Spin-Crossover Compounds: Switchable Materials from Simple Metal Complexes

Spin-crossover is a high-spin-to-low-spin transition at a transition metal centre, in response to a change in temperature or pressure. This is common in some types of transition metal compound, and especially in iron chemistry. While the molecules in a material undergo spin-crossover individually, it leads to large changes in their size and shape which are propagated through the material in the solid state. <br /> <br /> As one molecule undergoes the transition and changes its size, it causes a change in pressure in the crystal lattice that in turn promotes the transition in its nearest neighbours. These effects are transmitted through a crystal lattice at differing rates, depending on the strength of the interactions between molecules. Hence, whether a particular material undergoes spin-crossover abruptly or gradually, with temperature or with time, is controlled by its crystal packing. As such, spin-crossover materials are good test-beds for theories about crystal engineering.<br /> <br /> Spin-crossover transtions also affect several physical properties of a solid material including its colour, magnetic moment, dielectric constant, hardness and size. These properties have been harnessed in materials applications such as thermochromic inks; stimuli-responsive polymers; switchable microwave absorbers; and solid state refrigeration. Moreover, nanostructures of spin-crossover materials retain their switching properties down to 30 nm length scales, and spin-crossover in single molecules has been detected inside a scanning tunneliing microscope (STM). Spin-crossover nanomaterials science is becoming increasingly sophisticated, and SCO nanoparticle constructs have performed well in prototype binary memory devices.<br /> <br /> Some spin-crossover materials also exhibit thermal hysteresis in their transitions; these are most suitable for the applications mentioned above. Whether a compound undergoes spin-crossover gradually or abruptly, with or without hysteresis, is controlled by the crystal packing in the bulk material rather than the molecule itself. We aim to understand the relationship between structure and function, so we can design new spin-crossover materials from scratch. We are also pursuing different ways to incorporate new functionality into spin-crossover materials.<br /> <br /> We have projects in various aspects of this chemistry, involving organic and inorganic synthesis; crystallography and powder diffraction; solid and solution-phase magnetic measurements; and other techniques as appropriate. Current goals include understanding the principles for designing spin-crossover crystals with bespoke switching properties; new liquid crystals and other soft materials showing spin-crossover switching properties; and, understanding and developing solid state refrigeration by spin-crossover materials.<br /> <br /> You can find a short introduction to spin-crossover materials and their applications in Chemical Communications 2013, 49, 10890.

<p>Spin-crossover is a high-spin-to-low-spin transition at a transition metal centre,&nbsp;in response to a change in temperature or pressure. This is common in some types of transition metal compound, and especially in iron chemistry. While the molecules in a material undergo spin-crossover individually, it leads to large changes in their size and shape which are propagated through the material in the solid state. As one molecule undergoes the transition and changes its size, it causes a change in pressure in the crystal lattice that in turn promotes the transition in its nearest neighbours. These effects are transmitted through a crystal lattice at differing rates, depending on the strength of the interactions between molecules. Hence, whether a particular material undergoes spin-crossover abruptly or gradually, with temperature or with time, is controlled by its crystal packing. As such, spin-crossover materials are good test-beds for theories about crystal engineering.</p> <p>Spin-crossover transtions also affect several physical properties of a solid material including its colour, magnetic moment, dielectric constant, hardness and size. These properties have been harnessed in materials applications such as thermochromic inks; stimuli-responsive polymers; switchable microwave absorbers; and solid state refrigeration. Moreover, nanostructures of spin-crossover materials retain their switching properties down to 30 nm length scales, and spin-crossover in single molecules has been detected inside a scanning tunneliing microscope (STM). Spin-crossover nanomaterials science is becoming increasingly sophisticated, and SCO nanoparticle constructs have performed well in prototype binary memory devices.</p> <p>A fraction of spin-crossover materials also exhibit thermal hysteresis in their transitions; these are most suitable for the applications mentioned above. Whether a compound undergoes spin-crossover gradually or abruptly, with or without hysteresis, is controlled by the crystal packing in the bulk material rather than the molecule itself. We aim to understand the relationship between structure and function, so we can design new spin-crossover materials from scratch. We are also pursuing different ways to incorporate new functionality into spin-crossover materials.</p> <p>We have projects in various aspects of this chemistry, involving organic and inorganic synthesis; crystallography and powder diffraction; solid and solution-phase magnetic measurements; and other techniques as appropriate.&nbsp;Current goals include understanding the principles for designing spin-crossover crystals with bespoke switching properties; new liquid crystals and other soft materials showing spin-crossover switching properies; and, understanding and developing solid state refrigeration by spin-crossover materials.</p> <p>You can find a short introduction to spin-crossover and its applications is in&nbsp;<em>Chemical Communications</em> <strong>2013</strong>, <em>49</em>, 10890.</p>

<p>Formal applications for research degree study should be made online through the&nbsp;<a href="https://www.leeds.ac.uk/info/130206/applying/91/applying_for_research_degrees">University&#39;s website</a>. Please state clearly in the Planned Course of Study that you are applying for <em><strong>PHD Chemistry FT</strong></em> and in the research information section&nbsp;that the research degree you wish to be considered for is <em><strong>Spin-crossover compounds &ndash; switchable materials from simple metal complexes</strong></em>&nbsp;as well as <a href="https://physicalsciences.leeds.ac.uk/staff/173/professor-malcolm-halcrow">Professor Malcolm Halcrow</a> as your proposed supervisor.</p> <p>If English is not your first language, you must provide evidence that you meet the University&#39;s minimum English language requirements (below).</p> <p style="margin-bottom:11px"><em>As an international research-intensive university, we welcome students from all walks of life and from across the world. We foster an inclusive environment where all can flourish and prosper, and we are proud of our strong commitment to student education. Across all Faculties we are dedicated to diversifying our community and we welcome the unique contributions that individuals can bring, and particularly encourage applications from, but not limited to Black, Asian, people who belong to a minority ethnic community, people who identify as LGBT+ and people with disabilities. Applicants will always be selected based on merit and ability.</em></p> <p style="margin-bottom:11px">&nbsp;</p> <p class="MsoNoSpacing">Applications will be considered on an ongoing basis. &nbsp;Potential applicants are strongly encouraged to contact the supervisors for an informal discussion before making a formal application. &nbsp;We also advise that you apply at the earliest opportunity as the application and selection process may close early, should we receive a sufficient number of applications or that a suitable candidate is appointed.</p> <p>Please note that you must provide the following documents in support of your application at the point of submission of your application:</p> <ul> <li>Full Transcripts of all degree study or if in final year of study, full transcripts to date</li> <li>Personal Statement outlining your interest in the project</li> <li>CV</li> </ul> <p style="margin-bottom:11px">&nbsp;</p> <p>&nbsp;</p>

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<p>For further information regarding your application, please contact Doctoral College Admissions by&nbsp;email: <a href="mailto:maps.pgr.admissions@leeds.ac.uk">maps.pgr.admissions</a><a href="mailto:EMAIL@leeds.ac.uk">@leeds.ac.uk</a>, or by telephone: +44 (0)113 343 5057.</p> <p>For further information about this project, please contact Professor Malcolm Halcrow&nbsp;by&nbsp;email:&nbsp;<a href="mailto:M.A.Halcrow@leeds.ac.uk">M.A.Halcrow@leeds.ac.uk</a></p>