Timehyphen;resolved electron paramagnetic resonance spectra of photoexcited triplet states of electronndash;donorndash;acceptor complexes in frozen solution: Methylated benzenes and chlorinated phthalic anhydrides

摘要

The excited triplet states of phthalic anhydride and its chlorinated derivatives in methyl substituted benzene derivatives were studied at 77 K by a timehyphen;resolved EPR technique. The increase of the number of the methyl group on the benzene decreased the zerohyphen;field splitting parameters of their triplet states. This was explained by the contribution of the electronndash;donorndash;acceptor (EDA) complex. Especially, in the case of tetrachlorophthalic anhydride in hexamethylbenzene, the apparent inversion of the spinhyphen;polarization was observed. These data evidenced the negative sign of theDvalue in highly chargehyphen;transferred (CT) complex. This experiment reveals that the employment ofDvalue instead ofDast; provides much better estimation of the CT character of the EDA complex.