CIDEP STUDY OF RADICAL-ION PAIR SYSTEMS - PHOTOOXIDATION REACTIONS OF N,N,N',N'-TETRAMETHYL-P-PHENYLENEDIAMINE BY MALEIC-ANHYDRIDE IN ALCOHOL SOLUTION

The photooxidation (electron transfer) reaction of TMPD (N,N,N'N'-tetramethyl-p-phenylenediamine) by maleic anhydride was studied in alcoholic media by a time-resolved ESR technique. The chemically induced dynamic electron polarization (CIDEP) spectra revealed that the main reaction channel was by way of the excited triplet state of TMPD and there existed a peculiar TM (triplet mechanism)-like emissive polarization along with an ordinary E/A (emission/absorption) pattern by RPM (radical pair mechanism). This TM-like polarization was tentatively explained by the level crossing (S-T--1) which Was induced by the interaction of the radical-ion pair under a confined circumstance in alcohols probably due to the Coulombic force.