Phosphorescent intramolecular charge transfer triplet states

A comparative study of the electronic structure of the lowest excited triplet state T1 is presented for a series of N-bonded donor-acceptor derivatives of 3,6-di-tert-butylcarbazole containing benzonitrile, nicotinonitrile or various dicyanobenzenes as electron acceptor. Solvent, temperature and concentration effects on phosphorescence, measurements of luminescence anisotropy and lifetimes, and ESR investigations of selected compounds show the dependence of the electronic structure of their T1 states on the electron affinity of the acceptor moiety and point to the 3CT character of the emitting triplet states in 3,6-di-tert-butylcarbazol-9-yl dicyanobenzenes.