Synthesis, structure and biological activity of silver(I) complexes of substituted imidazoles

[Ag2(9-aca)2] (9-acaH = 9-anthracenecarboxylic acid) interacts with DMSO and a selection of substituted imidazoles giving [Ag4(DMSO)4(9-aca)4]n (1), [Ag(2-Me-imH)2(9-aca)] (2), [Ag(4-Ph-imH)2(9-aca)] (3), [Ag(2-Mebenz-imH)2(9-aca)] (4), [Ag(2-Mebenz-im)] (6), [Ag(Benz-im)] (7), [Ag(2-Ph-im)] (8) and [Ag(4,5-CN-im)] (9) (2-Me-imH = 2-methylimidazole; 4-Ph-imH = 4-phenylimidazole; 2-Mebenz-imH = 2-methylbenzimidazole; Benz-imH = benzimidazole; 2-Ph-imH = 2-phenylbenzimidazole; 4,5-CN-imH = 4,5-dicyanoimidazole). In the carboxylate/imidazole complexes 2–4, the imidazole ligand is in the neutral form, whilst in complexes 6–9 the imidazolate ligand is deprotonated and no carboxylate ligand is present. Attempted recrystallization of 4 from EtOH gives the metal-free, imidazolium salt, 2-Mebenz-imH2)(9-aca)·H2O (5). The X-ray crystal structures of complexes 1 and 2 and the salt 5 were determined. Antimicrobial screening showed that the Ag(I) complexes were substantially more active against the fungus Candida albicans than the bacterial species, methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli. Some of the complexes offer a good prognosis for Galleria mellonella (larvae of the greater wax moth) infected with a lethal dose of C. albicans cell