Preparation, characterization and X-ray analysis of [Co2(Cl)2tpmc](BF4)2. Comparative structural analysis with the complexes having analogous geometries and ligands

A novel binuclear Co(II) complex, [Co2(Cl)2tpmc](BF4)2 (tpmc = N,N′,N″,N‴-tetrakis(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane), was prepared and structurally characterized by X-ray diffraction analysis at low temperature. The complex crystallizes in P21/c space group of the monoclinic crystal system, and its crystals are isomorphic with those of [Cu2(Br)2tpmc](ClO4)2 complex. In the crystal structure the complex cations [Co2(Cl)2tpmc]2+ are settled around the inversion centres. Cobalt(II) is exo coordinated with four macrocyclic N atoms, and Cl− supplements the fifth coordination site. Based on the index of trigonality, the coordination polyhedron formed around Co(II) ion is described as distorted trigonal bipyramid. Two metal centres are at a distance of 5.710 Å. This is the first Co(II) complex for which X-ray analysis confirmed a chair conformation of tpmc ligand. IR, EPR (X-band) and UV/VIS absorption and reflectance spectra, molar conductivities and magnetic measurements (SQUID) are used to study the investigated complex. A comparative structural analysis with some of the described Co(II) and Cu(II) complexes of analogous geometries and type of pendant azamacrocyclic ligands was also done.