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A series of new benzimidazolium salts as N-heterocyclic carbene (NHC) precursors has been synthesized. Reactions of these salts with Ag 2 O with varying metal-to-salt ratio facilitate the formation of a series of new binuclear and mononuclear Ag(I)-NHC complexes. All compounds were characterized using physicochemical and spectroscopic techniques. Single-crystal X-ray diffraction study reveals a binuclear structure for one of the complexes and a mononuclear one for two others. These complexes exist as cationic Ag(I)-NHC complexes with the chelation of carbene carbons to the silver centre in an almost linear manner. The compounds were screened for their anti-bacterial activities against Staphylococcus aureus (ATCC 12600) as a Gram-positive bacterium and Escherichia coli (ATCC 25922) as a Gram-negative bacterium. The results show that both bacteria appear markedly inhibited. Furthermore, the results suggest the possibility of steric variation as a modulation of the anti-bacterial activities. The nuclease activities of the compounds were assessed using gel electrophoresis and the results indicate that these complexes can cleave or degrade DNA and RNA via a non-oxidative mechanism.

Three photoluminescent isomeric complexes [Cu3(L4)3]2[CuI]2 (labeled as complexes 1, 2, and 3) were prepared from the same bifunctional organic ligand H L4 (3-(4-pyridyl)-5-methyl-1H-pyrazole) and CuI by careful manipulation of the reaction conditions. Planar trinuclear Cu3(L4)3 and CuI/Cu2I2 units are integrated via N–Cu coordination bonds into Cu3Pz3-Cu n I n systems (Pz = pyrazolate). Complex 1 is a discrete supramolecular aggregate via cooperative π-acid···base (Cu3···I) and Cu···Cu interactions. Complexes 2 and 3 are 2-fold interpenetrated three-dimensional frameworks. The small size of the Cu n I n (n = 1 or 2) units and structural diversities in such Cu3Pz3-Cu n I n systems were realized by preinstalling a methyl group on pyrazole at the 5-position of the ligand. The three complexes exhibit subtly different yellow emissions under UV irradiation in their solid states, originating from their respective triplet excited states of the supramolecular coordination luminophores. These results demonstrate that the structural and luminescent diversities of the Cu3Pz3-Cu n I n -based complexes can be regulated by substituents.

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