Synthesis and magnetic studies of pentagonal bipyramidal metal complexes of Fe, Co and Ni

Abstract

Three mononuclear model complexes with pentagonal bipyramidal geometry, [MII(L-N3O2)(MeCN)2][BPh4]2 (M = Fe, 1; Co, 2; Ni, 3) were isolated and found to exhibit large uniaxial (1 and 3) and easy-plane (2) magnetic anisotropy, respectively.

A ferromagnetic Ni(ii)–Cr(iii) single-chain magnet based on pentagonal bipyramidal building units

“…The obtained negative D parameter is in agreement with the easy-axis anisotropy expected for Ni(II) in pentagonal bipyramid coordination sphere and compares well with values mentioned in literature for heptacoordinated Ni complexes (from -15 to -6 cm -1 ). 5,8,9,19,36 The rather similar D values for 1 and 2 suggests that the nature of the apical ligands has a small effect on the anisotropy exhibited by the Ni; however, it is interesting to note that largest anisotropy is found with cyano-metallates in the apical positions. Despite their significant uniaxial magnetic anisotropy, no slow relaxing magnetization could be evidenced for these complexes.…”

“…2,3 For instance, Fe(II) and Ni(II) exhibit easy-axis anisotropy with zero-field splitting parameter D in the range of -10 to -20 cm -1 , whereas Co(II) has planar anisotropy with D values around 30 cm -1 . [4][5][6][7][8][9][10][11][12][13][14][15] Moreover, the structural robustness of this coordination geometry makes such complexes suitable building units for polynuclear compounds. 16 These characteristics provide a unique opportunity to design polynuclear nano-magnets taking advantage of the large magnetic anisotropy of the pentagonal bipyramid complexes, especially those with Ising-type anisotropy.…”

Trinuclear Cyanido‐Bridged [Cr2Fe] Complexes: To Be or not to Be a Single‐Molecule Magnet, a Matter of Straightness

“…[5,[13][14] In this context, heptacoordinated complexes with robust pentagonal bipyramid coordination geome-try (PBP hereafter) are interesting species as they can exhibit substantial magnetic anisotropy with axial Zero-Field Splitting (ZFS) D values ranging between À 20 and + 40 cm À 1 . [15][16][17][18][19][20][21][22][23][24][25][26] Such complexes can also be used as metalloligands by including in their apical positions groups such as cyanides, [27] which are certainly the most important bridging ligands in molecularbased magnetic systems, including molecular nanomagnets. [28][29][30][31][32] Following this approach, SCMs with nearly collinear local anisotropy directions have been obtained from heptacoordinated [CrL N3O2R (CN) 2 ] À (R = Ph, NH 2 , Scheme 1) and PBP Fe II or Ni II derivatives.…”

Alignment of Axial Anisotropy in a 1D Coordination Polymer shows Improved Field Induced Single Molecule Magnet Behavior over a Mononuclear Seven Coordinated FeII Complex

“…However, the value is significantly larger than the spin only value (3.0 cm 3 mol −1 K, S=2, g=2.0) expected for Fe(II) high spin system which indicates the presence of contribution from unquenched orbital angular momentum in compound 1 . Upon cooling the χ M T value remains almost constant down to 50 K and below that it decreases rapidly to 2.4 cm 3 mol −1 K at 2 K. The rapid decrease of χ M T at low temperature signifies the presence of strong magnetic anisotropy in the studied compound . Further to probe the magnetic anisotropy, the field‐dependence of magnetization measurements were performed in the range of field 0–7 T at temperatures 2, 4 and 6 K as shown in Figure .…”