Topological control in two-dimensional cobalt(II) coordination polymers by π-π stacking interactions:: Synthesis, spectroscopic characterization, crystal structure, and magnetic properties

The reactions of CoX2 (X = Br, Cl) with the planar, bidentate bridging ligand 2,1,3-benzothiadiazole (btd) in Me2CO led to the 2D coordination polymers {[CoBr2(btd)]}(n), (1) and {[CoCl2(btd)]}(n), (2). The structure of 1 was determined by single-crystal X-ray crystallography. Complex I (C6H4Br2CoN2S, monoclinic, P2(1)/m, a = 3.742(3), b = 13.075(9), c = 9.092(6) Angstrom, beta = 90.09(2)degrees, Z = 2, theta -2 theta, R-1 = 0.0298, wR(2) = 0.0793) consists of {[Co(mu -Br)(2)]}(n) linear chains running along the a axis linked via mu -btd ligands along the b axis. The columns of stacked btd molecules present in the crystal structure of the free ligand are maintained in the lattice of 1. XRD data revealed that 2 is isostructural with 1. The magnetic properties of both complexes can be explained by the presence of a very weak ferromagnetic intrachain Co . . . Co exchange interaction through the (mu -X)(2) bridges and a moderate antiferromagnetic Co . . . Co interaction through the mu -btd bridges. The new complexes were also characterized by EPR, IR, and UV/VIS spectra, and all data are discussed in terms of the nature of bonding and known structures. (C) 2001 Academic Press.