title: An NMR study on the 6,6'-(2-(diethylamino)ethylazanediyl)bis(methylene)bis(5-hydroxy-2-hydroxymethyl-4H-pyran-4-one) interaction with Al(III) and Zn(II) ions.
abstract: Here we report about the complex formation among an amine-bearing bis-kojic acid, 6,6'-(2-(diethylamino)ethylazanediyl)bis(methylene)bis(5-hydroxy-2-hydroxymethyl-4H-pyran-4-one) and two metal ions, the trivalent hard and not essential metal ion Al(III) and the borderline and essential divalent metal ion Zn(II). We carried out a thorough NMR study in order to reach the indispensable structural information on the behavior of these complexes in solution. A combination of 1D, 2D total correlation spectroscopy, heteronuclear single quantum coherence spectroscopy, nuclear Overhauser enhancement spectroscopy and rotating-frame Overhauser effect spectroscopy experiments was used to assign the signals of both free and metal-bound ligand at different pH values. Our results highlighted the different coordination behaviors of the ligand towards the different metal ions, depending on their hard or borderline character. The trivalent metal ion, Al(III), mainly forms dinuclear helicate complexes of M2L3 stoichiometry, and the coordination only involves both hydroxypyrone (O,O)-donor atoms. NMR data are in agreement with the presence of a rigid and symmetric structure of L9-Al(III) complexes up to physiological pH. On the contrary, with the divalent metal ion, NMR data showed the coexistence of several species in solution though Zn(II) forms complexes of ML stoichiometry at physiological pH, where the metal coordination involves the nitrogen atoms of both the linker and the side-chain amine groups together with the oxygen atoms of phenolate groups. The in solution study will be of interest for providing an insight on the ligand bioavailability and on its behavior in the chelation treatments.
authors: Department of Chemistry and Pharmacy, University of Sassari, Via Vienna 2, 07100 Sassari, Italy. Electronic address: peana@uniss.it.
authors: Massimiliano
authors: M
authors: Peana
authors: Department of Chemistry and Pharmacy, University of Sassari, Via Vienna 2, 07100 Sassari, Italy.
authors: Serenella
authors: S
authors: Medici
authors: Department of Chemical and Geological Sciences, University of Cagliari, Cittadella Universitaria, 09042 Monserrato, Italy.
authors: Valeria Marina
authors: VM
authors: Nurchi
authors: Department of Chemical and Geological Sciences, University of Cagliari, Cittadella Universitaria, 09042 Monserrato, Italy.
authors: Joanna Izabela
authors: JI
authors: Lachowicz
authors: Department of Chemical and Geological Sciences, University of Cagliari, Cittadella Universitaria, 09042 Monserrato, Italy.
authors: Guido
authors: G
authors: Crisponi
authors: Department of Chemical and Geological Sciences, University of Cagliari, Cittadella Universitaria, 09042 Monserrato, Italy.
authors: Miriam
authors: M
authors: Crespo-Alonso
authors: IST-UTL, Centro Química Estrutural, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
authors: Maria Amelia
authors: MA
authors: Santos
authors: Department of Chemistry and Pharmacy, University of Sassari, Via Vienna 2, 07100 Sassari, Italy. Electronic address: zoroddu@uniss.it.
authors: Maria Antonietta
authors: MA
authors: Zoroddu
mesh_terms: D000535:Aluminum / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D005029:Ethylenediamines / Q000737:chemistry* / Q000378:metabolism; D006860:Hydrogen Bonding; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D015394:Molecular Structure; D011753:Pyrones / Q000737:chemistry* / Q000378:metabolism; D015032:Zinc / Q000737:chemistry* / Q000378:metabolism
chemical_list: C000599650:6,6'-(2-(diethylamino)ethylazanediyl)bis(methylene)bis(5-hydroxy-2-hydroxymethyl-4H-pyran-4-one); D005029:Ethylenediamines; D007477:Ions; D011753:Pyrones; D000535:Aluminum; D015032:Zinc
keywords: Aluminium; Complex formation equilibrium; Kojic acid; Kojic acid derivative; NMR; Zinc