Atom-by-atom control for the targeted chemical synthesis of heterometallic molecular nanomagnets

Lead Research Organisation: University of Glasgow
Department Name: School of Chemistry

Abstract

Current magnetic materials are made using a 'top-down' approach. A random distribution of grains is dispersed across the hard drive surface: the media itself is featureless and the write head defines the bit locations. These magnetic particles (grains) cannot continue to decrease in size indefinitely as the thermal energy will become sufficient to flip the magnetisation of the magnetic domain, leading to data loss. Therefore, it is imperative that new magnetic materials are developed. If the bit size is to decrease further towards a few nanometres, we move into the realm of magnetic molecules, which are easy to synthesise, cheap and are monodisperse, allowing for self-assembly of an array of molecular bits on a surface. However, current synthetic approaches to these magnetic molecules rely heavily upon the random assembly of transition metal ions from a reaction mixture containing organic ligands. This method affords little synthetic control over the reaction product and hence, little control over the resultant magnetic properties of the molecule. Therefore, these magnetic molecules display their interesting properties only at very low temperatures. To increase the so-called blocking temperature, we need much greater control over their synthesis.We will use a step-by-step self-assembly synthetic approach to prepare improved molecular nanomagnets (single-molecule magnets or SMMs). We will track the assembly of these molecules in solution, from their carefully designed precursors, using mass spectrometry. This technique will allow us to control the synthesis of heterometallic complexes, which will contain between two and four different types of magnetic ions. We will be able to control exactly where each type of ion resides within the magnetic molecule, e.g. producing core-shell structures. This level of synthetic control will allow us to control both the magnetic exchange coupling and the magnetic anisotropy. This incredible level of control over the key magnetic properties will allow us to synthesise single-molecule magnets with unprecedented structures and blocking temperatures that surpass the current world record.

Planned Impact

Data storage represents a huge market force, but current magnetic materials are rapidly approaching their fundamental limit and it is imperative that new magnetic materials are developed. In order to reach even higher density, it is necessary to make smaller and smaller bits. If the bit size is to decrease further towards a few nanometres, we move into the realm of magnetic molecules, where properties can be designed by building up a molecule one magnetic atom at a time. Magnetic molecules are easy to synthesise, cheap and are monodisperse, allowing for self-assembly of an array of molecular bits on a surface. In the long term, the microelectronics / nano-fabrication industries will be the major beneficiaries of this research at all levels from multi-nationals to SMEs and spinout companies. In addition UK HEIs, students and the general public will also be beneficiaries, not to mention the UK-plc as a whole. Industry: Micro- / nanoelectronics are everywhere and very few people do not use any electronic technologies: new molecule-based technologies offer the promise of a disruptive technology for tomorrow's society, and their study triggers new fundamental research in emerging fields. The field of molecular magnetism is strongly connected with other nanosciences. The molecular approach can be exploited in the preparation of magnetic nanostructures, like nanoparticles, wires, or layers for use in industrial (semiconductor / microelectronics / nano-fabrication) or biomedical applications. A key advantage of the molecular approach to magnetism is the potential to remove non-uniformity and variability in devices, as one magnetic molecule will be exactly the same as the next. Also, this monodispersity will permit self-assembly of an array of molecular bits on a surface to overcome the challenges of patterning a magnetic film into nm-scale islands. These molecular systems could be of interest to SMEs and spin-outs in the development of niche applications such as magnetic refrigeration, magneto-optical data storage, novel MRI contrast agents and molecular spintronic devices or as components of 3rd party applications such as magneto-optical switches or sensors. The race towards the molecular limit is gathering pace and this research will produce a highly skilled scientist and add to the future economic competitiveness of the UK in a knowledge-based economy.

Publications

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Heras Ojea MJ (2015) Directed synthesis of {Cu2(II)Zn2(II)} and {Cu8(II)Zn8(II)} heterometallic complexes. in Dalton transactions (Cambridge, England : 2003)

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Heras Ojea MJ (2016) Enhancement of Tb(III) -Cu(II) Single-Molecule Magnet Performance through Structural Modification. in Chemistry (Weinheim an der Bergstrasse, Germany)

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Milway VA (2013) Directed synthesis of {Mn18Cu6} heterometallic complexes. in Angewandte Chemie (International ed. in English)

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Ojea MJH (2017) A topologically unique alternating {CoGd} magnetocaloric ring. in Chemical communications (Cambridge, England)

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Quinn S (2016) Surface Charge Control of Quantum Dot Blinking in The Journal of Physical Chemistry C

 
Description A new building-block approach for the preparation of heterometallic complexes with unprecedented structures. Using this approach, we have designed single molecule magnets, where the magnetic properties can be designed at the molecular level by using two different metal ions. This has led to a series of copper/lanthanide complexes that display single-molecule magnet behaviour that can be tuned in terms of both the topology of the complex and the individual lanthanide shape. Furthermore, we have shown how quantum tunneling, which destroys the magnetic properties, of lanthanide ions can be controlled by coupling the lanthanide ion to copper ions. We have found our synthetic approach can also be applied to design new materials for low temperature magnetic refrigerants by controlling the molecular structure, discovering one of the best molecule-based low temperature magnetic refrigerants in terms of cooling power. This research is important in order to find new low temperature refrigerants to replace systems such as those based on expensive 3He. Overall, this research contributes to the design and understanding of new high-technology molecule-based materials, which have potential long term applications in diverse areas such as ultra-high-density information storage, low temperature refrigeration or the emerging field of molecular spintronics.
Exploitation Route Our directed assembly synthetic methodology is adaptable and hence, will have wide appeal within the fields of not only molecular magnetism, but also coordination / inorganic / supramolecular / materials chemistry and crystal engineering. The magnetocaloric complex {Co3Gd3} published in Chem. Commun. (2017, 53, 4799) demonstrates a new synthetic approach to low temperature magnetic refrigerants.
Sectors Chemicals

URL http://www.chemistryviews.org/details/ezine/4308901/Angewandte_Chemie_72013_Everything_under_Control.html
 
Description College of Science and Engineering Studentship Bank
Amount £63,000 (GBP)
Organisation University of Glasgow 
Sector Academic/University
Country United Kingdom
Start 11/2013 
End 04/2017
 
Title Enhancement of TbIII-CuII single-molecule magnet performance through structural modification 
Description  
Type Of Material Database/Collection of data 
Year Produced 2016 
Provided To Others? Yes  
 
Title Rational serendipity: "undirected" synthesis of a large MnIII10CuII5 complex from pre-formed MnII building blocks 
Description  
Type Of Material Database/Collection of data 
Year Produced 2016 
Provided To Others? Yes  
 
Title Synthesis and magnetic studies of two Cu(II)/Zn(II) heterometallic complexes using bis-tris propane as a multidentate ligand. 
Description  
Type Of Material Database/Collection of data 
Year Produced 2015 
Provided To Others? Yes  
 
Description Computational studies 
Organisation Indian Institute of Technology Bombay
Country India 
Sector Academic/University 
PI Contribution We synthesized and characterized the samples, in particular using single-crystal X-ray diffraction.
Collaborator Contribution They used the single-crystal X-ray diffraction data to calculate key magnetic parameters such as the magnetic anisotropy.
Impact The collaboration brings computational chemistry (DFT and ab initio) expertise. Output = DOI: 10.1039/C7SC04460G.
Start Year 2016
 
Description Electrochem 
Organisation University of Tsukuba
Country Japan 
Sector Academic/University 
PI Contribution provision of samples for measurement
Collaborator Contribution measurement of samples (electrochemistry)
Impact Offshoot in the area of water oxidation catalysis by our molecules
Start Year 2013
 
Description HFEPR 
Organisation US National High Magnetic Field Laboratory
Country United States 
Sector Public 
PI Contribution Synthesis of samples for high-field high-frequency EPR
Collaborator Contribution Measurement of samples for high-field high-frequency EPR and data interpretation
Impact DOI: 10.1039/B807447J Multidisciplinary: Chemistry & Physics
Start Year 2006
 
Description INS 
Organisation Paul Scherrer Institute
Country Switzerland 
Sector Public 
PI Contribution Synthesis of samples for inelastic neutron scattering (INS)
Collaborator Contribution Measurement of INS spectra and interpretation of data
Impact Output DOI: 10.1021/ic500885r Multidisciplinary: chemistry & physics
Start Year 2012
 
Description Magnetocalorics 
Organisation University of Zaragoza
Country Spain 
Sector Academic/University 
PI Contribution We synthesized and characterized the new material, and provided samples for further measurements. We co-wrote the manuscript.
Collaborator Contribution They performed heat capacity measurements and analyzed the data. They co-wrote the manuscript.
Impact This collaboration brings expertise in condensed matter physics (low temperature magnetic refrigeration). Output = DOI: 10.1039/C7CC02243C
Start Year 2014
 
Description MicroSQUID 
Organisation National Center for Scientific Research (Centre National de la Recherche Scientifique CNRS)
Department Grenoble High Magnetic Field Laboratory
Country France 
Sector Public 
PI Contribution Synthesis of samples (single crystals) for ultra-low temperature magnetic measurements
Collaborator Contribution Measurement of magnetic properties of samples (single crystals) at ultra-low temperatures
Impact DOI: 10.1021/ic500885r Multidisciplinary: chemistry & physics