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Metal Complexes of Radical Ligands – Electron Hopping Leading to Novel Optical Properties


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Key facts

Type of research degree
Application deadline
Ongoing deadline
Project start date
Sunday 1 October 2023
Country eligibility
International (open to all nationalities, including the UK)
Competition funded
Professor Malcolm Halcrow
School of Chemistry
<h2 class="heading hide-accessible">Summary</h2>

This project involves the synthesis, electrochemistry and host: guest chemistry of metal complexes of redox-active (non-innocent) ligands. An example is the&nbsp;dioxolene ligands, which can readily cycle between the catechol, semiquinone and quinone oxidation states. Such processes allow electrons to shuttle between the metal and organic parts of a dioxolene complex molecule, giving them intensely dark colours that extend into the infra-red. Alternatively, with appropriate metal/dioxolene combinations similar electron rearrangements can take place abruptly under the action of a physical stimulus, leading to thermochromic or photochromic crystalline materials.<br /> <br /> We have been studying novel mixed-valent radical compounds supported by ligands containing multiple dioxolene rings. These are often stable under ambient conditions, strongly coloured and often exhibit intense near-infra-red absorptions. The intense colours arise from hopping of unpaired electrons around the poly-dioxolene ligand scaffold, between the part-oxidised aromatic rings. Analysis of these near-IR spectra defines the mechanism of this electron hopping, which we can turn on or off depending on the ligand design. An example of this is in Chemical Communications 2019, 55, 2281.<br /> <br /> We now want to apply the same principles to make electrochromic framework crystals, and molecular cage compounds, from similar components. The radical oxidation products have intense colours, with strong absorptions in the visible and near-IR regions. Near-IR absorbers like these, whose absorptions can be switched on and off electronically, can be very useful in fibre-optic communications devices.&nbsp;<br /> <br /> The electron-hopping process means the frameworks should also show semiconducting properties or even metallic conduction. If the frameworks can be made sufficiently porous, they could also serve as green oxidation catalysts for alcohol or aldehyde vapours, or as components in sensor devices for some small molecule gases like the nitrogen oxides. All these applications hinge on the unique properties of electron mobility around the metal/dioxolene scaffold used to construct these materials.&nbsp;<br /> <br /> This project involves organic and inorganic synthesis, crystallography, electrochemistry and other techniques for studying radical products (EPR, UV/vis/NIR and IR spectroscopies, magnetic measurements and DF calculations). Some of the dioxolene ligands we use require multi-step syntheses, so a PhD on this topic will involve a significant amount of organic ligand synthesis.

<h2 class="heading">How to apply</h2>

<p>Formal applications for research degree study should be made online through the&nbsp;<a href="">University&rsquo;s website</a>. Please state clearly in the Planeed Course of Study section that you are applying for <em><strong>PHD Chemistry FT</strong></em> and&nbsp;in the research information section&nbsp;that the research degree you wish to be considered for is <em><strong>Metal complexes of radical ligands</strong></em>&nbsp;as well as&nbsp;<a href="">Professor Malcolm Halcrow</a>&nbsp;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><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>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> <p>&bull;&nbsp;&nbsp; &nbsp;Full Transcripts of all degree study or if in final year of study, full transcripts to date<br /> &bull;&nbsp;&nbsp; &nbsp;Personal Statement outlining your interest in the project<br /> &bull;&nbsp;&nbsp; &nbsp;CV</p> <p>&nbsp;</p>

<h2 class="heading heading--sm">Entry requirements</h2>

Applicants to research degree programmes should normally have at least a first class or an upper second class British Bachelors Honours degree (or equivalent) in an appropriate discipline. The criteria for entry for some research degrees may be higher, for example, several faculties, also require a Masters degree. Applicants are advised to check with the relevant School prior to making an application. Applicants who are uncertain about the requirements for a particular research degree are advised to contact the School or Graduate School prior to making an application.

<h2 class="heading heading--sm">English language requirements</h2>

The minimum English language entry requirement for research postgraduate research study is an IELTS of 6.0 overall with at least 5.5 in each component (reading, writing, listening and speaking) or equivalent. The test must be dated within two years of the start date of the course in order to be valid. Some schools and faculties have a higher requirement.

<h2 class="heading">Funding on offer</h2>

<p><strong>Self-Funded or externally sponsored students are welcome to apply.</strong></p> <p><strong>UK&nbsp;</strong>&ndash;&nbsp;The&nbsp;<a href="">Leeds Doctoral Scholarships</a>,&nbsp;<a href="">Lund Stephenson Clarke</a>, <a href="">Akroyd &amp; Brown</a>, <a href="">Frank Parkinson</a>, <a href="">Henry Ellison-Charles Brotherton</a> and <a href="">Boothman, Reynolds &amp; Smithells</a> Scholarships are available to UK applicants. &nbsp;<a href="">Alumni Bursary</a> is available to graduates of the University of Leeds.</p> <p><strong>Non-UK</strong>&nbsp;&ndash;The&nbsp;<a href="">China Scholarship Council - University of Leeds Scholarship</a>&nbsp;is available to nationals of China. The&nbsp;<a href="">Leeds Marshall Scholarship</a>&nbsp;is available to support US citizens. &nbsp;<a href="">Alumni Bursary</a> is available to graduates of the University of Leeds.</p> <p>Please refer to the <a href="">UKCISA</a> website for information regarding Fee Status for Non-UK Nationals starting from September/October 2021.</p>

<h2 class="heading">Contact details</h2>

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

<h3 class="heading heading--sm">Linked research areas</h3>