Nitronyl Nitroxide Biradical-Based Binuclear Lanthanide Complexes: Structure and Magnetic Properties

Lu Xi,Jing Han,Xiaohui Huang,Licun Li

doi:10.3390/magnetochemistry6040048

Abstract

Employing a new nitronyl nitroxide biradical NITPhPzbis(NITPhPzbis = 5-(1-pyrazolyl)-1,3-bis(1’-oxyl-3’-oxido-4’,4’,5’,5’-tetramethyl-4,5-hydro-1H-imidazol-2-yl)benzene), a series of 2p-4f complexes [Ln2(hfac)6(H2O)(NITPhPzbis)] (LnIII = Gd1, Tb2, Dy3; hfac = hexafluoroacetylacetonate) were successfully synthesized. In complexes 1–3, the designed biradical NITPhPzbis coordinates with two LnIII ions in chelating and bridging modes to form a four-spin binuclear structure. Direct-current magnetic study of Gd analogue indicates that ferromagnetic exchange exists between the Gd ion and the radical while antiferromagnetic coupling dominates between two mono-radicals. Dynamic magnetic data show that the χ” signals of complex 3 exhibit frequency dependence under zero field, demonstrating slow magnetic relaxation behavior in complex 3. And the estimated values of Ueff and τ0 are about 8.4 K and 9.1 × 10−8 s, respectively.

Highlights

In recent years, radical-lanthanide architectures have been appealing candidates for molecular nanomagnets (i.e., single-molecule magnets (SMMs) and single-chain magnets (SCMs)) due to a beneficial combination of strong magnetic anisotropy originated from lanthanide ion and effective magnetic exchange between 4f ion and radical [1,2,3,4,5,6,7,8,9,10,11,12]
Only a handful of nitronyl nitroxide biradical-Ln compounds with slow relaxation of magnetization have been reported [25,26,27,28] due to the inherent difficulties encountered during the biradical preparation [30,31]
We reported a series of nitronyl nitroxide biradical bridged tetranuclear lanthanide

Summary

Introduction

Radical-lanthanide architectures have been appealing candidates for molecular nanomagnets (i.e., single-molecule magnets (SMMs) and single-chain magnets (SCMs)) due to a beneficial combination of strong magnetic anisotropy originated from lanthanide ion and effective magnetic exchange between 4f ion and radical [1,2,3,4,5,6,7,8,9,10,11,12] Using this intriguing strategy, some remarkable results have been obtained, e.g., a N2 3- radical-bridged binuclear.

Synthetic

Magnetic

Magnetic communications in complex

Materials and Characterizations

X-ray Crystallography

Conclusions