Enhanced single-molecule magnetism in dysprosium complexes of a pristine cyclobutadienyl ligand

Abstract

Cyclobutadienyl ligands can generate much stronger axial crystal fields in dysprosium single-molecule magnets (SMMs) than more common cyclopentadienyl ligands, providing clues as to how the performance of SMMs can be substantially improved.

Synthesis, bonding properties and ether activation reactivity of cyclobutadienyl-ligated hybrid uranocenes

“…12,16,17 We have shown that these alkali metal reagents can transfer the bulky [{C 4 (SiMe 3 ) 4 }] 2À dianion to lanthanides, either with the ligand remaining intact or undergoing activation processes, such as deprotonation of a silyl substituent and/or protonation of the four-membered ring, to give h 3 -allyl derivatives. [10][11][12] Similar reactivity of A 2 Cb 0000 towards uranium(IV) has also been observed, including formation of the half-sandwich complex [U(h 4 -Cb 0000 )(BH 4 ) 3 ] À in addition to sandwich complexes containing the Cb 0000 ligand in an activated form. 13,14 The bonding in uranium-cyclobutadienyl complexes features non-negligible covalency, with the overlap consisting of similar contributions from the uranium 5f and 6d orbitals.…”

“…Relative to transition metals, the differing chemistry of lanthanides and actinides means that current methodologies are largely reliant on the use of s-block cyclobutadienyl reagents in reactions with metal halide and pseudo-halide salts. [10][11][12][13][14][15] Since most routes to s-block cyclobutadienyl compounds involve reduction of cyclobutadienes with elemental s-block metals, the inherent instability of almost all anti-aromatic cyclobutadienes presents a challenge. However, following the seminal work of Sekiguchi et al, the stable cyclobutadiene C 4 (SiMe 3 ) 4 can be conveniently synthesized and converted into the reagents [A 2 {C 4 (SiMe 3 ) 4 }] (A 2 Cb 0000 , A ¼ Li, Na, K) on a multigram scale.…”

Organic magnetoelectric and optomagnetic couplings: perspectives for organic spin optoelectronics

“…Molecular magnets (MMs) containing metal ions and organic components can be used as a new generation of high-density information storage devices, quantum computing devices, or spintronic devices [16][17][18][19][20][21][22] . Usually, MMs have transition metal ions.…”

Fulvalene as a platform for the synthesis of a dimetallic dysprosocenium single-molecule magnet

“…[13][14][15][16][17][18][19][20][21] In the case of Dy 3+ , a 4f 9 ion with oblate spheroidal electron density, successful SMM synthesis strategies tend to produce compounds in which the metal occupies a coordination environment with a strong and highly axial crystal eld. [22][23][24] This approach partly explains why the highest-performing SMMs are based on metallocene cations of the type [Dy(h 5 -Cp R ) 2 ] + , where the bulky cyclopentadienyl ligands [Cp R ] À provide the strong, axial crystal eld whilst also blocking the formation of any deleterious equatorial crystal eld. 6,11,[25][26][27][28][29] Previous work on sandwich SMMs constructed with erbium-COT (COT ¼ cyclo-octatetraenyl) 30,31 and terbium-phthalocyanine 32,33 building blocks has shown that the parameters U eff and T B increase when two or more blocks are linked to form multidecker sandwich complexes.…”

“… 13 – 21 In the case of Dy 3+ , a 4f 9 ion with oblate spheroidal electron density, successful SMM synthesis strategies tend to produce compounds in which the metal occupies a coordination environment with a strong and highly axial crystal field. 22 – 24 This approach partly explains why the highest-performing SMMs are based on metallocene cations of the type [Dy(η 5 -Cp R ) 2 ] + , where the bulky cyclopentadienyl ligands [Cp R ] – provide the strong, axial crystal field whilst also blocking the formation of any deleterious equatorial crystal field. 6 , 11 , 25 – 29 …”