Supramolecular systems, which are formed by the noncovalent intermolecular interactions between molecules, are highly dynamic. The high reversibility of supramolecular systems leads to some functional features that cannot be achieved by the single chemical component. The kinetic information for the supramolecular systems can not be inferred from thermodynamic studies or structural studies. Furthermore, the information provided by the dynamic study can be employed to infer or explain the results from the thermodynamic study and the structural study.
The first objective of this work was to study the dynamics and the binding mechanism of cucurbit[7]uril with a charged guest molecule (2-naphthyl-1-ethylammonium cation, NpAmH+). In general, the binding affinity of cucurbit[7]uril to the positively charged guests are very high compared with other host systems such as cyclodextrins and bile salt aggregates. In this work, the complexation of cucurbit[7]uril and NpAmH+ was studied from a kinetic point of view. Results showed that the high binding affinity of cucurbit[7]uril to NpAmH+ was due to the high association rate constant and the low dissociation rate constant for the complexation of cucurbit[7]uril and NpAmH+. Moreover, the competition between co-cations and NpAmH+ for the binding sites of cucurbituril molecules retarded the complexation process for cucurbit[7]uril binding to NpAmH+ and decreased the overall equilibrium constant for the formation of cucurbit[7]uril-NpAmH+ complex.
The second objective of this work was to study the chiral recognition observed for the formation of 2:2 complexes between β-cyclodextrin and 2-naphthyl-1-ethanol (NpOH). The binding of β-cyclodextrin and NpOH leads to the formation of two 1:1 complexes and three 2:2 complexes. The binding dynamics of NpOH with β-cyclodextrin in the 1:1 complex is fast and occurs within microseconds. A much slower dynamics was observed for the formation of the 2:2 complex. Results showed that more 2:2 complex were formed for (R)-NpOH than for (S)-NpOH, which is due to the difference of the dissociation rate constant of the 2:2 complex for both NpOH enantiomers. The dissociation rate constant of the 2:2 complex for (R)-NpOH is 46.8% lower than that for (S)-NpOH while the association rate constant of the 2:2 complex are similar for both NpOH enantiomers.
The third objective of this work was to study the dynamics and the binding mechanism of octa acid with pyrene. As known from the work of other researchers, the accessibility of small molecules (e.g. I- or O2) to pyrene bound to octa acid is largely limited by the octa acid capsule. In this study, a two-step successive process was observed for the complexation of octa acid and pyrene. The first step, which was related to the formation of octa acid-pyrene 1:1 complex, was sufficiently fast to be viewed as a pre-equilibrium process. The second step, which was related to the formation of octa acid-pyrene 2:1 complex, was slow on the millisecond – second time scale. The high binding affinity of octa acid to pyrene was observed, which is due to the low dissociation rate constant for the octa acid-pyrene 2:1 complex. / Graduate
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/3557 |
| Date | 07 September 2011 |
| Creators | Tang, Hao |
| Contributors | Bohne, Cornelia |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | Available to the World Wide Web |
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