Uranyl-containing heterometallic coordination polymers based on 4-(4’-carboxyphenyl)-1,2,4-triazole ligand: structure regulation through subtle changes of the secondary metal centers

<p>Three uranyl-containing coordination polymers, Cd(UO<sub>2</sub>)<sub>2</sub>(cpt)<sub>4</sub>(bdc)(H<sub>2</sub>O)<sub>2</sub> (<b>1</b>), Zn(UO<sub>2</sub>)<sub>2</sub>(cpt)<sub>4</sub>(bdc)(H<sub>2</sub>O)<sub>2</sub> (<b>2</b>) and UO<sub>2</sub>(OH)(cpt) (<b>3</b>) (Hcpt =4-(4’-carboxyphenyl)-1,2,4triazole, H<sub>2</sub>bdc =1,4-benzenedicarboxylic acid), have been synthesized under hydrothermal conditions by employing a bifunctional ligand (Hcpt) with both O-donors and N-donors. Compound <b>1</b> represents a 3-D framework with the point symbol of (6<sup>2</sup>·8<sup>4</sup>)(6<sup>2</sup>·8)<sub>2</sub> by the intersection of two sets of 1-D [Cd<sub>2</sub>(UO<sub>2</sub>)<sub>2</sub>(cpt)<sub>4</sub>(bdc)]<sub>n</sub> loop chains extended along different directions. Compound <b>2</b> exhibits a 2-nodal (3,4)-connected 2-D network with the point symbol (4·6<sup>2</sup>)<sub>2</sub>(4<sup>2</sup>·6<sup>2</sup>·8<sup>2</sup>). Compound <b>3</b> shows a 2-D network by the assembly of uranyl dimers and the cpt<sup>-</sup> anions. Although <b>1</b> and <b>2</b> have similar chemical formulas and the same coordination modes of ligands and metal centers, they possess totally different molecular frameworks, derived from the different radii of the secondary metal centers, Cd(II) and Zn(II). In addition, the optimal synthesis condition, thermal stability, luminescent properties, and IR spectra of <b>1</b> and <b>2</b> were also investigated.</p>