Syntheses, Crystal Structures, and Antimicrobial Activities of Oxovanadium(V) Complexes with Tridentate Schiff base Ligand

Two structurally similar new oxovanadium complexes, [VO(L)(L-1)] (I) and [VO(L)(L-2)] (II), where L is the dianionic form of 3-((3-bromo-2-hydroxyphenyl)-{[1-(3-bromo-2-hydroxyphenyl)methylidene]amino}methyl)pentane-2,4-dione (H2L), L-1 is the deprotonated form of 8-hydroxyquinoline, L-2 is 2,2'-bipyridine, were prepared and characterized by spectroscopic and single crystal X-ray diffraction (CIF files CCDC nos. 1566824 (I), 1566825 (II)). Complex I crystallizes as the monoclinic space group P2(1)/c with unit cell dimensions a = 11.265(1), b = 18.179(2), c = 13.461(2) angstrom, = 103.376(3)degrees, V = 2681.8(5)angstrom(3), Z = 4, R-1 = 0.0659, wR(2) = 0.1318, GOOF = 1.003. Complex II crystallizes as the orthorhombic space group Pbca with unit cell dimensions a = 19.958(1), b = 13.600(1), c = 22.8713(2) angstrom, V = 6192.3(8) angstrom(3), Z = 8, R-1 = 0.0550, wR(2) = 0.1008, GOOF = 1.074. X-ray analysis indicates that the complexes are mononuclear oxovanadium(V) species with the V atoms in octahedral coordination. The complexes were evaluated for their antibacterial (Bacillus subtilis, Staphylococcus aureus, Escherichia coli, and Pseudomonas fluorescence) and antifungal (Candida albicans and Aspergillus niger) activities by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) method. Interestingly, complex II has strong activity against S. aureus.