| Abstract |
The reactions of [(VO)-O-IV(acac)(2)] (acac = acetylacetonato) with two ONO tridentate ligands, 4-[3,5-bis(2-hydroxyphenyl)-1,2,4-triazol-1-yl]benzoic acid (H2L1, I) and 3,5-bis(2-hydroxyphenyl)-1-phenyl-1,2,4-triazole (H2L2, II) in methanol lead to the formation of the oxidovanadium(V) complexes [(VO)-O-V(mu-L-1)(OMe)](2) (1) and [(VO)-O-V(mu-L-2)(OMe)](2) (2). In the presence of KOH/CsOH, they give the corresponding dioxidovanadium(V) complexes. The isolated complexes K(H2O)[(VO2)-O-V(L-1)] (3), K(H2O)[(VO2)-O-V(L-2)] (4), Cs(H2O)[(VO2)-O-V(L-1)] (5), and Cs(H2O)[(VO2)-O-V(L-2)] (6) along with 1 and 2 have been characterized by various spectroscopic techniques (FTIR; UV/Vis; H-1, C-13, and V-51 NMR), elemental analysis, thermal studies, MALDI-TOF MS analysis, and single-crystal analysis of 1a (complex 1 grown together with 4,4-bipyridyl). The oxidative bromination of thymol, catalyzed by these complexes, in the presence of KBr and HClO4 with H2O2 as an oxidant, gives 2-bromothymol, 4-bromothymol, and 2,4-dibromothymol. The amounts of the catalyst, oxidant, KBr, HClO4, and the solvent were optimized for the maximum conversion of thymol. Both ligands and all complexes were tested in vitro for antiamoebic activity against the HM1:IMSS strain of Entamoeba histolytica by a microdilution method. The complexes are more potent amoebicidal agents than the standard drug metronidazole. Toxicity studies against a human cervical cancer cell line (HeLa) also confirm that these compounds are less cytotoxic than metronidazole. |
