Zinc complexes with 1,2,4-triazole functionalized amino acid derivatives: Synthesis, structure and β-lactamase assay

Coordinating abilities of 4R-1,2,4-triazole derivatives (R = glycine ethyl ester (L1), glycine (L2), diethylamino malonate (L3), methionine (L4) and diethyl aminomethylphosphonate (L5)) towards ZnII ions have been studied in solution, in solid state and versus three zinc-β-lactamases. The crystal structure of [Zn3(L4)6(H2O)6] (6) is described; it is the first crystal structure involving a 1,2,4-triazole functionalized methionine. It forms a trinuclear complex with central zinc octahedrally coordinated by only L4, whereas terminal zinc ions coordination sphere is completed by three water molecules. L4 exhibits a dual functionality of a bridging bidentate ligand as well as an anion. A dense hydrogen bonding network connects these trinuclear entity into a 3D supramolecular network. The ZnII ions in 6 are held at equidistance (3.848 Å) which coincidently matches with the corresponding Zn⋯Zn distance in the binuclear zinc enzyme from Bacillus cereus (3.848 and 4.365 Å). Among L1–L5 screened for β-lactamase assay, L4 shows modest inhibition for BcII enzyme.