The crystal structure, magnetic and electrical properties of two polymeric chlorocuprate(II) compounds.

The crystal structures of piperidinium trichlorocuprate(II) [Hpip][CuCl3], and piperazinium hexachlorodicuprate(II), [H2pipz][Cu2Cl6], have been determined by X-ray diffraction techniques. [Hpip][CuCl3] is monoclinic, space group C2/c, with a = 18.385(7), b = 8.439(4), c = 11.878(5) Å, and β = 103.63(5)° while [H2pipz][Cu2Cl6] is triclinic, P1, with a = 7.984(4), b = 7.054(4), c = 6.104(3) Å, α = 111.23(8), β = 99.95(9), γ = 81.26(7)°. Both salts contain infinite chains of [Cu2Cl6]2- dimers. The [Cu2Cl6]2- dimers show significant distortions from planarity due to formation of semi-co-ordinate bonds between adjacent dimers, with a larger distortion for the Hpip salt. This bifold distortion gives each copper(II) ion a (4 + 1) co-ordination geometry. The chains have slightly different configurations. In the H2pipz salt, adjacent dimers are related by unit-cell translations, while in the Hpip salt they are related by a c-glide operation. Magnetic susceptibility measurements show that the H2pipz salt is an alternating antiferromagnetic chain with J/k = -13.35(7) K and J′/k = -7.6(3) K, while the Hpip salt is an alternating ferro- antiferro-magnetic chain with J/k = 26(3) K and J′/k = -0.24(1) K. Thus, the intradimer coupling (J) becomes less antiferromagnetic as the distortion from planarity increases. Comparison with other bifolded dimers confirms correlation of J with the bifold angle, both experimentally and theoretically. Electrical measurements reveal the presence of an activated process for electrical conduction with activation parameters of 0.44 eV for [Hpip][CuCl3] and 0.34 eV for [H2pipz][Cu2Cl6]. The charge carriers are proposed to be the protons in N-H ⋯ Cl hydrogen bonds