Mononuclear complexes of FeII, CoII and CoIII containing imine-based ligands of 8-aminoquinoline and 7-aminoindazole: spin state tuning of FeII complexes in solution?

New Journal of Chemistry Pub Date: 2019-06-04 DOI: 10.1039/C9NJ01622H

Abstract

Five mononuclear metal complexes were synthesised, three complexes of iron(II), one complex of cobalt(III) and one complex of cobalt(II) containing imine ligands based on 8-aminoquinoline or 7-aminoindazole and 2-formylpyridine or 3-formylpyrazole, namely [FeII(L1)2](BF4)2 (1), [CoIII(L1)(L1′)](BF4)2 (2), [FeII(HL2)2](BF4)2 (3), [FeII(HL3)2](BF4)2 (4) and [CoII(HL3)2](BF4)2 (5). Iron(II) complexes 1 and 3 derived from 8-aminoquinoline and 2-formylpyridine or 3-formylpyrazole, respectively, were stabilised in the LS-state (S = 0) as proven by NMR spectroscopy and X-ray crystallography, whereas complex 4, based on indazole and pyridine, shows a gradual and incomplete spin conversion in CD3CN solution (the Evans method). According to NMR spectroscopy and X-ray crystallography, the cobalt complexes 2 and 5 were stabilised in different oxidation states.

Graphical abstract: Mononuclear complexes of FeII, CoII and CoIII containing imine-based ligands of 8-aminoquinoline and 7-aminoindazole: spin state tuning of FeII complexes in solution
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