Synthesis, antimicrobial activity and application of polymers of praseodymium complexes based on pyridine nitrogen oxide

Abstract

The traditional pyridine nitrogen oxide-based antimicrobial agents are often associated with health risks due to heavy metal enrichment. To mitigate this concern, we synthesized two novel complexes, Pr₂(mpo)₆(H₂O)₂ and Pr(hpo)(mpo)₂(H₂O)₂, and integrated rare-earth salts, Hhpo (2-hydroxypyridine-N-oxide) and Nampo (2-mercapto-pyridine-N-oxide sodium salt). These complexes were characterized through infrared analysis, elemental analysis, thermogravimetric analysis, and X-ray crystallographic analysis. Our comparative analyses demonstrate that the synthesized rare-earth complexes exhibit stronger antimicrobial activity against Staphylococcus aureus (S. aureus ATCC6538) and Escherichia coli (E. coli ATCC25922) compared to the ligands and rare-earth salts alone. Quantitative results revealed the lowest inhibitory concentrations of the two complexes against S. aureus ATCC6538 and E. coli ATCC25922 at 3.125 μg mL⁻¹, 6.25 μg mL⁻¹, 3.125 μg mL⁻¹ and 6.25 μg mL⁻¹, respectively. Preliminary investigations indicated that the antibacterial mechanism of these complexes involved promoting intracellular substance exudation to achieve antibacterial effects. Incorporation of these complexes into polymeric antimicrobial films resulted in a potent antimicrobial effect, achieving a 100% inhibition rate against S. aureus ATCC6538 and E. coli ATCC25922 at a low addition level of 0.6 wt%. Our results suggest that nitrogen oxide-based praseodymium complexes have potential for various antimicrobial applications.