title: A novel dinuclear species in the aqueous distribution of aluminum in the presence of citrate.
abstract: The chemistry of aluminum was explored in the presence of the physiological ligand citric acid and in low-pH aqueous media. As a result, the first dinuclear aluminum-citrate complex (NH4)4[Al2-(C6H4O7)(C6H5O7)2].4H2O was isolated at low pH (approximately 3.5), and was characterized by FT-IR spectroscopy and X-ray crystallography. The structural analysis reveals the presence of a dinuclear assembly of two aluminum ions octahedrally coordinated to three citrate ligands of differing protonation state. The NMR solution behavior of this complex emphasizes its time-dependent transformation into a number of variable nature species, ultimately leading to the thermodynamically stable trinuclear species. It also establishes the participation of the dinuclear complex as a viable component of the aqueous Al(III)-citrate speciation. The chemical and structural features of this novel low molecular mass species provide considerable insight into citrate's ability, as a natural ligand, to influence the chemistry of aluminum in a pH-dependent fashion, and potentially affect aluminum's (bio)distribution, absorption, accumulation, and biotoxicity at sensitive biological sites.
authors.affiliation: Department of Chemistry, University of Crete, Heraklion 71409, Greece.
authors.forename: Maria
authors.initials: M
authors.lastname: Dakanali
authors.forename: Catherine P
authors.initials: CP
authors.lastname: Raptopoulou
authors.forename: Aristidis
authors.initials: A
authors.lastname: Terzis
authors.forename: Andrea
authors.initials: A
authors.lastname: Lakatos
authors.forename: Istvan
authors.initials: I
authors.lastname: Banyai
authors.forename: Tamas
authors.initials: T
authors.lastname: Kiss
authors.forename: Athanasios
authors.initials: A
authors.lastname: Salifoglou