Potentiometric, spectral and (1)H NMR relaxation studies are reported on the complex formation of VO(IV) with the bidentate chelating ligands oxalic and malonic acids, of a dicarboxylic nature, and maltol and kojic acid, of the hydroxy-4-pyrone type. Complexes with stochiometries VOA and VOA(2) were characterised in aqueous solution. Two main features were established for the complex systems. It was found that five-membered ring chelation favours the cis arrangement in the bis complexes of maltol and kojic acid to a higher extent than in those of oxalic and malonic acids. Moreover, previous investigations of VO(IV) binding to maltol or its analogues did not consider the formation of hydroxo species. Formation of dihydroxo bridged dimeric complexes of stoichiometry (VOAH(-1))(2) and monomeric hydroxo species VOA(2)H(-1) or VOA(2)(OH), are now taken into account in order to explain the equilibrium and spectroscopic results. (1)H NMR relaxation measurements strongly suggest an equilibrium between the two isomers of the bis complexes. (C) 2000 Elsevier Science S.A. All rights reserved.
Speciation and NMR relaxation studies of VO(IV) complexes with several O-donor containing ligands: oxalate, malonate, maltolate and kojate / Buglyo, P; Kiss, E; Fabian, I; Kiss, T; Sanna, D; Garribba, Eugenio; Micera, Giovanni. - In: INORGANICA CHIMICA ACTA. - ISSN 0020-1693. - 306:2(2000), pp. 174-183. [10.1016/S0020-1693(00)00168-7]
Speciation and NMR relaxation studies of VO(IV) complexes with several O-donor containing ligands: oxalate, malonate, maltolate and kojate
GARRIBBA, Eugenio;MICERA, Giovanni
2000-01-01
Abstract
Potentiometric, spectral and (1)H NMR relaxation studies are reported on the complex formation of VO(IV) with the bidentate chelating ligands oxalic and malonic acids, of a dicarboxylic nature, and maltol and kojic acid, of the hydroxy-4-pyrone type. Complexes with stochiometries VOA and VOA(2) were characterised in aqueous solution. Two main features were established for the complex systems. It was found that five-membered ring chelation favours the cis arrangement in the bis complexes of maltol and kojic acid to a higher extent than in those of oxalic and malonic acids. Moreover, previous investigations of VO(IV) binding to maltol or its analogues did not consider the formation of hydroxo species. Formation of dihydroxo bridged dimeric complexes of stoichiometry (VOAH(-1))(2) and monomeric hydroxo species VOA(2)H(-1) or VOA(2)(OH), are now taken into account in order to explain the equilibrium and spectroscopic results. (1)H NMR relaxation measurements strongly suggest an equilibrium between the two isomers of the bis complexes. (C) 2000 Elsevier Science S.A. All rights reserved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.