Synthesis, structures and antibacterial studies of non-functionalized and nitrile-functionalized bis-benzimidazolium salts and respective dinuclear silver(I)-N-heterocyclic carbene complexes

The in-situ deprotonation of N-heterocyclic carbene (NHC) in the reaction of bis-benzimidazolium bromide salts (1a–6a) with Ag2O, yielded the formation of six dinuclear silver(I)–NHC complexes [Ag2(L)2]·2PF6 (7–12) (where L = 1–6: 3,3-(butane-1,4-diyl)-1,1-(2′/3′/4′-methylbenzyl/methylbenzonitrile)bisbenzimidazolium). Bis-benzimidazolium hexafluorophosphate salts (1b–6b) and complexes 7–12 were characterized using 1H and 13C NMR spectroscopy, FTIR spectroscopy and elemental analysis technique. Additionally, complex 12 was structurally characterized by single crystal X-ray diffraction technique. Antibacterial studies of these compounds against the Gram-negative bacteria Escherichia coli (ATCC 25922) and the Gram-positive bacteria Staphylococcus aureus (ATCC 12600) proved all the Ag(I)–NHC complexes exhibit antibacterial activities while all the bis-benzimidazolium salts showed negative result.

Six dinuclear silver(I)–NHC complexes [Ag2(L)2]·2PF6 (7–12) were successfully synthesized in relatively good yield by the in-situ deprotonation reaction of respective bis-benzimidazolium bromide salts (1a–6a) with Ag2O (where L = 1–6: 3,3-(butane-1,4-diyl)-1,1-(2′/3′/4′-methylbenzyl/methylbenzonitrile)bisbenzimidazolium). Bis-benzimidazolium hexafluorophosphate salts (1b–6b) and complexes 7–12 were characterized using 1H and 13C NMR spectroscopy, FTIR spectroscopy and elemental analysis technique. Additionally, complex 12 was structurally characterized by single crystal X-ray diffraction technique. Antibacterial studies of these compounds against the Gram-negative bacteria Escherichia coli (ATCC 25922) and the Gram-positive bacteria Staphylococcus aureus (ATCC 12600) proved all the Ag(I)–NHC complexes exhibit antibacterial activities while all the bis-benzimidazolium salts showed negative result.Figure optionsDownload as PowerPoint slide