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)]center dot tcm}(n) (4) and {[Cu-2(tppz)(tcm)(4)]center dot 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) mu-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) angstrom (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-mu-1,5-tcm bridges with copper -copper separations of 7.969(1) and 7.270(1) angstrom, respectively. Five-and six-coordinated copper atoms with distorted square pyramidal and elongated octahedral environments occur in 3. Compound 5 is a neutral copper(II) chain with regular alternating bis-tridentate tppz and double mu-1,5-tcm bridges, the intrachain copper -copper distances being 6.549(7) and 7.668(1) angstrom, 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 mu-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.
Synthesis, crystal structures and magnetic properties of tricyanomethanide-containing polynuclear copper(II) complexes
ARMENTANO, Donatella;MARINO, Nadia;
2008-01-01
Abstract
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)]center dot tcm}(n) (4) and {[Cu-2(tppz)(tcm)(4)]center dot 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) mu-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) angstrom (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-mu-1,5-tcm bridges with copper -copper separations of 7.969(1) and 7.270(1) angstrom, respectively. Five-and six-coordinated copper atoms with distorted square pyramidal and elongated octahedral environments occur in 3. Compound 5 is a neutral copper(II) chain with regular alternating bis-tridentate tppz and double mu-1,5-tcm bridges, the intrachain copper -copper distances being 6.549(7) and 7.668(1) angstrom, 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 mu-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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
