Photophysical behaviour of zinc tetraphenylporphyrins in solutions and polymer films

Abstract

The fluorescence and phosphorescence of zinc tetraphenylporphyrin (ZnTPP) and its tatrasulfonated derivative (ZnTPPS) were evaluated using time-resolved luminescence and absorption measurements in three environments: dilute solution, solutions containing polyvinylpyridine (PVP) and quaternary-ammonium-ion-derivatized styrene copolymer and films of the polymers. Both the singlet and triplet lifetimes are reduced in highly doped films or in solution in the presence of small polymer concentrations where attachment of the porphyrin leads to low average porphyrin—porphyrin separations. In contrast, for poorly doped films or high polymer concentrations in solution, porphyrins bound to pyridine moieties in PVP or to the cation sites of the anionic copolymer exhibit increases in both the singlet and triplet lifetimes. There is no parallel effect for ZnTPP axially bound by dissolution in pyridine. Flash experiments reveal a new relaxation pathway for ZnTPP—pyridine.