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 emi ssion spectra of 4-(9-anthryl)julolidine and 4-(9-acridyl)julolidine a nd the determination of the corresponding electronic transition dipole moments have made it possible to estimate the electronic coupling ele ments V-0 and V-1 between the (CT)-C-1 state and the ground state S-0, or the (LE)-L-1 states excited locally within the acceptor subunit, r espectively. To describe the excited (CT)-C-1 state properties, the si gnificant contributions of both of the above interactions together wit h the solvent induced changes in V-0 and V-1 have to be taken into acc ount. In low polarity solvents the conformation of these compounds in the fluorescent (CT)-C-1 state is more planar than that in the ground state (and in the unrelaxed Franck-Condon CT excited state), whereas i n a highly polar environment the compounds probably do not undergo any significant conformational changes accompanying the excited state cha rge separation. (C) 1997 Elsevier Science B.V.