Structure, Antimicrobial Activity, Hirshfeld Analysis, and Docking Studies of Three Silver(I) Complexes-Based Pyridine Ligands

Abstract

Three broad spectrum Ag(I) complexes against MDR (multi drug resistance) and ATCC standard bacteria as well as the fungus C. albicans were presented. The three well-known structurally-related Ag(I) complexes, [Ag(pyridine-3-carboxaldhyde)2NO3], 1, [Ag3(2-pyridone)3(NO3)3]n, 2, and [Ag(3-hydroxypyridine)2]NO3, 3, were prepared by the direct combination of AgNO3 with the corresponding pyridine ligands in a water-ethanol mixture. 1 and 3 are molecular compounds while, 2 is a 2D coordination polymer with sheets bridged by strong homoleptic R2,2(8) hydrogen bonds between ligands giving the ins topology. Different contacts affecting the molecular packing in their crystal structures were computed by employing Hirshfeld analysis. Charge transferences from the ligand groups to Ag(I) were analyzed using natural population analysis. The effect of protonation and metal coordination on the tautomerism of 2-pyridone was analyzed using data from the Cambridge Structure Database (CSD). It was found that Lewis acid attachment to both N and O sites favor a state in between the two formal tautomers. All compounds were significantly more active than 17 tested commercial antibiotics against three clinically isolated strains of Ps. Aeruginosa, with 2 and 3 performing best on average against all ten tested bacterial strains but with 3 containing less Ag per weight. Finally, docking studies were carried out to unravel the inhibition mechanism of the synthesized silver(I) complexes.

Keywords

• Ag(I)-pyridine complexes
• Hirshfeld
• ins topology
• antimicrobial activity
• tautomerism