Photochemistry of low-valent platinum metal complexes and application to photocatalytic systems

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Synthesis of the complexes. [M(triphos)(PPh_3)], [M(binap)_2] (M=Pt and Pd) were synthesized and characterized by elemental analyses and NMR spectroscopy. (triphos = 1,1,1 -tris(diphenylphosphinomethyl)ethane, binap = 1,1' -bis(diphenyl-phosphino)-2,2' -binaphthyl).Analyses of the excited states. The luminescence of [Pd(triphos)(PPh_3)] shows a biexponential decay. The dynamics in the excited state was thoroughly examined.Photochemistry with oxygen. Formation of singlet oxygen is suggested in the initial stage of the photochemical reaction of [Pt(binap)_2] and oxygen. A simple infrared light detection system was constructed, and 1270 nm-light of the emission from singlet oxygen was successfully detected. The singlet oxygen may be formed via an energy-transfer mechanism.Photochemical reaction of the complexes with alcohol. The photochemical reactions of the Pd and Pt complexes with ethanol were, studied. A mercury lamp was used as a light source and, a gas chromatograph was used to identify the organic product in the products. The amounts of the produced acetaldehyde were up to 8 times that of the complex used as a catalyst.Photochemical reaction of the complexes with organic halides. The solution of [M(triphos)(PPh_3)] (or [M(binap)_2]) and 1,2-dichloroethane was irradiated with visible light promptly yielded ethylene quantitatively. In addition, the photochemical dehalogenation of dichloroethane and chlorobenzene by [Pd(triphos) (PPh_3)] catalyst was confirmed with a use of potassium methoxide.