ИСТИНА

The design of mononuclear pentagonal-bipyramidal (PBP) Dy complexes is one of the key trends in modern studies of single-molecule magnetism, since some of these complexes, containing weakly fielded ligands in the equatorial plane (water, pyridine) and strongly fielded ligands in axial positions, are single-ion magnets (SIM) with high magnetization barrier (Ueff) and blocking temperature values [1]. In this regard, the synthesis of sevencoordinated PBP dysprosium complexes with acyclic pentadentate (N3O2) ligands is promising direction because this type of ligands provides a rigid equatorial plane [1]. In the first time, the PBP dysprosium complex with an equatorial N3O2 ligand (Et3NH)+ [(DyH2daps)Cl2] – was synthesized in work [2]. This yttrium-doped complex showed slow magnetic relaxation with Ueff = 70 K when a dc magnetic field of 500 Oe was applied. The rather low value of the magnetization barrier for this complex can be understood from the qualitative Reinhart and Long electrostatic model [3]. According to this model, the axial field stabilizes the oblate shape of the 4f electron cloud, which is characteristic of the Dy3+ ion. The complex contains two Cl– ions in the axial positions, which are weaker field ligands compared to the donor N and O atoms in the equatorial plane, carrying two negative charge (H2daps)2– , so this complex has a low magnetization barrier and exhibits a slow magnetic relaxation only in the presence of a constant magnetic field. In order to further investigate the influence of axial ligands on the magnetic behavior of this family of complexes, neutral PBP Dy complexes [Dy(dapbh)(R3PO)Cl] were synthesized with strong donor ligands R3PO, where R =Ph, Cy [4]. A study of magnetic properties showed that these complexes exhibit slow magnetic relaxation with Ueff = 204–241 K when a dc magnetic field is applied. Thus, the barrier of magnetization was significantly increased compared to the barrier of magnetization for the complex with two Cl– ligands. However, application of a dc magnetic field was still required to manifest slow relaxation. Herein we report the synthesis, crystal structure and magnetic properties of the novel PBP Dy complex, [Dy(dapt)(Cy3PO)2]ClO4∙CH3CN. The study of the magnetic properties showed that this complex is a single-ion magnet with the value of magnetization barrier of 318 K without the application of dc magnetic field. [1] J.-P. Sutter, V. Béreau, V. Jubault, K. Bretosh, C. Pichon and C. Duhayon. Chem. Soc. Rev., 2022. 51, 3280- 3313; [2] A.K. Bar, P. Kalita, J.-P. Sutter and V. Chandrasekhar. Inorg. Chem., 2018, 57, 5, 2398-2401; [3] J.D. Rineharta and J.R. Long. Chem Sci., 2011, 2, 5, 2078-2085; [4] P. Kalita, N. Ahmed, A.K. Bar, S. Dey, A. Jana, G. Rajaraman, J.-P. Sutter and V. Chandrasekhar. Inorg. Chem., 2020, 59, 9, 6603-6612. Acknowledgements - This work was supported by the Ministry of Science and Higher Education of the Russian Federation (Grant No. 075-15-2020-779)