A new family of trinuclear nickel (II) complexes as single-molecule magnets

Biswas, Rituparna ; Ida, Yumi ; Baker, Michael L. ; Biswas, Saptarshi ; Kar, Paramita ; Nojiri, Hiroyuki ; Ishida, Takayuki ; Ghosh, Ashutosh (2013) A new family of trinuclear nickel (II) complexes as single-molecule magnets Chemistry - A European Journal, 19 (12). pp. 3943-3953. ISSN 0947-6539

Full text not available from this repository.

Official URL: http://onlinelibrary.wiley.com/doi/10.1002/chem.20...

Related URL: http://dx.doi.org/10.1002/chem.201202795


Three new trinuclear nickel (II) complexes with the general composition [Ni3L3(OH)(X)](ClO4) have been prepared in which X = Cl (1), OCN (2) or N3 (3) and HL is the tridentate N,N,O donor Schiff base ligand 2-[(3-dimethylaminopropylimino)methyl]phenol. Single-crystal structural analyses revealed that all three complexes have a similar Ni3 core motif with three different types of bridging, namely phenoxido (μ2 and μ3), hydroxido (μ3) and μ2-Cl (1), μ1,1-NCO (2) or μ1,1-N3 (3). The nickel (II) ions adopt a compressed octahedron geometry. Single-crystal magnetization measurements on complex 1 revealed that the pseudo-three-fold axis of Ni3 corresponds to a magnetic easy axis, being consistent with the magnetic anisotropy expected from the coordination structure of each nickel ion. Temperature-dependent magnetic measurements indicated ferromagnetic coupling leading to an S = 3 ground state with 2J/k = 17, 17 and 28 K for 1, 2, and 3, respectively, with the nickel atoms in an approximate equilateral triangle. The high-frequency EPR spectra in combination with spin Hamiltonian simulations that include zero-field splitting parameters DNi/k = −5, −4 and −4 K for 1, 2, and 3, respectively, reproduced the EPR spectra well after a anisotropic exchange term was introduced. Anisotropic exchange was identified as Di,j/k = −0.9, −0.8 and −0.8 K for 1, 2 and 3, respectively, whereas no evidence of single-ion rhombic anisotropy was observed spectroscopically. Slow relaxation of the magnetization at low temperatures is evident from the frequency-dependence of the out-of-phase ac susceptibilities. Pulsed-field magnetization recorded at 0.5 K shows clear steps in the hysteresis loop at 0.5–1 T, which has been assigned to quantum tunneling, and is characteristic of single-molecule magnets.

Item Type:Article
Source:Copyright of this article belongs to John Wiley and Sons, Inc.
Keywords:EPR Spectroscopy; Magnetic Properties; Nickel; Schiff Bases; X-ray Diffraction
ID Code:108259
Deposited On:13 Oct 2017 12:40
Last Modified:13 Oct 2017 12:40

Repository Staff Only: item control page