Picosecond kinetics of copper and silver protoporphyrins

Abstract

By the use of the dual beam picosecond absorption spectroscopy technique, the initial events in the energy relaxation process of Cu(II) and Ag(II) protoporphyrin IX dimethyl esters were studied. The energy decay channels were found to be as follows. Cu(II) (Z = 29) complex: After picosecond excitation, a Franck-Condon state of 2S1 is populated which decays into 2T1 within 8 psec. This state relaxes with a time constant of 450-460 psec to 2T1 and 4T1 equilibrium state from which phosphorescence is emitted. Ag(II) (Z = 47) porphyrin: Picosecond excitation to the 2S1 state results in energy relaxation to 2T1 state within 8 psec which is followed by equilibration between 2T1 and 4T1 with a time constant of 11-12 psec. Subsequently the relaxation proceeds via nonradiative channels to 2Td and 4Td or 2(d,π*) states. © 1979 American Institute of Physics.