Cobalt halide complexes of 2-, 3- and 4-methoxyaniline: Syntheses, structures and magnetic behavior

Abstract

A family of six cobalt(II) compounds of the general formula (nMeO-C6H4NH2)2CoX2, (X = Cl, Br; nMeO-C6H4NH2 = 2-MeO-, 3-MeO-, or 4-MeO-aniline) has been prepared and the compounds characterized by combustion analysis, IR, single-crystal X-ray diffraction and variable temperature magnetization measurements [(n-MeOC6H4NH2)2CoX2, (1, n = 2, X = Cl; 2, n = 2, X = Br; 3, n = 3, X = Cl; 4, n = 3, X = Br; 5, n = 4, X = Cl; 6, n = 4, X = Br]. Although the six compounds crystallize in a variety of space groups, they are all isocoordinate. The compounds are slightly distorted tetrahedra. In all compounds, hydrogen bonds and short intermolecular X…Co contacts link the molecules into chains. For 3–6, short halide…halide contacts, in some cases short enough to be considered halogen bonds, further link the chains into layer structures. The complexes have also been studied via variable temperature magnetic susceptibility measurements. All six compounds exhibit antiferromagnetic exchange and show maxima in χ in the range 2–5 K. They have been fit to a variety of models incorporating single-ion anisotropy (SIA), and/or Heisenberg or Ising 1D- and 2D-systems. The results indicate that both antiferromagnetic superexchange and SIA are likely present in all compounds to some degree, but their relative contributions vary greatly. The potential superexchange pathways are discussed in terms of the observed magnetic properties and structures.