One-dimensional Co(II) and Cu(II) coordination polymers and a discrete Cu(II)4 complex of carboxylate-appended (2-pyridyl)alkylamine ligands: spin-canting and anti-/ferromagnetic coupling.

Structural characterization of the newly synthesized complexes [M(I)I(L(1)OO)(xH2O)][ClO4] x 2 H2O [M = Co, x = 1 (1); M = Cu, x = 0 (2); L(1)OO- = 3-[(2-(pyridin-2-yl)ethyl){2-(pyridin-2-yl)methyl}amino]propionate] reveals that 1 and 2 are 1D chainlike coordination polymers. A tridentate variety of this ligand afforded a discrete tetranuclear complex {[Cu(I)I(L(2)OO)(OClO3)]}4 x MeCN (3) [L(2)OO- = 3-[N-methyl-{2-(pyridine-2-yl)ethyl}amino]propionate]. Analysis of the crystal packing diagrams reveals extensive pi-pi stacking in 1 and C-H...O hydrogen bonding interactions in 3, leading to the formation of network structures. For these complexes, absorption spectral properties have been investigated. All three complexes exhibit exchange interaction between the M(II) ions through a syn-anti bridging carboxylate pathway. Magnetic studies on 1 show spontaneous magnetization below 5 K, which corresponds to the presence of spin-canted antiferromagnetism. At T = 2 K, the values of coercive field (H(c)) and remnant magnetization (M(r)) are 200 G and 0.019 muB, respectively. Analysis of the magnetic data through spin Hamiltonians in the form HH = sigma(i<j)(n) -J(ij)S(i)S(j) (J is positive for a ferromagnetic interaction and negative for an antiferromagnetic interaction) leads to the following set of best-fit parameters: J = -2.65(2), -0.66(1), and +12.2(2) cm(-1) for 1, 2, and 3, respectively. An attempt has been made to rationalize the observed magnetic behavior.