Systematic Modulation of a Bichromic Cyclometalated Ruthenium(II) Scaffold Bearing a Redox-Active Triphenylamine Constituent

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• 作者：Kiyoshi C. D. Robson ; Barbora Sporinova ; Bryan D. Koivisto ; Eduardo Schott ; Douglas G. Brown ; Curtis P. Berlinguette
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：July 4, 2011
• 年：2011
• 卷：50
• 期：13
• 页码：6019-6028
• 全文大小：1043K
• 年卷期：v.50,no.13(July 4, 2011)
• ISSN：1520-510X

文摘

The syntheses and physicochemical properties of nine bis-tridentate ruthenium(II) complexes containing one cyclometalating ligand furnished with terminal triphenylamine (TPA) substituents are reported. The structure of each complex conforms to a molecular scaffold formulated as [Ru^II(TPA-2,5-thiophene-pbpy)(Me₃tctpy)] (pbpy = 6-phenyl-2,2鈥?bipyridine; Me₃tctpy = trimethyl-4,4鈥?4鈥测€?tricarboxylate-2,2鈥?6鈥?2鈥测€?terpyridine), where various electron-donating groups (EDGs) and electron-withdrawing groups (EWGs) are installed about the TPA unit and the anionic ring of the pbpy ligand. It is found that the redox chemistry of the Ru center and the TPA unit can be independently modulated by (i) placing EWGs (e.g., 鈭扖F₃) or EDGs (e.g., 鈭扥Me) on the anionic ring of the pbpy ligand (substituted sites denoted as R₂ or R₃) and/or (ii) installing electron-donating substituents (e.g., 鈭扝, 鈭扢e, 鈭扥Me) para to the amine of the TPA group (i.e., R₁). The first oxidation potential is localized to the TPA unit when, for example, EDGs are placed at R₁ with EWGs at R₂ (e.g., the TPA^鈥?/TPA⁰ and Ru^III/Ru^II redox couples appear at +0.98 and +1.27 V vs NHE, respectively, when R₁ = 鈭扥Me and R₂ = 鈭扖F₃). This situation is reversed when R₃ = EDG and R₁ = 鈭扝: TPA-based and metal-centered oxidation waves occur at +1.20 and +1.11 V vs NHE, respectively. The UV鈥搗is spectrum for each complex is broad (e.g., absorption bands are extended from the UV region to beyond 800 nm in all cases) and intense (e.g., 蔚 10⁴ M^鈥?路cm^鈥?) because of the overlapping intraligand charge-transfer and metal-to-ligand charge-transfer transitions. The information derived from this study offers guiding principles for modulating the physicochemical properties of bichromic cyclometalated ruthenium(II) complexes.