Crystal structure analysis of some mesogenic cyanoazines

Structural analysis of some benzoxazoles containing strong electron donor-acceptor groups

The crystal structure analysis of two benzoxazole containing molecules is reported: 2-[4-N,N-bis(2-hydroxyethyl)]phenyl-6-nitrobenzoxazole monohydrate (1) and 2-[4-N-(6-hydroxyhexyl)-/N-methyl] phenyl-6-nitrobenzoxazole (2). These compounds are monomer precursors of polymers with nonlinear optical properties of the second order. The crystal structures have been determined at room temperature by direct methods and refined by full-matrix least-squares method. Some differences have been found in the molecular geometry of 1 and 2 as compared to published data on similar benzoxazole containing compounds. These differences are due to the strong electron donor effect of the amino group and indicate enhanced conjugation in the molecules. The pattern of hydrogen bonding in the two compounds is also discussed.

Nonlinear optical properties of diazabutadienes and -hexatrienes; experimental and computational aspects

Donor-acceptor substituted diazabutadienes and -hexatrienes were prepared by straightforward procedures and their linear optical (UV-vis) and nonlinear optical second harmonic generation (SGH) properties investigated in a combined theoretical and experimental study. Theoretical and experimental results were in reasonable agreement. For the compounds in this study, which contained a p-nitrophenyl group as electron acceptor, the p-dimethylaminophenyl group was the most powerful electron-donating group, leading to the highest maximum absorption wavelengths, as well as to the maximum SHG efficiency.