The nature of the ground and excited singlet states of p-substituted ( N, N-dialkylamino)cinnamates and benzalmalonate

Abstract

The basic spectroscopic properties of benzyl 4-( N,N-dimethylamino)cinnamate (BDC), ethyl 4-( N, N-diethylamino)cinnamate (EDC) and diethyl 4-( N, N-dimethylamino)benzalmalonate (DBM) are described and discussed. The dipole moments, differences between the low and ambient temperature fluorescence, quantum yields of fluorescence, and the solvatochromic properties observed for BDC, EDC and DBM are shown to reflect different pathways for singlet state relaxation. The behaviors of BCD and EDC are attributed to the existence of a relaxed internal charge transfer state. The dual fluorescence of DBM is explained by the theory of twisted intramolecular charge transfer states. Results show that DBM is another molecule which relaxes to the ground state from two different excited states.