Preparation, characterization and X-ray analysis of [Co-2(Cl)(2)tpmc](BF4)(2). Comparative structural analysis with the complexes having analogous geometries and ligands
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A novel binuclear Co(II) complex, [Co-2(Cl)(2)tpmc](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 P2(1)/c space group of the monoclinic crystal system, and its crystals are isomorphic with those Of [Cu-2(Br)(2)tpmc](ClO4)(2) complex. In the crystal structure the complex cations [Co-2(Cl)(2)tpmc](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 angstrom. 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 m...agnetic 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.
Keywords:Co(II) dimeric complex / pendant azamacrocycles / chloro ligand / X-ray analysis / magnetic properties
Source:Journal of Molecular Structure, 2007, 827, 1-3, 80-87
- Elsevier Science BV, Amsterdam