Synthesis, characterization, and antibacterial activity of functionalized terpyridine silver(I) complexes

Abstract

Eight terpyridine ligands, 4′-methoxy-2,2′:6′,2″-terpyridine (L1), 2′-methoxy-2,2′:6′,2″-terpyridine (L2), 4′-hydroxyl-2,2′:6′,2″-terpyridine (L3), 4′-chloro-2,2′:6′,2″-tepyridine (L4), 2′-pyridinyl-2,2′:6′,2″-terpyridine (L5), 3′-pyridinyl-2,2′:6′,2″-terpyridine (L6), 2′-furanyl-2,2′:6′,2″-terpyridine (L7), and 2′-thiophenyl-2,2′:6′,2″-terpyridine (L8) were developed as multidentate chelating systems with AgSCN, AgOAc, and AgCN to produce twenty four silver(I) terpyridine complexes (1–24). The silver(I) complexes were characterized by various analytical and spectroscopic techniques, which suggest their distorted tetrahedral geometry. The single crystal X-ray diffraction of 23 revealed its dinuclear behaviour in solution by forming distorted tetrahedral and linear geometries around two silver(I) metal centres. The synthesized compounds were investigated for antibacterial activity. The antibacterial activity was conducted against Staphylococcus aureus, Methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli, Salmonella typhimurium, Pseudomonas aeruginosa, and Klebsiella pneumoniae at different concentrations. Complex 7 with a 2-furanylterpyridine moiety and with thiocyanate coordinating to the metal central had notable activity compared to Ciprofloxacin against E. coli, K. pneumoniae, and MRSA, but less than silver(I)-sulfadiazine. Complexes 9 and 15 with the 4-methoxy moiety and the 2-furanyl moieties also showed significant bacterial growth inhibition. Generally, AgOAc complexes had higher activity at low concentrations.