Counterintuitive Single-Molecule Magnet Behaviour in Two Polymorphs of One-Dimensional Compounds Involving Chiral BINOL-Derived Bisphosphate Ligands

Carlo Andrea Mattei,Gilles Argouarch,Vincent Dorcet,Fabrice Pointillart,Olivier Cador,Bertrand Lefeuvre,Claudia Lalli

doi:10.3390/magnetochemistry7110150

Abstract

The coordination reaction of the [Dy(hfac)3(H2O)2] units (hfac− = 1,1,1,5,5,5-hexafluoroacetylacetonate) with the [8′-(Diphenoxylphosphinyl)[1,1′-binaphthalen]-8-yl]diphenoxylphosphine oxide ligand (L) followed by a crystallisation in a 1:3 CH2Cl2:n-hexane solvent mixture led to the isolation of a new polymorph of formula [(Dy(hfac)3((S)-L))3]n (1). The X-ray structure on single crystal of 1 revealed the formation of a mono-dimensional coordination polymer with three crystallographically independent DyIII centres, which crystallised in the polar chiral P21 space group. Ac magnetic measurements highlighted single-molecule magnet behaviour under both zero and 1000 Oe applied magnetic field with magnetic relaxation through quantum tunneling of the magnetisation (QTM, zero field only) and Raman processes. Despite the three crystallographically independent DyIII centres adopting a distorted D4d coordination environment, a single slow magnetic relaxation contribution was observed at a slower rate than its previously studied [(Dy(hfac)3((S)-L))]n (2) polymorph.

Highlights

Single-molecule magnets (SMMs) have fascinated communities of chemists and physicists for the last 30 years because they display slow magnetic relaxation with magnetic bistability and quantum behaviours at low temperatures [1,2]
The addition of the chirality is probably the most popular choice because it leads to the observation of multiferroic materials [26,27,28,29], for instance when ferromagnetism cohabits with ferroelectricity and magneto-chiral anisotropy [30,31,32,33]
The polycrystalline powder of the latter polymer was obtained large excess of n-hexane into a CH2 Cl2 solution of 2 (CH2 Cl2 /n-hexane 1:40), while a by slow diffusion of a large excess of n-hexane into a CH2Cl2 solution of 2 (CH2Cl2/n-hexslow evaporation from a solution of the reagents in CH2 Cl2 quantitatively yielded the ane 1:40), while a slow evaporation from a solution of the reagents in CH2Cl2 quantitanew polymorph of formula [(Dy(hfac)3 ((S)-L))3 ]n (1) as single crystal suitable for X-ray tively yielded the new polymorph of formula [(Dy(hfac)3((S)-L))3]n (1) as single crystal diffraction study and confirmed by PXRD studies

Summary

Introduction

Single-molecule magnets (SMMs) have fascinated communities of chemists and physicists for the last 30 years because they display slow magnetic relaxation with magnetic bistability and quantum behaviours at low temperatures [1,2] The latter opens the door to potential applications in molecular spintronics [3,4,5,6,7], quantum computing [8,9,10,11,12] and magneto-optics [13]. The discovery of lanthanide SMMs [14] with blocking temperatures for the reversal magnetisation up to 80 K [15], push back SMMs into the race of applications in high-density data storage [16,17] To magnetism, another physical property can be added to achieve multi-property materials [18,19,20,21,22,23,24,25]. A few years ago, some of us demonstrated that chirality can indirectly modulate the SMM behaviour through the change of dipolar interaction due to different crystal packings in the racemic

Methods

Discussion

Conclusion