Richard E P Winpenny

The University of Manchester · School of Chemistry

Quantum information processing promises to revolutionise computing; quantum algorithms have been discovered that address common tasks significantly more efficiently than their classical counterparts. For a physical system to be a viable quantum computer it must be possible to initialise its quantum state, to realise a set of universal quantum logic...

Correction for ‘Synthesis and characterization of heterometallic rings templated through alkylammonium or imidazolium cations’ by Rajeh Alotaibi et al. , Dalton Trans. , 2023, 52 , 7473–7481, https://doi.org/10.1039/D3DT00982C.

We demonstrate here a synthetic strategy to prepare two distinct trimers of antiferromagnetically coupled {Cr7Ni} rings, substantially varying the magnetic interactions between the spin centres. The interactions were studied using multi‐frequency cw EPR: in a trimer linked via non‐covalent H‐bonding interactions no measurable interaction between ri...

Understanding the (dis)assembly mechanisms of large metallosupramolecules is critical in their design, stability and application. The inherent complexity of these structures leads to many potential pathways for combining (or separating) the constituent building blocks, which makes this task difficult. Here we use collision-induced dissociation mass...

The thermostable four-coordinate divalent lanthanide (Ln) bis-amidinate complexes [Ln(Piso)2] (Ln = Tb, Dy; Piso = {(NDipp)2CtBu}, Dipp = C6H3iPr2-2,6) were prepared by the reduction of parent five-coordinate Ln(III) precursors [Ln(Piso)2I] (Ln = Tb, Dy) with KC8; halide abstraction of [Ln(Piso)2I] with [H(SiEt3)2][B(C6F5)] gave the respective Ln(I...

Quantum information processing promises to revolutionise computing; quantum algorithms have been discovered that address common tasks significantly more efficiently than their classical counterparts. For a physical system to be a viable quantum computer it must be possible to initialise its quantum state, to realise a set of universal quantum logic...

We report the synthesis and structural characterization of a series of heterometallic rings templated via alkylammonium or imidazolium cations. The template and preference of each metal's coordination geometry can control the structure of heterometallic compounds, leading to octa-, nona-, deca-, dodeca-, and tetradeca-metallic rings. The compounds...

NMR spectroscopy is the standard method for establishing chemical structure in solution but relies on the compound being diamagnetic. When a compound is paramagnetic, NMR resonances are broad-ened and structural information lost. Other methods such as diffuse light scattering can establish the size of a compound but gives little structural informat...

Gadolinium is a special case in spectroscopy because of the near isotropic nature of the 4f7 configuration of the +3 oxidation state. Gd3+ complexes have been studied in several symmetries to understand the underlying mechanisms of the ground state splitting. The abundance of information in Gd3+ spectra can be used as a probe for properties of the...

We report two dichloride‐bridged dinuclear dysprosium(III) complexes based on salen ligands, namely, [Dy(L1)(μ‐Cl)(thf)]2 (1; H2L1 = N,Nʹ‐bis(3,5‐di‐tert‐butylsalicylidene)phenylenediamine) and [Dy2(L2)2(μ‐Cl)2(thf)2]2 (2; H2L2 = N,Nʹ‐bis(3,5‐di‐tert‐butylsalicylidene)ethylenediamine). These two complexes have two short Dy−O(PhO) bonds that have an...

Following electrospray ionization, it is common for analytes to enter the gas phase accompanied by a charge-carrying ion, and in most cases, this addition is required to enable detection in the mass spectrometer. These small charge carriers may not be influential in solution but can markedly tune the analyte properties in the gas phase. Therefore,...

Here we report the synthesis and structural characterization of four [7]rotaxanes formed by coordinating hybrid inorganic–organic [2]rotaxanes to a central {Ni12} core. X-ray single crystal diffraction demonstrate that [7]rotaxanes are formed, with a range of conformations in the crystal. Small angle X-ray scattering supported by molecular dynamic...

Understanding the (dis)assembly mechanisms of large metallosupramolecules is critical in their design, stability and diverse applications. Yet this task is difficult because of the inherent complexity of the structures, with many potential pathways of combining (or separating) the constituent building blocks. Here, we use collision-induced dissocia...

Addition of 1,4,8,11-tetrazacyclotetradecane (cyclam) to a reaction that produces octametallic rings when simpler amines are used, produces {Cr 11 M 2 } “pretzels” (M = Zn II or Cu II ) where the cyclam coordinates to the...

Understanding the fundamental reactivity of polymetallic complexes is challenging due to the complexity of their structures with many possible bond breaking and forming processes. Here, we apply ion mobility mass spectrometry coupled with density functional theory to investigate the disassembly mechanisms and energetics of a family of heterometalli...

Metal-organic materials such as [NH2(CH2-CH=CH2)2][Cr7NiF8(Pivalate)16] can act as negative tone resists for electron beam lithography (EBL) with high-resolution patterning of sub-40 nanometer pitch while exhibiting ultrahigh dry etch selectivities >100:1 and giving line dose exposures >11,000 pC/cm. It is clear that the resist sensitivity is too l...

Following electrospray ionization (ESI), it is common for analytes to enter the gas phase accompanied by an additional small ion or molecule. Although these may not be influential in solution, they often determine the charge of the entire complex and can markedly tune their properties in the gas phase. Therefore, measuring their relative influence...

Systems with weak dipolar interactions have the potential to be used for molecular quantum computing. Orientation selective pulsed EPR was used to model the conformational flexibility of a molecular multi-qubit model system. Spectrally addressable centres allowed for the individual manipulation of each spin qubit, while differing relaxation dynamic...

Dipolar coupled multi‐spin systems have the potential to be used as molecular qubits. Herein we report the synthesis of a molecular multi‐qubit model system with three individually addressable, weakly interacting, spin centres of differing g‐values. We use pulsed Electron Paramagnetic Resonance (EPR) techniques to characterise and separately addres...

We report a supramolecule that contains five spins of two different types and with, crucially, two different and predictable interaction energies between the spins. The supramolecule is characterized, and the interaction energies are demonstrated by electron paramagnetic resonance (EPR) spectroscopy. Based on the measured parameters, we propose exp...

Polymer beads have been used as the core of magnetic particles for around twenty years. Here we report studies to attach polymetallic complexes to polymer beads for the first time, producing beads of around 115 microns diameter that are attached to 1014 hybrid inorganic-organic [2]rotaxanes. The bead is then formally a [1014] rotaxane. The number o...

Understanding the fundamental reactivity of polymetallic complexes is challenging due to the complexity of their structures with many possible bond breaking and forming processes. Here we apply ion mobility mass spectrometry (IM-MS) coupled with density functional theory (DFT) to investigate the disassembly mechanisms and energetics of a family of...

Four new {Cr8} rings have been synthesized and characterized; they are all based on the classic [CrF(O2CtBu)2]8 ring 1. Three routes have been studied. The first is direct synthesis, by reacting hydrated chromium(III) fluorides with the acid; this has been used to produce LS[CrF(O2CEt)2]8 3. The second route uses 3 as a precursor and substitute wit...

A new class of electron bean negative tone resist materials has been developed based on heterometallic rings. The initial resist performance demonstrates a resolution of 15 nm half‐pitch but at the expense of a low sensitivity. To improve sensitivity a 3D Monte Carlo simulation is used that utilizes a secondary and Auger electron generation model....

Polymer beads have been used as the core of magnetic particles for around twenty years. Here we report studies to attach polymetallic complexes to polymer beads for the first time, producing beads of around 115 microns that are attached to 10^14 hybrid inorganic-organic [2]rotaxanes. The bead is then formally a [10^14] rotaxane. The number of compl...

Polymer beads have been used as the core of magnetic particles for around twenty years. Here we report studies to attach polymetallic complexes to polymer beads for the first time, producing beads of around 115 microns that are attached to 10^14 hybrid inorganic-organic [2]rotaxanes. The bead is then formally a [10^14] rotaxane. The number of compl...

Supramolecular chemistry has grown rapidly over the past three decades, yet synthetic supramolecular chemists still face several challenges when it comes to characterising their compounds. In this review, we present an introduction to structural characterisation techniques commonly used for non-crystalline supramolecular molecules, e.g. nuclear mag...

Three distorted tetrahedral Dy(III) aryloxide complexes, [Na(THF)6][Dy(OArAd2tBu)2Cl2] (1) (OArAd2tBu = OC6H2Adamantyl2-2,6-tBu-4) and [Na(THF)6][Dy(OMes*)3X] (X = Cl, 2; BH4, 3), (OMes* = OC6H2tBu3-2,4,6) exhibit easy axis magnetic anisotropy and slow magnetic...

We discuss a cost-effective approach to understand magnetic relaxation in the new generation of rare-earth single-molecule magnets. It combines ab initio calculations of the crystal field parameters, of the magneto-elastic coupling with local modes, and of the phonon density of states with fitting of only three microscopic parameters. Although much...

The implementation of a quantum computer requires both to protect information from environmental noise and to implement quantum operations efficiently. Achieving this by a fully fault-tolerant platform, in which quantum gates are implemented within quantum-error corrected units, poses stringent requirements on the coherence and control of such hard...

Mononuclear lanthanide (Ln) complexes can be high‐performing single‐molecule magnets (SMMs). Recently, there has been an influx of mononuclear Ln alkoxide and aryloxide SMMs. Here, mononuclear DyIII alkoxide and aryloxide SMMs with coordination numbers up to eight are covered in detail, with additional brief overviews of TbIII, HoIII, ErIII and YbI...

Gold(i) bridged dimeric and trimeric structures of a ground state spin S = 1/2 heterometallic {Cr7Ni} wheel have been prepared and studied by continuous wave (CW) and pulsed wave EPR spectrometry. The {Cr7Ni} relaxation time constants (T1 and Tm) show rates matching well with previous observations. Four pulse Double Electron Resonance (DEER) studie...

Recent studies have shown that mononuclear lanthanide (Ln) complexes can be high‐performing single‐molecule magnets (SMMs). Recently, there has been an influx of mononuclear Ln alkoxide and aryloxide SMMs, which have provided the necessary geometrical control to improve SMM properties and to allow the intricate relaxation dynamics of Ln SMMs to be...

The longest finite chain of metals is reported and the magnetic properties studied and modelled. Abstract A finite chain of thirty‐one paramagnetic centers is reported, synthesized by reaction of hydrated chromium fluoride, copper carbonate and pivalic acid in the presence of 1,4,7,10‐tetrazacyclododecane (cyclen). Magnetic studies show predominan...

p class="Abstract" style="margin: 0cm 0cm 12pt; text‐align: justify; line‐height: 11.25pt; font‐size: 8pt; font‐family: Arial, sans‐serif; caret‐color: rgb(0, 0, 0); color: rgb(0, 0, 0);">A finite chain of thirty‐one paramagnetic centers is reported, synthesised by reaction of hydrated chromium fluoride, copper carbonate and pivalic acid in the pre...

An accurate experimental characterization of finite antiferromagnetic (AF) spin chains is crucial for controlling and manipulating their magnetic properties and quantum states for potential applications in spintronics or quantum computation. In particular, finite AF chains are expected to show a different magnetic behaviour depending on their lengt...

The discovery of magnetic bistability in Mn$_{12}$ more than 20 years ago marked the birth of molecular magnetism, an extremely fertile interdisciplinary field and a powerful route to create tailored magnetic nanostructures. However, the difficulty to determine interactions in complex polycentric molecules often prevents their understanding. Mn$_{1...

The very recent literature on single molecule magnets is reviewed. The focus is on single molecule magnets (SMMs) that show high energy barriers to relaxation of magnetisation. The first section covers monometallic dysprosium based SMMs and shows correlations between the energy barrier and structural parameters. The second section includes a discus...

An approach is presented for nanoscale patterning of zinc oxide (ZnO) using electron beam (e-beam) lithography for future nanoelectronic devices and for hard lithographic masks. Zinc acetate (Zn₄O(CH₃COO)₆) films were exposed using a scanning electron microscope (SEM), causing decomposition of Zn₄O(CH₃COO)₆ into ZnO. The exposure of Zn₄O(CH₃COO)₆ u...

A series of heterometallic [TiIV7MIII] rings are reported which contain a single paramagnetic metal centre, either FeIII or CrIII. The structures contain an octagon of metals bridged by oxides within the ring and pivalate ligands outside the ring. The structures encapsulate a single cation, either a secondary ammonium cation or a cesium. Multi-freq...

We present a ¹H NMR investigation of spin dynamics in two finite integer spin molecular nanomagnetic rings, namely V7Zn and V7Ni. This study could be put in correlation with the problem of Haldane gap in infinite integer spin chains. While V7Zn is an approximation of a homometallic broken chain due to the presence of s = 0 Zn²⁺ ion uncoupled from n...

We report the synthesis and characterization of two symmetric homo-dimetallic lanthanide complexes based on methyl-substituted 8-hydroxyquinoline (HMeQ). The aryloxo-bridged core gives rise to weak magnetic coupling between pairs of ErIII and YbIII ions, as revealed by magnetic and EPR spectroscopy studies. EPR measurements of magnetically dilute s...

Four 3d-4f hetero-polymetallic complexes [Fe2Ln2((OCH2)3CR)2(O2C t Bu)6(H2O)4] (where Ln = La (1 and 2) and Gd (3 and 4); and R = Me (1 and 3) and Et (2 and 4)) are synthesized and analyzed using elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, and SQUID magnetometry. Crystal structures are obtained for both...

The synthesis, structures and properties of [4]- and [3]-rotaxane complexes are reported where [2]rotaxanes, formed from het-erometallic {Cr7Ni} rings, are bound to a fluoride-centered {CrNi2} triangle. The compounds have been characterized by sin-gle crystal X-ray diffraction and have the formulae [CrNi2(F)(O2CtBu)6]{(BH)[Cr7NiF8(O2CtBu)16]}3 (3)...

Paul O'Brien, known affectionately as ‘POB’, was one of the most imaginative and creative materials chemists of his generation. He brought a deep understanding and knowledge of classical coordination chemistry to bear on routes to thin films and nanoparticles of technologically important materials, particularly metal chalcogenides. His development...

Here we report stable p-quinone-radical-bridged rare-earth complexes involving the ligand tetramethylquinone (QMe4•-). The complexes, {Y[(QMe4)•-Cl2(THF)3]}2 (1) and {Gd[(QMe4)•-Cl2(THF)3]}2 (2), where THF = tetrahydrofuran, are sufficiently stable that we can measure the single-crystal structures and perform magnetic and electron paramagnetic reso...

We report a new family of five‐coordinate Lanthanide Single‐Molecule Magnets (Ln SMMs) [Dy(Mes*O) 2 (THF) 2 X] (Mes*= 2,4,6‐tri‐tert‐butylphenyl; X = Cl, 1 ; Br, 2 ; I, 3 ) with energy barriers to magnetic reversal amongst the highest reported for any SMM to date. The five‐coordinate Dy(III) ions have distorted square pyramidal geometries, with hal...

A dichlorido-bridged dinuclear dysprosium(III) single-molecule magnet [Dy 2 L 2 ( µ -Cl) 2 (THF) 2 ] has been made using a diamine-bis(phenolate) ligand, H 2 L. Magnetic studies show an energy barrier for magnetization reversal ( U eff ) around 1000 K. Exchange-biasing effect is clearly seen in magnetic hysteresis with steps up to 3 K. Ab initio ca...

Dysprosiacarborane complexes based on the interaction between η⁵-dicarbollide ligands [C2B9H11²⁻ and (o-xylylene-C2B9H9)²⁻] and the dysprosium(III) cation show large effective energy barriers for slow magnetic relaxation and a magnet-type hysteresis loop up to 6.8 K, which may provide a new type of organometallic ligand for the design of high-perfo...

The dicarbollide ion, nido ‐C 2 B 9 H 11 2‐ is isoelectronic with cyclopentadienyl. Here we make dysprosiacarboranes, namely [(C 2 B 9 H 11 ) 2 Ln(THF) 2 ][Na(THF) 5 ] (Ln = Dy, 1Dy ) and [(THF) 3 ( μ ‐H) 3 Li] 2 [{ η 5 ‐C 6 H 4 (CH 2 ) 2 C 2 B 9 H 9 }Dy{ η 2 :η 5 ‐C 6 H 4 (CH 2 ) 2 C 2 B 9 H 9 } 2 Li] 3Dy and show that dicarbollide ligands impose...

An accurate experimental characterization of finite antiferromagnetic (AF) spin chains is crucial for controlling and manipulating their magnetic properties and quantum states for potential applications in spintronics or quantum computation. In particular, finite AF chains are expected to show a different magnetic behaviour depending on their lengt...

Though the development of SMMs is rapid, there are only two families of high Ueff Dy(III) SMMs known so far: the cyclopentadienyl (Cp) family with sandwich structure and the pentagonal–bipyramidal (PB) family with D5h symmetry. We show here the latter family with the common formulae DyX1X2(Le)5]+ can be readily fine tuned with a range of axial and...

A dichlorido-bridged dinuclear dysprosium(III) single-molecule magnet [Dy₂L₂( µ -Cl)₂(THF)₂] has been made using a diamine-bis(phenolate) ligand, H₂L. Magnetic studies show an energy barrier for magnetization reversal ( U _eff) around 1000 K. Exchange-biasing effect is clearly seen in...

Dicarbollide ion, nido-C₂B₉H₁₁^2- is isoelectronic with cyclopentadienyl. Here we make dysprosiacarboranes, namely [(C₂B₉H₁₁)₂Ln(THF)₂][Na(THF)₅] (Ln = Dy, 1Dy ) and [(THF)₃(μ-H)₃Li]₂[{η⁵-C<sub>6</...

Low coordinate metal complexes can exhibit superlative physicochemical properties, but this chemistry is challenging for the lanthanides (Ln) due to their tendency to maximize electrostatic contacts in predominantly ionic bonding regimes. Although a handful of Ln2+ complexes with only two monodentate ligands have been isolated, examples in the most...

Field emission devices are promising candidates to replace silicon FinFETs as next-generation nanoelectronic components. For these devices to be adopted, nanoscale field emitters with nanoscale gaps between them need to be fabricated, requiring the transfer of e.g. sub-10 nm patterns with sub-20 nm pitch into substrates like silicon and tungsten. N...

Molecules that are the size of small proteins are difficult to make. The most frequently examined route is via self-assembly, and one particular approach involves molecular nano-capsules, where ligands are designed that will enforce the formation of specific polyhedra of metals within the core of the structure. Here we show that this approach can b...

We report a family of hybrid [2]rotaxanes based on inorganic [Cr7NiF8(O2C t Bu)16]- ("{Cr7Ni}") rings templated about organic threads that are terminated at one end with pyridyl groups. These rotaxanes can be coordinated to [Cu(hfac)2] (where Hhfac = 1,1,1,5,5,5-hexafluoroacetylacetone), to give 1:1 or 1:2 Cu:{Cr7Ni} adducts: {[Cu(hfac)2](py-CH2NH2...

Exposure of SO2 and H2S gases to green crystals of [CrF(O2CtBu)2]8 Cr8 metallacrown results in the binding of the gas molecules in the internal molecular cavity, despite the absence of any pores or channels in the structure. Single crystal X-ray diffraction studies show that the gas molecules bind weakly to the bridging fluoride ligands. The desorp...

The proposal that paramagnetic transition metal complexes could be used as qubits for quantum information processing (QIP) requires that the molecules retain the spin information for a sufficient length of time to allow computation and error correction. Therefore, understanding how the electron spin-lattice relaxation time (T1) and phase memory tim...

We report a six coordination Dy III single-molecule magnet (SMM) with an energy barrier of 1110 K for thermal relaxation of magnetization. The pure compound shows no retention of magnetization even...

Supramolecular Coordination Compounds (SCCs) represent the power of Coordination Chemistry methodologies to self-assemble discrete architectures with targeted properties. SCCs are generally synthesised in solution, with isolat-ed fully-coordinated metal atoms as structural nodes, thus severely limited as metal-based catalysts. Metal-Organic Framewo...

A simplified uniaxial anisotropic Heisenberg model is proposed which describes the observed magnetic properties of a family of the Cr 7 M (M = Cd, Ni, Mn) molecular rings, and allows the determination of the coupling parameters which are all transferable among this family of molecular nanomagnets.

We report magnetic hysteresis studies of three Dy(III) single-molecule magnets (SMMs). The three compounds are [Dy(tBuO)Cl(THF)5][BPh4] (1), [K(18-crown-6-ether)(THF)2][Dy(BIPM)2] (2, BIPM = C{PPh2NSiMe3}2), and [Dy(Cpttt)2][B(C6F5)4] (3), chosen as they have large energy barriers to magnetisation reversal of 665, 565, and 1223 cm-1, respectively....

We report an empirical correlation between the blocking temperature of large energy barrier SMMs and the relaxation time at the point where the Raman and Orbach relaxation mechanisms have the...