The effect of solvent deuteration on the photophysics of sulphonated aluminium phthalocyanine

Abstract

The photophysics of disulphonated aluminium phthalocyanine in protiated and deuterated aqueous phosphate-buffered saline solution are reported. In the deuterated solvent the rate coefficients of fluorescence and intersystem crossing are unaffected by the heavier isotope; however, the rate of internal conversion from S 1 to S 0 has been shown to be considerably reduced. This results in increased quantum yields of fluorescence and triplet-state formation and also increased triplet and singlet lifetimes in deuterium oxide (Φ f0.40±0.04, τ f5.1±0.1 ns and τ t600±30 μs in H 2O and Φ f0.52±0.06, τ f6.8±0.1 ns and τ t1590±100 μs in D 2O). The implications of this with respect to the determination of the quantum yields of singlet oxygen formation in D 2O are discussed.