http://theses.ncl.ac.uk/jspui/handle/10443/84 Tue, 03 Feb 2026 17:34:11 GMT 2026-02-03T17:34:11Z http://theses.ncl.ac.uk/jspui/handle/10443/5891 Title: Towards organic materials exhibiting thermally activated delayed fluorescence and circularly polarised luminescence Authors: Laidlaw, Beth Alexandra Abstract: Organic light emitting diodes (OLEDs) have come to the fore as the stateof-the-art technology for displays and lighting. Indeed, they are now standard for most recent smartphone designs. However, despite their success, advancements are still required to improve energy efficiency and sustainability, especially with the onset of 5G which has increased power consumption. This thesis studied two mechanisms to improve OLED efficiency. The first seeks to improve the internal quantum efficiency (IQE) of the emissive materials used within the OLED device by making non-emissive triplet states emit light. Statistically, only 25% of excitons formed by electrical excitation within the emissive material are singlets and can radiatively relax via fluorescence. The remaining 75% are triplet excitons which do not emit in conventional fluorescent materials and therefore, their energy is lost to heat. Recently, thermally activated delayed fluorescence (TADF) has emerged as a powerful approach to harvest these non-emissive triplet states. Importantly, previous work has demonstrated the importance of specific vibrational degrees of freedom to optimise the TADF process. This work examines how rotaxanes can be used to control vibrational modes of TADF molecules and therefore, fine-tune their properties and thus more efficiently re-engage the ’lost’ triplet states. In many of cases in organic electronics, due to the size of the molecules of interest, the excited state properties are described using time-dependent density functional theory (TDDFT) which provides the required balance between computational efficiency and accuracy. However, TADF materials display charge transfer (CT) characteristics, a property which is poorly described by standard approximations of the exchange correlation functional in TDDFT. Herein, we apply two tuning approaches to improve the description of excited states within TDDFT, with a particular focus upon the accuracy of excited state energies and chiroptical response. The latter being connected to the second way of improving the OLED efficiency. Indeed, OLED display technologies require anti-glare filters to improve viewing contrast when routinely used under conditions of high ambient light. Anti-glare filters use a double layer of linear polarisers and quarter wave plates to ensure that any ambient light which enters the device is not reflected off the cathode, back towards the viewer. However, this also absorbs ∼50% of the light generated by the OLED, meaning higher driving voltages are required to achieve the set brightness levels. This increases power consumption and decreases device operation lifetimes. Circularly polarised luminescence (CPL) is not absorbed by these filters, thus the integration of CPL could increase the energy efficiency of an OLED display. This work explores two mechanisms for generating CPL, firstly using small molecules and secondly with large polymer systems, which have been shown to exhibit large dissymmetry Description: PhD Thesis Sat, 01 Jan 2022 00:00:00 GMT http://theses.ncl.ac.uk/jspui/handle/10443/5891 2022-01-01T00:00:00Z http://theses.ncl.ac.uk/jspui/handle/10443/5861 Title: Advancing the Analysis of X-ray Absorption Spectroscopy using Deep Neural Networks Authors: Madkhali, Marwah Mohammed Abstract: X-ray absorption spectroscopy (XAS) is a core analytical technique that can provide users with highly detailed information about the electronic and geometric structure of matter. Its ability to be applied under a wide variety of different conditions means it has had a strong impact across the physical and natural sciences. However, one of the challenges of the technique is that difficult computational calculations are often required to extract the detailed information from the XAS spectra and, in complicated systems, e.g. in operating catalysts, batteries, and temporally-evolving systems, these can be particularly challenging. Due to the complexity and computational resource requirements, many users are unable to access the wealth of valuable information contained within their XAS spectra. In this Thesis, I describe my work developing a deep neural network (DNN) for X-ray absorption near edge (XANES) spectrum predictions. The DNN is a multi-layer perceptron (MLP) ML model which aims at minimising the mean-squared error (MSE) between predicted and calculated (theoretical) XANES spectra using featurised structures and the corresponding theoretical XANES spectra as input. After learning how to map the relationship between the local environment of an absorbing atom and the corresponding XANES spectrum from a reference dataset, the DNN is able to predict XANES spectra of materials outside of the scope of that dataset. The Thesis initially focuses upon how the data representation choices, i.e. the featurisation, affects the accuracy of the DNN at the Fe K-edge. Once optimised, the DNN is able to predict peak positions with sub-eV accuracy and peak intensities with errors over an order of magnitude smaller than the spectral variations in the reference dataset. Subsequently, the DNN is extended to the Co K-edge and applied to interpret T-jump-pump/X-rayprobe experiments investigating ligand exchange in an aqueous Co complex. The DNN greatly facilitates the analysis in this case, since it can quickly and cost-effectively predict the XANES spectra of thousands of geometric configurations sampled from ab initio molecular dynamics (MD), describing the disorder in the system. The final Chapter addresses the challenge of edge shifts: changes in the energetic position of the X-ray absorption edge in the XANES spectrum arising from changes in the electronic structure of the system(s) under study. It is demonstrated that, although the developed DNN model is more than satisfactory, improving it further would nonetheless require using significantly higher levels of theory to build the reference dataset, which would make developing sufficiently large reference datasets a significant challenge moving forwards. Description: Ph. D. Thesis. Sun, 01 Jan 2023 00:00:00 GMT http://theses.ncl.ac.uk/jspui/handle/10443/5861 2023-01-01T00:00:00Z http://theses.ncl.ac.uk/jspui/handle/10443/5160 Title: Novel Catalytic Transformations of Organophosphorus Compounds Authors: Perry, Daniel Oliver Abstract: The overall aim of this project was to investigate whether it would be possible to develop methods for the successful synthesis of biaryl monophosphonates by using a variety of cross-coupling reactions enhanced via palladium catalysis in which the phosphonate substituent is present on the nucleophilic component to produce potentially advantageous compounds. Three separate, quite distinct approaches to the synthesis of these nucleophilic components have been attempted in this thesis to find the optimal method : firstly, the synthesis of phosphonate-substituted aryl boronate esters by palladium-catalysed borylation of the corresponding aryl bromide; secondly the conversion of bromoaryl phosphonates into the corresponding organozinc pivalates by metal-halogen exchange; and finally, the synthesis of phosphonate-substituted aryl boronates by iridium-catalysed C-H borylation of the aromatic ring. The potential uses of the resulting biaryl monophosphonates are as precursors to phosphorus-containing ligands, in fine chemical synthesis and as leads in the search for new pharmaceuticals that counteract antibiotic resistance or in treatment of heart conditions. A short two-step synthetic route was successfully carried out to make the desired diethyl (2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)phosphonate from 1-bromo-2-iodobenzene. In a similar way, the desired naphthyl analogue was synthesised from 1-bromo-2-naphthol following an initial conversion to the corresponding triflate. Diethyl (2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)phosphonate was successfully used in a range of Suzuki-Miyaura cross-coupling reactions, utilising the designer monophosphine KITPHOS ligands made by the Knight/Doherty group with low catalyst loadings. The potassium trifluoroborate salt of the ortho-phosphonate phenyl boronate ester was successfully synthesised from diethyl (2-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)phosphonate using non-glassware etching conditions. However this method did not work when the same conditions were trialled on the corresponding naphthalene derivative. Transmetalation of the ortho-bromo phosphonate (used in the synthesis of the ortho-phosphonate phenyl boronate ester) was accomplished with iPrMgCl and the resulting Grignard reagent was subsequently converted into the corresponding pivalate by treatment with Zn(OPiv)2. Negishi cross-coupling of this species with a range of functionalised aryl bromides gave the biaryl phosphonates in moderate yield. Separation of the products from diethyl phenylphosphonate, produced by competing protonation of one of the organometallic intermediates, proved troublesome in some cases. Regioselective iridium-catalysed C-H borylation of three meta-substituted aryl phosphonates (methyl/methyl ester and trifluoromethyl substituents were used) gave the corresponding pinacol boronate esters in high conversions. Suzuki-Miyaura cross-coupling with a range of aryl bromides gave the corresponding 5-substituted biaryl phosphonates. All the above methods displayed success in synthesising the desired nucleophilic phosphonate coupling partners and in turn, these coupling partners have been successfully incorporated into the relevant cross coupling reactions, producing desired biaryl monophosphonates in good yield. These biaryl motifs can then be further developed in the synthesis of pharmaceuticals or as precursors to phosphine ligands. In the case of the ortho-biaryls made, their potential use as a ligand for asymmetric catalysis in the fine chemicals industry is an attractive proposition.   Description: PhD Thesis Wed, 01 Jan 2020 00:00:00 GMT http://theses.ncl.ac.uk/jspui/handle/10443/5160 2020-01-01T00:00:00Z http://theses.ncl.ac.uk/jspui/handle/10443/5040 Title: Molecular diversity from N-phenylquinoneimine Authors: Adesina, Adebimpe Dorcas Abstract: Diversity-oriented synthesis (DOS) continues to grow as an area of importance in the disciplines of organic synthesis and chemical biology.1-3 It involves the preparation of diverse scaffolds of varying complexity and enables the exploration of a greater range of ‘chemical space’ than hitherto possible through multicomponent-coupling and tandem reactions. Tandem reactions, also known as cascade or domino reactions, link several transformations together in a single process step. Simple starting materials can be used to rapidly build complex structures with high selectivity. The use and production of toxic and/or hazardous intermediates can be avoided/minimised and novel avenues of research and new reactions can be developed.4 In this work, azaquinone 1 has been studied as a new key intermediate in multicomponent coupling and tandem reactions (Scheme 1). As all six carbon atoms in the quinoid ring are different, it has the potential to serve as a novel building block to access a range of useful structural motifs as part of scaffold diversity synthesis and drug discovery. Conjugate addition to azaquinone 1 with nitrogen nucleophiles (aromatic amines) has been investigated, giving di-substituted arylamino compounds 2 in good yields (56–68%). Although the basic process has been reported,5 the regiochemistry of these compounds has now been confirmed by 2D NMR (COSY and NOESY) and also by determination of the crystal structure of the products. The reaction of aromatic amines with azaquinone occurred by both 1,4-conjugate addition to the α,β-unsaturated imine and the α,β-unsaturated ketone, resulting only in di-addition products. These diarylamino products 2 are coloured compounds which may be of importance in the dye industry, and those interested in development of diagnostic tools. Further reactions of compounds 2 could result in the production of azine, oxazine, and thiazine dyes. Description: PhD Thesis Wed, 01 Jan 2020 00:00:00 GMT http://theses.ncl.ac.uk/jspui/handle/10443/5040 2020-01-01T00:00:00Z