Picosecond timesolved investigation of singlet energy transfer in porphyrin hetero dimers

Abstract

Energy transfer and charge separation have been studied by picosecond timeresolved spectroscopy in a number of compounds consisting of free-base and zinc (Zn) tetraphenylporphyrin (TPP) units. Dimeric Zn-free-base TPP has been used to investigate energy transfer properties whereas monomeric and dimetric free-base TPP substituted with the electron acceptor quinone were synthesized to study charge separation. Energy transfer within the TPP dimers has been found to be dependent on the link between the monometric subunits. Experimental evidence favours a Dexter type as compared to Förster type energy transfer mechanism. The electron transfer rate from TPP to quinone is reduced in the dimers by a factor of two as compared to the monomers, which is due to fast energy hopping between the two TPP subunits.