Photophysical, crystallographic, and electrochemical characterization of novel conjugated thiopheno azomethines

New conjugated thiopheno azomethines using a stable 2,5-diamino thiophene precursor are presented. The spectroscopic and photophysical studies of these compounds confirm they dissipate their excited state energy predominately by internal conversion and not by intersystem crossing. Crystallographic data show the thermodynamically favourable E isomer is formed and that the highly conjugated azomethines are both linear and planar. Electrochemical oxidation of the azomethine compounds yields a persistent radical cation that cross couples. The resulting oxidative products undergo reversible radical cation formation and exhibit spectroscopic properties that are consistent with an increased degree of conjugation.