Pulsed electron paramagnetic resonance investigation of molecular magnetic systems
<p>Porphyrins, consisting of four pyrroles connected by methine bridges, can accommodate different types of metal ions or groups in the centre, because the four nitrogen atoms in the molecule function as outstanding ligands. In this thesis, a vanadyl group is incorporated in the centre in orde...
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| Format: | Thesis |
| Language: | English |
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2023
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| _version_ | 1797111632216719360 |
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| author | Huang, Z |
| author2 | Bogani, L |
| author_facet | Bogani, L Huang, Z |
| author_sort | Huang, Z |
| collection | OXFORD |
| description | <p>Porphyrins, consisting of four pyrroles connected by methine bridges, can accommodate different types of metal ions or groups in the centre, because the four nitrogen atoms in the molecule function as outstanding ligands. In this thesis, a vanadyl group is incorporated in the centre in order to investigate the electron spin–spin interactions and coherence properties, because the vanadyl group in the nuclear spin-free carbon−sulfide ligands has been found to have a long coherence time. Graphenoids, composed of annulated benzene rings, have the same basic unit of graphene. Because of the delocalisation of electrons in π-conjugation structure, graphenoids have many interesting electronic properties, and therefore have obtained attention from researchers in different fields. Through introducing different defects and side groups in the structures and adjusting the size and shape of the molecules, it is possible to tune the magnetic and coherence properties of graphenoids.</p>
<p>In this thesis, we use electron paramagnetic resonance spectroscopy to investigate the magnetic and coherence properties of an ensemble of isolated paramagnetic molecules. Vanadyl porphyrin dimers with different spacers are discussed, and we especially focus on the electron spin–spin interactions in these molecules. We use strongly and weakly coupled representations to describe the spin systems of triply linked dimers and all other dimers, respectively, because of different strengths of isotropic exchange coupling, compared with both the hyperfine coupling and the electron Zeeman anisotropy. The noncoincidence effects of different interaction tensors play an important role in the CW-EPR spectra and need to be considered in simulations. We also investigated the coherence properties dependence on different exchange coupling strengths and attached side groups. Furthermore, we discuss the temperature dependence of the coherence properties and structural effects on the magnetic properties by studying two types of graphenoids with two different defects, including two neighbouring five- and seven-membered rings and two disjoint five-membered rings.</p> |
| first_indexed | 2024-03-07T08:11:37Z |
| format | Thesis |
| id | oxford-uuid:c9028480-cca3-48d2-8535-0260c4609f86 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T08:11:37Z |
| publishDate | 2023 |
| record_format | dspace |
| spelling | oxford-uuid:c9028480-cca3-48d2-8535-0260c4609f862023-12-01T16:47:51ZPulsed electron paramagnetic resonance investigation of molecular magnetic systemsThesishttp://purl.org/coar/resource_type/c_bdccuuid:c9028480-cca3-48d2-8535-0260c4609f86MaterialsEnglishHyrax Deposit2023Huang, ZBogani, LSlota, M<p>Porphyrins, consisting of four pyrroles connected by methine bridges, can accommodate different types of metal ions or groups in the centre, because the four nitrogen atoms in the molecule function as outstanding ligands. In this thesis, a vanadyl group is incorporated in the centre in order to investigate the electron spin–spin interactions and coherence properties, because the vanadyl group in the nuclear spin-free carbon−sulfide ligands has been found to have a long coherence time. Graphenoids, composed of annulated benzene rings, have the same basic unit of graphene. Because of the delocalisation of electrons in π-conjugation structure, graphenoids have many interesting electronic properties, and therefore have obtained attention from researchers in different fields. Through introducing different defects and side groups in the structures and adjusting the size and shape of the molecules, it is possible to tune the magnetic and coherence properties of graphenoids.</p> <p>In this thesis, we use electron paramagnetic resonance spectroscopy to investigate the magnetic and coherence properties of an ensemble of isolated paramagnetic molecules. Vanadyl porphyrin dimers with different spacers are discussed, and we especially focus on the electron spin–spin interactions in these molecules. We use strongly and weakly coupled representations to describe the spin systems of triply linked dimers and all other dimers, respectively, because of different strengths of isotropic exchange coupling, compared with both the hyperfine coupling and the electron Zeeman anisotropy. The noncoincidence effects of different interaction tensors play an important role in the CW-EPR spectra and need to be considered in simulations. We also investigated the coherence properties dependence on different exchange coupling strengths and attached side groups. Furthermore, we discuss the temperature dependence of the coherence properties and structural effects on the magnetic properties by studying two types of graphenoids with two different defects, including two neighbouring five- and seven-membered rings and two disjoint five-membered rings.</p> |
| spellingShingle | Materials Huang, Z Pulsed electron paramagnetic resonance investigation of molecular magnetic systems |
| title | Pulsed electron paramagnetic resonance investigation of molecular magnetic systems |
| title_full | Pulsed electron paramagnetic resonance investigation of molecular magnetic systems |
| title_fullStr | Pulsed electron paramagnetic resonance investigation of molecular magnetic systems |
| title_full_unstemmed | Pulsed electron paramagnetic resonance investigation of molecular magnetic systems |
| title_short | Pulsed electron paramagnetic resonance investigation of molecular magnetic systems |
| title_sort | pulsed electron paramagnetic resonance investigation of molecular magnetic systems |
| topic | Materials |
| work_keys_str_mv | AT huangz pulsedelectronparamagneticresonanceinvestigationofmolecularmagneticsystems |