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 [VOL¹(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.

Keywords:

• Tetraazamacrocyclic ligands
• vanadium complexes
• spectroscopic studies
• substitution and anion exchange reactions
• antimicrobial activities

Additional information

Funding

The authors would like to extend their sincere appreciation to the Ministry of Education, Bangladesh, to sanction a research grant to Professor Dr. Tapashi Ghosh Roy and Professor Dr. Debashis Palit Department of Chemistry, University of Chittagong, Chittagong-4331, Bangladesh.