Weak ferromagnetic ground state in copper(II) linear chains

The linear chain Cu(II) compounds [{Cu(trpy)}2(μ-dicyd)] n[BPh4]2n, where trpy is 2,2′: 6′2″-terpyridine and dicyd^2- is 1,3-dicyanamidobenzene dianion, and [{Cu(trpy)(CF3SO3)} {Cu(trpy)}(μ- methyldicyd)]n[CF3SO3]n, where methyldicyd^2- is 1,3-dicyanamido-2-methylbenzene dianion, both possess a weak ferromagnetic ground state despite having dramatically different bridging geometries. We suggest that the topology of the bridging ligand induces spin canting superimposed onto a dominant antiferromagnetic exchange interaction between the Cu(II) ions of the chain.