Synthesis, crystal structure and magnetic properties of diaquabis(2,6-diamino-7H-purin-1-ium-κN 9)bis(4,4′-oxydibenzoato-κO)cobalt(II) dihydrate

Abstract

The title mononuclear CoII 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\overline{1}, with one formula unit per cell (Z = 1 and Z′ = 1 \over 2). It consists of a mononuclear unit with the CoII 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 CoII 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 CoII 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.