Structure and magnetic properties of one-dimensional metal complexes constructed from alternating dicyanamide linked through binuclear metal tetra-2-pyridylpyrazine subunits

The syntheses, structures and magnetic properties of three I-D complexes with the formulae [Co-2(tppz)(dca)(4)] (1), [Ni-2(tppz) (dca)(4)]C2H5OH (2) and [Cu-2(tppz)(dca)(Cl)(2)](dca) (.) H2O (3), where tppz = tetra-2-pyridylpyrazine and dca = dicyanamide, are described. Complexes 1-3 are one-dimensional metal-complexes. In 1 the dinuclear tppz-chelated Co(II) centers are linked by two double mu(1,5)-dca ligands. Compound 2 forms a ladder-like structure in which the rungs are formed by bis-chelating tppz bridged dinuclear Ni(II) ions and the uprights by 91,5-dca units. Compound 3. forms a helical chain structure which consists of alternately single mu(1,5)-dca linked dinuclear tppz-chelated Cu-centers. The temperature, dependence of magnetic measurements show antiferromagnetic couplings between two metal ions with a pathway through tppz and mu(1,5)-dca in all cases, with J=-1.10cm(-1), J'= -0.05 cm(-1) for 1, J = -1.28 cm(-1), J' = 0.11 cm(-1) and D = 9.50 cm(-1) for 2, and J = 10.26 cm(-1), J' = -0.06 cm(-1) for 3. (c) 2005 Elsevier Ltd. All rights reserved.