Zero-field splittings (zfs) of the lowest excited triplet states were obtained by time-resolved EPR for aromatic ring-bridged porphyrin dimers having different interplanar distances. The zfs parameter D (=-3Z/2) of the dimer decreased with decreasing the interplanar distance (R). From comparison of the D value of the dimer with that of the corresponding monomer, a contribution of CR character (b2) was evaluated as a function of R. An interplanar resonance integral (β1 + β2) was estimated from b2 and the magnitude of a red shift of T1 (ΔE(T1)). b2 and β1 + β2 correlated well with both of ΔE(T1) and the triplet lifetime in the dimer. All the results were interpreted well in terms of delocalization of excitation over the dimer molecule, namely the charge resonance interaction.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry