Non-linear optical properties of new bridged bis-thienyls - I. Pyrazine-based bridges: theory, synthesis and spectra

The conformational analysis of 2,3-bis(2'-thienyl)pyrazine (A), 2,3-dicyano -5,6-bis(2'-thienyl)pyrazine (B), 2,3-difluoro-5,6-bis-(2'-thienyl)pyrazine (C), 2,3-bis(2'-thienyl)furo[3,4-b]pyrazine (D), 2,3-bis(2'-thienyl)pyrrol o[3,4-b]pyrazine (E), 2,3-bis(2'-thienyl)thieno[3,4-b]pyrazine (F), 2.3-bis (2'-thienyl)quinoxaline (G). 2,3-bis(2'-thienyl)pyrido[3,4-b]pyrazine (H) a nd 2.3-bis(2'-thienyl)pyrido[2,3-b]pyrazine (I) is elaborated using semiemp irical Austin Model 1 (AM1) method. The electron absorption spectra for sta ble conformers are calculated by ZINDO/S method. The influence of the bridg e variations on the electronic polarisability and second hyperpolarisabilit y is investigated using the time-dependent Hartree-Fock method in AM1 appro ach. The synthesis and spectral measurements of the most promising B, F, G and I compounds are presented. Our results indicate that the G and I ones s eem to be suitable candidates for the subsequent preparation of the electro -optical materials. (C) 2001 Elsevier Science B.V. All rights reserved.