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  • Synthesis, crystal structur...
    Yuste, C; Armentano, D; Marino, N; Cañadillas-Delgado, L; Delgado, F S; Ruiz-Pérez, C; Rillema, D P; Lloret, F; Julve, M

    Dalton transactions : an international journal of inorganic chemistry, 01/2008 12
    Journal Article

    The preparation, crystal structures and magnetic properties of the copper(II) complexes of formula Cu(pyim)(tcm)(2)(n) (1), Cu(bpy)(tcm)(2)(n) (2), Cu(4)(bpz)(4)(tcm)(8) (3), {Cu(terpy)(tcm).tcm}(n) (4) and {Cu(2)(tppz)(tcm)(4).3/2H(2)O}(n) (5) pyim = 2-(2-pyridyl)imidazole, tcm = tricyanomethanide, bpy = 2,2'-bipyridine, bpz = 2,2'-bipyrazine, terpy = 2,2':6',2''-terpyridine and tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine are reported. Complexes, 1, 2 and 4 are uniform copper(II) chains with single- (1 and 4) and double-(2) micro-1,5-tcm bridges with values of the intrachain copper-copper separation of 7.489(1) (1), 7.520(1) and 7.758(1) (2) and 7.469(1) A (4). Each copper atom in 1, 2 and 4 is five-coordinate with bidentate pyim (1)/bpy (2) and tridentate terpy (4) ligands and nitrile-nitrogen atoms from bridging (1,2 and 4) and terminal (1) tcm groups building a distorted square pyramidal surrounding. The structure of 3 is made up of neutral centrosymmetric rectangles of (2,2'-bipyrazine)copper(II) units at the corners, the edges being built by single- and double-micro-1,5-tcm bridges with copper-copper separations of 7.969(1) and 7.270(1) A, respectively. Five- and six-coordinated copper atoms with distorted square pyramidal and elongated octahedral environments occur in . Compound 5 is a neutral copper(II) chain with regular alternating bis-tridentate tppz and double micro-1,5-tcm bridges, the intrachain copper-copper distances being 6.549(7) and 7.668(1) A, respectively. The two crystallographically independent copper atoms in 5 have an elongated octahedral geometry with three tppz nitrogen atoms and a nitrile-nitrogen atom from a bridging tcm group in the equatorial positions, and two nitrile nitrogen atoms from a terminal and a bridging tcm ligand occupying the axial sites. The investigation of the magnetic properies of 1-5 in the temperature range 1.9-295 K has shown the occurrence of weak ferro- J = +0.11(1) cm(-1) (2) and antiferromagnetic interactions J = -0.093(1) (1), -0.083(1) (4), -0.04(1) and 1.21(1) cm(-1) (3) across the micro-1,5-tcm bridges and intermediate antiferromagnetic coupling -J = 37.4(1) cm(-1) (5) through bis-tridentate tppz. The values of the magnetic interactions are analyzed through simple orbital symmetry considerations and compared with those previously reported for related systems.