Tetracoordinate Co(ii) complexes containing bathocuproine and single molecule magnetism

Abstract

Chlorido complex [Co(bcp)Cl2] exhibits a field-induced SMM behaviour, while in the bromide and iodido analogues only weak antiferromagnetic interactions are present.

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

“…The intermolecular interactions in 1 are different, and the presence of the antiferromagnetic interaction can be explained by the existence of supramolecular chains formed by π–π interactions. Similar magnetic behavior was observed for [Co(bcp)Br 2 ] and [Co(bcp)I 2 ], in which similar supramolecular chains are formed . It seems that the presence of the antiferromagnetic exchange between adjacent Co II atoms prevents slow magnetic relaxation, and none of these complexes behave as field‐induced SMMs.…”

“…Our recent studies of the series of mononuclear tetracoordinate complexes [Co(bcp)X 2 ] (bcp = bathocuproine; X = Cl, Br, I) and [Co(biq)X 2 ] (biq = 2,2′-biquinoline; X = Cl, Br, I) have shown that even small differences in the molecular structures or crystal packing can lead to different magnetic behavior; therefore, we decided to compare the complexes in the similar series of complexes with the neocuproine ligand. [14,15] All three complexes exhibit similar Co-N bond lengths and N-Co-N bite angles ( Table S2 in the Supporting Information), which are consistent with the values for previously reported tetracoordinate Co II complexes containing N,N′-donor chelate ligands. The Co-X bond lengths increase from 1 to 3 in accordance with the increasing ionic radius of the halogenido ligand.…”

“…[16][17][18] N-Co-N ( N ) and X-Co-X ( X ) angles were compared with those of the similar tetracoordinate complexes [Co(biq)X 2 ] and [Co(bcp)X 2 ], some of which have shown SMM behavior ( Table 1). [15,16] It can be seen from Table 1 that the R N parameter decreases slightly from 1 to 3, whereas the N parameter increases slightly. Similar observations can be made for the series of [Co(biq)X 2 ] complexes and could be caused by steric hindrance of the coordinated halogenido ligand; the bulkier bromido and iodido ligands shift the position of the central Co II atom closer to the nitrogen donor atoms of the ligand.…”

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.…”

Role of Halide Ions in the Nature of the Magnetic Anisotropy in Tetrahedral CoII Complexes

“…[5] Over ap eriod of three decades,i th as been realized that, due to the random easy-axis orientations in larger clusters, overall magnetic anisotropy D becomes small, although complexesw ere stabilized with relativelyl arge ground-state spin. For example, using substituents on the ligand to modulate U eff (by meanso fD), [2e, 9] in-plane and out-of-plane shifts of the metal ion in five-coordinate Co II complexes, [10] changing the halide ligandsi no ctahedral and certain tetrahedral complexes, [11] structural distortion around metal centers, and even more intricate measures, such as the significant effect of the secondary coordination sphereo nm odulating the D value, whichw as elegantly explained by Neese and co-workers theoretically and experimentally proven by us recently. [6] Due to this persistentp roblem researchers focused their attention on modulating the D value of mononuclear transition metalc omplexes.…”