Spectroelectrochemistry and DFT Analysis of a New {RuNO}n Redox System with Multifrequency EPR Suggesting Conformational Isomerism in the {RuNO}7 State

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• 作者：Priti Singh ; Jan Fiedler ; Stanislav Z&aacute ; li ; Carole Duboc ; Mark Niemeyer ; Falk Lissner ; Thomas Schleid ; Wolfgang Kaim
• 刊名：Inorganic Chemistry
• 出版年：2007
• 出版时间：October 29, 2007
• 年：2007
• 卷：46
• 期：22
• 页码：9254 - 9261
• 全文大小：287K
• 年卷期：v.46,no.22(October 29, 2007)
• ISSN：1520-510X

文摘

The compound [Ru(NO)(bpym)(terpy)](PF₆)₃, bpym = 2,2'-bipyrimidine and terpy = 2,2':6',2' '-terpyridine, with a{RuNO}⁶ configuration (angle Ru-N-O 175.2(4)) was obtained from the structurally characterized precursor [Ru(NO₂)(bpym)(terpy)](PF₆), which shows bpym-centered reduction and metal-centered oxidation, as evident fromEPR spectroscopy. The relatively labile [Ru(NO)(bpym)(terpy)]³⁺, which forms a structurally characterized acetonitrilesubstitution product [Ru(CH₃CN)(bpym)(terpy)](PF₆)₂ upon treatment with CH₃OH/CH₃CN, is electrochemically reducedin three one-electron steps of which the third, leading to neutral [Ru(NO)(bpym)(terpy)], involves electrode adsorption.The first-two reduction processes cause shifts of (NO) from 1957 via 1665 to 1388 cm^-1, implying a predominantlyNO-centered electron addition. UV-vis-NIR Spectroscopy shows long-wavelength ligand-to-ligand charge transferabsorptions for [Ru^II(NO^-I)(bpym)(terpy)]⁺ in the visible region, whereas the paramagnetic intermediate [Ru(NO)(bpym)(terpy)]²⁺ exhibits no distinct absorption maximum above 309 nm. EPR spectroscopy of the latter at 9.5, 95,and 190 GHz shows the typical invariant pattern of the {RuNO}⁷ configuration; however, the high-frequencymeasurements at 4 and 10 K reveal a splitting of the g₁ and g₂ components, which is tentatively attributed toconformers resulting from the bending of RuNO. DFT calculations support the assignments of oxidation states andthe general interpretation of the electronic structure.