Abstract:
The synthesis, structure and magnetic properties of the cobalt(II) complex (1) [Co(H2O)4(pyz)](NO3)2 • 2H2O is reported. The compound crystallizes in the triclinic system, space group P1̄, with cell constants: a = 7.0328(15) Å, b = 7.1255(16) Å, c = 8.4198(19) Å, α = 107.226(4)°, β = 114.242(4)°, γ = 90.487(4)°, Z = 1 and V = 363.35(14) Å3. The structure of 1 consists of elongated octahedral CoO4N2 chromophores with bridging pyrazine ligands forming a one-dimensional coordination polymer along the crystallographic b-axis. The nitrate ions hydrogen-bond to the water ligands (L) and guest water (G), and form H2O(L)⋯H2O(G)⋯NO3-⋯H2O(G)⋯H2O(L) chains which flank either side of the coordination polymer chains. Hydrogen-bonding is extended to neighboring chains forming a two-dimensional network. The solvent effect on the electronic spectra of pyrazine and pyrazine cobalt complex 1 has been investigated. The magnetic susceptibility of complex 1 versus temperature data showed a strong antiferromagnetic coupling between Co ions. The best fitting parameters were obtained for J1-kB = -26.4 K, J2-kB = -2.2 K and g = 2.3. © 2004 Elsevier Ltd. All rights reserved.