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Probing the nature of interactions in molecular materials using high-pressure single-crystal X-ray diffraction
Le Roux, S. G. 2023. Probing the nature of interactions in molecular materials using high-pressure single-crystal X-ray diffraction. Unpublished doctoral thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/9f81bf45-99d4-42e5-a9db-e0c3c1893e8b
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Stellenbosch : Stellenbosch University
2023
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| access_status_str | Open Access |
| author | Le Roux, Samantha Gailene |
| author2 | Haynes, Delia Ann |
| author_browse | Haynes, Delia Ann Le Roux, Samantha Gailene |
| author_facet | Haynes, Delia Ann Le Roux, Samantha Gailene |
| author_sort | Le Roux, Samantha Gailene |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Le Roux, S. G. 2023. Probing the nature of interactions in molecular materials using high-pressure single-crystal X-ray diffraction. Unpublished doctoral thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/9f81bf45-99d4-42e5-a9db-e0c3c1893e8b |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/128760 |
| institution | Stellenbosch University (South Africa) |
| last_indexed | 2026-06-10T12:44:45.702Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2023 |
| publishDateRange | 2023 |
| publishDateSort | 2023 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/128760 Probing the nature of interactions in molecular materials using high-pressure single-crystal X-ray diffraction Le Roux, Samantha Gailene Haynes, Delia Ann Stellenbosch University. Faculty of Science. Dept. of Chemistry and Polymer Science. Supramolecular chemistry X-ray crystallography Polymorphism (Crystallography) UCTD Le Roux, S. G. 2023. Probing the nature of interactions in molecular materials using high-pressure single-crystal X-ray diffraction. Unpublished doctoral thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/9f81bf45-99d4-42e5-a9db-e0c3c1893e8b Supplementary files for this record are available on the SU repository SUNScholarData at DOI: https://doi.org/10.25413/sun.24762522 Thesis (PhD)--Stellenbosch University, 2023. ENGLISH ABSTRACT: Fine-tuning properties using external stimuli is essential for the development of functional materials with dynamic properties. High pressure is an exciting and exceptionally useful stimulant in the field of supramolecular chemistry. High pressure can produce large changes in crystal and molecular structures, that consequently affect the physical properties of the materials. This dissertation reports the effect of high pressure, as an external stimulant, on the crystal and molecular structures of small organic molecules. We firstly describe the effect of pressure on the pancake bonding in 4-phenyl-1,2,3,5-dithiadiazolyl (1). 1 orders as dimers in the solid state with strong intermolecular interactions between the S atoms. The strong interactions between the heterocyclic rings, containing the delocalized radical electron, are known as pancake bonds. The study on 1 looks at the highpressure crystallographic structures and uses complementary density functional theory (DFT) to better understand the behavior of 1 under pressure. Quantum Theory of Atoms In Molecules (QTAIM) and Electron Localization Function (ELF) formalisms are used to rationalize the degree of charge-shift bonding character of the pancake bonding with increasing pressure. The second study looked at the effect of pressure on both polymorphs of 4-cyanotetrafluorophenyl-1,2,3,5-dithiadiazolyl (2). 2 is a widely studied dithiadiazolyl (DTDA) with supramolecular chains of radicals in the solid state. The application of pressure to both polymorphs has a significant effect on the magnetic exchange interaction, J, as determined by unrestricted DFT. 2α initially becomes more ferromagnetically coupled with increasing pressure, but eventually becomes antiferromagnetically coupled. 2β becomes more antiferromagnetically coupled under pressure and experiences a phase change at 0.97 GPa. This study shows how high pressure can be used as a suitable stimulant for magnetic property changes. The third and final study looks at using high pressure for achieving solid-state reactions. Cinnamic acid (3) undergoes [2+2] cycloaddition under ultra-violet (UV) irradiation. 3 undergoes isothermal compression with pressure but does not undergo [2+2] cycloaddition. A combination of UV irradiation and pressure is successful in achieving complete reaction in significantly reduced irradiation times. An inverse relationship between pressure and irradiation time necessary for complete reaction is identified. This study eloquently illustrates how high pressure can be used as an additional stimulus for solid-state reactions to proceed in a single-crystal to single-crystal fashion under drastically reduced reaction times. These studies clearly illustrate how high pressure can be used to enhance existing intermolecular interactions and synthons. This ultimately affects the physical properties of the crystals studied, making high pressure a successful stimulant for physical property switching in the solid state. AFRIKAANSE OPSOMMING: Fyn verstelling van eienskappe met behulp van eksterne invloede is noodsaaklik vir die ontwikkeling van funksionele materiale met dinamiese eienskappe. Hoë druk is 'n opwindende en buitengewoon nuttige stimulant op die gebied van supramolekulêre chemie. Hoë druk kan groot veranderinge in kristal- en molekulêre strukture veroorsaak, wat gevolglik die fisiese eienskappe van die materiale beïnvloed. Hierdie proefskrif rapporteer die effek van hoë druk, as 'n eksterne stimulant, op die kristal- en molekulêre strukture van klein organiese molekules. Ons beskryf eerstens die effek van druk op die pannekoekbinding in 4-feniel-1,2,3,5- ditiadiazolyl (1). 1 rangskik as dimere in die vaste toestand met sterk intermolekulêre interaksies tussen die S-atome. Die sterk interaksies tussen die heterosikliese ringe, wat die gedelokaliseerde radikale elektron bevat, staan bekend as pannekoekbindings. Die studie op 1 kyk na die hoë druk kristallografiese strukture en gebruik komplementêre digtheid funksionele teorie (DFT) om die gedrag van 1 onder druk beter te verstaan. Kwantumteorie van atome in molekules (QTAIM) en elektronlokaliseringsfunksie (ELF) formalismes word gebruik om die mate van lading-verskuiwing-bindingskarakter van die pannekoekbinding met toenemende druk te rasionaliseer. In die tweede studie is daar gekyk na die effek van druk op beide polimorfe van 4-sianotetrafluorofeniel-1,2,3,5-ditiadiazolyl (2). 2 is 'n wye bestudeerde ditiadiazolyl (DTDA) met supramolekulêre kettings van radikale in die vaste toestand. Die toepassing van druk op beide polimorfe het 'n beduidende effek op die magnetiese uitruilinteraksie, J, soos bepaal deur onbeperkte DFT. 2α word aanvanklik meer ferromagneties gekoppel met toenemende druk, maar die toenemende druk veroorsaak dat 2α later antiferromagneties koppel. Dit dui daarop dat 2α 'n gapende magnetiese reaksie het wat verder verstaan kan word deur magnetiese vatbaarheidmetings onder druk te gebruik. 2β word meer antiferromagneties gekoppel onder druk en ervaar 'n faseverandering by 0.97 GPa. Hierdie studie wys hoe hoë druk as 'n geskikte stimulant vir magnetiese eienskapveranderinge gebruik kan word. Die derde en laaste studie kyk hoe hoe druk gebruik kan word om vastestofreaksies te bereik. Kaneelsuur (3) ondergaan [2+2] sikloadisie onder ultra-violet (UV) bestraling. 3 ondergaan isotermiese kompressie met druk, maar ondergaan nie [2+2] sikloadisie nie. 'n Kombinasie van UV-bestraling en druk is suksesvol om ‘n volledige reaksie in aansienlike verminderde bestralingstye te bewerkstellig. 'n Omgekeerde verband tussen druk en bestralingstyd wat nodig is vir volledige reaksie word geidentifiseer. Hierdie studie illustreer hoe hoe druk as 'n bykomende stimulus gebruik kan word om soliede-toestandreaksies in 'n enkelkristal- tot enkelkristal-wyse laat voortgaan onder drastiese verminderde reaksietye. Al hierdie studies illustreer duidelik hoe hoe druk gebruik kan word om bestaande intermolekulere interaksies en sintone te verbeter. Dit beinvloed die fisiese eienskappe van die kristalle wat bestudeer is, en bewys dat hoe druk 'n suksesvolle stimulant is om fisiese eienskapwisseling in die vaste toestand te bereik. Doctoral 2023-12-07T09:16:18Z 2023-11-06T16:50:22Z 2023-12-07T09:16:18Z 2023-11-06T16:50:22Z 2023-12 Thesis https://scholar.sun.ac.za/handle/10019.1/128760 Stellenbosch University xiii, 212 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Supramolecular chemistry X-ray crystallography Polymorphism (Crystallography) UCTD Le Roux, Samantha Gailene Probing the nature of interactions in molecular materials using high-pressure single-crystal X-ray diffraction |
| title | Probing the nature of interactions in molecular materials using high-pressure single-crystal X-ray diffraction |
| title_full | Probing the nature of interactions in molecular materials using high-pressure single-crystal X-ray diffraction |
| title_fullStr | Probing the nature of interactions in molecular materials using high-pressure single-crystal X-ray diffraction |
| title_full_unstemmed | Probing the nature of interactions in molecular materials using high-pressure single-crystal X-ray diffraction |
| title_short | Probing the nature of interactions in molecular materials using high-pressure single-crystal X-ray diffraction |
| title_sort | probing the nature of interactions in molecular materials using high pressure single crystal x ray diffraction |
| topic | Supramolecular chemistry X-ray crystallography Polymorphism (Crystallography) UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/128760 |
| work_keys_str_mv | AT lerouxsamanthagailene probingthenatureofinteractionsinmolecularmaterialsusinghighpressuresinglecrystalxraydiffraction |