Polynitrile anions as ligands:: synthesis, structure and magnetic properties of a new three-dimensional coordination polymer with 2-dicyanomethylene-1,1,3,3-tetracyanopropanediide (tcpd2-) bridging ligand

Reaction between CuCl2 and K(2)tcpd (tcpd(2-) = {C[C(CN)(2)](3))(2-) = 2-dicyanomethylene-1,1,3,3-tetracyanopropanediide anion) in presence of the neutral ligand in (1,3-diaminopropane) in aqueous solution yields the new compound [Cu(tn)(tcpd)] (1) which was characterized by X-ray crystallography. The crystal structure of 1 consists of one [Cu(tn)](2+) unit and one tcpd(2-) anion, both located on general positions. Each Cu atom presents an essentially octahedral coordination with four nitrogen atoms arising from four polynitrile ligands and two nitrogen atoms from the chelating tn ligand. Despite its six nitrile groups potentially bridging, the tcpd ligand acts with a mu(4)-bridging mode via four nitrogen atoms of two different C(CN)(2) wings leading to a 3D structure. The magnetic behavior for compound 1 shows a very weak antiferromagnetic coupling of the Cu(II) ions through the NC-C-CN bridge that can be very well reproduced with a regular S = 1/2 antiferromagnetic chain model with g = 2.108 and J = -0.042.