Intramolecular Ferromagnetic Radical–Cu^II Coupling in a Cu^II Complex Ligated with Pyridyl-Substituted Triarylmethyl Radicals

Novel metal complexes M­(hfac)2(PyBTM)2 [M = CuII, ZnII; hfac = hexafluoroacetylacetonato; PyBTM = (3,5-dichloro-4-pyridyl)­bis­(2,4,6-trichlorophenyl)­methyl radical] were prepared. Both hexacoordinated complexes had elongated octahedral geometry, in which two PyBTM molecules coordinated at the equatorial positions in CuII(hfac)2(PyBTM)2 but at the axial positions in ZnII(hfac)2(PyBTM)2. Magnetic studies revealed an intramolecular ferromagnetic exchange interaction between the spins on PyBTM and CuII (JCu–R/kB = 47 K) based on the orthogonality of the two spin orbitals.