The Chilton Group

Design of high-temperature single-molecule magnets

The volume of stored digital information is increasing exponentially, and the economic and environmental costs could be mitigated by increasing data densities by orders of magnitude. In place of standard storage media, data could potentially be stored in individual molecules on the nanoscale using single-molecule magnets (SMMs). Molecular data storage could dramatically increase data densities, but memory must persist at economically viable temperatures. We have pioneered approaches for designing some of the best-performing SMMs known, and we are now working to understand in more detail the origins of magnetic relaxation (the process by which magnetic information is lost) to further improve magnetic memory in molecules.

• The first near-linear bis(amide) f-block complex: a blueprint for a high temperature single molecule magnet
• Design Criteria for High-Temperature Single-Molecule Magnets
• On Approaching The Limit of Molecular Magnetic Anisotropy: A Near-Perfect Pentagonal Bipyramidal Dy^III Single-Molecule Magnet
• Molecular magnetic hysteresis at 60 kelvin in dysprosocenium
• Field- and temperature-dependent quantum tunnelling of the magnetisation in a large barrier single-molecule magnet
• Correlating Blocking Temperatures with Relaxation Mechanisms in Single-Molecule Magnets
• Studies of Hysteresis and Quantum Tunnelling of the Magnetisation in Dysprosium(III) Single Molecule Magnets
• A Bis-Monophospholyl Dysprosium Cation Showing Magnetic Hysteresis at 48 Kelvin
• Ab initio prediction of high-temperature magnetic relaxation rates in single-molecule magnets
• Ultrahard magnetism from mixed-valence dilanthanide complexes with metal–metal bonding
• Strong Axiality in a Dysprosium(III) Bis(borolide) Complex Leads to Magnetic Blocking at 65 K
• Measurement of the Quantum Tunnelling Gap in a Dysprosocenium Single-Molecule Magnet

Understanding paramagnetic MRI contrast agents

Non-invasive bioimaging has revolutionised healthcare, and developing more sensitive and informative probes is paramount for early detection in a wide range of diseases. We are investigating prototype MRI contrast agents using a range of measurements and computational techniques to understand how molecules can be designed to elicit more diagnostic information from a single MRI scan.

• Spectroscopic and crystal field consequences of fluoride binding by [Yb.DTMA]³⁺ in aqueous solution
• Rationalisation of anomalous pseudo-contact shifts and their solvent dependence in a series of C₃-symmetric lanthanide complexes
• Lanthanide-induced relaxation anisotropy
• Exquisite Sensitivity of The Ligand Field to Solvation and Donor Polarisability in Coordinatively Saturated Lanthanide Complexes
• Sensitivity of Magnetic Anisotropy in the Solid State for Lanthanide Complexes with Small Crystal Field Splitting
• Periodic trends and hidden dynamics of magnetic properties in three series of triazacyclononane lanthanide complexes
• Unravelling the Complexities of Pseudocontact Shift Analysis in Lanthanide Coordination Complexes of Differing Symmetry
• How the Ligand Field in Lanthanide Coordination Complexes Determines Magnetic Susceptibility Anisotropy, Paramagnetic NMR Shift and Relaxation Behaviour
• Determination of molecular hydration in solution via changes in magnetic anisotropy

Designing molecular spin qubits for quantum information

Of the many potential implementations of quantum bits (qubits), molecular spin qubits are particularly favourable: e.g. they have a low fabrication cost, are perfectly identical and are chemically tuneable. Furthermore, they can be engineered to be robust against magnetic noise and exhibit quantum coherence times rivalling solid state qubits. We are investigating how they can be protected from other environmental degrees of freedom such as vibrational noise, such that they maintain their coherence properties in device-like architectures.

• Measuring spin···spin interactions between heterospins in a hybrid [2]rotaxane
• Engineering electronic structure to prolong relaxation times in molecular qubits by minimising orbital angular momentum
• Analysis of vibronic coupling in a 4f molecular magnet with FIRMS
• HYPERION: A New Computational Tool for Relativistic Ab Initio Hyperfine Coupling

Methods and tools for modelling magnetic properties

We are active in developing computational approaches for modelling, understanding, and predicting magnetic properties, which are implemented in three popular codes: PHI, MAGELLAN and CC-FIT2. We have also recently developed tools for calculating hyperfine coupling from first principles using CASSCF-SO methods, and calculating spin-phonon or vibronic coupling parameters analytically.

• PHI: A powerful new program for the analysis of anisotropic monomeric and exchange-coupled polynuclear d- and f-block complexes
• PHI software
• An electrostatic model for the determination of magnetic anisotropy in dysprosium complexes
• MAGELLAN software
• Uncertainty Estimates for Magnetic Relaxation Times and Magnetic Relaxation Parameters
• CC-FIT2 software
• Extraction of "hidden" relaxation times from AC susceptibility data
• Assessment of minimal active space CASSCF-SO methods for calculation of atomic Slater-Condon and spin-orbit coupling parameters in d- and f-block ions
• HYPERION: A New Computational Tool for Relativistic Ab Initio Hyperfine Coupling
• An analytic linear vibronic coupling method for first-principles spin-dynamics calculations in single-molecule magnets

Intramolecular magnetic interactions

We are interested in the fundamental intramolecular magnetic interactions that occur within complexes of d- or f-elements. This work encompasses both measurement and theory, and attempts to find appropriate models or rules that govern such interactions.

• Direct measurement of dysprosium(III)···dysprosium(III) interactions in a single-molecule magnet
• Analysis of Lanthanide-Radical Magnetic Interactions in Ce(III) 2,2′-Bipyridyl Complexes
• Measurement of Magnetic Exchange in Asymmetric Lanthanide Dimetallics: Toward a Transferable Theoretical Framework
• Assessing Crystal Field and Magnetic Interactions in Diuranium-μ-Chalcogenide Triamidoamine Complexes With U^IV-E-U^IV Cores (E = S, Se, Te): Implications for Determining the Presence or Absence of Actinide-Actinide Magnetic Exchange
• A Perfect Triangular Dysprosium Single-Molecule Magnet with Virtually Antiparallel Ising-like Anisotropy
• Magnetic Exchange Interactions in Symmetric Lanthanide Dimetallics
• Opening magnetic hysteresis by axial ferromagnetic coupling: from mono-decker to double-decker metallacrown
• Organometallic Lanthanide Bismuth Cluster Single-Molecule Magnets
• Ultrahard magnetism from mixed-valence dilanthanide complexes with metal–metal bonding
• Determinative Effect of Axial Linearity on Single-Molecule Magnet Performance in Dinuclear Dysprosium Complexes
• Taming Super-Reduced Bi₂³⁻ Radicals with Rare Earth Cations
• A Trinuclear Gadolinium Cluster with a Three-Center One-Electron Bond and an S = 11 Ground State

Unravelling the electronic structure of uranium molecules

We are using a huge array of physical techniques combined with theoretical modelling to shed light on the detailed electronic structure of uranium molecules. Such a fundamental study aims to provide information on physical and chemical properties of the heaviest elements, towards strategies for remediation and repurposing of nuclear waste.

• Molecular and Electronic Structure of Terminal and Alkali Metal-Capped Uranium(V)-Nitride Complexes
• Assessing Crystal Field and Magnetic Interactions in Diuranium-μ-Chalcogenide Triamidoamine Complexes With U^IV-E-U^IV Cores (E = S, Se, Te): Implications for Determining the Presence or Absence of Actinide-Actinide Magnetic Exchange
• Rare Earth- and Uranium-Mesoionic Carbenes: A New Class of f-Block Carbene Complex Derived from an N-Heterocyclic Olefin
• Anomalous Magnetism of Uranium(IV)-Oxo and -Imido Complexes Reveals Unusual Doubly-Degenerate Electronic Ground States
• Investigation of the Electronic Structure and Optical Spectra of Uranium-(IV), -(V) and -(VI) Complexes Using Multi-configurational Methods