Metal-controlled assembly tuning the topology and dimensionality of coordination polymers of Ag(I), Cd(II) and Zn(II) with the flexible 2-(1H-imidazole-1-yl)acetic acid (Hima)

Three new, inorganic–organic coordination polymers based on a versatile linking unit 2-(1H-imidazole-1-yl)acetate (ima) and AgI, CdII and ZnII ions, exhibiting one to three dimensionalities and different topology structures, have been prepared in water medium and structurally characterized by single-crystal X-ray diffraction analysis. Reaction of AgNO3 with Hima afforded a neutral one-dimensional (1-D) chains [Ag(ima)]n (1) which exhibits a pseudo two-dimensional (2-D) layered architecture through π–π stacking interaction between imidazole rings and intermolecular Ag⋯Ag interactions. Reaction of CdCl2 with Hima yielded neutral 2-D coordination polymers [Cd(ima)2]n (2) possessing (6, 3) topology structures, which further stack into 3-D supramolecular networks through C–H⋯O weak interactions. While Zn(NO3)2 was used, a non-centric 3-D coordination polymer [Zn(ima)2]n (3) featuring a 3-fold interpenetrating diamondoid net was isolated. Among these polymers, the building block ima anion exhibits different coordination modes. These results indicate that the versatile nature of this flexible ligand, together with the coordination preferences of the metal ions, play a critical role in construction of these novel coordination polymers. The spectral, thermal and SHG (second-harmonic generation) properties of these new materials have also been investigated.