Encapsulation of cyanometalates by a tris-macrocyclic ligand tricopper(II) complex: syntheses, structural variation, and magnetic exchange coupling pathways

The reaction of M(CN)(6)](3-) (M = Cr(3+), Mn(3+), Fe(3+), Co(3+)) and M(CN)(8)](4-/3-) (M = Mo(4+/5+), W(4+/5+)) with the trinuclear copper(II) complex of 1,3,5-triazine-2,4,6-triyltris3-(1,3,5,8,12-pentaazacyclotetradecane)] (Cu(3)(L)](6+)) leads to partially encapsulated cyanometalates. With hexacyanometalate(III) complexes, Cu(3)(L)](6+) forms the isostructural host-guest complexes Cu(3)(L)(OH(2))(2)]M(CN)(6)](2)]M(CN)(6)]]M(CN)(6)]30 H(2)O with one bridging, two partially encapsulated, and one isolated M(CN)(6)](3-) unit. The octacyanometalates of Mo(4+/5+) and W(4+/5+) are encapsulated by two tris-macrocyclic host units. Due to the stability of the +IV oxidation state of Mo and W, only assemblies with M(CN)(8)](4-) were obtained. The Mo(4+) and W(4+) complexes were crystallized in two different structural forms: Cu(3)(L)(OH(2))](2)Mo(CN)(8)]](NO(3))(8)15 H(2)O with a structural motif that involves isolated spherical Cu(3)(L)(OH(2))](2)M(CN)(8)]](8+) ions and a "string-of-pearls" type of structure Cu(3)(L)](2)M(CN)(8)]]M(CN)(8)]](NO(3))(4) 20 H(2)O, with M(CN)(8)](4-) ions that bridge the encapsulated octacyanometalates in a two-dimensional network. The magnetic exchange coupling between the various paramagnetic centers is characterized by temperature-dependent magnetic susceptibility and field-dependent magnetization data. Exchange between the CuCu pairs in the Cu(3)(L)](6+) "ligand" is weakly antiferromagnetic. Ferromagnetic interactions are observed in the cyanometalate assemblies with Cr(3+), exchange coupling of Mn(3+) and Fe(3+) is very small, and the octacoordinate Mo(4+) and W(4+) systems have a closed-shell ground state.