Anti-Bacterial and Anti-Fungal Properties of a Set of Transition Metal Complexes Bearing a Pyridine Moiety and [B(CF)] as a Counter Anion.

BACKGROUND

Transition metal complexes incorporating fluorinated counter anions represent a significant class of compounds with broad applications in industry, pharmaceuticals, and biomedicine. These fluorinated anions are known to enhance the solubility, stability, and reactivity of the complexes, thereby expanding their functional utility in various chemical and biological contexts.

METHODS

A set of metal(II) complexes of the general formula [MPy][B(CF)] where (Py = pyridine, M = Mn (), Fe (), Co (), Ni (), Cu (), Zn ()) have been synthesized by direct reaction of metal halides and pyridine in the presence of Ag[B(CF)]. The complexes were characterized using different techniques to assure their purity, such as elemental analysis (EA), electron paramagnetic resonance (EPR) spectroscopy, thermogravimetric analysis (TGA), ultraviolet-visible (UV-Vis) spectroscopy, B-NMR, H-NMR, and FT-IR spectroscopy. The antimicrobial and antifungal properties against different types of bacteria and fungi were studied for all prepared complexes.

RESULTS

The synthesized complexes exhibited broad-spectrum antimicrobial activity, demonstrating variable efficacy compared to the reference antibiotic, oxytetracycline (positive control). Notably, complex displayed exceptional antibacterial activity against , with a minimum inhibitory concentration (MIC) of 4 µg/mL, outperforming the control (MIC = 8 µg/mL). Complexes , , and showed promising activity against , , and , each with MIC values of 8 µg/mL. Conversely, the lowest activity (MIC = 512 µg/mL) was observed for complexes , , and against , , and , respectively. Regarding antifungal properties, complexes and demonstrated the highest activity against , with MIC values of 8 µg/mL, equivalent to that of the positive control, fluconazole. Density functional theory (DFT) calculations confirmed an overall octahedral coordination geometry for all complexes, with tetragonal distortions identified in complexes , , and .