The characterization and application of novel xanthenyland thioxanthenyl-derived compounds as hosts in the presence of various applicable guest mixtures
- Authors: Jooste, Daniel Victor
- Date: 2020
- Subjects: Organic compounds -- Synthesis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/49104 , vital:41601
- Description: In this work, the host potential of four novel, structurally-related compounds, trans- N,N’-bis(9-phenyl-9-xanthenyl)cyclohexane-1,2-diamine (1,2-DAX), trans-N,N’-bis(9- phenyl-9-thioxanthenyl)cyclohexane-1,2-diamine (1,2-DAT), trans-N,N’-bis(9-phenyl- 9-xanthenyl)cyclohexane-1,4-diamine (1,4-DAX), and trans-N,N’-bis(9-phenyl-9- thioxanthenyl)cyclohexane-1,4-diamine (1,4-DAT), were investigated for their possible employment in the separation of isomers and other related compounds using host– guest chemistry. These hosts were synthesized following a Grignard reaction with phenylmagnesium bromide on either xanthone or thioxanthone. The resultant alcohol was treated with perchloric acid, before finally being linked with either trans-1,2- or trans-1,4-diaminocyclohexane to afford the four title host compounds. Initially, the feasibility of these hosts for separating isomers and related compounds was investigated by recrystallizing each one independently from various guest compounds including the methylpyridines and pyridine, xylenes and ethylbenzene, heterocyclic six-membered ring compounds, aniline, N-methylaniline and N,Ndimethylaniline, and also the alkylbenzenes toluene, cumene and ethylbenzene. 1HNMR spectroscopy was used to ascertain if inclusion of the guest species had occurred in this manner and, if so, the host:guest ratio of the complex. Guest–guest competitions were subsequently conducted in order to establish the selectivity of the hosts when presented with a mixture of guests, and if the host would be able to discriminate between them. Gas chromatography-mass spectrometry (GC-MS) was the analytical method of choice here if 1H-NMR spectroscopy was not suitable owing to guest–guest signal overlap. Here, the host was recrystallized from binary, ternary and quaternary mixed guests, where each was present in equimolar amounts. Additionally, binary competition experiments were conducted in mixed guest solvents where the molar ratios of the guests were varied, and host selectivity for these guests evaluated visually by means of selectivity profiles. Single crystal X-ray diffraction (SC-XRD) and thermal analysis were performed on any complexes that afforded crystals of suitable quality in order to relate inherent host–guest interactions and thermal stability to the observed host selectivity from the competition experiments. The more prevalent interactions that were evident in these inclusion complexes between host and guest species were, more usually, and interactions, as well as other short contacts. Hydrogen bonding interactions were observed in only a few of the complexes. Guest accommodation type was also investigated, and these species resided in either discrete cavities or channels within the host crystal, depending on the guest. For the most part, traces obtained from thermal analyses were highly convoluted and difficult to interpret. As a result, guest release onset temperatures could not be determined for all of the inclusion complexes. In some cases, however, this temperature was successfully measured and correlated directly with the observed selectivity order of the host suggested by the competition experiments. Both enhanced and contrasting results were obtained for the four host compounds. In all cases, 1,2-DAX and 1,2-DAT successfully formed complexes with each of the guest species from each series. Interestingly, the 1,4-derived hosts, however, were more selective in that 1,4-DAX did not complex with only one of the guest solvents, while 1,4-DAT did not enclathrate as many as ten of these solvents. The competition investigations showed that, in most of these experiments, the host compounds displayed selectivity for one of the guests present in the mixture, and in some cases, this selectivity was pronounced, alluding to the feasibility of separating related guests from one another through host–guest chemistry principles. Computational calculations were, additionally, conducted on each of the host molecules in order to gain a better understanding of their geometries, and to compare these with the apohost crystal structures. Significant geometry differences were noted between the calculated and crystal structures.
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- Date Issued: 2020
Assessment of the host properties of selected optically pure, racemic and achiral compounds
- Authors: Jooste, Daniel Victor
- Date: 2017
- Subjects: Organic compounds -- Synthesis Cyclic compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/18826 , vital:28735
- Description: This study focussed on the synthesis and host properties of four different broad categories of potential host compounds, namely optically active and racemic TADDOL [(4R,5R)-α,α,α’,α’-tetraphenyl-1,3-dioxolane-4,5-dimethanol] and derivatives, TTFOL [(3R,4R)-2,2,5,5-tetraphenyltetrahydrofuran-3,4-diol], amino acid ester-derived compounds [(S)-4-(2-amino-3-hydroxy-3,3-diphenylpropyl)phenol], and compounds derived from xanthone [9-amino-9-phenylxanthene and 1,2-bis(9-phenyl-9H-xanthen-9-yl)hydrazine]. The potential hosts were recrystallized from a range of possible guest species and the resulting solids analysed by 1H-NMR spectroscopy. If inclusion was observed by this technique, the complexes were analysed further using single crystal X-ray techniques and thermal experiments where possible. Competition studies were carried out where these were deemed appropriate. Optically active and racemic TADDOLs were synthesized using L-(+) and DL-(±)-tartaric acid respectively. Two further derivatives were prepared whereby the hydroxyl groups were substituted for chlorine and azide in order to assess the effect of this change on the inclusion ability. Both the optically active and racemic TADDOLs displayed similar host abilities, complexing with guests with 1:1 host:guest ratios as determined through 1H-NMR spectroscopy. Competition experiments showed that both forms of TADDOL exhibited similar guest preferences for pyridine and the methylpyridine isomers. Pyridine however was preferred over 2-methylpyridine by optically active TADDOL while the racemic form preferred this methyl-substituted guest over pyridine. Thermal analysis studies showed, surprisingly, that the TADDOL complexes containing pyridine had higher relative thermal stabilities than those containing the methylpyridines, whether the host was optically active or not. The preference order of these hosts for these guests can, therefore, not be used as a predictor for the relative thermal stability of the complexes. TTFOL was found to include only ethanol, 2-methylpyridine and dioxane from the range of guest species used; the complex with dioxane did not produce X-ray quality crystals. The L-tyrosine derivative, (S)-4-(2-amino-3-hydroxy-3,3-diphenylpropyl)phenol, was an ineffective host incapable of including any of the guests used in these experiments. The two xanthone derivatives, 9-amino-9-phenylxanthene and 1,2-bis(9-phenyl-9H-xanthen-9-yl)hydrazine each formed complexes with one guest species (morpholine and DMF, respectively).
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- Date Issued: 2017