Synthesis, Light Harvesting, and Energy Transfer Properties of a Zinc Porphyrin Linked Poly(phenyleneethynylene)

The synthesis of a zinc porphyrin linked conjugated homopolymer is presented. The synthetic strategy employed a directional polymerization of 1-iodo-2,5-dioctyl-4‘-ethynyltolane in the presence of 10,20-bis(3,5-bis- tert -butylphenyl-5,15-diethynylporphinato]zinc(II) ( 12 ) or 10,20-bis(3,5-bis- tert -butylphenyl-5,15-dibromoporphinato]zinc(II) ( 10 ). In the case of 12 the reaction was found to give a polymer product with a constant ratio of zinc porphyrin to incorporated monomer units regardless of the molecular weight. In the case of 10, however, the ratio of zinc porphyrin to incorporated monomer units decreased with increasing molecular weight of the polymer product. The polymer products were separated into fractions using preparative SEC. Studies of the energy transfer properties from the polymer to the zinc porphyrin revealed that there was little energy transfer in solution but quantitative energy transfer in the solid state. The polymer products proved difficult to handle in terms of device construction where a thin polymer film is sandwiched between two electrodes. We found this to be a consequence of the palladium catalysis employed during the polymerization. We finally discuss the issues concerning the problems with remnants from the Pd catalyst in the polymer samples and their removal.