The electronic and solvatochromic properties of [Co(L)(bipyridine)2]+ (L = o-catecholato, o-benzenedithiolato) species: a combined experimental and computational study. Issue 39 (14th September 2016)

• Record Type: Journal Article
• Authors: Cioncoloni, Giacomo; Senn, Hans M.; Sproules, Stephen; Wilson, Claire; Symes, Mark D.
• Is Part Of: Dalton transactions. Volume 45:Issue 39(2016)
• Page Start: 15575
• Page End: 15585
• Publication Date: 2016-09-14
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c6dt02807a
• Languages: English
• ISSNs: 1477-9226

Abstract

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. 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 [Co III ( o -catecholate) (2, 2′-bipyridine)2 ] + (1 ), and also report the synthesis of [Co III ( o -catecholate)(5, 5′-dimethyl-2, 2′-bipyridine)2 ] + (2 ) and [Co III ( o -benezenedithiolate)(5, 5′-dimethyl-2, 2′-bipyridine)2 ] + (3 ) for the first time. Spectroscopic studies show that complex2 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 analogue3 are much weaker acceptors of hydrogen bonds from the solvent, meaning that complex3 is only very weakly solvatochromic. Finally, we show that complex2 has some potential as a molecular probe that can report on the composition of mixed solvent systems as a function of its absorbance spectrum.