From unprecedented 2,2′-bisimidazole-bridged rare earth organometallics to magnetic hysteresis in the dysprosium congener

Abstract

A new series of bisimidazole-bridged rare earth metallocene complexes, [(Cp*2RE)2[μ-bim] (RE = Y, Gd, and Dy), was isolated and studied by crystallography, magnetometry, spectroscopy, and computations. The Dy congener is a single-molecule magnet.

Guanidinate Yttrium Complexes Containing Bipyridyl and Bis(benzimidazolyl) Radicals

“…Very recently, the Demir group produced the first example of a trianionic paramagnetic state of Bbim 3–• , encased between two metallocene cations of the type {Cp* 2 RE} + . The isolation of the previously elusive radical state was accomplished by taking advantage of the lowering of the lowest unoccupied molecular orbital (LUMO) of Bbim upon coordination to the metallocene cation. , In addition to the influence of the metallocene unit on the molecular orbitals of the bridging ligand, DFT calculations uncovered the importance of the fused benzyl rings in the backbone of Bbim for access of its open-shell state because their absence precluded a stable paramagnetic species, which was the outcome of studies on the 2,2′-bis­(imidazole)-bridged congeners . The lack of other Bbim 3–• radical anions highlights its challenging isolation and emphasizes the role of the ligated cationic unit.…”

“… 13 , 35 In addition to the influence of the metallocene unit on the molecular orbitals of the bridging ligand, DFT calculations uncovered the importance of the fused benzyl rings in the backbone of Bbim for access of its open-shell state because their absence precluded a stable paramagnetic species, which was the outcome of studies on the 2,2′-bis(imidazole)-bridged congeners. 77 The lack of other Bbim 3–• radical anions highlights its challenging isolation and emphasizes the role of the ligated cationic unit. Thus, we were inspired to probe its accessibility in the realm of a guanidinium RE scaffold.…”

Dipolar Coupling as a Mechanism for Fine Control of Magnetic States in ErCOT-Alkyl Molecular Magnets

“…While SIMs have pushed the boundaries of controlling spin–lattice relaxation out to technologically relevant temperatures, many quantum technologies require arrays of multiple coupled spins; − such coupling strategies work to enhance SMM relaxation behavior by affecting QTM at zero and applied fields as well. , Several examples exist of molecular systems with exceptional hysteretic behavior and an effective quenching of QTM by coupling highly anisotropic magnetic states, either directly or through a molecular bridge bearing spin density, to yield highly anisotropic “giant spins” akin to the clusters that established SMMs. − One route to building higher nuclearity molecular magnets is that of the “building block” approach, wherein several magnetic units with well-defined and synthetically robust ground states are linked to build systems with conserved anisotropy. − However, compatibility with open-shell bridges is difficult due to the charge-dense and highly penetrating radicals either destroying the anisotropy enforced by the comparatively weak crystal field or introducing large coupling so that magnetic energy levels become close and can easily mix.…”

Ab initio-based determination of lanthanoid–radical exchange as visualised by inelastic neutron scattering

“…18 The overall magnetic moment of the complex can also be increased by coupling multiple spins into a "giant spin", which while a common approach for TM-SMMs, 19 has not been as widely used for Ln-SMMs, due to their typically weaker magnetic exchange coupling. 13,[20][21][22][23] Spectroscopic techniques to measure the lowest lying electronic energy levels in Ln(III) compounds with large spin-orbit coupling include EPR, [24][25][26] luminescence, [27][28][29][30][31] far infrared, 24,32,33 and inelastic neutron scattering spectroscopies. [34][35][36][37][38] Inelastic neutron scattering (INS) offers unique advantagesit requires no applied magnetic eld to identify magnetic transitions and doesn't rely on the oen weak luminescence of Ln(III) ions.…”

“…18 The overall magnetic moment of the complex can also be increased by coupling multiple spins into a “giant spin”, which while a common approach for TM-SMMs, 19 has not been as widely used for Ln-SMMs, due to their typically weaker magnetic exchange coupling. 13,20–23…”