Fine-Tuning of Uniaxial Anisotropy and Slow Relaxation of Magnetization in the Hexacoordinate Co(II) Complexes with Acidoligands

• Published in: Journal of physical chemistry. C 2020-11, Vol.124 (47), p.25957-25966
• Main Authors: Tupolova, Yulia P, Shcherbakov, Igor N, Korchagin, Denis V, Tkachev, Valery V, Lebedev, Vladimir E, Popov, Leonid D, Zakharov, Konstantin V, Vasiliev, Alexander N, Palii, Andrew V, Aldoshin, Sergey M
• Format: Article
• Language: English
• Subjects: C: Plasmonics; Optical, Magnetic, and Hybrid Materials
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.0c07552

A new hexacoordinate Co­(II) complex with the general formula [CoL­(NCS)2]·DMSO (1) (L = biscondensation product of diacetyl and 2-hydrazinyl-4,6-dimethylpyrimidine, DMSO = dimethylsulfoxide) exhibiting field-induced single-ion magnet (SIM) behavior has been obtained and characterized. To explain such field-induced SIM behavior, we have performed the analysis of the observed direct current (DC) magnetic properties based on the Griffiths Hamiltonian in combination with the high-level quantum-chemical calculations of the crystal field parameters. The complex has been shown to exhibit strong easy-axis-type magnetic anisotropy arising from a large negative value Δax = −1538.0 cm–1 of the axial crystal parameter, which is accompanied by a weak rhombic contribution with |Δrh| = 219.3 cm–1. Magnetic properties of 1 have been compared with the previously studied field-induced SIM compound [CoLCl2]·H2O (2). Introduction of a thiocyanide anion in 1 (instead of chloride in 2) in the Co­(II) coordination sphere resulted in improvement of uniaxial magnetic anisotropy and switch of the relaxation process from the combination of direct and Raman mechanisms in 2 to Orbach-type one in complex 1. Effects of substitution of acidoligands in the Co­(II) coordination sphere on the crystalline structure, DC magnetic properties, magnetic anisotropy, and magnetization relaxation processes have been rationalized.