Putting new twists on pi-Electron acceptor design

Background
Electron-deficient π-conjugated organic materials are the subject of intense research on account of the strong prospects to revolutionise efficient lighting and energy generation applications. Over the past decades of research, new materials sets have been discovered, optimised, and put into lab-scale application to develop efficient solutions to long-standing problems in energy science. However, continued innovation will falter if research is solely focused on continued mining of existing structural archetypes rather than on fundamental explorations of new paradigms for new types of electronic function and phenomena. This PhD project will involve hypothesis-driven exploratory research on new material manifestations of π-electronic stabilisation and delocalisation that may be relevant to improving their performances within organic electronics and energy technologies of the future.

Objectives
The main goal of this PhD project is to understand how electrochemical and energy transfer processes are influenced by the introduction of sterically-induced twist onto traditionally planar, ring-fused organic π-electron acceptors. Fundamental structure properties investigations will include examining the (i) degree of twist, (ii) structural symmetry, (iii) chirality and (iv) assembled states of twisted redox acceptors to (v) inform their rational design and (vi) optimisation as advanced functional materials relevant to organic electronics and energy technology development. The final objective of this PhD project is to achieve practical ’real-world’ demonstrations of these fundamentally assessed molecular material properties within prototypical organic devices, such as the active cathode material of rechargeable batteries, the electron acceptor component of organic photovoltaics, and in thin-film semiconductors.

Experimental Approach
Metal-catalysed C–C bond coupling, direct C–H activation, and oxidative aromatisation methods will be employed to generate electron-accepting twistacene and helicene derivatives with increasing redox-site density on relatively small molecular weight structures. The degree of twist in these molecular materials will be controlled either through the introduction of bulky substituents to the aromatic core, or by the intentional crowding of carbonyl-based redox centres. Products and key intermediates will be analysed structurally by NMR spectroscopy, mass spectrometry, circular dichroism and where possible, single-crystal X-ray analysis. Optical, chiroptical, and electronic properties will be examined by electrochemical methods (cyclic and pulse voltammetries, impedance) and photospectroscopy (absorption, emission, time-resolved, and spectroelectrochemical techniques), with special attention given towards understanding the impact on electron stabilisation, delocalisation, and energy band gaps. EPR spectroscopy and DFT computational modeling will future elucidate the nature of delocalised spins within these materials. In the advanced stages of the research, materials exhibiting promising properties will be investigated in the relevant prototypical organic devices, including the fabrication and testing of rechargeable coin cell batteries and solar cells.

Novelty
This PhD project delivers high novelty, drawing elements from high-profile research in twistacene/helicenes, nanographene derivatives and organic electronics, magnetism and chiral optics, to deliver a new class of functional organic materials for energy.

Training
The student will receive training in cutting-edge organic synthesis and purification, becoming well-versed in Schlenk-technique, air-free manipulations, glove box operation, and automated flash column chromatography, for example. Hands-on analytical technique development will include advanced 1D/2D NMR spectroscopy, mass spectrometry, single-crystal X-ray analysis, physical electrochemistry, impedance analysis, photospectroscopy (UV-Vis-NIR absorption, emission, spectroelectrochemistry), with exposure to DFT computational modeling to support their experimental results. Film analysis and device fabrication will be conducted both within the Avestro Group as well as in collaboration with groups in the JEOL Nanocentre (high-resolution materials imaging) and Physics (Centre for Energy Efficient Materials). Students progress will be monitored during their participation in weekly group research meetings and group forums, 1:1 supervisor meetings, monthly project workflow summaries, collaboration in group research projects, and their contributions to the overall positive and enthusiastic research dynamic cultivated in the Avestro Group and Molecular Materials Laboratory.

All Chemistry research students have access to our innovative Doctoral Training in Chemistry (iDTC): cohort-based training to support the development of scientific, transferable and employability skills: https://www.york.ac.uk/chemistry/postgraduate/idtc/

The Department of Chemistry holds an Athena SWAN Gold Award and is committed to supporting equality and diversity for all staff and students. The Department strives to provide a working environment which allows all staff and students to contribute fully, to flourish, and to excel: https://www.york.ac.uk/chemistry/ed/. This PhD project is available to study full-time or part-time (50%).

This PhD will formally start on 1 October 2020. Induction activities will start on 28 September.