Vanadium participation in cellular events entails in-depth comprehension of its soluble and bioavailable forms bearing physiological ligands in aqueous distributions of binary and ternary systems. Poised to understand the ternary V(V)-H(2)O(2)-amino acid interactions relevant to that metal ion's biological role, we have launched synthetic efforts involving the physiological ligands glycine and H(2)O(2). In a pH-specific fashion, V(2)O(5), glycine, and H(2)O(2) reacted and afforded the unusual complexes (H(3)O)(2)[V(2)(O)(2)(mu(2):eta(2):eta(1)-O(2))(2)(eta(2)-O(2))(2)(C(2)H(5)NO(2))]center dot 5/4H(2)O (1) and K(2)[V(2)(O)(2)(mu(2):eta(2):eta(1)-O(2))(2)(eta(2)-O(2))(2)(C(2)H(5)NO(2))]center dot H(2)O (2).1 crystallizes in the triclinic space group P (1) over bar, with a = 7.805(4) angstrom, b = 8.134(5) angstrom, c = 12.010(7) angstrom, alpha = 72.298(9)degrees, beta = 72.991(9)degrees, gamma = 64.111(9)degrees, V = 641.9(6) angstrom(3), and Z = 2. 2 crystallizes in the triclinic space group P (1) over bar, with a = 7.6766(9) angstrom, b = 7.9534(9) angstrom, c = 11.7494(13) angstrom, alpha = 71.768(2)degrees, beta = 73.233(2)degrees, gamma = 65.660(2)degrees, V = 610.15(12) angstrom(3), and Z= 2. Both complexes 1 and 2 were characterized by UV/visible, LC-MS, FT-IR, Raman, NMR spectroscopy, cyclic voltammetry, and X-ray crystallography. The structures of 1 and 2 reveal the presence of unusual ternary dinuclear vanadium-tetraperoxo-glycine complexes containing [(V(v)=O)(O(2))(2)](-) units interacting through long V-O bonds and an effective glycinate bridge. The latter ligand is present in the dianionic assembly as a bidentate moiety spanning both V(V) centers in a zwitterionic form. The collective physicochemical properties of the two ternary species 1 and 2 project the chemical role of the low molecular mass biosubstrate glycine in binding V(V)-diperoxo units, thereby stabilizing a dinuclear V(V)-tetraperoxo dianion. Structural comparisons of the anions in 1 and 2 with other known dinuclear V(V)-tetraperoxo binary anionic species provide insight into the chemical reactivity of V(V)-diperoxo species in key cellular events such as insulin mimesis and antitumorigenicity, potentially modulated by the presence of glycinate and hydrogen peroxide.
WASHINGTON
National Hellenic Research Foundation (NHRF)
