Aqueous V(V)-Peroxo-Amino Acid Chemistry. Synthesis, Structural and Spectroscopic Characterization of Unusual Ternary Dinuclear Tetraperoxo Vanadium(V)-Glycine Complexes

Abstract

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))] x 5/4 H(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))] x H(2)O (2). 1 crystallizes in the triclinic space group P1, with a = 7.805(4) A, b = 8.134(5) A, c = 12.010(7) A, alpha = 72.298(9) degrees, beta = 72.991(9) degrees, gamma = 64.111(9) degrees, V = 641.9(6) A(3), and Z = 2. 2 crystallizes in the triclinic space group P1, with a = 7.6766(9) A, b = 7.9534(9) A, c = 11.7494(13) A, alpha = 71.768(2) degrees, beta = 73.233(2) degrees, gamma = 65.660(2) degrees, V = 610.15(12) A(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.

A journey into the electrochemistry of vanadium compounds

“…Given that these species bear a physiologically important moiety present in human fluids, it seemed important to investigate whether glycinate V(V)-peroxo species exhibits biological activity, [V 2 (O) 2 ( 2 :Á 2 :Á 1 -O 2 ) 2 (Á 2 -O 2 ) 2 (Gly)] (GlyH = glycine [180] , Fig. 4).…”

Calcium and strontium salts of (glycinato-κ2N,O)oxidobis(peroxido-κ2O,O′)vanadate(V) tetrahydrate

“…Since vanadium is a good nucleus for NMR, the formation of monoand dinuclear complexes was examined by 51 V NMR. The 51 V chemical shift of (II) was not given in the literature by Gabriel et al (2009), and an attempt to get 51 V signals under the conditions of pH in the range 4-7, a glycine/vanadium ratio in the range 0-4 and a H 2 O 2 /vanadium ratio of 2, indicated that a signal possibly assigned to (II) appeared at À710 p.p.m. at a pH range of 4-6 and a glycine/vanadium ratio in the range 1-4.…”

Vanadium and molybdenum peroxides: synthesis and catalytic activity in oxidation reactions

“…This is true also with more complicated, often polynuclear, structures: see, as just a few examples, complexes 10, 39 and related structures. [32][33][34]48,55 A review with a collection of salient UV-vis data for monoperoxo vanadium species recently appeared. 27 Quite different is the scenario of the 51 V-NMR chemical shifts, related data are collected in Table 2.…”