Spectral and luminescent properties and photoisomerization of substituted styrylbenzoquinolines

The spectral, luminescent, and photochemical properties of 3-styrylbenzo[f]quinoline (3SBQ) derivatives containing methoxy and methoxycarbonyl groups have been studied. All of these compounds luminesce in the region of 380–480 nm with quantum yields up to 0.74 and undergo reversible photoisomerization with quantum yields of 0.2–0.5. It has been found that compounds with a methoxy group at the meta-position and a methoxycarbonyl group at the para-position of the styryl moiety are unstable photochromes and also undergo other photochemical reactions side relative to photoisomerization. The absorption spectra of the two 3SBQ s-conformers calculated by the density functional theory (DFT) method (TD-B3LYP/6-31G*) describe well the experimental spectrum. The analysis of the structures of molecular orbitals and transitions between them has made it possible to explain the observed effects of substituents on the absorption spectrum of 3SBQ.