Synthesis and characterization of vanadium(IV) and (V) complexes with 2-hydroxy-acetophenone-semicarbazone (H2hasc) as ligand.: X-ray crystal structures of [VO2(H2hasc)] and [VO2(Hhasc)]

Three novel vanadium complexes with pharmacologically active ligands were synthesized and characterized: [(VO)-O-1V(acac)(Hhasc)], [(VO2)-O-1V(H(2)hasc)], and [(VO2)-O-V(Hhasc)], where H(2)hasc = 2-Hydroxy-acetophenone-semicarbazone. The analytical methods used included FTIR, H-1-, C-13-, V-51-NMR and EPR spectroscopies, elemental analysis and X-ray diffractometry from single crystals. The crystal and molecular structures Of [(VO2)-O-1V(H(2)hasc)] and [(VO2)-O-V(Hhasc)] were determined. [(VO2)-O-1V(H(2)hasc)] crystallizes monoclinic [P2(1)/c, Z = 4, a = 783.4(2), b = 1024.9(2), c = 1365.5(3) pm, beta = 99.506(14)degrees]. The (VO2)(2+) core is coordinated to a neutral O,N,O-tridentate unit of the H(2)hasc ligand, with the vanadium atom showing a square pyramidal coordination sphere. In the crystal of [(VO2)-O-V(Hhasc)], triclinic [P (1) over bar, Z = 4, a = 858.73(11), b = 967.39(5), c = 1318.63(12) pm, alpha = 97.423(5), beta = 101.590(6), y = 98.144(5)degrees], two symmetry independent (VO2)(+) cores are observed. Each of them coordinates to a monodeprotonated Hhasc(-) unit, in a O,N,O-tridentate mode. One assumes a square pyramidal geometry for the pentacoordinate vanadium(V) center. An additional interaction is observed for the other one, involving the phenolate oxygen atom from a symmetry related unit, resulting in a [5+ 1]-coordination number for the transition metal atom.