Electronic Structure of Oxidized Complexes Derived from cis-[RuII(bpy)2(H2O)2]2+ and Its Photoisomerization Mechanism

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• 作者：Nora Planas ; Laura Vigara ; Clyde Cady ; Pere Mir贸 ; Ping Huang ; Leif Hammarstr枚m ; Stenbj枚rn Styring ; Nils Leidel ; Holger Dau ; Michael Haumann ; Laura Gagliardi ; Christopher J. Cramer ; Antoni Llobet
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：November 7, 2011
• 年：2011
• 卷：50
• 期：21
• 页码：11134-11142
• 全文大小：1036K
• 年卷期：v.50,no.21(November 7, 2011)
• ISSN：1520-510X

文摘

The geometry and electronic structure of cis-[Rup>IIp>(bpy)₂(H₂O)₂]p>2+p> and its higher oxidation state species up formally to Rup>VIp> have been studied by means of UV鈥搗is, EPR, XAS, and DFT and CASSCF/CASPT2 calculations. DFT calculations of the molecular structures of these species show that, as the oxidation state increases, the Ru鈥揙 bond distance decreases, indicating increased degrees of Ru鈥揙 multiple bonding. In addition, the O鈥揜u鈥揙 valence bond angle increases as the oxidation state increases. EPR spectroscopy and quantum chemical calculations indicate that low-spin configurations are favored for all oxidation states. Thus, cis-[Rup>IVp>(bpy)₂(OH)₂]p>2+p> (dp>4p>) has a singlet ground state and is EPR-silent at low temperatures, while cis-[Rup>Vp>(bpy)₂(O)(OH)]p>2+p> (dp>3p>) has a doublet ground state. XAS spectroscopy of higher oxidation state species and DFT calculations further illuminate the electronic structures of these complexes, particularly with respect to the covalent character of the O鈥揜u鈥揙 fragment. In addition, the photochemical isomerization of cis-[Rup>IIp>(bpy)₂(H₂O)₂]p>2+p> to its trans-[Rup>IIp>(bpy)₂(H₂O)₂]p>2+p> isomer has been fully characterized through quantum chemical calculations. The excited-state process is predicted to involve decoordination of one aqua ligand, which leads to a coordinatively unsaturated complex that undergoes structural rearrangement followed by recoordination of water to yield the trans isomer.