A time-dependent density-functional theory investigation of the fluorescence behavior of related cyano and di-cyano isomers of 4-(N,N-dimethylamino) benzonitrile

We present a time-dependent density-functional theory investigation of the absorption and emission energies for 2-CDMA, 3,5-DCDMA, and 3,4-DCDMA. Ground state geometries were optimized using density functional theory (DFT). Using the TICT (twisting intramolecular charge transfer) model to investigate the potential energy surface, we find that the non-dual fluorescence experimentally observed for all systems is explained by the presence of a large energy gap between the first and the second excited states. Our previous classification [submitted to JACS] established within the TICT model for this family of compounds also holds for the present systems.