Synthesis, crystal structures and thermal properties of new copper(I) halide coordination polymers

Abstract

Abstract The new copper(I) halide coordination polymers 3 ∞ poly[CuCl(μ-2,5-dimethylpyrazine-N,N′)] (I), 2 ∞ poly[CuBr(μ-2,5-dimethylpyrazine-N,N′)] (II) and 2 ∞ poly[Cu2X2(μ-2,5-dimethylpyrazine-N,N′)] (X=Br (III), I (IV)) were synthesized by the reaction of the copper(I) halides with 2,5-dimethylpyrazine in acetonitrile. In the crystal structure of I, helical CuCl chains are found, which are connected by the 2,5-dimethylpyrazine ligands forming a three-dimensional structure. In the structure of compound II Cu2Br2 dimers and in compounds III and IV CuX double chains (X=Br, I) occur which are connected via the ligands to sheets. The thermal properties of all compounds were investigated using simultaneously differential thermoanalysis (DTA), thermogravimetry (TG) and mass spectroscopy (MS) as well as temperature resolved X-ray powder diffraction. On heating compound I transforms into the new compound Cu2Cl2(2,5-dimethylpyrazine) (V), which forms CuCl on further heating. For compound II in the first step a transformation into the 2:1 compound III is observed, which loses again a part of the ligands forming the new copper(I) halide rich compound Cu4Br4(2,5-dimethylpyrazine) (VI). A halide rich compound Cu4I4(2,5-dimethylpyrazine) (VII) which is presumably isotypic to VI is also observed during the thermal decomposition of IV. On further heating both 4:1 compounds transform directly to CuBr and CuI.