Substituent effect on electronic transition energy of dichlorobenzyl radicals

Abstract Ring-substituted benzyl radicals exhibit electronic energies of the D 1  ⿿ D 0 transition being shifted to red region with respect to the benzyl radical. The red-shifts of disubstituted benzyl radicals are highly dependent on the substitution positions irrespective of substituents. By analyzing the red-shifts of dichlorobenzyl radicals observed, we found that the substituent effect on electronic transition energy is attributed to the molecular plane shape of delocalized Ͽ electrons. We will discuss the influences of locations of Cl substituents on the D 1  ⿿ D 0 transition energies of dichlorobenzyl radicals using Huckel's molecular orbital theory.