Structures and Magnetic Properties of an Antiferromagnetically Coupled Polymeric Copper(II) Complex and Ferromagnetically Coupled Hexanuclear Nickel(II) Clusters

Reactions between 2,6-diformy1-4-methylphenol (DFMF) and tris(hydroxymethyl) aminomethane (THMAM = H(3)L2) in the presence of copper(II) salts, CuX2 (X = CH3CO2-, BF4-, ClO4-, Cl-, NO3-) and Ni(CH3CO2)(2) or Ni(ClO4)(2)/NaC6H5CO2, sodium azide (NaN3), and triethylamine (TEA), in one pot self-assemble giving a coordination polymer consisting of repeating pentanuclear copper(II) clusters {[Cu-2(H5L2-)(mu-N-3)](2)[Cu(N-3)(4)]center dot 2CH(3)OH}(n) (1) and hexanuclear Ni(II) complexes [Ni-6(H(3)L1(-))(2)(HL22-)(2)(mu-N-3)(4)(CH3CO2)(2)]center dot 6C(3)H(7)NO center dot C2H5OH (2) and [Ni-6(H(3)L1(-))(2)(HL22-)(2)(mu-N-3)(4)(C6H5CO2)(2)]center dot 3C(3)H(7)NO center dot 3H(2)O center dot CH3OH (3). In 1, H5L2- and in 2 and 3 H3L1- and HL2(2-) represent doubly deprotonated, singly deprotonated, and doubly deprotonated Schiff-base ligands H7L and H(4)L1 and a tripodal ligand H(3)L2, respectively. 1 has a novel double-stranded ladder-like structure in which [Cu(N-3)(4)](2-) anions link single chains comprised of dinuclear cationic subunits [Cu-2(H5L2-)(mu-N-3)](+), forming a 3D structure of interconnected ladders through H bonding. Nickel(II) clusters 2 and 3 have very similar neutral hexanuclear cores in which six nickel(II) ions are bonded to two H4L1, two H3L2, four mu-azido, and two mu-CH3CO2-/mu-C6H5CO2- ligands. In each structure two terminal dinickel (Ni-2) units are connected to the central dinickel unit through four doubly bridging end-on (EO) mu-azido and four triply bridging mu(3)-methoxy bridges organizing into hexanuclear units. In each terminal dinuclear unit two nickel centers are bridged through one mu-phenolate oxygen from H3L1-, one mu(3)-methoxy oxygen from HL22-, and one mu-CH3CO2- (2)/mu-C6H5CO2- (3) ion. Bulk magnetization measurements on 1 show moderately strong antiferromagnetic coupling within the [Cu-2] building block (J(1) = -113.5 cm(-1)). Bulk magnetization measurements on 2 and 3 demonstrate that the magnetic interactions are completely dominated by ferromagnetic coupling occurring between ions for bridges with coupling constants (J(1), J(2), and J(3)) ransing from 2.10 to 14. 56 cm(-1) (in the (H) over cap = -J(1)((S-1) over cap(S-2) over cap) - J(1)((S-2)over cap>(S-3) over cap) - J(2)((S-3)over cap>(S-4) over cap) - J(1)((S-4)over cap>(S-5) over cap) - J(1)((S-5)over cap>(S-6) over cap) - J(2)((S-1)over cap>(S-6) over cap) - J(3)((S-2)over cap>(S-6) over cap) - J(3)((S-2)over cap>(S-5) over cap) - J(3)((S-3)over cap>(S-5) over cap) convention).