Field‐Induced Slow Magnetic Relaxation in Mononuclear Tetracoordinate Cobalt(II) Complexes Containing a Neocuproine Ligand

Abstract

The mononuclear tetracoordinate [Co(dmphen)X2] (dmphen = 2,9‐dimethyl‐1,10‐phenanthroline = neocuproine; X = Cl, Br, I) complexes were prepared by a solvothermal method. X‐ray diffraction experiments showed that they possess analogous molecular structures, even though the chlorido complex crystallizes in a different crystal system and space group. The crystal structures of the complexes are stabilized by π–π interactions. Alternating‐current (AC) susceptibility measurements show that the bromido and iodido complexes behave as field‐induced single‐molecule magnets with several slow relaxation channels, whereas the chlorido complex exhibits antiferromagnetic interactions and does not display slow relaxation of magnetization.

Field-induced slow relaxation of magnetization in the S = 3/2 octahedral complexes trans-[Co{(OPPh2)(EPPh2)N}2(dmf)2], E = S, Se: effects of Co–Se vs. Co–S coordination

“…70,71 In the above context, the coordination of heavier halogeno ligands to Ni(II) 72 or Cr(II) 73 has been shown to confer increased axial anisotropies. Similar effects, on the magnitude of the axial anisotropy due to the coordination of heavier halides, have also been established in tetrahedral [74][75][76][77][78][79][80] Co(II) complexes, in some instances imposing a concomitant change in the sign of D as well. 76,77 On the other hand, contrary to the above observations, lower axial anisotropy due to the coordination of heavier halides has been observed in squarepyramidal 81,82 and pentagonal bipyramidal 83 Co(II) complexes.…”

Tuning electronic structure through halide modulation of mesoionic carbene cobalt complexes

“…The two components contributing to ZFS are the minor direct spin-spin interactions and the dominant second-order spin-orbit coupling (SOC) introduced by mixing of ground and excited states. 37 Computational 31,38 and experimental [39][40][41][42][43] works have shown how anisotropy can be influenced via heavy atom coordination with further corroboration for ligand influence on ZFS in tetrahedral Co halide complexes emerging over the past five years. 14,[40][41][42][43][44][45] Complexes 1-3 show a clear trend in their |D| values consistent with the expected electronic-structure effect.…”

“…37 Computational 31,38 and experimental [39][40][41][42][43] works have shown how anisotropy can be influenced via heavy atom coordination with further corroboration for ligand influence on ZFS in tetrahedral Co halide complexes emerging over the past five years. 14,[40][41][42][43][44][45] Complexes 1-3 show a clear trend in their |D| values consistent with the expected electronic-structure effect. Specifically, we can attribute this trend to three effects: (1) Ligand-field strength correlates inversely with halide size, bringing the Co excited-states lower in energy for larger halides (Figure 4).…”

Complexes of Cobalt(II) Iodide with Pyridine and Redox Active 1,2-Bis(arylimino)acenaphthene: Synthesis, Structure, Electrochemical, and Single Ion Magnet Properties

“…As an additional object of research, we studied the complex of cobalt(II) iodide with pyridine. Despite their chemical simplicity, it is surprising that the coordination compounds of CoI 2 with substituted pyridine ligands have received scarce attention [30][31][32][33][34][35][36]. A comparison study of these two systems allowed us to draw preliminary conclusions about the potential use of redox-active ligands of the Ar-BIAN class in the Co(II)-SIM-directed design.…”