Synthesis, characterization, and antibacterial studies of some vanadium complexes with hexamethyl tetraazamacrocycles

Abstract

The hexamethyl tetraazacyclotetradecadiene diperchlorate ligand salt, Me6[14]diene.2HClO4 (L1.2HClO4) on reduction yielded two isomeric C-chiral ligands “tet-a” and “tet-b”. Open air reactions of the ligands, L1.2HClO4, “tet-a,” and “tet-b” with vanadyl acetylacetonate produced octahedral green complexes, [VOL1(acac)](ClO4), [VO(“tet-a”)(H2O)](ClO4)2, and [VO(“tet-b”)(acac)](ClO4), respectively, in which vanadium was in +4 oxidation state. The complex [VOL1(acac)](ClO4) underwent axial substitution with KCNS, KBr, KI, and NaNO2 in the ratio of 1:12 in ethanol to yield axial substitution products, [VOL1(SCN)](ClO4)2, [VOL1Br](ClO4)2, [VOL1I](ClO4)2, and [VOL 1 (NO2)](ClO4)2, respectively, in which vanadium was in +5 oxidation state. On the other hand, [VO(“tet-b”)(acac)](ClO4) underwent simultaneous axial substitution and anion exchange reactions with KCNS and KBr in the same ratio to furnish corresponding vanadium(V) complexes, [VO(“tet-b”)(SCN)](SCN)2 and [VO(“tet-b”)Br]Br2, respectively. These complexes were characterized on the basis of elemental, spectroscopic, magneto-chemical, and conductometric analyses. The antibacterial activities of the ligands and their complexes have been investigated toward different Gram-positive and Gram-negative bacteria.