Volume 26, Issue 26 p. 5893-5902
Full Paper

A Study of Magnetic Relaxation in Dysprosium(III) Single-Molecule Magnets

Dr. You-Song Ding

Dr. You-Song Ding

Frontier Institute of Science and Technology (FIST), State Key Laboratory for Mechanical Behavior of Materials, MOE Key Laboratory for Nonequilibrium Synthesis and, Modulation of Condensed Matter, and School of Science, Xi'an Jiaotong University, 99 Yanxiang Road, Xi'an, Shaanxi, 710054 P.R. China

Department of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL UK

These authors contributed equally to this work.

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Dr. Tian Han

Dr. Tian Han

Frontier Institute of Science and Technology (FIST), State Key Laboratory for Mechanical Behavior of Materials, MOE Key Laboratory for Nonequilibrium Synthesis and, Modulation of Condensed Matter, and School of Science, Xi'an Jiaotong University, 99 Yanxiang Road, Xi'an, Shaanxi, 710054 P.R. China

These authors contributed equally to this work.

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Yuan-Qi Zhai

Yuan-Qi Zhai

Frontier Institute of Science and Technology (FIST), State Key Laboratory for Mechanical Behavior of Materials, MOE Key Laboratory for Nonequilibrium Synthesis and, Modulation of Condensed Matter, and School of Science, Xi'an Jiaotong University, 99 Yanxiang Road, Xi'an, Shaanxi, 710054 P.R. China

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Dr. Daniel Reta

Dr. Daniel Reta

Department of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL UK

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Dr. Nicholas F. Chilton

Dr. Nicholas F. Chilton

Department of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL UK

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Prof. Dr. Richard E. P. Winpenny

Corresponding Author

Prof. Dr. Richard E. P. Winpenny

Department of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL UK

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Prof. Dr. Yan-Zhen Zheng

Corresponding Author

Prof. Dr. Yan-Zhen Zheng

Frontier Institute of Science and Technology (FIST), State Key Laboratory for Mechanical Behavior of Materials, MOE Key Laboratory for Nonequilibrium Synthesis and, Modulation of Condensed Matter, and School of Science, Xi'an Jiaotong University, 99 Yanxiang Road, Xi'an, Shaanxi, 710054 P.R. China

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First published: 19 February 2020
Citations: 114

A previous version of this manuscript has been deposited on a preprint server (https://doi.org/10.26434/chemrxiv.7083038).

Graphical Abstract

Pyramid scheme: An extended and systematic study of a family of lanthanide single-molecule magnets (SMMs) with pentagonal-bipyramidal geometry reveals the relaxation parameters and correlations. The energy barriers correlate with structure, mainly the electronegativity of donor atoms on the axial sites (the axial Dy−X bond lengths), and the energy barriers correlate with the blocking and hysteresis temperatures.

Abstract

Although the development of single-molecule magnets (SMMs) is rapid, there are only two families of high energy barrier (Ueff) dysprosium(III) SMMs known so far: the cyclopentadienyl (Cp) family with a sandwich structure and the pentagonal-bipyramidal (PB) family with D5h symmetry. These high-barrier SMMs, which usually possess Ueff>500 cm−1 allow the separate study of the four magnetic relaxation paths, namely, direct, quantum tunnelling, Raman and Orbach processes, in detail. Whereas the first family is chemically more challenging to modify the Cp rings, it is shown herein that the latter family, with the common formulae [DyX1X2(Leq)5]+, such as X1/X2=OCMe3, OSiMe3, OPh, Cl or Br; Leq=THF/pyridine/4-methylpyridine, can be readily fine-tuned with a range of axial and equatorial ligands by simple substitution reactions. This allows unambiguous confirmation that the Ueff mainly depends on the identity of X1 and X2, rather than on Leq. More importantly, the fitted parameters are barrier dependent. If X1 is an O donor and X2 is a halide, 500<Ueff<600 cm−1, log τ0avg (s)=−10.66, log Cavg (s−1 Kn)= −5.05, navg=4.1 and TH=9 K (in which τ0 is the pre-exponential factor for the Orbach relaxation process, C and n are parameters used to describe Raman relaxation, and TH is the highest temperature at which magnetic hysteresis is observed). For cases in which both X1 and X2 are O donors, 900<Ueff<1300 cm−1, log τ0avg (s)=−11.63, log Cavg (s−1 Kn)= −6.03, navg=4.1 and 18<TH<25 K. Based on these results, it can be further concluded that Ueff not only has a linear correlation to the axial Dy−X bond lengths, but also to TH for these PB SMMs. This represents the first systematic study of a family of lanthanide SMMs and derives the first magneto-structural correlation in Dy SMMs.

Conflict of interest

The authors declare no conflict of interest.