Synthesis and photophysical studies of non-covalently linked porphyrin dyads and triads

Non-covalent porphyrin dyads and triads containing N3S porphyrin and RuN4 porphyrin subunits were synthesized by treating meso-pyridyl-21-thiaporphyrin with RuTPP(CO)(EtOH) in toluene at refluxing temperature. The dyads and triads were characterized by various spectroscopic techniques and the properties were compared with the reported dyad containing N-4 and RuN4 porphyrin subunits. The H-1 NMR study of dyads and triads indicated that the inner NH, beta-heterocycle and meso-pyridyl protons of the 21-thiaporphyrin unit experienced large upfield shifts as compared to their corresponding monomeric meso-pyridyl-21-thiaporphyrins due to the ring current effect of RuTPP(CO) subunit. The singlet state photophysical properties of N3S porphyrin subunit in dyads and triads showed 50-80% quenching of fluorescence as observed previously for N-4-RuN4 dyad due to heavy ruthenium ion(s). Copyright (c) 2007 Society of Porphyrins & Phthalocyanines.