Luminescence of some metalloporphins including the complexes of the IIIb metal group

Abstract

Luminescence yields and decay lifetimes were measured on some metalloporphyrins including the complexes of the IIIb metal group. The S2 emission was observed for AlClTPP (TPP: tetraphenylporphin), GaClTPP, and InClTPP as well as some other TPP metal complexes, ZnP (P:porphin) and H4P2+ (diacid), while it was not detected for H2TPP, H2OEP (OEP: octaethylporphin), AlClOEP as well as other OEP metal complexes. The rate of S2→S1 internal conversion is dependent upon the peripheral substituents rather than the central metal ion and is enhanced in the porphyrins which do not emit the S2 fluorescence. On the other hand, the intersystem crossing plays a more important part in the relaxation process of the S1 state. With increase in the atomic number of the central metal ion as well as its axial ligand, the yield and decay lifetime of the S1 emission are reduced. In the relaxation of the T1 state, the radiative decay is also accelerated for the central metal ion with higher atomic number.