Issue 7, 1992

Semiconductor photocatalysis: visible light induced photoreduction of aromatic ketones and electron-deficient alkenes catalysed by quantised cadmium sulfide

Abstract

Colloidal CdS suspensions (CdS-0) prepared at 0 °C from methanolic Cd(ClO4)2 and Na2S solutions consist of quantised CdS microcrystallites (2–5 nm) and their loose aggregates, which catalyse the effective photoreduction of aromatic ketones and electron-deficient alkenes with triethylamine as electron donor. Under visible light induced photolysis, the methanolic CdS-0 suspension becomes brown owing to the reduction of lattice Cd2+ to Cd0, leading to the effective formation of alcohols from ketones, and dihydro compounds from alkenes. With the reduction potential < – 1.56 V vs. standard calomel electrode (SCE), ketones were partly photoreduced to pinacols in methanol. Compared with highly pure bulk CdS (CdS-Ald), CdS-0 is more effective for photoreduction because of the size quantisation effect. The presence of an excess of sulfide ion (S2–) in the CdS-0 system, however, suppresses the formation of lattice Cd0, inducing one-electron transfer photoreductions which result in the exclusive formation of pinacols and 1,2,3,4-tetra(methoxycarbonyl)butane from the respective ketones and dimethyl maleate. The relationship between the two-electron reductions and photogenerated lattice Cd0 is discussed in terms of the regulation of semiconductor photocatalysis.

Article information

Article type
Paper

J. Chem. Soc., Faraday Trans., 1992,88, 1055-1061

Semiconductor photocatalysis: visible light induced photoreduction of aromatic ketones and electron-deficient alkenes catalysed by quantised cadmium sulfide

T. Shiragami, H. Ankyu, S. Fukami, C. Pac, S. Yanaglda, H. Mori and H. Fujita, J. Chem. Soc., Faraday Trans., 1992, 88, 1055 DOI: 10.1039/FT9928801055

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