Dokument: Photophysical Properties of Chromophores studied by Multimodal Fluorescence Spectroscopy
| Titel: | Photophysical Properties of Chromophores studied by Multimodal Fluorescence Spectroscopy | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=65676 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20240503-112125-3 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | Sretenovic, Dragana [Autor] | |||||||
| Dateien: |
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| Beitragende: | Prof. Dr. Seidel, Claus A. M. [Gutachter] Prof. Dr. Gilch, Peter [Gutachter] | |||||||
| Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 540 Chemie | |||||||
| Beschreibung: | Although the phenomenon of thermally activated delayed fluorescence (TADF) was already known several decades ago, it gained significant attention in recent years in the field of organic electronics because of its capability to harvest triplet excitons in organic light-emitting diodes (OLEDs) through fluorescence. Concerning that, the research training group ModISC was formed to study the processes responsible for TADF: intersystem crossing (ISC) and reverse intersystem crossing (rISC). This thesis is a result of collaborative work within this graduate school. Three families of chromophores divided into three project areas were investigated: A. Organic donor-acceptor conjugates, B. Organometallic donor-acceptor complexes of copper(I) and C. Organic compounds that are derivatives of flavins. The first two compound families are investigated with respect to TADF. One of the main goals of this thesis was to establish ultrasensitive fluorescence methods for the detection of TADF and find a correlation between structure and photophysical properties.
In project class A, five organic donor-acceptor conjugates were designed with a twisted conformation and the steric demand on the linker between the donor and acceptor was controlled to study the influence of the resulting torsion angle on the TADF properties of the chromophores. The diffusion-controlled quenching effect of oxygen was tremendous in our study, and special care had to be taken to ensure that oxygen was efficiently removed and that the deoxygenated samples were preserved for an extended period of time, which was achieved by extensive bubbling with inert gas and storage in hermetically sealed glass ampoules. The TADF properties are verified by temperature-dependent time-resolved measurements and time-resolved emission spectroscopy, which confirmed the same origin of the prompt and delayed emission. The compound with the highest steric torsion was proven to be the most efficient TADF emitter. In project class B, the photophysical properties of four copper(I) complexes bearing an anionic diamido-N-heterocyclic carbene ligand and and pyridine-based ligands were investigated. Due to chemical instabilities in solution, all fluorescence measurements were performed in cyclohexane suspension which allowed the use of standard cuvettes. Validation of the employed approach was obtained through fluorescence measurements of neat powders. Complexes with pyridine and lutidine ligands exhibit luminescence characteristics for locally-excited states, namely fluorescence and phosphorescence. However, the situation changes when the respective ligands are tuned in the electron-withdrawing direction by the addition of formyl groups. In this case, charge-transfer states are stabilized, which opens a pathway to TADF. Temperature-dependent time-resolved measurements and time-resolved emission spectroscopy are conducted across three distinct time regimes (nanoseconds, microseconds and milliseconds) in the temperature range from 10 K to 270 K to study luminescence properties and establish their relation with the nature of the excited states predicted by quantum chemical calculations. Moreover, our research extended beyond TADF: an example of that is project class C which includes fluorinated flavin derivatives chosen for their significance in biological systems. Their photophysical properties strongly depend on the applied fluorination pattern. Theoretical calculations enabled the synthesis of a derivative with strengthened fluorescence properties, which are further increased by using deuterated solvents, i.e., D2O instead of H2O. Overall, this thesis provides joint synthetic and theoretical efforts in the rational design of novel chromophores, with particular reference to detailed spectroscopic characterization and investigation of their photophysical properties. | |||||||
| Lizenz: |  Dieses Werk ist lizenziert unter einer Creative Commons Namensnennung 4.0 International Lizenz | |||||||
| Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät » WE Chemie » Physikalische Chemie und Elektrochemie | |||||||
| Dokument erstellt am: | 03.05.2024 | |||||||
| Dateien geändert am: | 03.05.2024 | |||||||
| Promotionsantrag am: | 11.10.2023 | |||||||
| Datum der Promotion: | 21.12.2023 |
