Properties of the Intramolecular Excited Charge-Transfer States of Carbazol-9-yl Derivatives of Aromatic Ketones

Abstract

Photoinduced intramolecular charge transfer (ICT) in a series of a newly synthesized N-bonded donor−acceptor derivatives of 3,6-di-tert-butylcarbazole containing benzophenone and acetophenone as an electron acceptor has been studied in solutions. In solvents more polar than butyl ether, excitation leads to an emissive singlet state. Solvatochromic effects on the spectral position and profile of the stationary fluorescence spectra clearly indicate the CT character of the emitting singlet states of all the compounds studied. An analysis of the CT fluorescence and absorption band shapes leads to the quantities relevant for the electron transfer in the Marcus inverted region. The analysis of the fluorescence rate constants (kf) and corresponding transition dipole moments (M) indicate that Marcus theory can be applied for the quantitative description of the radiationless charge recombination processes in such cases, when an intersystem crossing to the excited triplet states may be neglected (i.e., in the polar...