Synthesis, crystal structure and magnetic properties of diaquabis(2,6-diamino-7H-purin-1-ium-κN⁹)bis(4,4′-oxydibenzoato-κO)cobalt(II) dihydrate

The title mononuclear Co^II complex, [Co(C₅H₇N₆)₂(C₁₄H₈O₅)₂(H₂O)₂]·2H₂O, has been synthesized and its crystal structure determined by X-ray diffraction. The complex crystallizes in the triclinic space group P, with one formula unit per cell (Z = 1 and Z′ =). 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 κO-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···O^- bridge, with a short N···O distance of 2.5272 (18) Å, 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. A variable-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, λ (spin-orbit coupling) = -59.9 cm^-1, g (Landé factor) = 2.58 and zJ (exchange coupling) = -0.5 cm^-1.