β Scribed by Haim Levanon; P. Neta
No coin nor oath required. For personal study only.
Formation of cation radicals by pulse radiolysis of metalloporphyrins and chlorophyll a in 1,2dichIoroethane is reported. Demetalation of the metalloporphyrin by radiolytically produced HCl is also observed. Rate constants for demetalation of ZnTPP and Chl a are 1 .I X IO8 and = 3 X IO8 h!-' s-I_ Oxidation of Chl a by ZnTPPt has a rate constant of = 4 X IO9 M-1 s-1. introduction Studies OR one-ele&ron oxidation and reduction of metalloporphyrins and chlorophylls provide valuable background information for understanding the primary events in photosynthesis. Several techniques have been used t,o generate and observe cation and anion radicals of porphyrins +. Apart from studies on photoexcited transients and photcelectron transfer reactions, most techniques used do not provide fast kinetic data. We have [5] recently utilized the pulse radiolysis technique for the determination of rate constants for the electron transfer from porphyrin anion radicals (PT) to various acceptors. In this communication we wish to repcrt on the chemistry involved in the formation of cation radicals in irradiated 12dichforoethane (DCE) solutions.This solvent was chosen because pulse radiolytic formation of aromatic cation radicals in DCE was extensively studied by Dorfman and co-workers [6,7] _ Furthermore, a similar solvent, dichloromethane, was used for the electrochemical generation of porphyrin cation radicals [2] _
π SIMILAR VOLUMES
The transient absorption bands dm 3 9 Οͺ1 ( Ο 330, 525 nm, k Ο 5 Ο« 10 mol max f obtained on pulse radiolysis of N 2 O-saturated neutral aqueous solution of 4,4Π-thiodi-Οͺ1 s ) phenol (TDPH) are due to the reaction of TDPH with ΠΈOH radicals and are assigned to phenoxyl radical formed on fast deprotonat
The nlion rJdinl of Icad(ll)Ictraphenylporphyrin W;IS produced by yndlolysisnnd by photolysis of the 1,1.2,2-tetrachloroethanc solutions at 77 K. The hfcc (0 0391 c~') dot to paired electron IS predommantly located m the porphyry ring. "'Pb observed in the CSR spectrum mduates lhat the un-1. introdu