Cuprous Halide Coordination Polymers Based on Cationic [Cu4X2] and [Cu3X] Clusters and [Cu2Br]n Layers with Tetrazolates as Assembling Ligands: Highly Connected Networks and Halide-Dependent Luminescence

Five tetrazolate-based coordination polymers with cationic copper(I) halide motifs, namely, Cu-4(tta)(2)Cl-2 (1, tta = tetrazolate), Cu-4(tta)(2)Br-2 (2), Cu-2(tta)I (3), Cu-3(mtta)(2)Cl (4, mtta = 5-methyltetrazolate), and Cu-2(tta)Br (5) were prepared by hydro(solvo) thermal reactions of CuX2 or CuX with tetrazolato ligands in the presence of HX. Compounds 1, 2, and 3 show eight-connected square-planar layered structures constructed with butterfly-like [Cu4X2](2+) (X = Cl, Br, I) clusters and mu(4)-tta groups. Isomorphs 1 and 2 crystallize in the orthorhombic space group Pbca, but 3 crystallizes in the orthorhombic space group Pbam, because each mu(4)-tta group is co-ordinated to three butterfly-like clusters rather than four in 1 and 2. To the best of our knowledge, 1, 2, and 3 represent the only 2D coordination polymers with eight-connected square planar topology to date. Compound 4 is a [Cu3Cl](2+) cluster based on the undocumented ten-connected ZrIn2 topological framework. Compound 5 has a 3D pillar layered framework constructed with [Cu2Br](n)(n+) cationic layers. Compounds 1, 2, 4, and 5 exhibit strong green-blue emission in the solid state at room temperature, whereas cuprous iodide complex 3 shows strong red luminescence.