Control of photoinduced charge transfer lifetimes in porphyrin arrays by ligand addition

Abstract

We demonstrate that the binding of N-donor ligands (4-picoline, imidazole) or anions (chloride) to the terminal zinc(II) porphyrin of selectively metalated triad and tetrad porphyrin arrays allows unprecedented control of photoinduced energy and charge transfer processes. Detailed electrochemical and photophysical studies of the arrays, and also of dyadic and monomeric reference compounds, show that the main effect of ligation is to alter the redox potentials of the zinc(II) porphyrin, making the final step of trans-array charge transfer (between the zinc(II) porphyrin and an adjacent free-base porphyrin) more exothermic. The result of this increased exothermicity is a reduced reversibility ..