Silver(I) complexes ofN,N′‐diarylformamidine ligands: Synthesis, crystal structures, and in vitro antibacterial studies

Abstract

AbstractNine silver(I)N,N′‐diarylformamidine complexes of type [Ag (Ln)2X] (where X = NO3−, CF3COO−, and CF3SO3−,n = 1–5) were synthesised and characterised by physiochemical and spectroscopic techniques. Further confirmation for the formation of the complexes was provided by single‐crystal X‐ray crystallography. All complexes (but one) adopted linear geometry in which coordination was via twoNatoms of two formamidine ligands with the anion (X) displaced from coordination sphere. In the structure of the exception, the anion is part of the coordination sphere and a T‐shaped geometry was adopted. The antimicrobial activity of the Ag(I) complexes were investigated against two Gram‐positive bacteria, that is,S. aureusATCC 25923 andMethicillin‐resistant S. aureusATCC 700699 (MRSA) and four Gram‐negative bacteria, that is,K. pneumoniaeATCC 31488,S. typhimuriumATCC 14026,P. aeruginosaATCC 27853 andE. coliATCC 25922 and they were evaluated based on ciprofloxacin and silver nitrate standards. The newly synthesised target complexes demonstrated promising antibacterial activity against Gram‐positive bacteria although less than the reference drug ciprofloxacin. The best active silver(I) complex contains a nitrate counter‐ion.