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

• Published in: Polyhedron Vol. 157; pp. 396 - 405
• Main Authors: Al-Riyahee, Ali A.A., Horton, Peter N., Coles, Simon J., Amoroso, Angelo J., Pope, Simon J.A.
• Format: Journal Article
• Language: English
• Published: OXFORD Elsevier Ltd 01.01.2019; Elsevier
• Subjects: Chemistry; Chemistry, Inorganic & Nuclear; Chromium; Complex; Crystallography; Luminescence; Physical Sciences; Quinolate; Science & Technology; Structures; Chromium; Structures; Quinolate; Luminescence; Complex; CELLS; STATE; NMR; DFT; 8-HYDROXYQUINOLINES; PHOTOPHYSICS; PHOTOCHEMISTRY; SPECTRA
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2018.10.019

A series of Cr(III) complexes have been synthesised that incorporate (substituted) 8-quinolinato type ligands into the coordination sphere. Both homo- and heteroleptic examples are described together with X-ray structures and luminescence properties. [Display omitted] 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.