Nanosecond time-resolved resonance Raman (ns-TR3) spectroscopy was used in this thesis to
study the photoreduction reactions and the photochemistry of chloro-substituted benzophenone
(ClBP) triplets. The 3-chlorobenzophenone (3-ClBP), 4-chlorobenzophenone (4-ClBP) and
4,4′-dichlorobenzophenone (4,4′-diClBP) triplets exhibit similar properties to the parent BP
triplet. In isopropyl alcohol (IPA), the hydrogen abstraction reactions were observed for the
3-ClBP, 4-ClBP and 4,4′-diDlBP triplets. The diphenylketyl (DPK) radicals produced from the
hydrogen abstraction reactions were observed and the recombination of the DPK and
dimethylketyl radicals at the para-position was observed to form a light absorption transient
(LAT) species. In MeCN:H2O/1:1 aqueous solutions, these DPK radicals were also observed but
with a slower formation rate and the LAT species was produced by reaction with OH radicals.
Density functional theory (DFT) calculations were employed to help identify the intermediates
seen in the TR3 spectra and to help provide information about the vibrational motions of the
molecules examined. The 2-Cl-DPK radical was also observed in the TR3 spectra obtained in an
IPA solvent. However, the yield of the 2-Cl-DPK radical and the hydrogen abstraction rate was
observed to be significantly lower than that of the other ClBP examined here under the same
experimental conditions. The results DFT calculations show that the 2-chloro substituent changes
the geometry and the electron density of the molecular orbitals of the BP triplet so that the
2-chloro substituent reduces the hydrogen abstraction ability the triplet state, which is different
the hypothesis put forward by some previous studies that an electron-withdrawing group should
increase the photoreduction ability of BP derivatives.
Norfloxacin (NF) and Enoxacin (EN) are representative derivatives of Fluoroquinolones (FQ).
There are four forms of NF and EN and these different forms can coexist in aqueous solutions.
The UV-vis absorption and resonance Raman (RR) spectra of NF and EN have been obtained in
neat acetonitrile (MeCN), MeCN:HClO4-H2O/1:1 (pH?1), MeCN:H2O/1:1 (pH?7.5) and
MeCN:NaOH-H2O/1:1 (pH?13) solutions. The species observed in the spectra are assigned by
comparison of the experimental spectra to the DFT calculated spectra and the vibrational modes
are also described from the results of the DFT calculations. The absorption spectra of NF and EN
obtained in MeCN:H2O/1:1 solutions show that some other species coexist with the tautomeric
forms in the neutral aqueous solution. The RR spectra of the tautomeric forms of NF and EN
were obtained by subtraction of the RR spectra of the neutral and anionic forms from the RR
spectra of NF and EN in neutral aqueous solutions. The results suggest that NF and EN exists in
neutral, anionic and tautomeric forms in neutral aqueous solutions. The time dependant DFT
calculation results suggest that the fluorine atom has little contribution to the lowest unoccupied
molecular orbitals of the different forms of NF and EN. / published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy
| Identifer | oai:union.ndltd.org:HKU/oai:hub.hku.hk:10722/161569 |
| Date | January 2012 |
| Creators | Li, Wen, 李闻 |
| Contributors | Phillips, DL |
| Publisher | The University of Hong Kong (Pokfulam, Hong Kong) |
| Source Sets | Hong Kong University Theses |
| Language | English |
| Detected Language | English |
| Type | PG_Thesis |
| Source | http://hub.hku.hk/bib/B48079741 |
| Rights | The author retains all proprietary rights, (such as patent rights) and the right to use in future works., Creative Commons: Attribution 3.0 Hong Kong License |
| Relation | HKU Theses Online (HKUTO) |
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