Anti-Bacterial and Anti-Fungal Properties of a Set of Transition Metal Complexes Bearing a Pyridine Moiety and [B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>]<sub>2</sub> as a Counter Anion

Anti-Bacterial and Anti-Fungal Properties of a Set of Transition Metal Complexes Bearing a Pyridine Moiety and [B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>]<sub>2</sub> 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,...

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Main Authors: Ahmed K. Hijazi, Mohammad El-Khateeb, Ziyad A. Taha, Mohammed I. Alomari, Noor M. Khwaileh, Abbas I. Alakhras, Waleed M. Al-Momani, Ali Elrashidi, Ahmad S. Barham
Format: Article
Language:English
Published: MDPI AG 2025-07-01
Series:Molecules
Subjects:
metal(II) complexes
antimicrobial
MIC
counter anion
pyridine
Online Access:https://www.mdpi.com/1420-3049/30/15/3121
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Summary: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<sub>6</sub>][B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>]<sub>2</sub> where (Py = pyridine, M = Mn (<b>1</b>), Fe (<b>2</b>), Co (<b>3</b>), Ni (<b>4</b>), Cu (<b>5</b>), Zn (<b>6</b>)) have been synthesized by direct reaction of metal halides and pyridine in the presence of Ag[B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>]. 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, <sup>11</sup>B-NMR, <sup>1</sup>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 <b>6</b> displayed exceptional antibacterial activity against <i>Streptococcus pyogenes</i>, with a minimum inhibitory concentration (MIC) of 4 µg/mL, outperforming the control (MIC = 8 µg/mL). Complexes <b>1</b>, <b>2</b>, and <b>4</b> showed promising activity against <i>Shigella flexneri</i>, <i>Klebsiella pneumoniae</i>, and <i>Streptococcus pyogenes</i>, each with MIC values of 8 µg/mL. Conversely, the lowest activity (MIC = 512 µg/mL) was observed for complexes <b>3</b>, <b>5</b>, and <b>6</b> against <i>Pseudomonas aeruginosa</i>, <i>Escherichia coli</i>, and <i>Klebsiella pneumoniae</i>, respectively. Regarding antifungal properties, complexes <b>5</b> and <b>6</b> demonstrated the highest activity against <i>Candida albicans</i>, 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 <b>3</b>, <b>4</b>, and <b>5</b>.
ISSN:1420-3049

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