Mimicking the photosynthetic system with strong hydrogen bonds to promote proton electron concerted reactions |
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Authors: | Isamu Kinoshita Hideki Hashimoto Takanori Nishioka Riichi Miyamoto Naoto Kuwamura Yuki Yoshida |
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Institution: | (1) Graduate School of Science, Osaka-City University, Osaka 558-8585, Japan |
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Abstract: | A Copper(2+) complex with a CuII–C bond containing sp3 configuration was used to investigate the role of strong hydrogen bonds in proton coupled electron transfer (PCET) reactions.
The only example of a CuII–C system realized so far is that using tris-(pyridylthio)methyl (tptm) as a tetradentate tripodal ligand. Using this ligand,
CuF(tptm)] and Cu(tptm)(OH)] have been prepared. The former complex forms supra-molecular arrays of layers of the complex
between which hydroquinone is intercalated in the crystalline phase. This hydroquinone intercalation crystal was prepared
via the photochemical conversion of quinone during the crystallization process. This conversion reaction probably involves
a proton coupled electron transfer process. The nuclear magnetic resonance spectroscopic analysis of the reaction mixture
shows the presence of Cu(III) during the conversion reaction. These results strongly suggest the presence of the molecular
aggregate of the CuF(tptm)] complex, water and quinone in the solution phase during the quinone to hydroquinone conversion.
The presence of this type of aggregate requires a strong hydrogen bond between the CuF(tptm)] complex and water. The presence
of this particular hydrogen bond is a unique character of such a complex that has the CuII–C bond. This complex is used as a model for photosynthetic water splitting since the photoconversion of quinone to hydroquinone
also involves the production of oxygen from water. |
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Keywords: | Proton coupled electron transfer Quinone hydroquinone conversion Copper complex |
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