Vanadium(IV) and vanadium(V) complexes: Syntheses, structural characterization, DFT studies and impact of oral uptake on enhancing insulin activity of diabetic albino rats

Abstract

Two vanadium complexes in two oxidation states (IV) and (V) have were prepared with 3,4-diaminobenzoic acid and acetylacetone ligands. The chemical formula of the complexes is [VO(DABA)(acac)].3H2O (C1) and [VO2(DABA)(acac)].1/2H2O (C2). The complexes are characterized by using different tools such as; molar conductivity, magnetic susceptibility, spectroscopic techniques (FTIR, UV-Vis., mass, and 1H-NMR), and finally by the DFT calculations. The collected data showed that the ligands bound through two amines (NH2) groups for (DABA) ligand and two carbonyls (C=O) groups for (acac) ligand. The spectroscopic data and the DFT calculations confirmed the mononuclear structure of both complexes. Distorted square pyramidal geometry for the C1 complex and distorted octahedral geometry for the C2 complex have been proposed. The calculations confirmed that the C2 complex is more stable than the C1 complex and the electronic energies are (-1098.98 and -1023.04 a.u.); respectively. The HOMO and the LUMO orbitals of the C2 complex (H = -0.385 and L = -0.228 a.u.) are more negative than that of the C1 complex (H = -0.248 and L = -0.206 a.u.). The bond angles in the two complexes have deviated from that of perfect octahedral and square planar (90° and 180°). The bond lengths between the vanadium atoms and the surrounded nitrogen and oxygen atoms are in the constituted range. The double bond between the vanadium atoms and the oxygen atoms (V=O) is 1.587 in the C1 complex and (1.60 and 1.62) in the C2 complex. The mimic insulin study showed that the C1 and the C2 complexes possess a good insulin-enhancing activity. The study of liver and kidney function parameters demonstrated the superiority of the C2 complex, so it promising result that as an insulin-enhancing factor with the low side effect. However, the C2 complex showed non-toxicity toward liver and kidney biochemical parameters, and that may be due to the oxidation state and the structure of the vanadium metal ion.