Coordination Chemistry of 6‑Thioguanine Derivatives with Cobalt: Toward Formation of Electrical Conductive One-Dimensional Coordination Polymers

In this work we have
synthetized and characterized by X-ray diffraction
five cobalt complexes with 6-thioguanine (6-ThioGH), 6-thioguanosine
(6-ThioGuoH), or 2′-deoxy-6-thioguanosine (2′-d-6-ThioGuoH)
ligands. In all cases, these ligands coordinate to cobalt via N7 and S6 forming a chelate ring. However, independently
of reagents ratio, 6-ThioGH provided monodimensional cobalt­(II) coordination
polymers, in which the 6-ThioG– acts as bridging
ligand. However, for 2′-d-6-ThioGuoH and 6-ThioGuoH, the structure
directing effect of the sugar residue gives rise to mononuclear cobalt
complexes which form extensive H-bond interactions to generate 3D
supramolecular networks. Furthermore, with 2′-d-6-ThioGuoH
the cobalt ion remains in the divalent state, whereas with 6-ThioGuoH
oxidation occurs and Co­(III) is found. The electrical and magnetic
properties of the coordination polymers isolated have been studied
and the results discussed with the aid of DFT calculations, in the
context of molecular wires.