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Change in Spin State and Enhancement of Redox Reactivity of Photoexcited States of Aromatic Carbonyl Compounds by Complexation with Metal Ion Salts Acting as Lewis Acids. Lewis Acid-Catalyzed Photoaddition of Benzyltrimethylsilane and Tetramethyltin via Photoinduced Electron Transfer

2001; American Chemical Society; Volume: 123; Issue: 32 Linguagem: Inglês

10.1021/ja010125j

1943-2984

Shunichi Fukuzumi, Naoya Satoh, Toshihiko Okamoto, Kiyomi Yasui, Tomoyoshi Suenobu, Yasuyo Seko, Mamoru Fujitsuka, Osamu Ito,

Oxidative Organic Chemistry Reactions

The lowest excited state of aromatic carbonyl compounds (naphthaldehydes, acetonaphthones, and 10-methylacridone) is changed from the n,π* triplet to the π,π* singlet which becomes lower in energy than the n,π* triplet by the complexation with metal ions such as Mg(ClO4)2 and Sc(OTf)3 (OTf = triflate), which act as Lewis acids. Remarkable positive shifts of the one-electron reduction potentials of the singlet excited states of the Lewis acid−carbonyl complexes (e.g., 1.3 V for the 1-naphthaldehyde−Sc(OTf)3 complex) as compared to those of the triplet excited states of uncomplexed carbonyl compounds result in a significant increase in the redox reactivity of the Lewis acid complexes vs uncomplexed carbonyl compounds in the photoinduced electron-transfer reactions. Such enhancement of the redox reactivity of the Lewis acid complexes leads to the efficient C−C bond formation between benzyltrimethylsilane and aromatic carbonyl compounds via the Lewis-acid-promoted photoinduced electron transfer. The quantum yield determinations, the fluorescence quenching, and direct detection of the reaction intermediates by means of laser flash photolysis experiments indicate that the Lewis acid-catalyzed photoaddition reactions proceed via photoinduced electron transfer from benzyltrimethylsilane to the singlet excited states of Lewis acid−carbonyl complexes.