Redox and Spectroscopic Orbitals in Ru(II) and Os(II) Phenolate Complexes

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• 作者：Tia E. Keyes ; Deirdre Leane ; Robert J. Forster ; Colin G. Coates ; John J. McGarvey ; Mark N. Nieuwenhuyzen ; Egbert Figgemeier ; and Johannes G. Vos
• 刊名：Inorganic Chemistry
• 出版年：2002
• 出版时间：November 4, 2002
• 年：2002
• 卷：41
• 期：22
• 页码：5721 - 5732
• 全文大小：279K
• 年卷期：v.41,no.22(November 4, 2002)
• ISSN：1520-510X

文摘

A detailed spectroscopic and electrochemical study of a series of novel phenolate bound complexes, of generalformulas [M(L-L)₂(box)](PF₆), where M is Os and Ru, L-L is 2,2-bipyridine or 2,2-biquinoline, and box is 2-(2-hydroxyphenyl)benzoxazole, is presented. The objectives of this study were to probe the origin of the LUMOs andHOMOs in these complexes, to elucidate the impact of metal and counter ligand on the electronic properties of thecomplex, and to identify the extent of orbital mixing in comparison with considerably more frequently studied quinoidcomplexes. [M(L-L)₂(box)](PF₆) complexes exhibit a rich electronic spectroscopy extending into the near infraredregion and good photostability, making them potentially useful as solar sensitizers. Electrochemistry and spectroscopyindicate that the first oxidation is metal based and is associated with the M(II)/(III) redox states. A second oxidativewave, which is irreversible at slow scan rates, is associated with the phenolate ligand. The stabilities of the oxidizedcomplexes are assessed using dynamic electrochemistry and discussed from the perspective of metal and counterligand (LL) identity and follow the order of increasing stability [Ru(biq)₂(box)]⁺ < [Ru(bpy)₂(box)]⁺ < [Os(bpy)₂(box)]⁺. Electronic and resonance Raman spectroscopy indicate that the lowest energy optical transition for theruthenium complexes is a phenolate (ges/gifchars/pi.gif" BORDER=0 >) to L-L (ges/gifchars/pi.gif" BORDER=0 >*) interligand charge-transfer transition (ILCT) suggesting theHOMO is phenolate based whereas electrochemical data suggest that the HOMO is metal based. This unusuallack of correlation between redox and spectroscopically assigned orbitals is discussed in terms of metal-ligandorbital mixing which appears to be most significant in the biquinoline based complex.