Slow magnetic relaxation in a homoaxially phosphine oxide coordinated pentagonal bipyramidal Dy(iii) complex

We report the synthesis of [(L)Dy-III(Cy3PO)(2)]center dot [BPh4] (1-Dy) (where H2L = 2,6-diacetylpyridine bis-benzoylhydrazone and Cy = cyclohexyl) which crystallized in the triclinic, P1 space group. The local geometry around Dy(iii) in 1-Dy was found to be pentagonal bipyramidal (pseudo-D-5h). The AC magnetic susceptibility measurements performed on 1-Dy and on its diluted 1-Y(Dy) samples showed a typical single-molecule magnet signature revealed by the appearance of AC-frequency dependent out-of-phase susceptibility signals in the absence of a static magnetic field. The out-of-phase AC susceptibility signals were well resolved on the application of a small magnetic field (H-DC = 500 Oe) and yielded an energy barrier for magnetization flipping of U-eff/k(B) = 50 K for the diluted derivative. The magnetic studies on 1-Dy and 1-Y(Dy) and data analysis further confirm that Raman and QTM under-barrier magnetic relaxations play a crucial role in lowering U-eff despite the almost axial nature of the Dy(iii) ion in 1-Dy. We have rationalized these observations through detailed ab initio calculations performed on the X-ray crystal structure of 1-Dy.

Automated summary

We synthesized [(L)Dy-III(Cy3PO)(2)]center dot [BPh4] (1-Dy) and determined its crystal structure to be triclinic, P1 space group. The local geometry around Dy(iii) in 1-Dy was pentagonal bipyramidal (pseudo-D-5h). AC magnetic susceptibility measurements on 1-Dy and its diluted 1-Y(Dy) samples revealed single-molecule magnet behavior with out-of-phase susceptibility signals, and an energy barrier for magnetization flipping of U-eff/k(B) = 50 K for the diluted derivative. Detailed ab initio calculations on the X-ray crystal structure of 1-Dy supported these observations.