PICOSECOND STUDIES ON THE ELECTRON-TRANSFER FROM PYRENE AND PERYLENE EXCITED SINGLET-STATES TO N-HEXADECYL PYRIDINIUM CHLORIDE

Picosecond laser flash photolysis studies have been carried out on two aromatic solutes, pyrene (Py) and perylene (Pe), in methanolic and aq ueous micellar solutions of a cationic surfactant, hexadecyl pyridiniu m chloride (CPC) on excitation at 355 nm. In methanolic solutions, the addition of CPC quenches the singlet state of the aromatics giving ri se to cation radicals, Py+. and Pe(+.), respectively. The cation radic als either decay by geminate recombination or escape in the bulk solut ion phase in approximate to 1000 ps. In aqueous micellar solutions of CPC, only Py+. is observed, while for Pe, initially both the singlet a nd the cation radical are observed immediately after the 35 ps laser p ulse. The observed decay kinetics are explained in terms of electron t ransfer and geminate recombination processes.