Substitution Effects on the Water Oxidation of Ruthenium Catalysts: A Quantum-Chemical Look

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• 作者：Abu Md Asaduzzaman ; Derek Wasylenko ; Curtis P. Berlinguette ; Georg Schreckenbach
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：January 8, 2015
• 年：2015
• 卷：119
• 期：1
• 页码：242-250
• 全文大小：301K
• ISSN：1932-7455

文摘

Quantum chemistry has been used to investigate the oxidation of water by a family of seven catalysts based on [Ru(tpy)(bpy)(OH₂)]p>2+p> (tpy = 2,2鈥?6鈥?2鈥测€?terpyridine, bpy = 2,2鈥?bipyridine). The electron-donating 鈭扥Me and 鈭扤H₂ groups (EDG) and electron-withdrawing 鈭扖OOH and 鈭扤O₂ groups (EWG) are installed in the catalyst by replacing hydrogen atoms on the bpy and tpy ligands. The EDG induces an increase in the electron density at the Ru center, whereas the EWG does the opposite. Reduced electron density at the metal center facilitates Ru(N+1)/Ru(N) reduction and thus a higher reduction potential. Catalytic evolution of one oxygen molecule from two water molecules using all catalysts is an exothermic process if driven by Cep>IVp>. The exothermicity increases from EDG to EWG via parents. Regarding intermediates, the singlet states of 7-coordinated catalysts are slightly more stable than the triplet states of 6-coordinated catalysts for most catalysts. Only for a strong EWG (鈭扤O₂) containing catalyst, the triplet 6-coordinated states complex is the most stable. Calculated Ru鈥揙 and O鈥揙 distances suggest that oxygen will be liberated favorably from the triplet state of 6-coordinated complexes, whose stability increase (with respect to the singlet of 7-coordinated complexes) with increasing electron-withdrawing nature.