306
Views
9
CrossRef citations to date
0
Altmetric
Original Articles

Mononuclear silver(I)-N-heterocyclic carbene complexes with benzimidazole-2-ylidene ligands: synthesis, crystal structure analyses and comparative antibacterial studies

, , & ORCID Icon
Pages 2698-2717 | Received 15 Jul 2020, Accepted 18 Sep 2020, Published online: 14 Oct 2020
 

Abstract

The synthesis, characterization and antibacterial studies of N-heterocyclic carbene (NHC) precursors and their respective silver(I)-NHC complexes are reported. Five non-symmetric benzimidazolium bromide salts were synthesized through the addition of N-alkylbenzimidazole and various alkylbromides. These n-butyl-n’-alkylbenzimidazolium bromide salts (alkyl = methyl, ethyl, pentyl, hexyl, heptyl) 1, 2 and 46 were further used as precursors to synthesize silver(I)-NHC complexes, 8, 9 and 1113, respectively, via in situ deprotonation. In addition, 14 was synthesized from its reported precursor salt, 1-benzyl-3-butylbenzimidazolium bromide (7) through the same procedure. Complex 8 is present as monomeric cation in the form of [NHC-Ag-NHC]PF6, as illustrated by single crystal X-ray crystallography analyses. In order for a full series of antibacterial studies, 1-butyl-3-propylbenzimidazolium bromide, 3, and respective complex, 9, were synthesized according to the reported procedure. All benzimidazolium salts (17) and silver(I)-NHC complexes (814) were evaluated for antibacterial activities. All benzimidazolium salts show no antibacterial activities while all silver(I)-NHC complexes show lower activities against Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 12600) compared to the standard antibiotic drug Amoxicillin. Nevertheless, these mononuclear silver(I)-NHC complexes show lower antibacterial activities compared to the reported dinuclear silver(I)-NHC complexes with the same substituents in the ligands.

Graphic abstract

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors thank USM and Ministry of Education for financial support (FRGS Grant 203/PKIMIA/6711791).

Reprints and Corporate Permissions

Please note: Selecting permissions does not provide access to the full text of the article, please see our help page How do I view content?

To request a reprint or corporate permissions for this article, please click on the relevant link below:

Academic Permissions

Please note: Selecting permissions does not provide access to the full text of the article, please see our help page How do I view content?

Obtain permissions instantly via Rightslink by clicking on the button below:

If you are unable to obtain permissions via Rightslink, please complete and submit this Permissions form. For more information, please visit our Permissions help page.