Influence of intermolecular hydrogen bonds on the luminescence properties of α-substituted cinnamonitriles

In view of the dramatic difference in the spectral-luminescence properties of alpha-(p-chlorobenzoyl)-4-diethylaminocinnamonitrile and alpha-ethoxycarbonyl-4-diethylaminocinnamonitrile in solutions and in the crystalline state, X-ray diffraction analysis has been applied to study crystals of these compounds. The intermolecular C-H...N and C-H...O hydrogen bonds are found to contribute to the quinoidization of molecules, which leads to a bathochromic shift in the absorption and fluorescence spectra. A spectral-luminescence study of the aforementioned compounds has revealed that the solvent temperature and polarity affect the position of absorption and luminescence peaks: a decrease in these parameters causes a hypsochromic shift.