The potential antimicrobial properties of a tridentate polypyridyl ligand 4-butoxy-N,N-bis(pyridin-2-ylmethyl)aniline (BUT) 1\nand its corresponding mixed ligand ruthenium complexes were investigated on drug-resistant and non-drug-resistant bacterial\nspecies. Theligand and its complexes were synthesized and successfully characterized by 1HNMR, UV/Vis, and FTIR spectra; ESIMS;\nand magnetic susceptibility. Electronic spectra and magnetic susceptibility of these Ru(II)/(III) complexes suggest that they\nare of a low spin crystal field split, where the Ru(III) is a d5 and Ru(II) d6 low spin. These compounds were tested for antibacterial\nactivity on two bacterial species: Staphylococcus aureus (S. aureus) and Klebsiella pneumoniae (K. pneumoniae), as well as their\ndrug-resistant strains methicillin-resistant Staphylococcus aureus (MRSA) and multidrug resistant Klebsiella pneumoniae (MDR\nK. pneumoniae). All the compounds inhibited growth of the two non-drug-resistant bacteria and only one drug-resistant strain\nMRSA. However, only the ligands BUTand 2,2-dipyridylamine showed activity against MRSA, while all complexes did not show\nany antibacterial activity on MRSA. We observed large zones of inhibition for the Gram-positive S. aureus and MRSA bacteria,\ncompared to the Gram-negative K. pneumoniae bacteria. DNA cleavage studies with gel electrophoresis showed denatured\nbacterial DNA on the gel from all the complexes, with the exception of the ligand, suggesting DNA nuclease activity of the\ncomplexes in the bacterial DNA.
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