Crystal structures and Hirshfeld surface analysis of four 1,4-bis(methoxyphenyl)-2,3-diazabuta-1,3-dienes: comparisons of the intermolecular interactions in related compounds

The crystal structures of four azines, namely 1-3-bis(4-methoxyphenyl)-2,3-diaza-1,4-butadiene, 1, 1,3-bis(2,3-dimethoxyphenyl)-2,3-diaza-1,4-butadiene, 2, 1,3-bis(2-hydroxy-3-methoxyphenyl)-2,3-diaza-1,4-butadiene, 3, and 1,3-bis(2-hydroxy-4-methoxyphenyl)-2,3-diaza-1,4-butadiene, 4, are reported. Molecules of 3 and 4, and both independent molecules of 2, Mol A and Mol B, possess inversion centers. The central C=N–N=C units in each molecule is planar with an (E,E) conformation. The intermolecular interactions found in the four compounds are C–H···O, C–H–N, C–H---π and π---π interactions. However, there is no consistent set of intermolecular interactions for the four compounds. Compound, 1, has a two-dimensional undulating sheet structure, generated from C–H···O and C–H···N intermolecular hydrogen bonds. The only recognized intermolecular interaction in 2 is a C–H···O hydrogen bond, which results in a zig-zag chain of alternating molecules, Mol A and Mol B. While 3 forms a puckered sheet of molecules, solely via C–H···π interactions, its isomeric compound, 4, has a more elaborate three-dimensional structure generated from a combination of C–H···O hydrogen bonds, C–H···π and π···π interactions. The findings in this study, based on both PLATON and Hirshfeld approaches, for the four representative compounds match well the reported structural findings in the literature of related compounds, which are based solely on geometric parameters.

Synthesis and Properties of a New Unsymmetrical Diarylethene Bearing Benzothiophene and Thiophene Rings

A new unsymmetrical isomeric diarylethene was synthesized, namely1-[2-methyl-(5-(4-hydroxyl) phenyl) -3-thieny-2-(2-methyl-3-benzothiophene) perfluorocyclopentene (1o). Its photochromic reactivity both in solution and in PMMA film, photoconversion ratio at photostationary state, and fluorescence were investigated in detail. The compound displayed excellent photochromism both in solution and in PMMA film. The isomeric compound also functioned as a fluorescence switch and concentration dependence on the fluorescence spectrum in hexane.

Synthesis and Properties of a New Unsymmetrical Diarylethene Bearing Two Thiophene Rings

A new unsymmetrical photochromic diarylethene has been synthesized, namely {1-(2,5-dimethyl-3-thienyl),2-[2-methyl-5-(4-trifluoromethylphenyl)-3-thienyl]}perfluorocyclopentene. Its properties, including photochromic reactivity in solution and fluorescence property both in solution and in PMMA film were investigated. It underwent reversible cyclization and cycloreversion reactions upon alternating irradiation with UV and visible light. The isomeric compound functioned as a fluorescence switch by photoirradiation both in solution and in PMMA film. The fluorescence intensity also showed regular changes along with the change of concentration.

Synthesis, Photochromism and Fluorescence of a Novel Diarylethene Having Thiazole Unit

A new unsymmetrical isomeric diarylethene was synthesized, namely 1-(2,4-dimethyl-5-thiazolyl)-2-[2-methyl-5- (3-methoxyphenyl)-3-thienyl] perfluorocyclopentene (1o). Its photochromic reactivity both in solution and in PMMA film, photoconversion ratio at photostationary state, and fluorescence were investigated in detail. The compound displayed excellent photochromism both in solution and in PMMA film. The isomeric compound also functioned as a fluorescence switch and concentration dependence on the fluorescence spectrum in hexane.

Synthesis, Properties and Application in Optical Recording of a New Diarylethene Bearing an Isoxazole Unit

A new photochromic diarylethene bearing an isoxazole unit has been synthesized, namely {1-(3,5-dimethyl-4-isoxazolyl), 2-[2-methyl-5-(3-methoxyphenyl)-3-thienyl]}perfluorocyclopentene. Its properties, including photochromic reactivity both in solution and in PMMA film, photoconversion ratio at photostationary state, fluorescence and optical recording property were investigated. It underwent reversible cyclization and cycloreversion reactions upon alternating irradiation with UV and visible light both in hexane and in PMMA. The isomeric compound also functioned as a fluorescence switch by photoirradiation. Using this dithienylethene as optical storage was performed successfully.

Photochromism of a New Unsymmetrical Diarylethene Bearing both Thiazole and a Methoxyl Group

A new unsymmetrical isomeric diarylethene bearing an electron-donating methoxyl group atortho-positions of the terminal phenyl ring was synthesized, namely 1-(2,4-dimethyl-5-thiazolyl) -2-[2-methyl-5-(2-methoxyphenyl)-3-thienyl]perfluorocyclopentene (1o). The compound displayed excellent photochromism both in solution and in PMMA film. The isomeric compound also functioned as a fluorescence switch by photoirradiation in solution. In addition, cyclic voltammetry tests showed that the electron-donating methoxyl group at the terminal benzene ring had a significant effect on the electrochemical properties of the isomeric diarylethene.

Three isomeric 1-(2-chloronicotinoyl)-2-(nitrophenyl)hydrazines, including three polymorphs of 1-(2-chloronicotinoyl)-2-(2-nitrophenyl)hydrazine: hydrogen-bonded supramolecular structures in two and three dimensions

1-(2-Chloronicotinoyl)-2-(2-nitrophenyl)hydrazine, C12H9ClN4O3, crystallizes in three polymorphic forms, two monoclinic forms in space groups Cc (Ia) and P21 (Ib), and an orthorhombic form in space group Pbcn (Ic). In the Cc polymorph (Ia) the molecules are linked into sheets by combinations of one N—H...O and two C—H...O hydrogen bonds, while in the P21 polymorph (Ib) the molecules are linked into sheets by combinations of three hydrogen bonds, one each of N—H...O, C—H...N and C—H...O types. In the orthorhombic polymorph (Ic) the molecules are linked into a complex three-dimensional framework structure by a combination of one N—H...O, one N—H...N and three C—H...O hydrogen bonds, and an aromatic π...π stacking interaction. In the isomeric compound 1-(2-chloronicotinoyl)-2-(3-nitrophenyl)hydrazine (II) the molecules are again linked into a three-dimensional framework, this time by a combination of three hydrogen bonds, one each of N—H...O, N—H...N and C—H...O types, weakly augmented by a π...π stacking interaction. The molecules of 1-(2-chloronicotinoyl)-2-(4-nitrophenyl)hydrazine (III) are linked into sheets by a combination of three hydrogen bonds, one each of N—H...O, N—H...N and C—H...O types.

Isomeric iodo-N-(nitrobenzyl)anilines: interplay of hard and soft hydrogen bonds, iodo...nitro interactions and aromatic π...π stacking interactions

Molecules of 2-iodo-N-(4-nitrobenzyl)aniline, 4-O2NC6H4CH2NHC6H4I-2′ (1) are linked into chains by C—H...O hydrogen bonds. In the isomeric compound 3-iodo-N-(4-nitrobenzyl)aniline (2) a combination of N—H...O and C—H...O hydrogen bonds and iodo...nitro and aromatic π...π stacking interactions links the molecules into a three-dimensional framework structure. The two-dimensional supramolecular structure of 4-iodo-N-(4-nitrobenzyl)aniline (6) is built from a combination of C—H...O and N—H...π(arene) hydrogen bonds and aromatic π...π stacking interactions. 2-Iodo-N-(2-nitrobenzyl)aniline (7) crystallizes with two molecules in the asymmetric unit and these molecules are linked into ladders by a combination of N—H...O and C—H...O hydrogen bonds and iodo...nitro and aromatic π...π stacking interactions. Comparisons are made between the supramolecular structures of these compounds and those of other isomers, in terms both of the types of direction-specific intermolecular interactions exhibited and the dimensionality of the resulting supramolecular structures.