Syntheses, crystal structures and fluorescent properties of imidazole based mixed-ligand nickle and cadmium complexes

Four novel mixed-ligand nickle and cadmium complexes [Cd(tolu)2(imi)3] (1) [CdCl2(imi)2]n (2), [Ni(imi)6](tolu)2 (3) and [Ni(mand)2(imi)2]·H2O (4) (imi = imidazole, Htolu = o-toluic acid, Hmand = mandelic acid) were synthesized and isolated in solid state based on nickle and cadmium salts, imidazole and different carboxylic acids. These complexes were characterized by FT-IR, elemental analyses, thermogravimetric (TG) analyses, UV–vis, X-ray structural analyses and fluorescence spectra. Complexes 1 and 4 are neutral mixed-ligand molecules. Complex 2 exhibits a 2D chain constructed by [CdCl2(imi)2] units. Complex 3 possesses [Ni(imi)6]2- anions with uncoordinated tolulate anions. In complexes 1–4, each imidazole ligand provides one nitrogen atom for coordination. Tolulate and mandelate ligands coordinate to the metal through carboxyl oxygen or hydroxyl oxygen atoms. Plenty of intramolecular hydrogen bonds as N–H⋯O and O–H⋯O interactions are observed in these complexes. Fluorescence properties of the complexes have been deeply investigated and the result reveals that Fe3+ ion has the greatest effect on fluorescence intensity of complex 3. The fluorescence intensity decreases with the increase of iron concentration. [Display omitted] •Four novel mixed-ligand nickle and cadmium complexes were synthesized and characterized.•Intramolecular hydrogen bonds as N–H⋯O and O–H⋯O interactions are observed in the complexes.•Fluorescence properties of the complexes have been deeply investigated.•[Ni(imi)6](tolu)2 can possibly used for a fluorescent probe.