Abstract
The photoreactivity of the water-soluble zinc derivative of 5,10,15,20-tetra(N-methyl-pyridinium-3-yl)porphyrin [Zn(MePy)4P4+] has been investigated using the laser-photolysis technique and shown to be the same as that of the pyridinium-4-yl isomer. Electron transfer from the triplet state of this porphyrin to methyl viologen is greatly influenced by coulombic effects. In the presence of chloride ions, the existence of (MV2+·Cl–) ion pairs could explain the observed kinetics for direct electron transfer. Cupric ion quenches the triplet, and the second-order rate constant kT + Cu2+=(1.5 + 0.1)× 106 dm3 mol–1 s–1 is similar to that observed with methyl viologen. However, no indication of a photoredox process was found.We have also measured the rate constants of the (T + T) reaction, 2kTT=(3.1 ± 0.4)× 107 dm3 mol–1 s–1, and the (T + O2) reaction, kT + O2=(1.2 ± 0.1)× 109 dm3 mol–1 s–1.
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Schedule a callMore From: Journal of the Chemical Society, Faraday Transactions 2
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