Photoinduced intermolecular and intramolecular actions between eosin and porphyrin

Two dyads of eosin and porphyrin linked with a semi-rigid (-CH(2)phCH(2)-) or flexible (-(CH2)(4)-) bridge and their reference model compounds were synthesized and characterized. The intermolecular interaction and intramolecular photoinduced singlet energy transfer and electron transfer were studied by their absorption spectra, fluorescence emission, excitation spectra and fluorescence lifetime. The model compounds, ethyl ester of eosin (EoEt) and porphyrin (PorEt), could form complexes in the ground state. When the eosin moieties in dyads were excited, they could transfer some singlet energy to the porphyrins; in the meantime, they could also induce electron transfer between two chromophores. Exciting the porphyrin moieties in dyads could induce electron transfer from eosin moieties to porphyrin moieties. The efficiencies (Phi(EnT), Phi(ET)) and rate constants (k(Ent), k(ET)) were related to the polarity of solvents and mutual orientation of the two chromophores in dyads.