Structure diversity and reversible anion exchange properties of cadmium(ii) complexes with 1,3,5-tris(imidazol-1-ylmethyl)benzene: counteranion-directed flexible ligand conformational variation

Abstract

Six cadmium(II) coordination polymers, {[Cd(tib)₂](BF₄)₂}_n (1), {[Cd(tib)₂](NO₃)₂·2EtOH}_n (2) (EtOH = ethanol), {[Cd(tib)(OAc)₂]·4.5 H₂O}_n (3) (OAc = acetate anion), {[Cd(tib)(μ₂-Cl)Cl]·MeOH}_n (4) (MeOH = methanol), {[Cd(tib)₂(H₂O)₂]Cl₂·4 H₂O}_n (5) and {[Cd(tib)₂][Cd₂I₆]}_n (6), were obtained by reactions of flexible tripodal ligand 1,3,5-tris(imidazol-1-ylmethyl)benzene (tib) with the corresponding metal salts, respectively. Their structures were determined by X-ray crystallography. Complexes 1 and 6 have infinite 2D cationic double layered structures with different shapes. Complex 2 possesses a 3D framework structure with two different kinds of channels. The structure of 3 is a two-fold interpenetrated 3D framework. Complexes 4 and 5, synthesized by the same reactants in the same solvent, have different 2D network structures due to the different synthetic methods. The distinct structures of the complexes (e.g.1, 2 and 6) indicate that the counteranions have significant influence on the structures of coordination polymers. In addition, the results also attest that the flexible ligand tib can adopt different conformations and coordination modes to form complexes with varied structures. Furthermore, the reversible anion exchange properties of 1 and 2 were studied.