Association of copper(II) isonicotinamide moieties via different anionic bridging ligands: Two paths of ferromagnetic interaction in the azide coordination compound

Three isonicotinamide (isn) copper(II) complexes with different bridging ligands, azide, thiocyanate and sulfate, have been prepared. The molecular structure of [Cu-2(mu-1,1-N-3)(2)(mu-1,3-N-3)(2)(isn)(2)](n) (1) is composed of binuclear species, Cu-2(mu-1,1-N-3)(2)(isn)(2), inter-connected by additional four azide bridges in the end-to-end mode (1,3). This gives a CuN4N square-pyramidal coordination sphere around each copper(II) ion. A trans mononuclear octahedral coordination sphere CuN4S2 is present in [Cu(mu-N,S-NCS)(2)(isn)(2)](n) (2), with thiocyanato ligands serving as bridges between the adjacent Cu(isn)2 moieties. The third anionic ligand, i.e. sulfate, in {[Cu(mu-O,O'-SO4)(H2O)(isn)(2)]center dot 2H(2)O}(n) (3) completes the CuO2N2O square-pyramidal coordination sphere, and thus enables bridging between the mononuclear Cu(H2O)(isn)(2) moieties. The ligands that bridge the principal building blocks, i.e. binuclear in 1 and mononuclear in 2 and 3, connect the axial ligands with the equatorial positions of the copper(II) coordination spheres in all three cases. A ferromagnetic interaction FM is found for 1, while 2 and 3 are paramagnetic. Therefore, the key structural difference between 1 on one hand, and 2 and 3 on the other, is found in the anionic ligand, serving in 1 also as the intra-binuclear bridge, showing the main path (J(1)) for the FM interaction. Additionally, the inter-binuclear pathway in 1 gives another contribution (J(2)) to the whole FM interaction seen herein (J(1)= 18.5 cm(-1),J(2) = 4.9 cm(-1)). (c) 2010 Elsevier Ltd. All rights reserved.