Synthesis, characterization, biological and computational studies of Ni(II) compounds with flexible carboxylic acids

Abstract

Two Ni(II) based coordination compounds, [Ni(toua)(H2O)].2H2O (1), and [Ni(eoba)(H2O)2] (2) are reported in this work (where toua = 3,6,9-trioxaundecanedioate, and eoba = 2,2-ethylenebis(oxy)bisacetate). These are synthesized in good yields from the one-pot self-assembly method in methanol at ambient conditions. Both compounds 1 & 2 are thoroughly characterized by elemental analysis, FTIR and XPS spectroscopy, TGA analysis and FE-SEM. The antibacterial and antioxidant activities of these coordination compounds were systematically investigated. The antibacterial efficacy was assessed against Gram-negative bacteria, Escherichia coli and Pseudomonas aeruginosa, as well as against the Gram-positive bacterium Bacillus subtilis, utilizing the microdilution method to determine minimum inhibitory concentrations (MICs). The results revealed that these coordination compounds exhibited significantly enhanced antibacterial activity in comparison to the free dicarboxylic acid and the corresponding metal ion, with compound 1, demonstrating the highest potency. These compounds were also tested for antioxidant properties by DPPH radical scavenging assay. The findings indicated that the compound 1 has more antioxidant activity as compared to compound 2. Furthermore, these experimental results were also supported by computational studies such as molecular docking, DFT calculations and ADME calculations. In silico molecular docking studies analysis revealed that compound 1 showed relatively stronger binding affinity against three target proteins one each from E.coli, P. aeruginosa and B. subtilis. Density functional theory (DFT) calculations were executed to validate the molecular structure and examine the characteristics of frontier orbital through frontier molecular orbital analysis of the geometrically optimized structures. To predict the drug's likeness and bioavailability, ADME calculations were carried out, and these studies revealed that both compounds 1 & 2 have good potential to be used as orally active drugs.