Structural and Biological Evaluation of Manganese(II) and Copper(II) Complexes with 2,5-Pyridinedicarboxylate Ligands: Experimental and Theoretical Insights into Antibacterial Potential and Antibiofilm Property

Abstract

Two novel coordination complexes, [Mn(HPDC)2(H2O)2] (YS-Mn) and [Cu(HPDC)2][NH(CH3)2]2 (YS-Cu), were successfully synthesized utilizing 2,5-pyridinedicarboxylic acid as the ligand. These complexes were comprehensively characterized using a variety of spectroscopic and analytical techniques, including single-crystal X-ray diffraction, infrared spectroscopy, and elemental analysis. The structural analysis revealed that YS-Mn crystallizes in a monoclinic system with a C2/c space group, while YS-Cu adopts a triclinic system with a P-1 space group. The biological activities of these complexes were evaluated against a panel of microbial strains to assess their potential as antimicrobial agents. The Mn(II) complex demonstrated significant antibacterial activity, with the lowest minimum inhibitory concentration (MIC) of 128 µg/mL observed against S. aureus 3160, followed by B. cereus and E. coli at 256 µg/mL. Against K. pneumoniae 1705 and S. marcescens 97, the MIC was determined to be 512 µg/mL. Furthermore, the Mn(II) complex exhibited potent biofilm inhibitory effects, particularly against S. aureus 3160, at sub-MIC concentrations. Molecular docking studies suggested that the Mn(II) complex interacts with MetAPs in E. coli, interfering with protein and DNA synthesis, thus contributing to its antimicrobial activity. The promising biological activity exhibited by the Mn(II) and Cu(II) complexes, particularly the Mn(II) complex, highlights their potential as promising candidates for further development as therapeutic agents to combat drug-resistant pathogens.