Salicylaldimine based complexes and their Ascorbic acid ternary Analogues: Synthesis, Characterisation, Antimicrobial Evaluation, Molecular docking and DFT Considerations
DOI:
https://doi.org/10.33003/Keywords:
Salicylaldehyde, Schiff Bases, Binary/Mixed-Ligand Complexes, Biological Evaluation, DFT CalculationAbstract
This study reports a series of complexes with the general formula [M(A1)2(H2O)2]·nH2O (1 – 4) and [M(A1)(A2)(H2O)2]·nH2O (5 – 8) {where M = Co, Ni, Cu and Zn; HA1 = (E)-2-(hydrazineylidenemethyl)phenol and HA2 = ascorbic acid}. The prepared compounds were characterised by 1H nmr, Fourier Transform infrared (FTIR) and electronic spectroscopies as well as magnetic susceptibility measurement. Quantum calculation were carried out using DFT/B3LYP-D3/6-31G** for the ligands and DFT/B3LYP-D3/LACVP** for the complexes. The magnetic moments for the Co(II) {5.06–5.49 B.M} and Ni(II) {3.15–3.16 B.M} complexes suggest octahedral geometry, with orbital contribution. The Cu(II) complexes appear to be octahedral with the homoleptic complex (3) displaying a subnormal value (1.58 B.M). Generally, the complexes showed better antimicrobial activity than the ligands. The mixed ligand complexes showed better activity than respective homoleptic analogue – while the mixed ligand complexes displayed Minimum Inhibitory Concentration (MIC) in the range 0.125–2.00 mg/mL, the homoleptic complexes displayed MIC in range 0.50–2.00 mg/mL. The Ni(II) mixed ligand complex, 6, recorded the highest (negative) docking scores; -5.667 kcal/mol, -6.614 kcal/mol and -5.542 kcal/mol against E. coli, S. aur and C. alb, respectively – with better scores than ciprofloxacin (-5.379 kcal/mol and -4.183 kcal/mol against E. coli and S. aur, respectively) but lower than ketoconazole (-8.288 kcal/mol against C. alb); 6 also displayed the best global softness (0.6196 eV-1), in comparison to other complexes (except for the spin down {β} variants of compounds 3 and 7 {3β and 7β}). Thus, the prepared compounds are potential antimicrobial agents.
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