Syntheses, X-ray structures and characterisation of luminescent chromium(III) complexes incorporating 8-quinolinato ligands

Al-Riyahee, Ali A.A., Horton, Peter N., Coles, Simon J., Amoroso, Angelo J. and Pope, Simon J.A. (2019) Syntheses, X-ray structures and characterisation of luminescent chromium(III) complexes incorporating 8-quinolinato ligands. Polyhedron, 157, 396-405. (doi:10.1016/j.poly.2018.10.019).

Abstract

A series of six coordinate homoleptic and heteroleptic Cr(III) complexes have been formed that incorporate 8-quinolinato ligands. Three classes of complex have been synthesised and characterised: (i) [Cr(Q)3]; (ii) [Cr(Q)2(H2O)2]Cl; (iii) [Cr(Q)(N^N)2](PF6)2 (where Q is a ligand, 8-hydroxyquinoline, 8-hydroxy-2-methyl-quinoline, or 8-hydroxy-5-nitroquinoline; N^N = 1,10-phenanthroline or 2,2′-bipyridine). Single crystal X-ray structures were obtained for four complexes giving examples of [Cr(Q)2(H2O)2]Cl, two [Cr(Q)(bipy)2](PF6)2 and [Cr(Q)(phen)2](PF6)2. Each complex shows the ligands in the expected coordination mode with a distorted octahedral geometry evident at the metal centre. The UV–Vis. absorption data allowed assignments of the quinolinato-centred electronic transitions together with a much weaker spin allowed d–d transition (4A2 → 4T2) around 550 nm. Each complex was found to be luminescent in aerated MeCN solution at room temperature, which was attributed to a ligand-centred fluorescence based on the coordinated quinolinato ligand.

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Contributors

Author: Peter N. Horton

Author: Simon J. Coles

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