FEMTOSECOND PICOSECOND LASER PHOTOLYSIS STUDIES ON THE DYNAMICS OF EXCITED CHARGE-TRANSFER COMPLEXES IN SOLUTION .3. DISSOCIATION INTO FREE IONS AND CHARGE RECOMBINATION DECAY FROM THE ION-PAIR STATE FORMED BY CHARGE SEPARATION IN THE EXCITED-STATE OF 1,2,4,5-TETRACYANOBENZENE AROMATIC HYDROCARBON COMPLEXES IN POLAR-SOLVENTS

Picosecond laser photolysis studies have been made on the ionic dissociation and charge recombination (CR) processes of geminate ion pairs (IPs) formed by exciting 1,2,4,5-tetracyanobenzene (TCNB)-aromatic hydrocarbon complexes, for which results of our recent femtosecond-picosecond laser photolysis investigations concerning the relaxation from the excited Franck-Condon state leading to the compact IP or contact IP (CIP) formation were accumulated. We have demonstrated various different cases of ionic dissociation and CR decay of IPs depending on the molecular nature and strength of aromatic hydrocarbon donors. The obtained results, including those indicating strongly the existence of loose IP (LIP) or solvent-separated IP (SSIP) in the course of the ionic dissociation from the CIP, those showing rapid CR decay of CIP without ionic dissociation, and also some other cases, have been discussed on the basis of some theoretical considerations. © 1990 American Chemical Society.