NMR and ESI mass spectra.

26,28-Diallyloxy-5,11,17,23-tetra-tert-butyl-25,27-bis(cyanomethoxy)calix[4]arene in the partial cone conformation

The title compound, C54H66N2O4, crystallizes with two mol­ecules in the asymmetric unit. Both adopt the typical partial cone conformation which was also found for 26,28-diall­yloxy-5,17-di-tert-butyl-25,27-bis­(cyano­meth­oxy)-11,23-dinitrocalix[4]arene [Danila, Bohmer & Bolte (2005). Org. Biomol. Chem. 3, 3508–3513]. The crystal structure of the title compound in the 1,2-alternate conformation has been determined recently [Danila, Bohmer & Bolte (2005). Org. Biomol. Chem. 3, 3508–3513].

Die Synthese reiner Oligo[hydroxy-5-nitro1,3-phenylen)-methylen]e, Verbindungen mit mehreren ortho- bzw. para-Nitrophenolbausteinen im Molekül

Zur Synthese der Oligo[(hydroxy-5-nitro-1,3-phenylen)methylen]e dienten chlormethylierte Nitrophenole sowie mono- und bischlormethylierte Bis- und Tris[(hydroxy-5-nitro-1,3-phenylen)methylen]e. Die Chlormethylierung erfolgte durch Umsetzung mit Chlormethylmethylather in Gegenwart von Zinkchlorid. Die Synthese der Oligomeren gelang mit guten Ausbeuten, wenn die chlormethylierten Verbindungen mit stark uberschussigem Nitrophenol und Zinkchlorid als Katalysator kondensiert wurden. Reaktionsbedingungen und unterschiedliche Reaktionsfahigkeiten werden mitgeteilt. Einige Verbindungen wurden in ihrer Struktur bestatigt, indem sie auf zwei voneinander unabhangigen Wegen dargestellt wurden. Damit wa…

ChemInform Abstract: Double- and Multicalixarenes

Zwei Chloridionen als Templat bei der Bildung eines cyclischen Hexaharnstoff-Moleküls

Polyamides 3 containing constant and definite numbers of oxyethylene units were prepared by condensation polymerization of suitable diamines and diesters, both of which containing oxyethylene units. The polymer structure was determined by IR and 1H NMR spectroscopy. Almost all polymers are crystals melting at ≈ 40°C and show a complexation ability towards alkalimetal cations. It was also found that diesters containing oxyethylene units show a higher condensation rate than alkylene diesters, which is explained by an inductive effect of the ether oxygene. However, no remarkable difference in the condensation rate was found between diamines containing oxyethylene units and the corresponding al…

Highly efficient separation of amines by electrokinetic chromatography using resorcarene-octacarboxylic acids as pseudo-stationary phases

Abstract Resorcarene-octacarboxylic acids, macrocyclic molecules built up by four alkylidene-bridged resorcinol units, were synthesized and used as pseudostationary phases in electrokinetic chromatography (EKC). Resorcarenes provide a stable structure and good solubility in electrolytes even with organic modifiers. The high electrophoretic mobility of the resorcarene-octacarboxylic acids introduced here as pseudostationary phases is based on the eight partly deprotonated carboxylic groups. This offers a broad migration time window, which is the main parameter for the resolution of peaks. From three compounds with different alkyl chain lengths (C 1 , C 5 , C 11 ), the C 11 -resorcarene-octa-…

Calixarenes as Stoppers in Rotaxanes

The synthesis of the amide-based rotaxane 7a bearing calix[4]arene blocking groups is described for the first time. While rotaxane formation fails if a calix[4]arene is functionalized at the upper rim with only an amino or methylamino group lacking any spacer, the prolonged amine 5a works successfully as stopper unit preventing dethreading of the dimeric wheel 1a by its size. Rotaxane formation of 8b was observed only by MALDI-TOF mass spectrometry of the reaction mixture of the amine 5b, the axle 6 and 1a. With the larger trimeric wheel 1b no stable rotaxane could be obtained. It either does not act as a concave template or its opening is too wide, even for the bulky calixarene stoppers.

Mass spectrometric study of oligourea macrocycles and their anion binding behavior

Two series, one of tris-urea macrocycles and another of hexakis-urea macrocycles, are examined by (tandem) Fourier-transform ion cyclotron resonance (FTICR) mass spectrometry with respect to their fragmentation patterns and anion binding properties. All macrocycles are based on two different building blocks, one of which is a very rigid xanthene unit and the other one is a more flexible diphenyl ether. The composition and the sequence of these units thus determine their flexibility. During the fragmentation of deprotonated oligourea macrocycles in the gas phase, one urea N-CO bond is cleaved followed by a scrambling reaction within the macrocycle structure. Consequently, fragments are obser…

Self-Assembled Polymers Based on bis-Tetra-Urea Calix[4]arenes Connected via the Wide Rim

Six double calixarenes were synthesised in which two tetra-urea calix[4]arenes are linked by a rigid spacer between the urea functions at their wide rim. The dimerisation of their tetra-urea parts leads to hydrogen-bonded polymeric assemblies in apolar solvents. The addition of the stoichiometric amount of a tetra-tosylurea calix[4]arene disrupts the polymeric structures due to the preferred formation of heterodimeric capsules between tetra-aryl and tetra-tosylurea calix[4]arenes. The existence of polymeric assemblies was further established by AFM studies on spin-coated samples.

A calixarene-based chromoionophore for the larger alkali metals

Abstract A bis(arylazo)calix[5]arene crown ether derivative displays large spectral changes upon complexation of cesium and rubidium salts, with good selectivity over the smaller alkali metals.

Inherently Chiral Calixarenes

Due to the nonplanarity of the basic 1 n -metacyclophane system, calixarenes and resorcarenes can be transformed into molecules with inherent chirality. Various attempts to achieve this goal are reviewed. Special emphasis is given to derivatives with C n -symmetry, including derivatives of spherand calixarenes and other calixarene-like macrocycles.

Separation of lanthanides and actinides using magnetic silica particles bearing covalently attached tetra-CMPO-calix[4]arenes

Calix[4]arene tetraethers in the cone conformation bearing four –NH–CO–CH2–P(O)Ph2 (= CMPO) residues on their wide rim and one, two or four ω-amino alkyl residues of various lengths at the narrow rim were synthesized. Reaction with dichlorotriazinyl (DCT) functionalized magnetic particles led to complete coverage of the available surface by covalently linked CMPO-calix[4]arenes in all cases. Magnetically assisted removal of Eu(III) and Am(III) from acidic solutions was distinctly more efficient with these particles in comparison to analogous particles bearing the same amount of analogous single-chain CMPO-functions. The best result, an increase of the extraction efficiency by a factor of 14…

Calix[4]arenes bridged at the lower rim

Calix[41 arenes, in which two opposite p-positions are linked by an aliphatic chain, and their derivatives show transport or complexation properties strongly dependent on the length of this chain. Bicyclo-calix[4]arenes, a special case of 1,3-bridged calix[41 arenes, and annelated calix[41 arenes, a special case of 1 ,&bridged calix [4] arenes, are also described. Although the preferred conformation of calix[4]arenes is the coneconformation due to its stabilization by a cyclic array of hydrogen bonds between the phenolic hydroxyl goups, these molecules are flexible, with a cone to cone inversion rate of about 150 8-1 for a calix[glarene at 47OC (ref. 1). The cone (or any other) conformation…

Redetermination of 5,11,17,23-tetra-tert-butyl-25,27-di(ethoxycarbonylmethoxy)-26,28-dihydroxycalix[4]arene chloroform disolvate at low temperature

The title compound, C52H68O8·2CHCl3, previously reported by Ferguson et al. [Supramol. Chem. (1996), 7, 223–228], has been rerefined against new intensity data. The geometric parameters are comparable, as far as they are available. However, the results of the present structure determination are of significantly higher precision.

Hydrogen-bonded dimers of tetra-urea calix[4]arenes stable in THF.

[structure: see text]. Whereas tetra-urea derivatives of tetra-alkoxy calix[4]arenes 1 exist as single molecules in THF, dimeric hydrogen-bonded capsules are exclusively found for the corresponding calix[4]arene derivatives 3 and 2 with two or four free hydroxyl groups. Comparison with the rigidified tetra-urea 5 suggests that this increased stability of the dimers is due to the stabilization of their four-fold symmetry by intramolecular hydrogen bonds between the phenolic hydroxyl groups.

5,11,17,23-Tetra-tert-butyl-25,26,27,28-tetrapentoxycalix[4]arene

The mol­ecule of the title compound, C64H96O4, adopts the typical pinched-cone conformation. The dihedral angles between the reference plane (defined by the C atoms of the methyl­ene bridges) and the benzene rings are 86.88 (4), 136.64 (5), 87.22 (4) and 133.99 (4)°.

Macrocyclic hexaureas: synthesis, conformation, and anion binding.

Varied flexibility: Cyclic oligoureas are formed by using anions as templates. Linking of six xanthene and/or diphenyl ether fragments by urea groups leads to the formation of five macrocyclic compounds with a 48-membered ring with variable flexibility (see picture). Their interaction with anions shows a strong influence of acetate and chloride ions on the cyclization from four precursor molecules. Five macrocylic compounds XXXXXX, XXDXXD, XDXDXD, XDDXDD, and DDDDDD with 48-membered rings, in which six xanthene and/or diphenyl ether fragments are linked through six urea (-NH-C(O)-NH-) groups, have been synthesized. In the cyclization step, a linear diamine was allowed to react with the appr…

Preferred dimerization of tetra-tolyl- and tetra-tosylurea derivatives of flexible and rigidified calix[4]arenes

The dimerization of tetratolyl- and tetratosyl-urea derivatives 1 and 2, derived from a tetrapentoxy calix[4]arene in the cone conformation and of the corresponding tetra-urea derivatives 3 and 4, in which the cone conformation is rigidified by the two crown-3 tethers, have been studied. All six possible equimolar mixtures were examined by 1H NMR using CDCl3 and CD2Cl2 as solvents. While no heterodimers are found for the combinations 1/3 and 2/4 in either solvent, all remaining combinations lead to the (exclusive) formation of heterodimers in CD2Cl2. In CDCl3 heterodimers are only observed for the combinations of 3 with 2 or 4. These results are discussed in terms of entropic and enthalpic …

Lanthanide complexation with CMPO and CMPO-calix[4]arenes in solution: spectrophotometric and electrospray mass spectrometric approaches.

The binding of lanthanide(III) cations with organophosphorous ligands like CMPO and related calix[4]arene-based derivatives have been investigated using two experimental methods. The stability constants of the lanthanum, europium and ytterbium complexes were first determined in methanol by UV absorption spectrophotometry in the presence of nitrate or chloride anions. The results showed that the stoichiometry and the stability of the complexes formed depend on the position of the CMPO moieties either on the wide or the narrow rim of the calixarene scaffold, the nature of the medium, the conformational mobility of the ligands. Complexation of lanthanum was also followed by ESI-mass spectromet…

Dissymmetric calix[4]arenes: Optical resolution of some conformationally fixed derivatives

Various possibilities to obtain intrinsically chiral calix[4]arenes are discussed. The enantiomers of three 1,3-dietheresters and one monoether compound derived from dissymmetric calix[4]arenes with C4 symmetry were separated by HPLC using chiral stationary phases and characterized by their CD spectra. © 1993 Wiley-Liss, Inc.

Kinetik der bromierung von phenolen und phenolischen mehrkernverbindungen, 3. Die reaktionsfähigkeit isomerer dreikernverbindungen und einer homologen reihe von mehrkernverbindungen

Die Geschwindigkeit der Bromierung von drei isomeren Dreikernverbindungen und einer homologen Reihe von Mehrkernverbindungen mit bis zu sechs Methylphenolbausteinen pro Molekul wurde in Eisessig bei 22°C UV-spektroskopisch gemessen. Alle Verbindungen waren so gewahlt, das sie nur eine reaktionsfahige ortho-Stellung in bezug auf die Hydroxy-Gruppe besasen. Es zeigte sich, das die Reaktionsgeschwindigkeit im wesentlichen dadurch bestimmt wird, ob zwischen den phenolischen Hydroxy-Gruppen des reagierenden Endbausteins und des unmittelbar benachbarten Bausteins eine intramolekulare Wasserstoffbrucke moglich ist. Ist dies nicht der Fall, so sind die Geschwindigkeitskonstanten zweiter und dritter…

Tropylium cation capsule of hydrogen-bonded tetraurea calix[4]arene dimers

The interaction between tropylium salts and tetraurea calix[4]arene derivatives (such as 1 and 2) was studied in solution using 1D, 2D, diffusion, VT NMR and UV–visible spectroscopy. It was found that tropylium salts form charge transfer complexes with both the monomers and dimers of the tetraurea calix[4]arene derivatives depending on the experimental conditions. Compound 1 increases dramatically the solubility of tropylium salts in apolar solvents such as C2D4Cl2, CDCl3 and CD2Cl2 by forming the molecular capsule 1·C7H7+·1. In contrast to the benzene capsule of 1, in 1·C7H7+·1 the hydrogen bonds in the equatorial region that hold together the two parts of the dimer change their directiona…

Unusual conformations of 1,3-dialkoxythiacalix[4]arenes in the solid state

The structures of three syn-1,3-dialkoxythiacalix[4]arenes with unusual conformations in the solid state are reported. The pinched cone conformation of syn-2 2 ,4 2 -dihydroxy-1 2 ,3 2 -bis-(prop-2-enyloxy)thiacalix[4]arene, C 30 H 24 O 4 S 4 , (3a), is stabilized by two intramolecular hydrogen bonds, remarkably formed from both OH groups to the same ether O atom. In syn-22,42-dihydroxy-1 5 ,2 5 ,3 5 ,4 5 -tetranitro-12,32-bis(prop-2-enyloxy)thiacalix[4]arene acetone disolvate, C 30 H 20 N 4 O 12 S 4 ·-2C 3 H 6 O, (3b1), the molecule is found in the 1,3-alternate conformation. The crystallographic C2 symmetry is due to a twofold rotation axis running through the centre of the calixarene rin…

Modification of calix[4]arenes with CMPO-functions at the wide rim. Synthesis, solution behavior, and separation of actinides from lanthanides

Two calix[4]arene tetraethers (Y = C5H11, C14H29) bearing on their wide rim four –N(Me)–CO–CH2–P(O)Ph2 residues were synthesized for the first time. Their ability to extract lanthanides and actinides from an acidic aqueous phase to organic phases (CH2Cl2, NPHE) was studied. In comparison to the corresponding –NH-analogs, they are less efficient extractants, the selectivity for the light over the heavy lanthanides is less pronounced, while there is still an interesting selectivity of Am3+ over Eu3+. Stability constants for selected lanthanide salts were determined also in homogenous phase (methanol, acetonitrile) but do not account for the different extraction results. The complexation of Gd…

Untersuchungen zurFriesschen Verschiebung von Estern derortho- undpara-Methoxybenzoes�ure

TheFries rearrangement of different methoxy benzoates has been investigated. Frompara-methoxy benzoates the corresponding hydroxy-4′-methoxy benzophenones could be obtained in good yields by treatment withLewis acids (especially TiCl4) in nitromethane at 20°C (4-hydroxy derivatives) or without solvent at 120°C (2-hydroxy derivatives). Under the same conditions only demethylation occurs withortho-methoxy benzoates leading to the corresponding salicylates. Small amounts of hydroxy-2′-methoxy benzophenones were obtained by treatment with polyphosphoric acid.

Water soluble polyamides with iminoethylene and oxyethylene units in the main chain were obtained by condensation polymerization of diethylenetriamine and triethylenetetramine with suitable dimethylesters containing two or three oxyethylene units. The molecular weights were in the range of Mn = 5000–7000. By potentiometric and conductometric titration only 80–85% of the expected amount of basic groups was found which was probably caused by branching. Durch Polykondensation von Diethylentriamin und Triethylentetramin mit Dimethylestern von Sauren, die zwei oder drei Oxyethyleneinheiten enthalten, wurden wasserlosliche Polyamide mit Iminoethylen- und Oxyethyleneinheiten in der Hauptkette erha…

CMPO-substituted calix[6]- and calix[8]arene extractants for the separation of An3+/Ln3+ from radioactive waste

Abstract Three calix[6]arene derivatives ( 1a – c ) and two calix[8]arene derivatives ( 2a , b ), with six and eight CMPO residues, respectively, attached to the narrow/lower rim via ether links, were synthesised. Preliminary liquid–liquid extraction studies for Eu(III) and Am(III) from aqueous nitric acid to o -nitrophenylhexyl ether reveal remarkable properties with respect to efficiency and selectivity, especially for the tert -butylcalix[6]arene derivative with a –(CH 2 ) 3 – spacer.

Die darstellung nitrierter phenolischer mehrkernverbindungen durch kondensation von nitrophenol und seinen derivaten

Es wurden einige Mehrkernverbindungen dargestellt, die aus Nitrophenoleinheiten bestehen, welche in ortho-Stellung zur phenolischen OH-Gruppe uber Methylengruppen verbunden sind. Die Nitrierung fertiger phenolischer Mehrkernverbindungen ist hierzu nicht geeignet. Jedoch gelingt die Darstellung durch Kondensation von Nitrophenolen mit Formaldehyd oder durch Kondensation von chlormethylierten Nitrophenolen mit anderen Nitrophenolen. Im ersten Fall ist die Bildung des Benzdioxanringes als Nebenreaktion zu beobachten. All dargestellten Mehrkernverbindungen wurden dunnschichtchromatographisch auf Reinheit gepruft; ihre Struktur wurde in beinahe allen Fallen durch voneinander unabhangige. Synthes…

Selective Derivatization of Calix[4]arenes via Amino Groups Attached to the Wide Rim

A new strategy is proposed for the synthesis of tetraether derivatives of calix[4]arenes bearing at the wide rim nitro and phthalimido groups in well defined positions. Since both groups are precursors of amino functions, calix[4]arenes substituted by different N-acylamino residues are easily available in four steps. The essential steps during the synthesis of the precursor consist in the protection of amino groups by the formation of their phthalimides followed by ipso-nitration of the remaining tert-butylphenol ether units. This nitration occurs without side reactions at the phthalimido substituted units, in contrast to simple N-acyl derivatives.

Selbstorganisierte, über Wasserstoffbrücken gebundene dimere Kapseln mit hoher kinetischer Stabilität

Fourfold [2]rotaxanes of calix[4]arenes by ring closure.

Dimeric Capsules Formed by Tetra-CMPO Derivatives of (Thia)Calix[4]arenes

Thiacalix[4]arene 2, calix[4]arene 3 a and its tetraether fixed in the cone conformation 3 b form homo- and heterodimeric capsules in apolar solvents, which are held together by a seam of NH⋅⋅⋅O=P hydrogen bonds between carbamoylmethyl phospine oxide functions attached to their wide rim. Their internal volume of ∼370 A3 requires the inclusion of a suitable guest. Although neutral molecules such as adamantane (derivatives) or tetraethylammonium cations form kinetically stable complexes (1H- and 31P-time scale), the included solvent is rapidly exchanged. The internal mobility of the included tetraethylammonium cation is distinctly higher (ΔG=42.5 and 49.7 kJ mol−1 for 3 a and 3 b) than that f…

Die Dissoziationskonstanten von 2,3?-und 2,4?-Dihydroxydiphenylmethanderivaten

The pK-values of the first and second degree of dissociation of 2.3′-dihydroxy-6′-methyl-3.5-dinitro-diphenylmethane, 2.3′-dihydroxy-6′-methyl-5-nitro-diphenylmethane, 2.3′-dihydroxy-5.6′-dimethyl-3-nitro-diphenylmethane, 2.4′-dihydroxy-3′. 5′-dimethyl-3.5-dinitro-diphenylmethane, 2.4′-dihydroxy-3′. 5′-dimethyl-5-nitro-diphenylmethane and 2.4′-dihydroxy-3′.5.5′-trimethyl-3-nitrodiphenylmethane were determined in aqueous solution at 25°C by the spectrophotometric method. The observed pK-values are compared with those of 2-methyl-4.6-dinitro-phenol, 2-methyl-4-nitrophenol, 2.4-dimethyl-6-nitrophenol, 3.4-dimethylphenol and 2.4.6-trimethylphenol which serve as model compounds for the single ph…

Self-assembled dimers with supramolecular chirality

The possibilities to form dimeric capsules with supramolecular chirality from tetraurea calix[4]arenes composed of two different phenolic urea units are discussed in general and demonstrated experimentally for various selected examples.

Rational Synthesis of Multicyclic Bis[2]catenanes

Bis-loop tetraurea calix[4]arene 6 has been prepared by acylation of the wide-rim calix[4]arene tetraamine 1 with the activated bis(urethane) 8 under dilution conditions. Similarly the bis(Boc-protected) tetraamine 2 is converted into the mono-loop derivative 3 which after deprotection and acylation gives the bisalkenyl derivative 5. In apolar solvents this tetraurea calix[4]arene 5 forms regioselectively a single hydrogen-bonded homodimer, from which the bis[2]catenane 10 a is formed in 49 % by a metathesis reaction followed by hydrogenation. Bis-loop derivative 6 forms no homodimers for steric reasons, but a stoichiometric mixture with the open-chain tetraalkenyl derivative 7 a contains e…

Wasserstoffbrücken-gebundene Analoga von Cavitanden

Dimeric capsules of tetraurea calix[4]arenes. MD simulations and X-ray structure, a comparison

The single crystal X-ray structure of a homodimer of a tetra(tolylurea) calix[4]arene including a tetraethylammonium cation as guest shows an expansion of the capsule and a distortion of its shape, in comparison to the structure of a similar dimer with an encapsulated benzene molecule. Thus, only 8 of 16 possible hydrogen bonds are present in the hydrogen bonded belt holding together the two hemispheres. The encapsulated cation is disordered over two equivalent positions with two methyl groups pointing to the equator, while two methyl groups pointing to the poles form CH–π interactions with the inner surfaces of the calixarene cavities. MD simulations are in agreement with the distorted X-r…

1,3-Alternate calix[4]arenes, selectively functionalized by amino groups

General strategies are described to synthesize calix[4]arenes which are fixed in the 1,3-alternate conformation and substituted selectively by amino groups. These derivatives are useful starting materials for the attachment of various groups via amide bonds, as demonstrated by several examples, but may be converted also to ureas, imides or azomethines. Four amino groups may be attached to the narrow rim via(several) methylene groups as spacer by O-alkylation with omega-bromophthalimides or omega-bromonitriles. From the resulting tetraethers the amino functions are obtained by cleavage with hydrazine or by hydrolysis, allowing a selective functionalisation of both sides of the molecule (phen…

ChemInform Abstract: Chirality in Calixarenes and Calixarene Assemblies

Mannich Reactions with Amino Alcohols

The condensation of resorcarenes 1 with various amino alcohols and an excess of formaldehyde was studied. The tetrabenzoxazines 2a−e were found as the only products in the reaction with 6-aminohexan-1-ol, 4-aminobutan-1-ol, and 2-aminoethanol, while 3-aminopropan-1-ol forms the tetraoxazine 3 as the main product. In the case of aminoethanols substituted at the 2-position with alkyl groups, the tetraoxazolidines 4 are the preferred reaction products, while 1-methyl aminoethanol (1-amino-propan-2-ol) yields predominantly the tetrabenzoxazine 2f. The structures of all these compounds have been confirmed by NMR spectroscopy and additionally by single-crystal X-ray analysis in the case of 2a and…

Book Review: Resorcinol. Its Uses and Derivatives.(Series: Topics in Applied Chemistry.) By H. Dressler

Aminolysis of monoacetyl derivatives of 2,2′ -dihydroxydiphenylmethanes

A neighboring group effect was found for the aminolysis of the second acetyl group in acetates of 2,2′-dihydroxydiphenylmethane derivatives containing a nitrophenol and a methylphenol unit. Kinetic measurements with an excess of n-butylamine in dioxane were done with 2-(2-hydroxy-3, 5-dinitrobenzyl)-4-methylphenyl acetate (1), 2-(2-hydroxy-5-nitro-benzyl)-4-methylphenyl acetate (2), and 2-(2-hydroxy-3-nitro-5-methylbenzyl)-4-methyl-phenyl acetate (3). The maximum rate was found for compound 2. When the concentration of n-butylamine was varied over a large range, the results obtained for compound 2 could be explained best, by assuming that the acetyl group in the methylphenol unit is aminoli…

HALOGEN AS A READILY CLEAVABLE PROTECTIVE GROUP FOR REACTIVE POSITIONS IN PHENOLS AND PHENOLIC COMPOUNDS

Die Dissoziationskonstanten von 2,2?-Dihydroxydiphenylmethanderivaten

The pK-values of the first and second degree of dissociation of 2.2′-dihydroxy-5-methyl-3′.5′-dinitro-diphenylmethane, 2.2′-dihydroxy-5-methyl-5′-nitro-diphenylmethane and 2.2′-dihydroxy-5.5′-dimethyl-3′-nitro-diphenylmethane were determined in aqueous solution at 25°C spectrophotometrically. Comparing the observed pK-values with those of 2-methyl-4.6-dinitrophenol, 2-methyl-4-nitrophenol, 2.4-dimethyl-6-nitro-phenol and 2.4-dimethylphenol, we found a decrease of the values of pK1 and an increase of pK2. We explain this by the formation of an intramolecular hydrogen bridge which stabilizes the anion of the half dissociated form. This assumption is supported by the UV spectra.

Cyclic triureas—synthesis, crystal structures and properties

The synthesis of 24-membered macrocycles is described, in which rigid xanthene units (X) and/or diphenyl ether units (D) as flexible analogues are linked via urea groups. All four possible combinations (XXX, XXD, XDD, DDD) have been obtained with yields of 40-72% for the cyclisation step. In two cases, the respective cyclic hexamers (XXDXXD, XXXXXX) were also isolated. Two compounds have been characterised by a single crystal X-ray analysis of the free triurea (XXD, XDD) and one example (DDD) by its complex with tetrabutylammonium chloride. It shows the chloride anion in the centre of the macrocycle, held by six NH...Cl- hydrogen bonds. The interaction with various other anions has been stu…

Molecular Motions within Self-Assembled Dimeric Capsules with Tetraethylammonium Cations as Guest

Hydrogen-bonded, dimeric capsules of calix[4]arenes substituted at the wide rim by four urea functions show unprecedented dynamic features when a tetraethylammonium cation is included as a guest. The seam of hydrogen bonds C=O...(HN)2C=O in the equatorial region which holds the two calixarene counterparts together changes its directionality fast (at 25 degrees C), while the dimer itself is kinetically stable on the NMR time scale. An energy barrier of deltaG++ = 49.9 kJmol(-1) (Tc 276 K) was estimated for this reorientation from variable-temperature (VT) NMR measurements. Lowering the temperature to about -50 degrees C restricts also the rotation of the encapsulated tetraethylammonium catio…

Informational rigidity in mesitylene-based calix[4]arenes adopting a 1,3-alternate conformation

Abstract Two chiral derivatives of a mesitylene-based calix[4]arene known to exist in the 1,3-alternate conformation were prepared by the attachment of homochiral residues to the four exo -hydroxy groups. Thus, the enantiotopic protons of the central scaffold became diastereotopic, leading to a doubling of their 1 H NMR signals in one example. From the temperature independence of the NMR spectrum, a lower limit of 24.2 kcal/mol could be estimated for the barrier of ring inversion. MM3 calculations confirm the 1,3-alternate conformation as the energy minimum, and estimate a barrier of 25.7 kcal/mol for the 1,3-alternate-to-1,3-alternate* interconversion process. This high barrier is due to t…

A macrocyclic diurea derived from diphenylether

Abstract A new 16-membered cyclic diurea was synthesized and tested as potential receptor for fluoride. 1 H and 19 F NMR spectroscopy revealed an unexpected deprotonation of both urea groups after initial 1:1 binding. A single crystal X-ray structure shows bifurcated hydrogen bonds to two DMSO molecules.

Fine-Tuning the Dimerization of Tetraureacalix[4]arenes

Calix[4]arenes substituted by four urea residues at their wide rim form hydrogen-bonded homo- and heterodimeric capsules in apolar solvents. If urea groups are covalently connected to loops or substituted by bulky residues, the dimerization may be restricted to those pairs in which the loops do not overlap and for which the residues are small enough to pass the loops. In the present study, we describe the dimerization properties of tetraureas with one, two (adjacent or opposite), three, or four loops and those bearing (additionally) up to four residues of different size: a = tolyl, b = 3,5-di-tertbutylphenyl, c = 4-propyloxy-3,5-di-(tert-butylphenyl)phenyl, and d=4-[tris-(4-tert-butylphenyl…

Rational Synthesis of Resorcarenes with Alternating Substituents at Their Bridging Methine Carbons

Diastereoselective Functionalization of a Spherand‐Type Calixarene

Condensation of 5,5'-di-tert-butyl-2,2'-dihydroxybiphenyl (1) with formaldehyde yields a cyclic trimer 2 (and tetramer 3) having three (four) methylene groups less than a calix[6]arene (calix[8]arene). Alkylation of the (flexible) trimer with ethyl bromoacetate gives exclusively the stereoisomer 4 with C 2 symmetry, while the isomer with D 3 symmetry is not observed. Two isomers 6a and 6b (C 2 and C 1 symmetry) are obtained by treatment with tert-butyl bromoacetate which both are converted by transesterification with methanol into the same hexamethyl ester 5 having C 2 symmetry. These results are rationalized by restricted rotation around Ar-Ar bonds for larger O-alkyl groups also around Ar…

Tetra-Urea Calix[4]arenes— From Dimeric Capsules to Novel Catenanes and Rotaxanes

Rotaxanes and Catenanes Derived from Tetra-Urea Calix[4]arenes

Calix[ 4] arenes, substituted by four urea groups at their wide rim, form dimeric capsules in apolar solvents, which are held together by a seam of intermolecular hydrogen bonds. The heterodimerisation of tetra-aryl and tetratosyl ureas was used to synthesize various derivatives, in which adjacent urea residues are connected to form two, three or four loops. The aliphatic connections were tied by olefin metathesis between adjacent alkenyl residues followed by hydrogenation. Heterodimers of tetra-alkenyl substituted tetra-ureas and bis- or tetraloop derivatives were converted analogously to multiple catenanes. Tetra[2]rotaxanes were obtained in a similar manner. In addition to the spectrosco…

Untersuchungen zur friesschen verschiebung an hydroxybenzylphenol-derivaten

An den Acetaten 2a–c, 3b, 4b und 4d von sechs Hydroxybenzylphenol-Derivaten wurde die Friessche Verschiebung mit AlCl3 als Katalysator in Nitrobenzol bei Temperaturen zwischen 40 und 70°C durchgefuhrt. Neben den zu erwartenden Hauptprodukten der Friesschen Verschiebung konnte durch Saulenchromatographie eine Reihe von Zwischen- und Nebenprodukten isoliert werden. Daraus ging hervor, das wahrscheinlich eine teilweise Verseifung der Acetate als Nebenreaktion stattfindet. Eine Wanderung der Acetylgruppe an den benachbarten Phenolbaustein des gleichen Molekuls konnte nicht beobachtet werden. Samtliche Verbindungen, einschlieslich der Ausgangsprodukte, wurden durch ihre IR- und 1H-NMR-Spektren c…

The interaction of poly(L-glutamic acid) with 3,6-dioxaoctamethylenediamine was studied by circular dichroism spectroscopy under different conditions. In aqueous solution at pH 5,6 and in aqueous 1,4-dioxane (30–50 vol.-%) at pH 7,3 the conformation of poly(L-glutamic acid) was completely changed from α-helical to random coil in the presence of an excess of the diamine.

1H NMR-spektroskopische Untersuchungen zur Strukturaufklärung von Oligo(hydroxy-5-nitro-1,3-phenylen)methylen Verbindungen

Die 1H NMR-Spektren von 51 Oligo(hydroxy-5-nitro-1,3-phenylen)methylen Verbindungen (17 Zwei-, 18 Drei-, 14 Vier- und 2 Funfkernverbindungen) wurden in Pyridin als Losungsmittel aufgenommen. Bei Verbindungen mit ortho-Nitrophenolbausteinen zeigten die Signale fur die Protonen der Methyl- bzw. Methylengruppen in allen Fallen charakteristische chemische Verschiebungen δ, so das eine eindeutige Unterscheidung zwischen Methylgruppen in para- (δ=2,09−2,15 p.p.m.) und ortho-Stellung (δ=2,22−2,28 p.p.m.) zur phenolischen Hydroxyl-Gruppe, sowie zwischen para-para- (δ=3,77−3,97 p.p.m.), ortho-para- (δ=4,02−4,12 p.p.m.) und ortho-ortho-Methylenbrucken (δ=4,21−4,32 p.p.m.) moglich war. Bei Verbindunge…

Wide Rim Urethanes Derived from Calix[4]arenes:  Synthesis and Self-Assembly

[reaction: see text] Calix[4]arenes 4, substituted at the wide rim by four N-tolyl-urethane groups, were synthesized, as well as derivatives 10a,b bearing two or three tolyl-urea groups beside of one or two urethane group(s). In contrast to tetra-tolyl urea 11, the urethane derivatives do not form hydrogen-bonded, dimeric capsules in CDCl3 or benzene-d6, but the dimerization can be induced for the triurea 10b by tetraethylammonium cations as guests. The quantitative formation of heterodimers is observed for all urethanes 4 and 10a,bin benzene-d6 in mixtures with a "tetra-loop" tetraurea 14, while "bisloop" tetraureas 13 require di- or triurea derivatives 10a,b for a clean heterodimerization.

Dendritic octa-CMPO derivatives of calix[4]arenes

Abstract Calix[4]arenes substituted at the narrow or wide rim by eight carbamoylmethyl-phosphine oxide (CMPO) functions in a dendritic manner were synthesised and studied in extraction of Eu 3+ and Am 3+ from aqueous nitric acid into o -nitrophenylhexyl ether. 1 H NMR relaxivity titrations for a wide rim octa-CMPO reveal the clear formation of a solvent-free 1:2 ligand/metal complex, while the wide rim tetra-CMPO formed oligomeric complexes under similar conditions.

The synthesis of double-calixarenes

Abstract Macrocyclic molecules consisting of two calix[4]arene moieties linked via their p-positions by one 1, two 2 or four 3 aliphatic chains were synthetized for the first time.

Carbamoylmethylphosphinoxide derivatives based on the triphenylmethane skeleton. Synthesis and extraction properties.

Two different strategies were used to synthesize tri(2-alkoxy-5-nitrophenyl)methanes 6a,b. The X-ray structures of 6a and its precursor 5 show the molecules in a conformation with a syn-orientation of the nitro and alkoxy groups. Hydrogenation and acylation by the appropriate active ester gave the corresponding tri-CMPO derivatives 4a,b. Their ability to complex lanthanide ions was studied by NMR spectroscopy and by nuclear magnetic relaxation dispersion and further characterized by quantum mechanical calculations. Extraction experiments from acidic solution to dichloromethane reveal a reasonable selectivity of Am(III) over Eu(III), but in contrast to similar tetra-CMPOs derivatives of cali…

The Cone-to-Cone Interconversion of Partially O-Methylated Calix[4]arenes:  First Experimental Values for the Energy Barriers

Reversible Dimerization of Tetraureas Derived from Calix[4]Arenes

Calix[4]arene derivatives, substituted at the wider rim by four urea functions are easily available in great variety. In apolar solvents like benzene or chloroform they dimerize via NH…O=C hydrogen bonds encapsulating a single solvent molecule as guest. The exclusive formation of dimers has been proved in solution by NMR, while their shape has been characterized by single crystal X-ray analysis. The kinetic stability and the rate of the guest exchange have been studied by NOESY experiments using a derivative with lower symmetry.

Darstellung von Oligo[(hydroxy-1,3-phenylen)methylen]en mit Hydroxynitrophenylen- und Alkylhydroxyphenyleneinheiten

Possibilities to synthesize substituted oligo[(hydroxy-1,3-phenylene)methylene]s containing hydroxynitrophenylene and alkylhydroxyphenylene units are discussed. The only successful way to introduce the hydroxynitrophenylene unit consists in the condensation of chloromethylated nitrophenols with an excess of alkylphenols. The resulting compounds can be prolonged stepwise at the alkylhydroxyphenylene end group by alternating hydroxymethylation and further condensation with alkylphenols. Thus, including the hydroxymethylated compounds, 11 dinuclear, 17 trinuclear, and 5 tetranuclear compounds were obtained for the first time. Some of them were characterized by their acetyl derivatives.

Anionic tert-butyl-calix[4]arenes substituted at the narrow and wide rim by cobalt bis(dicarbollide)(1−) ions and CMPO-groups. Effect of stereochemistry and ratios of the functional groups on the platform on the extraction efficiency for Ln(III)/An(III)

Abstract Two ionic calix[4]arenes substituted at the narrow rim with an unpaired number ( n ) of cobalt bis(dicarbollide)(1−) anions ( 1 − ) ( n  = 1 and 3) and (4 −  n ) CMPO groups ( 3c , 4c ) have been synthesized via a three-step procedure based on nitrile substituted calix[4]arene precursors. Conjointly with them, the compound with a paired ratio of the groups, where n  = 2 and the same substituents are located in mutually adjacent 1,2-positions, is reported ( 5c ). Another compound with the paired ratio, but from a wide rim series ( 6c ) ( n  = 2) was successfully prepared starting from calix[4]arenes substituted with two nitro functions and two –OH sites available for further modific…

ChemInform Abstract: Selective Dimerization of Tetraurea Calix[4]arenes

Guest exchange in dimeric capsules formed by tetra-urea calix[4]arenes

Ten tetra-urea calix[4]arene derivatives with different ether residues (methyl, pentyl, benzyl, all combinations of methyl and pentyl, 1,3-dibenzyl-2,4-dipentyl), including also the tetrahydroxy compound and the 1,3-dipentyl ether, were synthesised. Their urea groups were substituted with a lipophilic residue to ensure sufficient solubility in cyclohexane. Thus, kinetics for the exchange of the included guest (benzene) against the solvent (cyclohexane) could be followed by 1H NMR spectroscopy. The apparent first order rate constants decrease with increasing size of the ether residues from methyl to benzyl by more than three orders of magnitude. This can be understood by a decreasing flexibi…

Control of surface plasmon resonances in dielectrically coated proximate gold nanoparticles immobilized on a substrate

We present experimental and theoretical results for the changes in the optical-plasmon resonance of gold-nanoparticle dimers immobilized on a surface when coated with an organic dielectric material. The plasmon band of a nanoparticle dimer shifts to a higher wavelength when the distance between neighboring particles is decreased, and a well-separated second peak appears. This phenomenon is called cross-talk. We find that an organic coating lets cross-talk start at larger separation distances than for uncoated dimers by bridging the gap between immobilized nanoparticles (creating optical clusters). We study this optical clustering effect as a function of the polarization of the applied light…

Calixarenes as Stationary Phases

Der einfluß benachbarter grundbausteine auf die ammonolyse von essigsäureestern phenolischer mehrkernverbindungen

Die Ammonolyse der Essigsaureester verschiedener phenolischer Zwei- und Dreikernverbindungen, die neben Methylphenolbausteinen jeweils einen Nitrophenolbaustein enthalten, wurde untersucht. In allen Fallen wird wie bei einkernigen Nitrophenylestern die Esterbindung im Nitrophenolbaustein ammonolytisch gespalten. Wenn die Bausteine uber Methylenbrucken in ortho-Stellung zu den phenolischen Hydroxylgruppen verknupft sind, werden jedoch auch die Esterbindungen in den Methylphenolbausteinen gespalten, obwohl die Ester von Methylphenolen und Mehrkernverbindungen, die nur Methylgruppen als Substituenten tragen, unter gleichen Bedingungen durch Ammoniak nicht angegriffen werden. In ubereinstimmung…

Supramolecular structures formed by calix[8]arene derivatives.

Octamethoxy calix[8]arenes substituted in the para position by amide, urea, and imide functions were synthesized from the octamethyl ether of tert-butylcalix[8]arene by ipso nitration, reduction, and acylation. Scanning force microscopy of spin coated samples on graphite suggests that these derivatives self-organize into tubular nanorods via hydrogen bonds between p-amide functions. A single-crystal X-ray structure reveals a centrosymmetric conformation for the octanitro derivative. [structure: see text]

Double- and Multi-Calixarentes

Calixarenes are easily (and often selectively) functionalized and therefore they can be combined in various ways to larger molecules containing more than one calixarene substructure. In the following chapter we will try to give an overview on such multicalixarenes held together by "conventional" covalent links. Self-assembled structures are treated separately in Chapter 8. The earliest examples for double calixarenes of importance are the carcerands and hemicarcerands of D. Cram in which two resorcarene derived cavitands are combined. Due to their unique properties to include (more or less permanently) smaller molecules, they are treated separately in Chapter 10. Further combinations of cav…

Hydrogen bonded calixarene capsules kinetically stable in DMSO.

Half-life times up to 4 days in DMSO at room temperature are observed for the decomposition of dimeric capsules of urea substituted calix[4]arenes held together by a combination of hydrogen bonds, mechanical entanglement and cation–π interactions.

Selective Derivatizations of Resorcarenes. 4. General Methods for the Synthesis of C2v-Symmetrical Derivatives