A Homoleptic Trisbidentate Ru(II) Complex of a Novel Bidentate Biheteroaromatic Ligand Based on Quinoline and Pyrazole Groups: Structural, Electrochemical, Photophysical, and Computational Characteriz

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• 作者：Martin Jarenmark ; Lisa A. Fredin ; Joachim H. J. Hedberg ; Isa Doverbratt ; Petter Persson ; Maria Abrahamsson
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：December 15, 2014
• 年：2014
• 卷：53
• 期：24
• 页码：12778-12790
• 全文大小：569K
• ISSN：1520-510X

文摘

We synthesized a new homoleptic, tris-bidentate complex [Ru(QPzH)₃]²⁺ based on the novel biheteroaromatic, 8-(3-pyrazolyl)-quinoline ligand QPzH. The QPzH ligand was designed to reduce the distortions typically observed in complexes incorporating the 8-quinolinyl group into the ligand framework. This was indeed observed, and was also, as anticipated, found to facilitate the formation of tris-homoleptic Ru(II) complexes; [Ru(QPzH)₃]²⁺ is the first reported tris-homoleptic complex with ligands based on the 8-quinolinyl group. The synthesis can either result in a statistical 3:1 mer/fac ratio of the complex, or, through controlled exposure to light, be tweaked to allow isolation of the pure mer isomer only. X-ray crystallography reveals three nonequivalent ligands, with significantly less strain than other quinoline-based bidentate ligands. The complex exhibits a nearly octahedral coordination geometry but shows large differences in bond lengths between the Ru core and the quinoline and pyrazoles, respectively. The Ru鈥揘(pyrazole) bond distances are 鈭?.04 脜, while the corresponding distances for Ru鈥揘(quinoline) are 鈭?.12 脜. Structural, photophysical, electrochemical, and theoretical characterization revealed a mer-Ru(II) complex with a low oxidation potential (0.57 V vs ferrocene^0/+) attributed to the incorporation of the pyrazolyl group, a ground state absorption that is sensitive to the local environment of the complex, and a short-lived ³MLCT excited state.