Synthesis, crystal structure and magnetic properties of diaquabis(2,6-diamino-7H-purin-1-ium-kappa N-9)bis(4,4 '-oxydibenzoato-kappa O)cobalt(II) dihydrate

Abstract

The title mononuclear Co-II complex, [Co(C5H7N6)(2)(C14H8O5)(2)(H2O)(2)]center dot 2H(2)O, has been synthesized and its crystal structure determined by X-ray diffraction. The complex crystallizes in the triclinic space group P (1) over bar, with one formula unit per cell (Z = 1 and Z' = 1/2). It consists of a mononuclear unit with the Co-II ion on an inversion centre coordinated by two 2,6-diamino-7H-purin-1-ium cations, two 4,4'-oxydibenzoate anions (in a nonbridging kappa O-monodentate coordination mode, which is less common for the anion in its Co-II complexes) and two water molecules, defining an octahedral environment around the metal atom. There is a rich assortment of nonbonding interactions, among which a strong N+-H center dot center dot center dot O- bridge, with a short N center dot center dot center dot O distance of 2.5272 (18) angstrom, stands out, with the H atom ostensibly displaced away from its expected position at the donor side, towards the acceptor. The complex molecules assemble into a three-dimensional hydrogen-bonded network. Avariable-temperature magnetic study between 2 and 300 K reveals an orbital contribution to the magnetic moment and a weak antiferromagnetic interaction between Co-II centres as the temperature decreases. The model leads to the following values: A (crystal field strength) = 1.81, lambda (spin-orbit coupling) = -59.9 cm(-1), g (Lande factor) = 2.58 and zJ (exchange coupling) = -0.5 cm(-1).