Synthesis, characterization, antimicrobial screening and DNA binding of novel silver(I)–thienylterpyridine and silver(I)–furylterpyridine complexes

Abstract

Six new silver(I) complexes, [(AgL1)2](ClO4)2 (1), [(AgOTfL1)2] (2), [(AgO2CF3L1)2] (3), [AgL2](ClO4)2 (4), [(AgOTfL2)2] (5) and [(AgO2CF3L2)2] (6), were synthesized by reaction of 4′‐(2‐thienyl)‐2,2′;6′,2″‐terpyridine (L1) or 4′‐(2‐furyl)‐2,2′;6′,2″‐terpyridine (L2) with the respective silver salts, i.e. AgClO4, AgOTf or AgTFA. The complexes are dinuclear of the type Ag2L2 in which the two ligands utilize the pyridinyl N atoms from the central rings and one of the peripheral rings to coordinate to one of the silver(I) centres while the remaining pyridinyl N atoms coordinate to the second silver(I) centre. Complexes 2 and 5 have the trifluoromethanesulfonate anion remotely coordinating via a single O atom while complex 3 has the trifluoroacetate anion coordinating to a single silver(I) centre in a bidentate mode. The perchlorate anion in complex 4 is excluded from the silver(I) coordination sphere. All complexes demonstrate moderate to high antimicrobial activity against the Gram‐negative bacteria Escherichia coli and Salmonella typhimirium and the fungus Candida albicans. Complexes 1–6 interact strongly with salmon testes DNA as indicated by the steady increase in the relative viscosity of DNA solutions with increasing concentration of the silver(I) complexes and the relatively large intrinsic binding constants measured. There was substantial hyperchromism and hypsochromism recorded in solutions of complexes 1–6 with increasing concentration of salmon testes DNA. Complexes 1–6 interact with DNA via intercalation, and groove and external binding.