Electron energy loss and DFT/SCI study of the singlet and triplet excited states of aminobenzonitriles and benzoquinuclidines: Role of the amino group twist angle

Spectroscopic consequences of varying the twist angle of the amino group ir i aminobenzonitrile systems in the electronic ground state are investigated by applying electron energy loss (EEL) spectroscopy and density functional theory to 4-N,N-dimethylaminobenzonitrile (DMABN), 4-N,N-dimethylamino-3,5 -dimethylbenzonitrile (MMD), benzoquinuclidine (BQ), and 6-cyanobenzoquinuc lidine (CBQ). A number of singlet and triplet excited states was observed a nd assigned with the help of DFT/SCI theory. The results characterize the g as-phase spectroscopy of the molecules and verify to within 0.3 eV the pred ictive power of DFT/SCI theory for vertical states over a wide range of twi st and pyramidalization angles. The amino group configuration in the relaxe d charge-transfer state of dual fluorescent aminobenzonitriles in solution cannot be directly deduced from the present data, however.