SYNTHESIS AND STRUCTURAL, THERMAL AND ELECTRICAL-PROPERTIES OF PIPERAZINIUM IODOCUPRATES(I)

The iodocuprate(I) systems [H-2pipz]2[Cu2I6].H2O 1 and [H-2pipz] [Cu2I 4] 2 (L = pipz = piperazine) have been prepared and their structural, thermal and electrical properties investigated. Compound 1 is monoclin ic, space group P2(1)/n, a = 8.609(3), b = 20.072(4), c = 13.763(4) an gstrom, beta = 101.3(l)-degrees, Z = 4, R = 0.050. The crystal structu re consists of organic cations, unco-ordinated water molecules and dim eric [Cu2I6]- anions composed of two CuI4 tetrahedra sharing a common edge. Hydrogen bonds between organic counter cations and water molecul es are present. Compound 2 is triclinic, space group P1BAR, a = 7.559( 3), b = 7.465(3), c = 6.826(3) angstrom, alpha = 68.1 (1 ), beta = 69. 1 (1 ), gamma = 89.4(l)-degrees, Z = 1, R = 0.050. The crystal structu re consists of organic dications and infinite chains of [CuI2]- units forming a one-dimensional polymer running along the [001] axis. The ch ains are composed of edge-sharing CuI4 tetrahedra. Hydrogen-bond inter actions between organic counter cations and inorganic chains are prese nt and contribute to the crystal packing. Differential scanning calori metry measurements did not show the presence of any structural phase t ransitions. Electrical measurements revealed an essentially ionic mech anism of conduction, especially at high temperature, protons involved in the hydrogen bonds being the charge carriers.