Silver(I) complexes with quinolyl and pyridyl terpyridines: Synthesis, structural evaluation and antimicrobial activity

• 4ˈ-(pyridyl)- & 4ˈ-(quinolyl)-terpyridine ligands synthesized in a single pot reaction. • The ligands reacted with silver(I) salts yielding discrete & polymeric architectures. • Synthesized compounds characterised via spectroscopic and some SCXRD techniques. • Synthesized compounds were investigated for antibacterial and antifungal activity. The management of bacteria and fungi infections remain a challenge due to resistance and unwanted side effects of available drugs. Faced with increased resistance to antimicrobials in use, new and more effective antimicrobial agents are needed. Silver(I) ions and silver(I)-based compounds are well known to show strong biocidal effects against pathogenic microorganisms. In advancement of this knowledge and studies on antimicrobial studies, we report synthesis of a series twelve new silver(I) complexes using four ligands namely; 4ˈ-(isoquinolyl)-2,2′:6′,2′'-terpyridine ( L1 ), 4ꞌ-(4-quinolyl)-2,2′:6′,2′'-terpyridine ( L2 ), 4′-(2-pyridyl)-2,2′:6′,2′'-terpyridine ( L3 ) and 4′-(3-pyridyl)-2,2′:6′,2′'-terpyridine ( L4 ) with either AgO 2 C 2 F 3 , AgO 3 SCF 3 or AgClO 4 . The newly synthesised compounds were characterised by various spectroscopic and analytical techniques. The structures of complexes 7, 8, 11 and 12 were also unequivocally determined by single crystal X-ray diffraction technique. Complexes 7 and 8 are discrete dinuclear species, while 11 and 12 are isostructural coordination polymers. In 7 , Ag(I) adopts a distorted tetrahedral geometry via three terpyridine N atoms and an anion O atom, whereas 8 exhibits a distorted square pyramidal geometry with additional pyridine N coordination. In polymers 11 and 12 , Ag(I) coordinates through terpyridine and 3-pyridine N atoms, forming chains along the a-axis. The antimicrobial activity of the synthesized silver(I) complexes was evaluated against Staphylococcus aureus, Escherichia coli, Salmonella typhimurium , and Candida albicans using disk diffusion and microdilution methods. The complexes exhibited enhanced activity against Gram-negative bacteria and fungi compared to the Gram-positive strain. The multitopic terpyridine ligands not only improved biological activity but also facilitated metal-directed polymeric chain formation as well as discrete complex formation. These findings highlight the potential of silver(I) terpyridine complexes as lead compounds for antimicrobial therapies.