Generation of Powerful Tungsten Reductants by Visible Light Excitation

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• 作者：Wesley Sattler ; Maraia E. Ener ; James D. Blakemore ; Aaron A. Rachford ; Paul J. LaBeaume ; James W. Thackeray ; James F. Cameron ; Jay R. Winkler ; Harry B. Gray
• 刊名：The Journal of the American Chemical Society
• 出版年：2013
• 出版时间：July 24, 2013
• 年：2013
• 卷：135
• 期：29
• 页码：10614-10617
• 全文大小：285K
• 年卷期：v.135,no.29(July 24, 2013)
• ISSN：1520-5126

文摘

The homoleptic arylisocyanide tungsten complexes, W(CNXy)<sub>6sub> and W(CNIph)<sub>6sub> (Xy = 2,6-dimethylphenyl, Iph = 2,6-diisopropylphenyl), display intense metal to ligand charge transfer (MLCT) absorptions in the visible region (400鈥?50 nm). MLCT emission (位<sub>maxsub> 鈮?580 nm) in tetrahydrofuran (THF) solution at rt is observed for W(CNXy)<sub>6sub> and W(CNIph)<sub>6sub> with lifetimes of 17 and 73 ns, respectively. Diffusion-controlled energy transfer from electronically excited W(CNIph)<sub>6sub> (*W) to the lowest energy triplet excited state of anthracene (anth) is the dominant quenching pathway in THF solution. Introduction of tetrabutylammonium hexafluorophosphate, [Bu<sup>nsup><sub>4sub>N][PF<sub>6sub>], to the THF solution promotes formation of electron transfer (ET) quenching products, [W(CNIph)<sub>6sub>]<sup>+sup> and [anth]<sup>鈥⑩€?/sup>. ET from *W to benzophenone and cobalticenium also is observed in [Bu<sup>nsup><sub>4sub>N][PF<sub>6sub>]/THF solutions. The estimated reduction potential for the [W(CNIph)<sub>6sub>]<sup>+sup>/*W couple is 鈭?.8 V vs Cp<sub>2sub>Fe<sup>+/0sup>, establishing W(CNIph)<sub>6sub> as one of the most powerful photoreductants that has been generated with visible light.