Crystal structure of ∞2[Cu2I2(μ-4,4′-bipyridine)] and investigations on the thermal decomposition of CuX-4,4′-bipyridine coordination polymers

The inorganic-organic coordination polymer (2)(infinity)[Cu2I2(mu -4,4'-bipyridine)] was prepared by the reaction of Cu(I)I and 4,4'-bipyridine in acetonitrile. Its structure consists of staircase-like CuX double chains which are connected to sheets by the 4,4'-bipyridine ligands. The thermal decomposition of the corresponding 1:1 copper(I) halide-4,4-bipyridine compounds (2)(infinity)[CuX(mu -4,4'-bipyridine)] (X=Cl, Br, I) was investigated using simultaneous difference thermal analysis and thermogravimetry (DTA-TG), thermomicroscopy, and temperature resolved X-ray powder diffraction in air or argon. Upon heating (2)(infinity)[CuX(mu -4,4'-bipyridine)], several changes in sample mass are observed which correspond to a stepwise loss of the organic ligands. Temperature-resolved X-ray powder diffraction proves that (2)(infinity)[CuX(mu -4,4'-bipyridine)] transforms to (2)(infinity)[Cu2X2(mu -4,4'-bipyridine)] during the decomposition; the latter looses the remaining ligands when heated further, forming the corresponding copper(I)halides. When the experiments were performed under an argon atmosphere, the 2:1 coordination polymers were obtained as phase-pure compounds.