Electronic and molecular structure of charge transfer singlet states: 4-(9-anthryl)julolidine and 4-(9-acridyl)julolidine

A quantitative analysis of the charge transfer (CT) absorption and emission spectra of 4-(9-anthryl)julolidine and 4-(9-acridyl)julolidine and the determination of the corresponding electronic transition dipole moments have made it possible to estimate the electronic coupling elements V0 and V1 between the 1CT state and the ground state S0, or the 1LE states excited locally within the acceptor subunit, respectively. To describe the excited 1CT state properties, the significant contributions of both of the above interactions together with the solvent induced changes in V0 and V1 have to be taken into account. In low polarity solvents the conformation of these compounds in the fluorescent 1CT state is more planar than that in the ground state (and in the unrelaxed Franck-Condon CT excited state), whereas in a highly polar environment the compounds probably do not undergo any significant conformational changes accompanying the excited state charge separation.