Second-Order Optical Nonlinearities of Substituted Stilbenes and the Related Compounds Containing a Trifluoromethyl as the Electron-Withdrawing Group

Abstract

Abstract The second-order optical nonlinearities and transparencies of seventeen 4,4′-disubstituted stilbenes and ten related compounds containing a trifluoromethyl group at the para position, as the electron-withdrawing group, were examined. The introduction of a trifluoromethyl group produces a shorter-wavelength shift of the UV-vis absorption spectra without any decrease in the magnitude of the second-order molecular hyperpolarizability (β), as compared with the corresponding nitro-derivatives. The absorption cutoff (λcutoff) of 4-methoxy-4′-trifluoromethylstilbene (1) was observed at 375 nm, which is by ca. 90 nm shorter than that (463 nm) of p-nitroaniline (p-NA); the β value (12.2 × 10−30 esu) of 1, however, is almost equal to that (12.6 × 10−30 esu) of p-NA. The bromo- or methylthio-substituted stilbenes (12 and 16) with a cyano group on the central double bond show SHG activity. The relative intensities of SHG are 3.0 and 1.5, respectively.