Reversible dehydration polymerization of terephthalate bridged [{Cu2(2,2′-bpy)2(tp)(H2O)3(NO3)}·H2O·NO3]2

2006

The title compound is the first example of a molecular magnet sponge, which exhibits a carboxylate-assisted unique reversible dehydrative polymerization–rehydrative monomerization phenomenon.

Unique copper ion catalyzed hydrolytic cleavage of C–N(2) bond of thiosemicarbazide

2006

Abstract For the first time, stable but coordinatively unsaturated Cu(II) complexes [Cu(2,2′-bpy)X2] · xH2O (X = ClO4, NO3, CH3COO and 2,2′-bpy = 2,2′-bipyridyl) have been found to promote the hydrolysis of C–N(2) bond of thiosemicarbazide (tsc) at 25 °C and at neutral pH yielding monomeric [Cu(2,2′-bpy)(NCS)2]. Direct reaction between [Cu(2,2′-bpy)2]Cl2 · 6H2O, KSCN and CuCl2 results in polymeric [Cu(2,2′-bpy)(NCS)2]n [1] [Inorg. Chim. Acta. 286 (1999) 108]. Similarly tsc is cleaved by Cu(I) complex [Cu(ϕ3P)2(CH3CN)2]ClO4 [ϕ3P = triphenylphosphine] which itself is converted into dimeric [Cu(ϕ3P)2(NCS)]2.

Complexation behaviour of hexadentate ligands possessing N2O4and N2O2S2cores: differential reactivity towards Co(ii), Ni(ii) and Zn(ii) salts and str…

2004

Reactions of divalent metal salts of Co, Ni and Zn with 1,2-di(salicylaldimino-o-phenylthio) ethane (H2L1) and 1,2-di(naphthaldimino-o-phenylthio) ethane (H2L2), having N2O2S2 cores, and 1,2-di(O-salicylaldimino-o-hydroxyphenyl) ethane (H2L3), having a N2O4 core, have been explored. Out of the three ligands and the nine products obtained from the corresponding reactions, two ligands and seven products were crystallographically characterized. However, all the ligands and the products were characterized by analytical and spectral methods. Reaction of H2L1 and H2L2 with Co(II) salts results in oxidative cleavage of the C-S bond to produce a Co(III) product bound to two dissimilar tridentate li…

Anion template effect and the polymerization degree

2005

Two 2D (M1 and M2) and one 1D (M3) metal‐organic frameworks (MOFs) have been prepared from pyridine functionalized tetradentate ligand tetrakis(nicotinoxymethyl)methane TNM with silver tetrafluoroborate, nickel chloride, and copper hexafluorophosphate. M1 manifests a previously unpresented mode of 4,4 threefold parallel interpenetration for 2D MOFs. Large channels (vdW diameter 9.4 Å) through eclipsed 2D layers of M2 were observed. While the open space percentage in the noninterpenetrated M2 was 38.0 %, the triple interpenetration of the sheets of M1 reduced the void to 10.8 %. With the same ligand and a similar, weakly coordinating anion as that in M1, the structure M3 was rendered one‐dim…

Unusual interaction extended between the pyranose ring oxygen and Zn(II) center in the complexes derived from 4,6-O-butylidene/ethylidene-N-(α-hydrox…

2003

The Zn(II) complexes of 4,6-O-butylidene/ethylidene-N-(α-hydroxynaphthylidene/o-hydroxybenzylidene)-β-Image -glucopyranosylamine have been synthesized and characterized using spectral and analytical methods and structure for one of the products was established. The geometry of the complexes vary from unusual distorted trigonal bipyramidal to pseudo-bicapped tetrahedron depending upon the extent of binding of pyranose ring oxygens to the Zn(II) ion, as evidenced from crystal structures. Such interaction is also reflected on the optical rotation and CD spectral properties of these complexes in solution.

N-Heterocyclic Phosphenium, Arsenium, and Stibenium Ions as Ligands in Transition Metal Complexes: A Comparative Experimental and Computational Study

2005

Reaction of 2-chloro-1,3,2-diazaarsolenes and -diazaphospholenes with Tl[Co(CO)4] gives instable complexes of type [Co(ER2)(CO)4] which decarbonylated to yield [Co(ER2)(CO)3]. Spectroscopic and X-ray diffraction studies revealed that the tetracarbonyl complexes can be formulated as ion pair for E = P and as covalent metalla-arsine for E = As, and the tricarbonyl complexes as carbene-like species with a formal E=Co double bond. A similar reactivity towards Tl[Co(CO)4] was also inferred for 1,3,2-diazastibolenes although the products were not isolable and their constitution remained uncertain. Evaluation of structural and computational data suggests that the weak and polarized Co–As bond in […

4,4'-[Thiophene-2,5-diylbis(ethyne-2,1-diyl)]dibenzonitrile

2008

In the solid state, the title compound, C(22)H(10)N(2)S, forms centrosymmetric dimers by pairs of non-classical C-H⋯S hydrogen bonds linking approximately coplanar mol-ecules. The benzene ring involved in this inter-action makes a dihedral angle of only 7.21 (16)° with the thio-phene ring, while the other benzene ring is twisted somewhat out of the plane, with a dihedral angle of 39.58 (9)°. The hydrogen-bonded dimers stack on top of each other with an inter-planar spacing of 3.44 Å. C-H⋯N hydrogen bonds link together stacks that run in approximately perpendicular directions. Each mol-ecule thus inter-acts with 12 adjacent mol-ecules, five of them approaching closer than the sum of the van …

cis-Diazido[bis(diphenylphosphino)methane-κ2P,P′]ruthenium(II) dichloromethane 0.42-solvate

2006

Submitted by António Freitas (amsf@uma.pt) on 2019-06-13T13:44:22Z No. of bitstreams: 1 cis-Diazidobis(diphenylphosphino)methane-j2PP000ruthenium(II) dichloromethane 0.42-solvateJoãoRodrigues.pdf: 167616 bytes, checksum: 2ba0b7a76027be3eda26ce11d43fec66 (MD5) Made available in DSpace on 2019-06-13T13:44:22Z (GMT). No. of bitstreams: 1 cis-Diazidobis(diphenylphosphino)methane-j2PP000ruthenium(II) dichloromethane 0.42-solvateJoãoRodrigues.pdf: 167616 bytes, checksum: 2ba0b7a76027be3eda26ce11d43fec66 (MD5) Previous issue date: 2006 info:eu-repo/semantics/publishedVersion

Apparent interfacial shear strength of short-flax-fiber/starch acetate composites

2016

Abstract The paper deals with an indirect industry-friendly method for identification of the interfacial shear strength (IFSS) in a fully bio-based composite. The IFSS of flax fiber/starch acetate is evaluated by a modified Bowyer and Bader method based on an analysis of the stress–strain curve of a short-fiber-reinforced composite in tension. A shear lag model is developed for the tensile stress–strain response of short-fiber-reinforced composites allowing for an elastic-perfectly plastic stress transfer. Composites with different fiber volume fractions and a variable content of plasticizer have been analyzed. The apparent IFSS of flax/starch acetate is within the range of 5.5–20.5 MPa, de…

The transfer of tin and germanium atoms from N-heterocyclic stannylenes and germylenes to diazadienes.

2005

New N-heterocyclic stannylenes and germylenes were synthesized by transamination of E[N(SiMe3)2] (E = Ge, Sn) with alpha-amino-aldimines or ethylidene-1,2-diamines and were characterized by spectroscopic methods and in the case of the germylene 10 g by X-ray diffraction. The reactions of several germylenes and stannylenes with diazadienes were studied by using dynamic NMR and computational methods. Experimental and theoretical studies confirmed that metathesis with exchange of the Group 14 atom is feasible for both stannylenes and germylenes, with exchange rates being generally higher for stannylenes. The metathesis of the diazadiene 3 b and the stannylene 1 b follows second-order kinetics …

A new isomer of [{Zn(IX)2(NO3)2}·2.5H2O]n [IX = 1,4-bis(imidazole-1-methylene)-benzene] as a rare example of topological isomerism in coordination po…

2006

Reaction of complex ligands: Part 95. Chromium tricarbonyl complexes of polysubstituted naphthohydroquinones: regioselective synthesis via [3+2+1]-be…

2003

Abstract A series of polysubstituted naphthohydroquinoid tricarbonyl chromium complexes were prepared by chromium mediated [3+2+1]-benzannulation of Fischer-type carbene complexes with alkynes. The kinetics and the thermodynamic data of the η6-η6-haptotropic rearrangements were investigated by in-situ NMR spectroscopy. The free activation energies ΔG# range from 23 to 26 kcal mol−1 and only slightly depend on the bulk and the donor/acceptor properties of the substituents. Equilibrium of metal migration was observed for naphthohydroquinone complexes bearing methoxy substituents at the non-hyroquinoid ring (ring A). In complexes bearing methyl groups or only hydrogen substituents at ring A th…

Synthesis, characterization and crystal structure of the bimetallic cyano-bridged [(η5-C5H5)(PPh3)2Ru(μ-CN)Ru(PPh3)2(η5-C5H5)][PF6]

2005

Abstract The bimetallic cyano-bridged [(η 5 -C 5 H 5 )(PPh 3 ) 2 Ru(μ-CN)Ru(PPh 3 ) 2 (η 5 -C 5 H 5 )][PF 6 ] ( 1 ) was prepared by reaction of [(η 5 -C 5 H 5 )(PPh 3 ) 2 RuCl] with N , N ′-bis(cyanomethyl)ethylenediamine. The single crystal structure determined by X-ray diffraction showed crystallization on the triclinic P1 space group with a perfect alignment of the cyanide bridges. This accentric crystallization was explored having in view the NLO properties at the macroscopic level, determined by the Kurtz Powder technique. Besides the very low efficiency values for the second harmonic generation, the value obtained for the bimetallic complex 1 showed to be higher than one of the parent…

3,4,5-Trimethoxy-4'-methylbiphenyl

2013

In the title compound, C16H18O3, the dihedral angle between the benzene rings is 33.4 (2)°. In the crystal, mol­ecules are packed in a zigzag arrangement along the b-axis and are inter­connected via weak C—H⋯O hydrogen bonds, and C—H⋯π inter­actions involving the meth­oxy groups and the benzene rings of neighbouring molecules.

Structurally diverse second-generation [2.2]paracyclophane ketimines with planar and central chirality: syntheses, structural determination, and eval…

2005

A set of 20 novel [2.2]paracyclophane ketimines with planar and central chirality has been synthesized from enantiomerically pure and racemic 5-acyl-4-hydroxy[2.2]paracyclophane and alpha-branched chiral amines. Their X-ray structures were determined to elucidate the three-dimensional structures and the absolute configuration. The ketimines were used as catalysts in the asymmetric 1,2-addition reactions of diethylzinc with substituted benzaldehydes to furnish chiral alcohols in up to 95 % ee.

Synthesis, thermal properties and X-ray structural study of weak C–H⋯OC hydrogen bonding in aliphatic polyester dendrimers

2004

Dendritic polyester compounds based on polyol with three, four and six reactive hydroxy groups as a molecular core, chloroacetyl chloride (or bromoacetyl bromide) and sodium metal enolate were prepared by a simple two-step synthetic procedure. The compounds were characterised by using the NMR and MS techniques, and the thermal properties were measured by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The structures of the crystalline compounds were determined by X-ray single crystal diffraction. Detailed analysis of the structures showed that the self-complementarity of the molecules together with a multitude of weak C-H⋯O=C hydrogen bonding results in crystal…

The Reaction Mechanism of Spirocylization and Stereoselectivity Studies for the Calyculin C16 -C25 Fragment

2005

The mechanism of the double intramolecular hetero-Michael addition, a key reaction in the planned synthesis of the natural product calyculin C, has been studied by NMR. The cyclization follows Baldwin’s rules and proceeds first through a six-membered ring closure (6-endo-dig), followed by a five-membered ring cyclization (5-exo-trig). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

3,5-Dimethoxy-4'-methylbiphenyl

2013

The title compound, C15H16O2, crystallizes with three independent mol­ecules in the asymmetric unit. The intra­molecular torsion angle between the aromatic rings of each mol­ecule are −36.4 (3), 41.3 (3) and −37.8 (3)°. In the crystal, the complicated packing of the mol­ecules forms wave-like layers along the b and c axes. The mol­ecules are connected via extensive meth­oxy–phenyl C—H…π inter­actions. A weak C—H…O hydrogen-bonding network also exists between meth­oxy O atoms and aromatic or meth­oxy H atoms.

Strength of cellulosic fiber/starch acetate composites with variable fiber and plasticizer content

2014

In this experimental study, the performance of injection-molded short flax and hemp fibers in plasticized starch acetate were analyzed in terms of strength. Parameters involved in the analysis are a variable fiber and plasticizer content. The measured strength of the composites varies in the range of 12–51 MPa for flax fibers and 11–42 MPa for hemp fibers, which is significantly higher than the properties of the unreinforced starch acetate matrix. The micro-structural parameters used in modeling of composite strength were obtained from optical observations and indirect measurements. Some of these parameters were qualitatively verified by X-ray microtomography.

Methyl 3',5'-dimethoxybiphenyl-4-carboxylate

2013

In the title compound, C16H16O4, the dihedral angle between the benzene rings is 28.9 (2)°. In the crystal, mol­ecules are packed in layers parallel to the b axis in which they are connected via weak inter­molecular C-H...O contacts. Face-to-face π-π inter­actions also exist between the benzene rings of adjacent mol­ecules, with centroid-centroid and plane-to-plane shift distances of 3.8597 (14) and 1.843 (2) Å, respectively.

A Trinuclear Aqua Cyano‐Bridged Ruthenium Complex [{(η 5 ‐C 5 H 5 )(PPh 3 ) 2 Ru(μ‐CN)} 2 RuCl 2 (PPh 3 )(H 2 O)]PF 6 : Synthesis, Characterization a…

2007

The organometallic trinuclear aqua cyano-bridged complex [{(η5-C5H5)(PPh3)2Ru(μ-CN)}2RuCl2(PPh3)(H2O)]PF6 (1), in which the fragment [RuCl2(PPh3)(H2O)] acts as a bridge and an acceptor group between the two terminal cyclopentadienyl ruthenium cyano moieties, was isolated in moderate yield from the reaction of [(η5-C5H5)(PPh3)2RuCN] with [RuCl2(PPh3)3] in THF. To the best of our knowledge, compound 1 is one of the few examples of a trinuclear array of ruthenium fragments bridged by the nitrogen atom of the–C≡N– group (Ru–C≡N–Ru′–N≡C–Ru) with a Ru-coordinated water molecule. The new aqua complex was structurally characterized by FTIR, 1H, 13C, and 31P NMR spectroscopy, mass spectrometry, elem…

Dimensionality Variation in Polymeric Metallo‐Organic Frameworks

2003

Single crystal X-ray crystallography was used to determine the structures of four metallo-organic complexes derived from pyridyl ligands and the metal ions, Cu2+, Zn2+ and Ag+. Two metallo-organic layer framework structures (1 and 3), a strand (2) and a dimer (4) structure were formed when the tetradentate ligands, tetrakis(nicotinoxymethyl)methane (TNM) and tetrakis(isonicotinoxymethyl)methane (TINM), were reacted with the first and second row transition metal cations, copper, silver, and zinc. The choice of anion and ligand was found to affect the outcome of the structure. Contrary to our previous results with the same ligands and similar transition metal cations, no genuine 3D metallo-or…

Novel [6]- and [7]Helicene-Like Quinones via Mono- and Bidirectional Chromium-Templated Benzannulation of Bridged Binaphthyl Carbene Complexes

2005

A new organometallic approach to novel, functionalised, helicene-like quinones and bisquinones has been developed based on the chromium-templated [3+2+1] benzannulation reaction. The [5]helicene-analogous monocarbene chromium complexes 4, 5, 17 and 19, derived from dibromo-substituted methylene- or silylene-tethered binaphthols 2 and 3, react with various alkynes to give [6]helicene-like quinones 6–13 and 20–29 after oxidative work-up. A rare competition of angular vs. linear annulation is observed for the incorporation of phenylacetylene that affords quinones 21/22 and 28/29. Protection of the phenolic benzannulation product with camphanic acid chloride 14, followed by chromatographic sepa…

Syntheses and crystal structures of three novel Cu(II) coordination polymers of different dimensionality constructed from Cu(II) carboxylates (carbox…

2004

Abstract We herein report three new coordination polymers generated from Cu(II) carboxylates (mal, 2ac, fum) and conformationally flexible bifunctional IX as building blocks. All the three complexes adopt unique structures in the solid state. The complex [Cu2(mal)2(IX)2(H2O)6]n crystallizes as orthorhombic co-linear rods with space group P2(1) P2(1) P2(1). Each rod is further formed of two tightly intertwined strings. The second polymer [Cu2(ac)4(IX)2]n crystallizes with space group P1 which consists of two sets of intersecting 2D sheets composed of parallel rods which interpenetrate to form a fully interlocked 3D structure. In both these complexes IX coordinates in the anti mode. The third…

Non-destructive automatic determination of aspect ratio and cross-sectional properties of fibres

2015

A novel method for computerised estimation of the aspect ratio distribution and various cross-sectional geometrical properties of fibres in short-fibre reinforced composites is proposed. The method, based on X-ray micro-computed tomography, is non-destructive and does not require user intervention. Based on results on specially fabricated model material, the accuracy and precision of the method seems adequate. The method is applied in analysing a manufacturing process of wood fibre reinforced thermoplastic composite. The results indicate a significant decrease of the aspect ratio of fibres during the processing steps. Finally, the feasibility of the method is assessed by estimating paramete…

Calcium dicaesium silver thiocyanate dihydrate.

2001

The title compound, CaCs2[Ag2(SCN)6]·2H2O, forms a continuous structure where the Ag atoms form chains with S atoms in the c-axis direction. The chains are bonded together through Cs and Ca atoms. The crystal water of the structure is bonded to the Ca atoms, which lie on centers of symmetry.

Chloride–hydrogen interactions of picolinic, nicotinic and isonicotinic acid chloride hydrochlorides in the crystalline state

2003

The crystal structures of the three isomers of the chemically labile pyridinecarboxylic acid chloride hydrochlorides were analyzed in order to study the weak interactions of the chloride anion with hydrogens. The chloride anions in the crystal structure of 1a have a slightly distorted square-planar interaction sphere with four hydrogens in the equatorial plane (plane of the molecule) with Cl−⋯H distances varying from 2.041(1) A [NH+⋯Cl−] to 2.933(1) A [CH⋯Cl−]. Nicotinic and isonicotinic acid chloride hydrochloride 1b and 1c show that chloride anion has a crucial role in the formation of bridged dimeric structures. The crystal lattices of 1b and 1c manifest similar herring-bone packing patt…

Mixed-Valence, Mixed-Spin-State, and Heterometallic [2×2] Grid-type Arrays Based on Heteroditopic Hydrazone Ligands: Synthesis and Electrochemical Fe…

2005

Une famille de complexes heterometalliques [M 1 2 M 2 2 (L - ) 4 ] n + du type grille [2×2] 1-9 a ete preparee. Les trois approches synthetiques multietapes des ligands hydrazone heteroditopiques A-C possedent chacune des caracteristiques regio-, redox-, enantio-selectives. Ces ligands possedent un groupement NH ionisable et un groupement hydrazone non-ionisable NMe, qui permettent un controle des proprietes redox du metal complexe en fonction de la charge de la cavite coordinante. Les substituants 2-pyrimidine (R) et 6-pyridine (R') influencent de maniere significative la geometrie des complexes formes ainsi que leurs proprietes electrochimiques et magnetiques. Les etudes par spectroscopie…

Ligand entrapment in twofold interpenetrating PtS matrixes by metallo-organic frameworks.

2003

Single-crystal X-ray crystallography was used to determine the structures of four metallo-organic frameworks (MOFs). A dendritic tetradentate ligand (tetrakis(isonicotinoxymethyl)methane, TINM) was used with first-row transition-metal elements copper, nickel, and cobalt to synthesize MOFs with a PtS interpenetration, due to both planar and tetrahedral junctions being present in the framework. Two different polymeric complexes, 1 and 2, were obtained from similar starting materials, TINM and Cu(NO(3))(2).3H(2)O, but different solvents. The use of dichloromethane in addition to methanol and water promoted the coordination of nitrate ions to the copper. With only methanol and water used as sol…

Methyl 3',4',5'-trimethoxybiphenyl-4-carboxylate

2013

In the title compound, C17H18O5, the dihedral angle between the benzene rings is 31.23 (16)°. In the crystal, the mol­ecules are packed in an anti­parallel fashion in layers along the a axis. In each layer, very weak C-H...O hydrogen bonds occur between the meth­oxy and methyl ester groups. Weak C-H...[pi] inter­actions between the 4'- and 5'-meth­oxy groups and neighbouring benzene rings [meth­oxy-C-ring centroid distances = 4.075 and 3.486 Å, respectively] connect the layers.

CCDC 216935: Experimental Crystal Structure Determination

2004

Related Article: Gudneppanavar Rajsekhar, Chebrolu P. Rao, Pauli Saarenketo, Kalle Nättinen, Kari Rissanen|2004|New J.Chem.|28|75|doi:10.1039/b305313j

CCDC 216932: Experimental Crystal Structure Determination

2004

Related Article: Gudneppanavar Rajsekhar, Chebrolu P. Rao, Pauli Saarenketo, Kalle Nättinen, Kari Rissanen|2004|New J.Chem.|28|75|doi:10.1039/b305313j

CCDC 216934: Experimental Crystal Structure Determination

2004

Related Article: Gudneppanavar Rajsekhar, Chebrolu P. Rao, Pauli Saarenketo, Kalle Nättinen, Kari Rissanen|2004|New J.Chem.|28|75|doi:10.1039/b305313j

CCDC 216933: Experimental Crystal Structure Determination

2004

Related Article: Gudneppanavar Rajsekhar, Chebrolu P. Rao, Pauli Saarenketo, Kalle Nättinen, Kari Rissanen|2004|New J.Chem.|28|75|doi:10.1039/b305313j

CCDC 216931: Experimental Crystal Structure Determination

2004

Related Article: Gudneppanavar Rajsekhar, Chebrolu P. Rao, Pauli Saarenketo, Kalle Nättinen, Kari Rissanen|2004|New J.Chem.|28|75|doi:10.1039/b305313j

CCDC 216930: Experimental Crystal Structure Determination

2004

Related Article: Gudneppanavar Rajsekhar, Chebrolu P. Rao, Pauli Saarenketo, Kalle Nättinen, Kari Rissanen|2004|New J.Chem.|28|75|doi:10.1039/b305313j

CCDC 216929: Experimental Crystal Structure Determination

2016

Related Article: Gudneppanavar Rajsekhar, Chebrolu P. Rao, Pauli Saarenketo, Kalle Nättinen, Kari Rissanen|2004|New J.Chem.|28|75|doi:10.1039/b305313j

4,4'-[Thiophene-2,5-diylbis(ethyne-2,1-diyl)]dibenzonitrile

2008

In the solid state, the title compound, C₂₂H₁₀N₂S, forms centrosymmetric dimers by pairs of non-classical C-H...S hydrogen bonds linking approximately coplanar molecules. The benzene ring involved in this interaction makes a dihedral angle of only 7.21 (16)° with the thiophene ring, while the other benzene ring is twisted somewhat out of the plane, with a dihedral angle of 39.58 (9)°. The hydrogen-bonded dimers stack on top of each other with an interplanar spacing of 3.44 Å. C-H...N hydrogen bonds link together stacks that run in approximately perpendicular directions. Each molecule thus interacts with 12 adjacent molecules, five of them approaching closer than the sum of the van der Waals…