A Homoleptic Trisbidentate Ru(II) Complex of a Novel Bidentate Biheteroaromatic Ligand Based on Quinoline and Pyrazole Groups: Structural, Electrochemical, Photophysical, and Computational Characterization
Journal article, 2014

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-N(pyrazole) bond distances are similar to 2.04 angstrom, while the corresponding distances for Ru-N(quinoline) are similar to 2.12 angstrom. 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 (LCT)-L-3 excited state.


M. Jarenmark

Lund University

L. A. Fredin

Lund University

Joachim Hedberg

Chalmers, Chemical and Biological Engineering, Physical Chemistry

I. Doverbratt

Lund University

P. Persson

Lund University

Maria Abrahamsson

Chalmers, Chemical and Biological Engineering, Physical Chemistry

Inorganic Chemistry

0020-1669 (ISSN) 1520-510X (eISSN)

Vol. 53 24 12778-12790

Areas of Advance

Nanoscience and Nanotechnology (2010-2017)

Subject Categories

Chemical Sciences



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