Influence of the Coligand onto the Magnetic Anisotropy and the Magnetic Behavior of One-Dimensional Coordination Polymers

Reaction of Co­(NCS)₂ with different coligands leads to the formation of three compounds with the general composition [Co­(NCS)₂(L)₂]_n (L = aniline (1), morpholine (2), and ethylenethiourea (3)). In all of these compounds the cobalt­(II) cations are octahedrally coordinated by two trans thiocyanate N and S atoms and the apical donor atoms of the coligands and are linked into linear chains by pairs of anionic ligands. The magnetic behavior was investigated by a combination of static and dynamic susceptibility as well as specific-heat measurements, computational studies, and THz-EPR spectroscopy. All compounds show antiferromagnetic ordering as observed for similar compounds with pyridine derivatives as coligands. In contrast to the latter, for 1–3 significantly higher critical temperatures and no magnetic single-chain relaxations are observed, which can be traced back to stronger interchain interactions and a drastic change in the magnetic anisotropy of the metal centers. These results are discussed and compared with those of the pyridine-based compounds, which provides important insights into the parameters that govern the magnetic behavior of such one-dimensional coordination polymers.