TRIPLET-STATE POTENTIALS IN THE COMPETITIVE EXCITATION MECHANISMS OF INTRAMOLECULAR PROTON-TRANSFER

A phenomenological analysis is given of the three cases of lowest trip let state potentials relative to ground singlet and lowest excited sin glet state potentials in the presence of intramolecular proton transfe r. In each case, singular excitation phenomena are observed respective ly: enhanced normal tautomer molecule phosphorescence (T-1 --> S-0), d ual phosphorescence, and unique proton-transfer (PT) tautomer phosphor escence (T-1' --> S-0'). The application of these model cases to proto n-transfer examples involving radiation-detector scintillators, biomol ecule fluorescence probes, and four-level lasers is discussed. The dev elopment of the potential curve interaction models permits the optimiz ation of the desirable large wavelength shift and maximization of quan tum yield of the PT fluorescence. The competition of normal tautomer a nd PT tautomer phosphorescences with the PT fluorescence is discussed as a limiting factor.