Energy transfer in a porphyrin chelate assembly

Energy transfer among isoenergetic pigments, three oxinyl-substituted free-base porphyrins in an octahedral chelate Ga(III) complex, has been studied by the femtosecond fluorescence up-conversion technique. The anisotropy decay of the complex has a fast component of ∼10 ps which is assigned to the energy transfer between the nearest porphyrin units in the complex. The anisotropy decay of the monomer (oxinyl-substituted porphyrin) is much slower and reflects monomer rotational dynamics in solution with decay times of 50 and ∼200 ps in dichloromethane.