Autori: C. Gabriel, E. Kioseoglou, J. Venetis, V. Psycharis, C. P. Raptopoulou, A. Terzis, G. Voyiatzis, M. Bertmer, C. Mateescu, A. Salifoglou

Editorial: Richard Eisenberg, American Chemical Society Publications, Inorganic Chemistry, 51(11), p.6056-6069, 2012.

Rezumat:

Vanadium involvement in cellular processes requires deep understanding of the nature and properties of its soluble and bioavailable forms arising in aqueous speciations of binary and ternary systems. In an effort to understand the ternary vanadium–H2O2–ligand interactions relevant to that metal ion’s biological role, synthetic efforts were launched involving the physiological ligands betaine (Me3N+CH2CO2–) and H2O2. In a pH-specific fashion, V2O5, betaine, and H2O2 reacted and afforded three new, unusual, and unique compounds, consistent with the molecular formulation K2[V2O2(O2)4{(CH3)3NCH2CO2)}]·H2O (1), (NH4)2[V2O2(O2)4{(CH3)3NCH2CO2)}]·0.75H2O (2), and {Na2[V2O2(O2)4{(CH3)3NCH2CO2)}2]}n·4nH2O (3). All complexes 1–3 were characterized by elemental analysis; UV/visible, FT-IR, Raman, and NMR spectroscopy in solution and the solid state; cyclic voltammetry; TGA-DTG; and X-ray crystallography. The structures of 1 and 2 reveal the presence of unusual ternary dinuclear vanadium–tetraperoxido–betaine complexes containing [(VV═O)(O2)2] units interacting through long V–O bonds. The two V(V) ions are bridged through the oxygen terminal of one of the peroxide groups bound to the vanadium centers. The betaine ligand binds only one of the two V(V) ions. In the case of the third complex 3, the two vanadium centers are not immediate neighbors, with Na+ ions (a) acting as efficient oxygen anchors and through Na–O bonds holding the two vanadium ions in place and (b) providing for oxygen-containing ligand binding leading to a polymeric lattice. In 1 and 3, interesting 2D (honeycomb) and 1D (zigzag chains) topologies of potassium nine-coordinate polyhedra (1) and sodium octahedra (3), respectively, form. The collective physicochemical properties of the three ternary species 1–3 project the chemical role of the low molecular mass biosubstrate betaine in binding V(V)–diperoxido units, thereby stabilizing a dinuclear (V)–tetraperoxido dianion. Structural comparisons of the anions in 1–3 with other known dinuclear V(V)–tetraperoxido binary anionic species provide insight into the chemical reactivity of V(V)–diperoxido systems and their potential link to cellular events such as insulin mimesis and anitumorigenicity modulated by the presence of betaine.

Cuvinte cheie: Vanadium, betaine, spectroscopy, x-ray crystallography, cellular processes