Issue 47, 2021

Macrocycle based dinuclear dysprosium(iii) single molecule magnets with local D5h coordination geometry

Abstract

Targeted approaches for manipulating the coordination geometry of lanthanide ions are a promising way to synthesize high-performance single-molecule magnets (SMMs), but most of the successful examples reported to date focus on mononuclear complexes. Herein, we describe a strategy to assemble dinuclear SMMs with DyIII ions in approximate D5h coordination geometry based on pyrazolate-based macrocyclic ligands with two binding sites. A Dy4 complex with a rhomb-like arrangement of four DyIII as well as two dinuclear complexes having axial chlorido ligands (Dy2·Cl and Dy2*·Cl) were obtained; in the latter case, substituting Cl by SCN gave Dy2·SCN. Magneto-structural studies revealed that the μ-OH bridges with short Dy–O bonds dominate the magnetic anisotropy of the DyIII ions in centrosymmetric Dy4 to give a vortex type diamagnetic ground state. Dynamic magnetic studies of Dy4 identified two relaxation processes under zero field, one of which is suppressed after applying a dc field. For complexes Dy2·Cl and Dy2*·Cl, the DyIII ions feature almost perfect D5h environment, but both complexes only behave as field-induced SMMs (Ueff = 19 and 25 K) due to the weak axial Cl donors. In Dy2·SCN additional MeOH coordination leads to a distorted D2d geometry of the DyIII ions, yet SMMs properties at zero field are observed due to the relatively strong axial ligand field provided by SCN (Ueff = 43 K). Further elaboration of preorganizing macrocyclic ligands appears to be a promising strategy for imposing a desired coordination geometry with parallel orientation of the anisotropy axes of proximate DyIII ions in a targeted approach.

Graphical abstract: Macrocycle based dinuclear dysprosium(iii) single molecule magnets with local D5h coordination geometry

Supplementary files

Article information

Article type
Paper
Submitted
23 ago. 2021
Accepted
08 nov. 2021
First published
19 nov. 2021
This article is Open Access
Creative Commons BY-NC license

Dalton Trans., 2021,50, 17573-17582

Macrocycle based dinuclear dysprosium(III) single molecule magnets with local D5h coordination geometry

J. Wu, S. Demeshko, S. Dechert and F. Meyer, Dalton Trans., 2021, 50, 17573 DOI: 10.1039/D1DT02815D

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