Visible light-induced reduction system of diphenylviologen derivative with water-soluble porphyrin for biocatalytic carbon–carbon bond formation from CO2

Abstract

Abstract From the view point of green chemistry, CO2 utilization technologies with solar energy including the photoredox system have been received a lot of attention. As one of them, photoredox system containing a photosensitizer and a catalyst catalyzing a reaction of a carbon–carbon bond formation from CO2 as a feed stock were constructed. In a recent study, we reported the visible light-induced malate (C4 compound) production from pyruvate (C3 compound) and CO2 due to carbon–carbon bond formation with the system consisting an electron donor, a photosensitizer, diphenylviologen (PV2+) derivative as an electron mediator in the presence of malic enzyme (ME). However, the interaction between a photosensitizer and PV2+ derivative has not been clarified yet. In this study, water-soluble PV2+ derivative, 1,1′-bis(p-sulfonatophenyl)-4,4′-bipyridinium salt (PSV2+) was synthesized, and its electro-, photochemical properties were evaluated. Moreover, the photoredox properties of PSV2+ with water-soluble Zn porphyrin were studied using fluorescence spectroscopy and steady state irradiation. The fluorescence of Zn porphyrin was quenched by PSV2+ and the two-electron reduced form of PSV2+ were produced with Zn porphyrin with steady state irradiation. In addition, reaction solution containing triethanolamine, tetraphenylporphyrin tetrasulfonate, pyruvate, ME, Mg2+ and PSV2+ in CO2 saturated bis-tris buffer (pH 7.4) was irradiated with visible light, the oxaloacetate and malate were produced. This result indicates that PSV2+ is an efficient electron mediator in the visible light-induced redox system for carbon–carbon bond formation with ME from CO2 as a feedstock.