Synthesis and structural, thermal and electrical properties of piperazinium lodocuprates(I)

The iodocuprate(I) systems [H2pipz]2[Cu2l6]·H 2O 1 and [H2pipz][Cu2l4] 2 (L = pipz = piperazine) have been prepared and their structural, thermal and electrical properties investigated. Compound 1 is monoclinic, space group P21/n, a = 8.609(3), b = 20.072(4), c = 13.763(4) Å, β = 101.3(1)°, Z = 4, R = 0.050. The crystal structure consists of organic cations, unco-ordinated water molecules and dimeric [Cu2l6]- anions composed of two Cul4 tetrahedra sharing a common edge. Hydrogen bonds between organic counter cations and water molecules are present. Compound 2 is triclinic, space group P1, a = 7.559(3), b = 7.465(3), c = 6.826(3) Å, α = 68.1(1), β = 69.1(1), γ = 89.4(1)°, Z = 1, R = 0.050. The crystal structure consists of organic dications and infinite chains of [Cul2]- units forming a one-dimensional polymer running along the [001] axis. The chains are composed of edge-sharing Cul4 tetrahedra. Hydrogen-bond interactions between organic counter cations and inorganic chains are present and contribute to the crystal packing. Differential scanning calorimetry measurements did not show the presence of any structural phase transitions. Electrical measurements revealed an essentially ionic mechanism of conduction, especially at high temperature, protons involved in the hydrogen bonds being the charge carriers.