The first 1,3-dithiol-2-ylidene donor-pi-acceptor chromophores containing an azine spacer: synthesis, electrochemical and nonlinear optical properties

The first push-pull 1,3-dithiol-2-ylidene derivatives containing an azine s pacer have been prepared in order to evaluate the effect of the azine bridg e on the second-order NLO properties of these compounds, which show mu beta (0) values lower than those of similar derivatives endowed with ethylenic spacers. The linear and nonlinear optical properties of these compounds hav e been studied both experimentally and theoretically by TD-DFT and ab initi o CPHF calculations respectively. Moreover, the E-Z photoisomerization of o ne of these azines is reported.