Azobenzene, crystal structure

Perez et al. [128] investigated the crystal structure of 4-(4 -ethoxybezoy-loxy)-2-butoxy-4 -(4-butoxysalicylaldimine)azobenzene. This compound contains four rings in the main core and a lateral alkoxy branch on one of the inner rings. The lateral butoxy chain is nearly perpendicular to the long axis of the main core. This molecular conformation induces the molecules to make a very complex network in the solid. The crystal cohesion is due to van der Waals interactions. The change of the lateral chain conformation in the solid and nematic phases is discussed. 

Crystal structure determinations have been carried out for the tetracyano-ethylene (139), azobenzene (52) and diphenylacetylene (52a) complexes, with molecular structures (XXXII) and (XXXIII). These complexes may... 

The crystal structure can be considered as a structure regularly stacked with bimolecular layers along the a-axis. Within the bimolecular layer, two molecules related by inversion symmetry face each other in the tail-to-tail fashion with their molecular axes inclined by about 26° to the bilayer surface. This inclination enables the head-to-tail arrangement of azobenzene chromophores as expected from the spectroscopic study. 

Smaragdyrin-azobenzene conjugates of the type 80 have been crystal structure determined and studied with respect to their photochemical and electrochemical behavior. It could be concluded that the relatively electron-withdrawing azobenzene moiety is responsible for a corresponding energy transfer to the smaragdyrin 7t-system <2007EJ0191>. 

Bouwstra, J. A., Schouten, A., and Kroon, J. (1983). Structural Studies of the System trans-Azobenzene/trans-Stilbene. I. A Reinvestigation of the Disorder in the Crystal Structure of trans-Azobenzene C12H10N2. Acta Crystallogr. Sect. C. 39, 1121-1123. 

Figure 7.8 Crystal structures of straight single-chain (a) and tilted double-chain (b) ammonium salts. Similar single-chain ammonium salts with azobenzene units in the centre interdigitate, so that the chains lie perpendicular to the head group area (c) or do not interdigitate, which introduces a 30° angle (d). As a result the chromophores form J- or H-aggregates. ...

A partially rigid foldamer system was recently reported by Parquette et al. [79]. The oligomers were derived from alternating sequences of pyridine-2,6-dicarboxamides and raeta-(phenylazo)azobenzenes. The helical conformations were revealed by crystal structures. In solution, the folded conformations and their corresponding dynamics were probed by NMR. 

The crystal structure and molecular configuration of cis- and trans-azobenzene has been satisfactorily determined by Robertson with... 

Okuyama, K., Watanabe, H., Shimomura, M., Hirabayashi, K., Kunitake, T., Kajiyama, T., Yasuoka, N. (1986). Molecular and crystal structure of an azobenzene-linked amphiphile, C33H5 N303Br, Bull. Chem. Soc. Jpn., 59 3351. 

Brown CJ. 1966. A refinement of the crystal structure of azobenzene. Acta Cryst 21(1) 146 152. 

Norikane Y, Kitamoto K, Tamaoki N. 2003. Novel crystal structure, cis trans isomeriza tion, and host property of meta substituted macrocyclic azobenzenes with the shortest linkers. J Org Chem 68(22) 8291 8304. 

Cudic P, Vigneron J-P, Lehn J-M, Cesario M, Prange T. Molecular recognition of azobenzene dicarboxylates by acridine-based receptor molecules crystal structure of the supramolecular inclusion complex of trans-3,3 -azobenzene dicarboxylate with a cyclo-bis-intercaland receptor. Eur J Org Chem. 1999 1999 2479-2484. 

Gyclometallated Pd(ii) complexes with bridging or terminal imidato ligands were studied by Serrano et The crystal structures of [ Pd(/x-succinimide)(phpy) 2] (phpy = 2-phenylpyridine) and [Pd(azb)(succinimide)(PPh3)] (azb = azobenzene) were determined. 

Figure 2 Davydov splitting and crystal structures of azobenzene 2 bUayer assemblies, (a) UV-vis absorption spectra of aqueous bilayer solutions and ethanol solution. Similar spectral splitting is observed in east films, (b) Schematic illustration of molecular orientation in single crystals.

In early studies designed to explore the chemistry of samarium pentamethylcyclopentadienide complexes, azobenzene was added to two equivalents of Sm(Cp )2(THF)2 in toluene. After reaction for six hours, [(Cp )2Sm]2N2(C6H5)2 was isolated in a 90% yield (124) (Evans et al., 1986b). Examination of the crystal structure... 

Subsequent to the discovery and identification of the thermally unstable Z-isomer of azobenzene by Hartley (see Scheme 2), the crystal structures of the E- and Z-isomers were determined by Robertson. " The benzene ring of the Z-isomer of azobenzene is rotated by 56" from the planar position and the distance between the 4 and 4 -carbons is shortened from 9.0 A in the E-isomer to 5.5 A in the Z-isomer. Since then, the generahty of the photoisomerization reaction has been demonstrated with a variety of... 

Tamaoki and co-workers have reported the synthesis of several azobenzenophanes, and their most recent work includes the synthesis of [l,l]-(3,3 ) a2obenzenophane, in which two azobenzene units are connected by -CH - chains at the meta positions.They isolated the three isomers, EE, EZ, and ZZ, (Scheme 59) and determined the crystal structures. The x-ray crystal structures disclosed sHghtly and... 

Norikane, Y, Kitamoto, K., and Tamaoki, N., [1,1] (3,3 )-Azobenzenophane novel crystal structure and cis-trans isomerization of distorted azobenzene, Org. Lett., 4. 3907, 2002, and theearly papers cited therein. 

Jones R, Tredgold R H, Hoorfar A, Allen R A and Hodge P 1985 Crystal-formation and growth in Langmuir-Blodgett multilayers of azobenzene derivatives—optical and structural studies Thin Solid Films 134 57-66... 

In 1990, Baumeister et al. [127] described the crystal and molecular structure of 4-ethoxy-3 -(4-ethoxyphenyliminomethyl)-4 -(4-methoxy-benzoy-loxy)azobenzene. The molecules have a bifurcated shape. The phenyliminom-ethyl branch is bent markedly from the nearly linear three ring fragment, but is almost coplanar with the azobenzene moiety. They found that the molecular conformation is affected by an intramolecular interaction of the carboxylic and azomethine groups. The crystal packing was described in terms of a sheet structure with interdigitating rows of molecules. 

A series of aggregation structures of bilayer forming azobenzene amphiphiles, CnAzoCmN+Br, both in single crystals and cast films was determined by the X-ray diffraction method and uv-visible absorption spectroscopy. From the relationship between chemical structures and their two-dimensional supramolecular structure, factors determining the molecular orientation in bilayer structure were discussed. Some unique properties based on two-dimensional molecular ordering were also discussed. 

In this paper, UV-visible absorption spectra and X-ray diffraction experiments of single crystals and solvent cast films of the azobenzene amphiphiles, CnAzoCmN+Br, were systematically investigated. Structural characterization of the cast bilayer films are discussed in comparison with aqueous solutions and single crystals. Some novel functional properties of the cast films are described, too. We also emphasize that the two-dimensional molecular assemblies, cast films and crystals of bilayer-forming amphiphiles, are suitable candidates for "crystal engineering" because of their simple structures compared with usual three-dimensional molecular crystals. 

X-RAY STRUCTURAL ANALYSES OF AZOBENZENE AMPfflPHELES 3.1. X-ray analyses of single crystals... 

Recently, Okuyama et al. succeeded to prepare single crystals of some azobenzene amphiphiles and decided molecular and aggregation structure of single crystals [14-19], The spectral prediction of the chromophore orientation in the bilayer assemblies were very consistent with the X-ray structural analyses of the single crystals. 

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