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Metal ion cages with stabilized conformations : synthesis, characterization and properties
The stabilized conformers lel₃, lel₂ob, ob₂lel and ob₃ of the [Co(±pn)₃]³⁺ system have previously been synthesized giving relative equilibrium (100 °C) amounts of 35.0 : 41.1 : 18.0 : 4.0. With the recent encapsulation of the resolved lel₃-[Co(pn)₃₋]Cl₃ complexes, and their subsequent interconversio...
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| Language: | English |
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Department of Chemistry
2016
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| _version_ | 1867613345091158016 |
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| access_status_str | Open Access |
| author | Naidoo, Kevin Jonathan |
| author2 | Hendry, Tony |
| author_browse | Hendry, Tony Naidoo, Kevin Jonathan |
| author_facet | Hendry, Tony Naidoo, Kevin Jonathan |
| author_sort | Naidoo, Kevin Jonathan |
| collection | Thesis |
| description | The stabilized conformers lel₃, lel₂ob, ob₂lel and ob₃ of the [Co(±pn)₃]³⁺ system have previously been synthesized giving relative equilibrium (100 °C) amounts of 35.0 : 41.1 : 18.0 : 4.0. With the recent encapsulation of the resolved lel₃-[Co(pn)₃₋]Cl₃ complexes, and their subsequent interconversion to the ob₃-[Co(NH₃)₂-pnsar]Cl₅ diastereomers, the synthesis of the lel₂ob and ob₂lel cage complexes is a necessity to complete the investigation of the [Co(NH₃)₂-pnsar]⁵⁺ system. Consequently the eight Δ, Λ isomers of the lel₂ob-[Co(NH₃)₂-pnsar]Cl₅ complex were synthesised in a one pot reaction and resolved into the respective isomers having the following relative yields: lel₂ob-1 (~ 24% ), lel₂ob-2 ( ~ 43% ), lel₂ob-3 ( ~ 28%) and lel₂ob-4 (~ 5%). The resolution order of these isomers on SP Sephadex C-25 was used to tentatively identify the (3 mer and 1 fac) geometrical isomers of these lel₂ob diastereomers. For the first time ob character was directly encapsulated with the synthesis of the ob₂lel-[Co(NH₃)₂-pnsar]Cl₅ conformers ( ~ 1 % ). NMR analysis showed these to consist almost entirely (80%) of the ob₂lel-1 isomer. The geometry of this isomer was later discovered to be most favourable when the lel₂ob-1 isomer gave a 50% conversion to the ob₂lel-1 isomer, unlike the poor conversions of the ob₂lel-2 (~ 5%) and the ob₂lel-3 (~ 15%). The electronic spectra (UV /VIS and CD) of the individual isomers were investigated and revealed the presence of large distortion of the CoN₆ chromophore from regular Oh geometry. This was confirmed by the crystal structural analysis of the lel₂ob-2 isomer which reveal a trigonal twist angle (ф) of ~ 45°. The crystal structure also proved the identification logic right, which was based on the relation between chemical and resolution order evidence. The infrared spectra of [Co(NH₃)₂-sar]⁵⁺ ion was analysed using isotopic labelling methods in combination with the results of group theory calculations. These assignments make it possible to study the spectra of the [Co(NH₃)₂-pnsar]⁵⁺ isomeric complexes. Comparison of the infrared spectra of these complexes reflect the increase in number of bands on progressing from D₃, through C₃ to C₁ symmetry. Even the orientation of methyl groups in the different conformer types affect the symmetry of the CoN₆ core. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/18805 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:34:40.191Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2016 |
| publishDateRange | 2016 |
| publishDateSort | 2016 |
| publisher | Department of Chemistry |
| publisherStr | Department of Chemistry |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/18805 Metal ion cages with stabilized conformations : synthesis, characterization and properties Naidoo, Kevin Jonathan Hendry, Tony Thornton, David A Chemistry The stabilized conformers lel₃, lel₂ob, ob₂lel and ob₃ of the [Co(±pn)₃]³⁺ system have previously been synthesized giving relative equilibrium (100 °C) amounts of 35.0 : 41.1 : 18.0 : 4.0. With the recent encapsulation of the resolved lel₃-[Co(pn)₃₋]Cl₃ complexes, and their subsequent interconversion to the ob₃-[Co(NH₃)₂-pnsar]Cl₅ diastereomers, the synthesis of the lel₂ob and ob₂lel cage complexes is a necessity to complete the investigation of the [Co(NH₃)₂-pnsar]⁵⁺ system. Consequently the eight Δ, Λ isomers of the lel₂ob-[Co(NH₃)₂-pnsar]Cl₅ complex were synthesised in a one pot reaction and resolved into the respective isomers having the following relative yields: lel₂ob-1 (~ 24% ), lel₂ob-2 ( ~ 43% ), lel₂ob-3 ( ~ 28%) and lel₂ob-4 (~ 5%). The resolution order of these isomers on SP Sephadex C-25 was used to tentatively identify the (3 mer and 1 fac) geometrical isomers of these lel₂ob diastereomers. For the first time ob character was directly encapsulated with the synthesis of the ob₂lel-[Co(NH₃)₂-pnsar]Cl₅ conformers ( ~ 1 % ). NMR analysis showed these to consist almost entirely (80%) of the ob₂lel-1 isomer. The geometry of this isomer was later discovered to be most favourable when the lel₂ob-1 isomer gave a 50% conversion to the ob₂lel-1 isomer, unlike the poor conversions of the ob₂lel-2 (~ 5%) and the ob₂lel-3 (~ 15%). The electronic spectra (UV /VIS and CD) of the individual isomers were investigated and revealed the presence of large distortion of the CoN₆ chromophore from regular Oh geometry. This was confirmed by the crystal structural analysis of the lel₂ob-2 isomer which reveal a trigonal twist angle (ф) of ~ 45°. The crystal structure also proved the identification logic right, which was based on the relation between chemical and resolution order evidence. The infrared spectra of [Co(NH₃)₂-sar]⁵⁺ ion was analysed using isotopic labelling methods in combination with the results of group theory calculations. These assignments make it possible to study the spectra of the [Co(NH₃)₂-pnsar]⁵⁺ isomeric complexes. Comparison of the infrared spectra of these complexes reflect the increase in number of bands on progressing from D₃, through C₃ to C₁ symmetry. Even the orientation of methyl groups in the different conformer types affect the symmetry of the CoN₆ core. 2016-04-12T09:37:46Z 2016-04-12T09:37:46Z 1989 Master Thesis Masters MSc http://hdl.handle.net/11427/18805 eng application/pdf Department of Chemistry Faculty of Science University of Cape Town |
| spellingShingle | Chemistry Naidoo, Kevin Jonathan Metal ion cages with stabilized conformations : synthesis, characterization and properties |
| thesis_degree_str | Master's |
| title | Metal ion cages with stabilized conformations : synthesis, characterization and properties |
| title_full | Metal ion cages with stabilized conformations : synthesis, characterization and properties |
| title_fullStr | Metal ion cages with stabilized conformations : synthesis, characterization and properties |
| title_full_unstemmed | Metal ion cages with stabilized conformations : synthesis, characterization and properties |
| title_short | Metal ion cages with stabilized conformations : synthesis, characterization and properties |
| title_sort | metal ion cages with stabilized conformations synthesis characterization and properties |
| topic | Chemistry |
| url | http://hdl.handle.net/11427/18805 |
| work_keys_str_mv | AT naidookevinjonathan metalioncageswithstabilizedconformationssynthesischaracterizationandproperties |