Zinc(ii) and cadmium(ii) coordination polymers mediated by rationally designed symmetrical/asymmetrical V-shaped heterocyclic aromatic ligands exhibiting different supramolecular architectures

Abstract

Two novel V-shaped heterocyclic aromatic ligands, i.e., 3,4-diimidazol-thiophene (Lsym, symmetrical) and 3-imidazol-4-pyridinyl-thiophene (Lasym, asymmetrical), have been designed and prepared from the carbon–nitrogen and carbon–carbon bond cross-coupling reactions. X-Ray single-crystal structural studies for these ligands and their zinc(II) and cadmium(II) fluorescent coordination polymers reveal that they are formulated as {[Zn(Lasym)₂]₃(ClO₄)₆(H₂O)}_n (1), {[Cd(Lasym)₂Cl₂]}_n (2), {[Zn(Lsym)₂(CH₃OH)₂](NO₃)₂(CH₃OH)₂}_n (3) and {[Cd(Lsym)₂(CH₃OH)₂](NO₃)₂(CH₃OH)₂}_n (4). The coordination geometry of the metal centers and the molecular conformation of the symmetrical/asymmetrical V-shaped ligands Lsym and Lasym, namely variation of the bite angle θ between the two coordination nitrogen atoms and the central sulfur atom of thiophene ring as well as the dihedral angles between adjacent aromatic rings, play important roles in tuning the different supramolecular architectures of their metal complexes.