Publications by authors named "Nicholas Chilton"

Benzene reduction by molecular complexes remains an important synthetic challenge, requiring harsh reaction conditions involving group I metals. Reductions of benzene, to date, typically result in a loss of aromaticity, although the benzene tetra-anion, a 10π-electron system, has been calculated to be stable and aromatic. Due to the lack of sufficiently potent reductants, four-electron reduction of benzene usually requires the use of group I metals.

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Dysprosium single-molecule magnets (SMMs) with two mutually -anionic ligands have shown large crystal field (CF) splitting, giving record effective energy barriers to magnetic reversal ( ) and hysteresis temperatures ( ). However, these complexes tend to be bent, imposing a transverse field that reduces the purity of the projections of the CF states and promotes magnetic relaxation. A complex with only one charge-dense anionic ligand could have more pure CF states, and thus high and .

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Modulation of the crystal field (CF) in lanthanide (Ln) complexes can enhance optical and magnetic properties, and large CF splitting can be achieved with low coordination numbers in specific geometries. We previously reported that the homoleptic near-linear Sm complex [Sm{N(SiPr)}] () is oxidized by the 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) radical to give the heteroleptic, approximately trigonal planar Sm complex, [Sm{N(SiPr)}(TEMPO)] (). Here, we report the synthesis of homologous [Ln{N(SiPr)}(TEMPO)] (; Ln = Tm, Yb) complexes by the oxidation of the parent [Ln{N(SiPr)}] (; Ln = Tm, Yb) with TEMPO; complexes all contain TEMPO anions.

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Developing molecular spin technologies requires microscopic knowledge of their spin-dynamics. Calculation of phonon modes, phonon scattering and spin-phonon coupling for a dysprosocenium single-molecule magnet (SMM) give simulations of spin-dynamics that agree with experiment. They show that low-energy phonon scattering is a significant contribution to the high-performance of dysprosocenium SMMs.

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An organometallic erbium bismuth cluster complex, [K(THF)][Cp*ErBi] (), featuring a heterometallocubane core was isolated. The cube emerges from the rare Bi Zintl ion, bridging two erbium centers for the first time. SQUID magnetometry and calculations uncovered dominant antiferromagnetic coupling enabled through the chair-like hexabismuth anion.

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Nonsymmetric 6π-electron ("oxidized") 6-oxoverdazyls have been synthesized for the first time. After formal incorporation of a hydrogen atom, the corresponding 7π-electron neutral verdazyl radical is generated. The 7π radical can undergo a further electrochemically reversible reduction to an 8π anion.

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(2,3)-4-Fluorovaline (FVal) is an analogue of valine, where a single CH group is substituted by a CHF group. In the absence of valine, valyl-tRNA synthetase uses FVal as a substitute, enabling the production of proteins uniformly labeled with FVal. Here, we describe the production and analysis of peptidyl-prolyl isomerase B where all 16 valine residues have been replaced by FVal synthesized with a C-labeled CHF group.

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Current scalable quantum computers require large footprints and complex interconnections due to the design of superconducting qubits. While this architecture is competitive, molecular qubits offer a promising alternative due to their atomic scale and tuneable properties through chemical design. The use of electric fields to precisely, selectively and coherently manipulate molecular spins with resonant pulses has the potential to solve the experimental limitations of current molecular spin manipulation techniques such as electron paramagnetic resonance (EPR) spectroscopy.

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Landmark advances in rare earth (RE) chemistry have shown that divalent complexes can be isolated with non-Aufbau 4f {5d/6s} electron configurations, facilitating remarkable bonding motifs and magnetic properties. We report a series of divalent bis-tethered arene complexes, [RE(NHAr )] (2RE; RE = Sc, Y, La, Sm, Eu, Tm, Yb; NHAr = {N(H)CH-2,6-(CH-2,4,6-Pr)}). Fluid solution EPR spectroscopy gives < 2.

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Reactions between [(Tren)UN] (1, Tren = {N(CHCHNSiPr)}) and [M(η-CR)] (M/R = Cr/H, Mn/H, Fe/H, Ni/H) were intractable, but M/R = Co/H or Co/Me afforded [(Tren)UN-(η:η-CH)Co(η-CH)] (2) and [(Tren)U-NH] (3), respectively. For M/R = V/H [(Tren)U-NV(η-CH)] (4), was isolated. Complexes 2-4 evidence one-/two-electron uranium reductions, nucleophilic nitrides, and partial N-atom transfer.

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The paramagnetism of f-block ions has been exploited in chiral shift reagents and magnetic resonance imaging, but these applications tend to focus on H NMR shifts as paramagnetic broadening makes less sensitive nuclei more difficult to study. Here we report a solution and solid-state (ss) Si NMR study of an isostructural series of locally -symmetric early f-block metal(III) -hypersilanide complexes, [M{Si(SiMe)}(THF)] (; M = La, Ce, Pr, Nd, U); were also characterized by single crystal and powder X-ray diffraction, EPR, ATR-IR, and UV-vis-NIR spectroscopies, SQUID magnetometry, and elemental analysis. Only one SiMe signal was observed in the Si ssNMR spectra of , while two SiMe signals were seen in solution Si NMR spectra of and .

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Mixed-valence dilanthanide complexes of the type (Cp)LnI (Cp = pentaisopropylcyclopentadienyl; Ln = Gd, Tb, Dy) featuring a direct Ln-Ln σ-bonding interaction have been shown to exhibit well-isolated high-spin ground states and, in the case of the Tb and Dy variants, a strong axial magnetic anisotropy that gives rise to a large magnetic coercivity. Here, we report the synthesis and characterization of two new mixed-valence dilanthanide compounds in this series, (Cp)LnI (; Ln = Ho, Er). Both compounds feature a Ln-Ln bonding interaction, the first such interaction in any molecular compounds of Ho or Er.

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Dy(III) bis-cyclopentadienyl (Cp) sandwich compounds exhibit extremely strong single-ion magnetic anisotropy which imbues them with magnetic memory effects such as magnetic hysteresis, and has put them at the forefront of high-performance single-molecule magnets (SMMs). Owing to the great success of design principles focused on maximising the anisotropy barrier, ever higher values have been reported leading to significant slow down of single-phonon Orbach spin relaxation. However, anisotropy-based SMM design has largely ignored two-phonon Raman spin relaxation, which is still limiting the temperatures at which a memory effect can be observed.

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We investigate actinide covalency effects in two [AnCp] (An = Th, U) complexes recently studied with pulsed electron paramagnetic resonance spectroscopy, using the Hyperion package to obtain relativistic hyperfine coupling constants from relativistic multiconfigurational wave functions. H and C HYSCORE simulations using the computed parameters show excellent agreement with the experimental data, highlighting the accuracy of modern relativistic ab initio methods. The extent of covalency indicated from the calculations on [ThCp] is in agreement with the original report based on traditional spectral fitting methods, while the covalency in [UCp] is found to be previously overestimated.

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We examine lanthanide (Ln)-ligand bonding in a family of early Ln complexes [Ln(Cp)] (1-Ln, Ln = La, Ce, Nd, Sm; Cp = CHBu-1,3) by pulsed electron paramagnetic resonance (EPR) methods, and provide the first characterization of 1-La and 1-Nd by single crystal XRD, multinuclear NMR, IR and UV/Vis/NIR spectroscopy. We measure electron spin and relaxation times of 12 and 0.2 μs (1-Nd), 89 and 1 μs (1-Ce) and 150 and 1.

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The decamethyldysprosocenium cation, [Dy(Cp*)] (Cp* = {CMe}), was a target single-molecule magnet (SMM) prior to the isolation of larger dysprosocenium cations, which have recently shown magnetic memory effects up to 80 K. However, the relatively short Dy···Cp* distances of [Dy(Cp*)], together with the reduced resonance of its vibrational modes with electronic states compared to larger dysprosocenium cations, could lead to more favorable SMM behavior. Here, we report the synthesis and magnetic properties of a series of solvated adducts containing bis-halobenzene decamethyldysprosocenium cations, namely [Dy(Cp*)(PhX-κ-)][Al{OC(CF)}] (X = F or Cl) and [Dy(Cp*)(CHF-κ-,)(CHF-κ-)][Al{OC(CF)}].

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Article Synopsis
  • Dysprosium complexes, especially isolated dysprosocenium cations, show potential as single-molecule magnets (SMMs) for high-density data storage, particularly with observable magnetic hysteresis above liquid nitrogen temperatures.
  • The research investigates how equatorial coordination of halobenzenes alters magnetic behavior, which is attributed to increased relaxation mechanisms that depend on halide electronegativity and interaction number.
  • Despite the introduction of transverse fields from halobenzenes, the barriers to magnetization reversal in these complexes remain relatively high and close to those of the original dysprosocenium complex.
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Organoplutonium chemistry was established in 1965, yet structurally authenticated plutonium-carbon bonds remain rare being limited to π-bonded carbocycle and σ-bonded isonitrile and hydrocarbyl derivatives. Thus, plutonium-carbenes, including alkylidenes and N-heterocyclic carbenes (NHCs), are unknown. Here, we report the preparation and characterization of the diphosphoniomethanide-plutonium complex [Pu(BIPMH)(I)(μ-I)] (, BIPMH = (MeSiNPPh)CH) and the diphosphonioalkylidene-plutonium complexes [Pu(BIPM)(I)(DME)] (, BIPM = (MeSiNPPh)C) and [Pu(BIPM)(I)(I)] (, I = C(NMeCMe)), thus disclosing non-actinyl transneptunium multiple bonds and transneptunium NHC complexes.

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The isolation of formally two-coordinate lanthanide (Ln) complexes is synthetically challenging, due to predominantly ionic Ln bonding regimes favoring high coordination numbers. In 2015, it was predicted that a near-linear dysprosium bis(amide) cation [Dy{N(SiPr)}] could provide a single-molecule magnet (SMM) with an energy barrier to magnetic reversal () of up to 2600 K, a 3-fold increase of the record for a Dy SMM at the time; this work showed a potential route to SMMs that can provide high-density data storage at higher temperatures. However, synthetic routes to a Dy complex containing only two monodentate ligands have not previously been realized.

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Article Synopsis
  • Single-molecule magnets have potential for molecular-scale data storage and processing due to their unique magnetization dynamics influenced by electronic and vibrational interactions.
  • A non-perturbative vibronic model is developed to analyze low-energy magnetic behaviors, incorporating both electronic and vibrational aspects in monometallic single-molecule magnets.
  • The formation of magnetic polarons impacts quantum tunneling of magnetization, reducing its probability by stabilizing low-energy spin states, indicating that spin-phonon coupling plays a significant role in magnetic relaxation even at very low temperatures.
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The thermostable four-coordinate divalent lanthanide (Ln) bis-amidinate complexes [Ln(Piso)] (Ln = Tb, Dy; Piso = {(NDipp)CBu}, Dipp = CHPr-2,6) were prepared by the reduction of parent five-coordinate Ln(III) precursors [Ln(Piso)I] (Ln = Tb, Dy) with KC; halide abstraction of [Ln(Piso)I] with [H(SiEt)][B(CF)] gave the respective Ln(III) complexes [Ln(Piso)][B(CF)]. All complexes were characterized by X-ray diffraction, ICP-MS, elemental analysis, SQUID magnetometry, UV-vis-NIR, ATR-IR, NMR, and EPR spectroscopy and CASSCF-SO calculations. These data consistently show that [Ln(Piso)] formally exhibit Ln(II) centers with 4f5d (Ln = Tb, = 8; Dy, = 9) valence electron configurations.

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Molecular materials are poised to play a significant role in the development of future optoelectronic and quantum technologies. A crucial aspect of these areas is the role of spin-phonon coupling and how it facilitates energy transfer processes such as intersystem crossing, quantum decoherence, and magnetic relaxation. Thus, it is of significant interest to be able to accurately calculate the molecular spin-phonon coupling and spin dynamics in the condensed phase.

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Correction for 'Synthesis and characterization of heterometallic rings templated through alkylammonium or imidazolium cations' by Rajeh Alotaibi , , 2023, , 7473-7481, https://doi.org/10.1039/D3DT00982C.

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