Breaking the axiality of pentagonal–bipyramidal dysprosium(iii) single-molecule magnets with pyrazolate ligands

Abstract

A range of pyrazolate-based ligands have been used to balance the multidentate-chelating feature and the magnetic axiality in “destroyed” pentagonal-bipyramidal (DPB) dysprosium(III) single-molecule magnets (SMMs). This family of complexes are...

Magnetic anisotropy of transition metal and lanthanide ions in pentagonal bipyramidal geometry

“…The nature of the negatively charged ligand coordinated in axial positions to the rare earth seems to be a predominant criterion for the optimization of the magnetic properties of these systems. This is clearly illustrated by the Dy III complexes [DyX 1 X 2 (THF) 5 ]·BPh 4 (with X 1 = Cl, OPh, OCMe 3 and OSiMe 3 ; X 2 = Cl, Br, OPh, OCMe 3 and OSiMe 3 ; Table 10, entries 17, 18, 21, 22, 27 and 28) 144–147 and [DyX 2 (THF) 5 ]·BPh 4 (X 2 = CH 3 (C 6 F 5 )CHO − , pyrazolate, PhO − , Me 3 CO − , Me 3 SiO − , Table 10, entries 19, 20, 24, 26, 29 and 30, 34). 143–146 When one and then the two axial Cl − ligands of [DyCl 2 (THF) 5 ] + are replaced by phenolate ligands to give [DyCl(PhO)(THF) 5 ] + and [Dy(PhO) 2 (THF) 5 ] + , respectively, the effective energy barrier for magnetization reversal, U eff / k B , increases from 83 K to 1329 K with a blocking temperature shift from 7 K to 12 K. 145 This trend is corroborated by the remarkable results obtained for [Dy(CH 3 CH(C 6 F 5 )O) 2 (THF) 5 ]·BPh 4 (entry 34), where the Dy–alkoxyl bond distance is shorter.…”

Unravelling the role of spin–vibrational coupling in designing high-performance pentagonal bipyramidal Dy(iii) single ion magnets

“…5 In this regard, the pentagonal bipyramidal family of SIMs has an edge due to a large variation in the U eff (37-1200 cm −1 ) and T B (2-30 K) values observed, offering signicant room for further improvement in T B values. 10,11,35,36,[38][39][40]42,[59][60][61][62][63][64][65][66][67][68][69][70][71] It is noteworthy to mention that raising the T B value from 60 K to 80 K in dysprosocenium complexes is related to the judicial design of ligands to efficiently decouple the vibrationally active normal mode coupled to the spin states. 46 To ne-tune the magnetic anisotropy in pentagonal bipyramidal Dy(III) SIMs, one needs a thorough understanding of the related spin-phonon coupling.…”

Photoresponsive Magnetic Relaxation Behavior of a Highly Stable π···π Interaction-Stacked Framework Based on a DyIII Single-Ion Magnet

“…With the advancement of performance tuning, the improvement of the stability of Ln-SIMs has become one of the new pursuits in this field but still faces challenges. At present, most of the reported systems are air stable, such as [Dy­(L N6 )­(Ph 3 SiO) 2 ]­[BPh 4 ], , [DyX 1 X 2 (L eq ) 5 ]­[BPh 4 ] (X 1 and X 2 = pyrazolate-based ligands or chloride; L eq = THF, pyridine or thiazole), and [Dy­(H 2 O) 5 (HMPA) 2 ]­Cl 3 ·HMPA·H 2 O (HMPA = hexamethylphosphoramide) . Several thermostable Ln-SIMs have also been developed.…”