INTRAMOLECULAR ENERGY TRANSFER AND THE TRIPLET STATE IN PHTHALOCYANINE COMPLEXES OF PLATINUM METALS

Abstract

The luminescence properties of phthalocyanine complexes of the platinum group in solution between $1.3^{0} K$ and $300^{0} K$ are reported. From these properties, including the observed lifetimes, approximate quantum-efficiencies and external and internal heavy atom-effects, a detailed model for the energy transfer processes between ground singlet, first excited singlet and lowest lying triplet states is obtained. We could also obtain reliable estimates for the various rate constants in these processes at low temperatures. It is shown that the zero field splitting of the triplet results in an upper sublevel which is the one populated by intersystem crossing and which does not decay radiatively to the ground state, and two lower lying sublevels which are populated by spin-lattice relaxation only and which are radiatively coupled to the ground state, thus being responsible for the observed phosphorescences. Also reported are luminescences resulting from molecular aggregates.