Substituent effect on the fluorescence quenching of various tetraphenylporphyrins by ruthenium tris(2,2′-bipyridine) complex

The fluorescence quenching of various substituted tetraphenylporphyrins and their zinc complexes by ruthenium(II) tris(2,2′-bipyridine) has been investigated in dichloromethane. While fluorescence quenching was not effective for free base porphyrins, but in the case of zinc porphyrins fairly efficient. Plots for the Stern–Volmer quenching constant versus the calculated free energy change (Δ G red ) for photoinduced oxidative electron transfer (ET) processes from the excited singlet porphyrins to ruthenium(II) tris(2,2′-bipyridine) were shown to be linear. Among porphyrins/ruthenium(II) tris(2,2′-bipyridine) pairs examined in this study, ZnTMeOPP/ruthenium(II) tris(2,2′-bipyridine) pair exhibited most efficient fluorescence quenching as predicted to carry out most favorable photoinduced oxidative electron transfer processes by the calculated free energy changes (Δ G red ).