Syntheses, crystal structures, and magnetic properties of first row transition metal coordination polymers containing dicyanamide and 4,4′-bipyridine

Abstract

The complexes of formulae M(dca)2(bipy) (M = Fe 1, Co 2, Ni 3; dca = dicyanamide, N(CN)2−; bipy = 4,4′-bipyridine) and M(dca)2(bipy)(H2O)·0.5MeOH (M = Mn 4, Fe 5, Co 6), have been synthesized and characterized by single crystal and powder X-ray diffraction. Compounds 1–3 contain two interpenetrating 3D α-Po related networks. Bidentate dca ligands bridge the octahedral metal atoms to form square-grid like M(dca)2 sheets, with the bipyridine ligands linking these sheets together to form the α-Po-like 3D networks. The large amount of space within a single 3D network allows the interpenetration of the second 3D network. Compounds 4–6 contain 1D 'tubes' packing together in a parallel interdigitated fashion. Water ligands coordinated to the octahedral metal ions and intercalated methanol molecules occupy the inside of the M(dca)2 tubes while protruding monodentate bipyridine ligands participate in both π-stacking and hydrogen bonding interactions between adjacent tubes. Co(dca)2(bipy)·0.5H2O·0.5MeOH 7 and Cu(dca)2(bipy)·H2O 8 consist of inclined interpenetrating 2D sheets of M(dca)2(bipy), while Cu(dca)2(bipy)·MeOH 9 and Cu(dca)2(bipy)·2H2O 10 contain 2D zigzag sheets of Cu(dca)2(bipy) with parallel packing. Fe(dca)2(bipy)(H2O)2·(bipy) 11 contains 1D chains of Fe(bipy) with hydrogen bonding extending the topology to that of two 3D interpenetrating α-Po related networks. Compounds 7 and 11 contain octahedral metal ions, while 8 and 9 have five-coordinate Cu atoms. Variable temperature magnetic susceptibility studies (2–300 K; H = 1 T) have shown that these framework compounds generally display very weak antiferromagnetic coupling because of the long bipy and μ1,5 bridging pathways. Consequently no long-range magnetic order occurs.