title: The electronic and solvatochromic properties of [Co(L)(bipyridine)2]+(L = o-catecholato, o-benzenedithiolato) species: a combined experimental and computational study.
abstract: Complexes of Co(iii) containing mixed chelating diimine and o-quinone ligand sets are of fundamental interest on account of their fascinating magnetic and electronic properties. Whilst complexes of this type containing one diimine and two o-quinone ligands have been studied extensively, those with the reverse stoichiometry (two diimines and one o-quinone) are much rarer. Herein, we describe a ready route to the synthesis of the complex [CoIII(o-catecholate) (2,2'-bipyridine)2]+(1), and also report the synthesis of [CoIII(o-catecholate)(5,5'-dimethyl-2,2'-bipyridine)2]+(2) and [CoIII(o-benezenedithiolate)(5,5'-dimethyl-2,2'-bipyridine)2]+(3) for the first time. Spectroscopic studies show that complex 2 displays intriguing solvatochromic behaviour as a function of solvent hydrogen bond donation ability, a property of this type of complex which has hitherto not been reported. Time-dependent density function theory (TD-DFT) shows that this effect arises as a result of hydrogen bonding between the solvent and the oxygen atoms of the catecholate ligand. In contrast, the sulfur atoms in the benzenedithiolate analogue 3 are much weaker acceptors of hydrogen bonds from the solvent, meaning that complex 3 is only very weakly solvatochromic. Finally, we show that complex 2 has some potential as a molecular probe that can report on the composition of mixed solvent systems as a function of its absorbance spectrum.
authors.affiliation: WestCHEM, School of Chemistry, University of Glasgow, University Avenue, Glasgow, G12 8QQ, UK. mark.symes@glasgow.ac.uk.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Cioncoloni
authors.affiliation: WestCHEM, School of Chemistry, University of Glasgow, University Avenue, Glasgow, G12 8QQ, UK. mark.symes@glasgow.ac.uk.
authors.forename: Hans M
authors.initials: HM
authors.lastname: Senn
authors.affiliation: WestCHEM, School of Chemistry, University of Glasgow, University Avenue, Glasgow, G12 8QQ, UK. mark.symes@glasgow.ac.uk.
authors.forename: Stephen
authors.initials: S
authors.lastname: Sproules
authors.affiliation: WestCHEM, School of Chemistry, University of Glasgow, University Avenue, Glasgow, G12 8QQ, UK. mark.symes@glasgow.ac.uk.
authors.forename: Claire
authors.identifier: http://orcid.org/0000-0002-0090-5374
authors.initials: C
authors.lastname: Wilson
authors.affiliation: WestCHEM, School of Chemistry, University of Glasgow, University Avenue, Glasgow, G12 8QQ, UK. mark.symes@glasgow.ac.uk.
authors.forename: Mark D
authors.identifier: http://orcid.org/0000-0001-8067-5240
authors.initials: MD
authors.lastname: Symes