Crystal structure and magnetic properties of an infinite chainlike and a tetranuclear bimetallic copper(II)-chromium(III) complex with bridging cyanide ions

The crystal structures of two CN- bridged bimetallic copper(II)-chromiun(III) complexes, [{(Cu(dien))(2)Cr(CN)(6)}(n)][Cu(dien)(H2O)Cr(CN)(6)](n) . 4nH(2)O (1) and [(Cu(edma))(3)Cr(CN)(6)] (2) (where dien and edma are diethylenetriamine and ethylenediaminemonoacetate respectively), have been determined. Complex I (C24H49N21O5Cr2Cu3) crystallizes in the monoclinic system, space group P2(1)/c, with a = 20.509(2) Angstrom, b = 14.376(3) Angstrom, c = 15.040(4) Angstrom, beta = 96.03(2),degrees and Z = 4. In the crystal structure, complex 1 has two distinct ionic units: one is a cationic polymeric chain formed by [(Cu(dien))(2)Cr(CN)(6)](+) and the other is a CN--bridged binuclear anion [(Cu(dien)(H2O)Cr(CN)(6)](-). Complex 2 crystallizes in the trigonal system, space group R(3C), with a = 24.446(2) Angstrom, b = 14.446(2). Angstrom, c = 22.685(1) Angstrom, and Z = 6. Complex 2 consists of discrete tetranuclear molecule [(Cu(edma))(3)Cr(CN)(6)](-). In both complexes, the Cr atoms all have an octahedral configuration with six coordinated CN- ions and connect to the copper atoms via the CN- ions. At higher temperature, the chi T of both complexes increases with decreased temperature showing the ferromagnetic behavior which is due to the ferromagnetic exchange interaction between Cu and Cr atoms through the bridging CN- ions. However at lower temperature, chi T decreases with decreased temperature. this can be attributed to the occurrence of the antiferromagnetic intramolecular interaction (zJ'). The fitting to the experimental magnetic susceptibilities gives g = 2.10, J(a) = 7.24 cm(-1), J(c) = 6.41 cm(-1), and zJ' = -0.16 cm(-1) for 1 and g = 2.09, J = 9.16 cm(-1), and zJ' = -0.09 cm(-1) for 2.