title: Study of the influence of the bridge on the magnetic coupling in cobalt(II) complexes.
abstract: Two new cobalt(II) complexes of formula [Co(2)(bta)(H(2)O)(6)](n) x 2nH(2)O (1) and [Co(phda)(H(2)O)](n) x nH(2)O (2) [H(4)bta = 1,2,4,5-benzenetetracarboxylic acid, H(2)phda = 1,4-phenylenediacetic acid] have been characterized by single crystal X-ray diffraction. Compound 1 is a one-dimensional compound where the bta(4-) ligand acts as 2-fold connector between the cobalt(II) ions through two carboxylate groups in para-conformation. Triply bridged dicobalt(II) units occur within each chain, a water molecule, a carboxylate group in the syn-syn conformation, and an oxo-carboxylate with the mu(2)O(1);kappa(2)O(1),O(2) coordination mode acting as bridges. Compound 2 is a three-dimensional compound, where the phda(2-) group acts as a bridge through its two carboxylate groups, one of them adopting the mu-O,O' coordination mode in the syn-syn conformation and the other exhibiting the single mu(2)-O'' bridging mode. As in 1, chains of cobalt(II) ions occur in 2 with a water molecule, a syn-syn carboxylate group, and an oxo-carboxylate constitute the triply intrachain bridging skeleton. Each chain is linked to other four ones through the phda(2-) ligand, giving rise to the three-dimensional structure. The values of the intrachain cobalt-cobalt separation are 3.1691(4) (1) and 3.11499(2) A (2) whereas those across the phenyl ring of the extended bta(4-) (1) and phda(2-) (2) groups are 10.1120(6) and 11.4805(69 A, respectively. The magnetic properties of 1 and 2 have been investigated in the temperature range 1.9-300 K, and their analysis has revealed the occurrence of moderate intrachain ferromagnetic couplings [J = +5.4 (1) and +2.16 cm(-1) (2), J being the isotropic magnetic coupling parameter], the magnetic coupling through the extended bta(4-) and phda(2-) with cobalt-cobalt separations larger than 10 A being negligible. The nature and magnitude of the magnetic interactions between the high-spin cobalt(II) ions in 1 and 2 are compared to those of related systems and discussed as a function of the complementarity-countercomplementarity effects of the triple bridges.
authors.affiliation: Laboratorio de Rayos X y Materiales Moleculares, Departamento de Física Fundamental II, Facultad de Física, Universidad de La Laguna, E-38071 La Laguna, Tenerife, Spain.
authors.forename: Oscar
authors.initials: O
authors.lastname: Fabelo
authors.forename: Laura
authors.initials: L
authors.lastname: Cañadillas-Delgado
authors.forename: Jorge
authors.initials: J
authors.lastname: Pasán
authors.forename: Fernando S
authors.initials: FS
authors.lastname: Delgado
authors.forename: Francesc
authors.initials: F
authors.lastname: Lloret
authors.forename: Joan
authors.initials: J
authors.lastname: Cano
authors.forename: Miguel
authors.initials: M
authors.lastname: Julve
authors.forename: Catalina
authors.initials: C
authors.lastname: Ruiz-Pérez
mesh_terms: D003035:Cobalt / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008280:Magnetics; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry*
chemical_list: D009942:Organometallic Compounds; D003035:Cobalt