Spectroscopy and DFT studies on Cr(III) complexes with saccharides, 8-hydroxyquinoline and their biological activity

Abstract

The current study reports on combined experimental and computational studies on chromium (III) complexes' molecular structure and spectroscopic assignments. Complexes of the general formulas [Cr (GLU) (HQ)] (1), [Cr (FRU) (QH)] (2), (where (GLU) is Glucose, (FRU) is Fructose, and (HQ) is 8-Hydroxyquinoline) were synthesized in two steps. Beginning with the reaction of [Cr(C5H7O2)3. nH2O] with GLU or FRU, followed by the addition of HQ as co-ligand. Initial characterization based on elemental and mass analyses has suggested possible structures of 1 and 2. In the suggested structures, the GLU or FRU and (8-HQ) ligands are bonded to the Cr(III) metal center. The information of powder X-ray diffraction (XRD) structure suggested molecular structures. Other spectroscopic properties of the complexes were examined by UV-Vis techniques. The detailed vibrational assignment which has been done for the observed FT-IR spectrum in solid-state was observed in the region of 4000–600 cm−1. Density Functional Theory (DFT) calculations were carried out to investigate the geometry of the coordination complex using the Amsterdam Molecular Simulation AMS2022.101 release code (vide supra) and Gaussian 09 program. The molecule geometry was optimized using Density Functional Theory with B3LYP functional and Triple-zeta (TZP) basis sets, in the ground state. The Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital (LUMO) were calculated using the DFT/B3LYP method with the SDD basis sets in the ground state. From the optimized geometry of the molecule, geometric parameters (bond lengths and bond angles) and vibrational assignments of the compounds have been calculated theoretically. Moreover, the new complexes were tested against the selected species of antibacterial types: Staphylococcus aureus (ve), Pseudomonas aeruginosa (-ve), Escherichia coli (-ve), and also against Candida albicans and Aspergillus flavus. The results revealed that the new compounds showed good efficacy at high concentrations toward the growth inhibition of the selected pathogenic microorganisms.