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Postgraduate Thesis: Resonance Raman and time-resolved spectroscopic studies of selected chlorobenzophenone and fluoroquinolones
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TitleResonance Raman and time-resolved spectroscopic studies of selected chlorobenzophenone and fluoroquinolones
 
AuthorsLi, Wen
李闻
 
Issue Date2012
 
PublisherThe University of Hong Kong (Pokfulam, Hong Kong)
 
AbstractNanosecond 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.
 
AdvisorsPhillips, DL
 
DegreeDoctor of Philosophy
 
SubjectBenzoates.
Organic compounds - Spectra.
Photochemistry.
Raman spectroscopy.
Time-resolved spectroscopy.
 
Dept/ProgramChemistry
 
DC FieldValue
dc.contributor.advisorPhillips, DL
 
dc.contributor.authorLi, Wen
 
dc.contributor.author李闻
 
dc.date.hkucongregation2012
 
dc.date.issued2012
 
dc.description.abstractNanosecond 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.
 
dc.description.naturepublished_or_final_version
 
dc.description.thesisdisciplineChemistry
 
dc.description.thesisleveldoctoral
 
dc.description.thesisnameDoctor of Philosophy
 
dc.identifier.hkulb4807974
 
dc.languageeng
 
dc.publisherThe University of Hong Kong (Pokfulam, Hong Kong)
 
dc.relation.ispartofHKU Theses Online (HKUTO)
 
dc.rightsThe author retains all proprietary rights, (such as patent rights) and the right to use in future works.
 
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License
 
dc.source.urihttp://hub.hku.hk/bib/B48079741
 
dc.subject.lcshBenzoates.
 
dc.subject.lcshOrganic compounds - Spectra.
 
dc.subject.lcshPhotochemistry.
 
dc.subject.lcshRaman spectroscopy.
 
dc.subject.lcshTime-resolved spectroscopy.
 
dc.titleResonance Raman and time-resolved spectroscopic studies of selected chlorobenzophenone and fluoroquinolones
 
dc.typePG_Thesis
 
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<item><contributor.advisor>Phillips, DL</contributor.advisor>
<contributor.author>Li, Wen</contributor.author>
<contributor.author>&#26446;&#38395;</contributor.author>
<date.issued>2012</date.issued>
<description.abstract>&#65279;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&#8242;-dichlorobenzophenone (4,4&#8242;-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&#8242;-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.</description.abstract>
<language>eng</language>
<publisher>The University of Hong Kong (Pokfulam, Hong Kong)</publisher>
<relation.ispartof>HKU Theses Online (HKUTO)</relation.ispartof>
<rights>The author retains all proprietary rights, (such as patent rights) and the right to use in future works.</rights>
<rights>Creative Commons: Attribution 3.0 Hong Kong License</rights>
<source.uri>http://hub.hku.hk/bib/B48079741</source.uri>
<subject.lcsh>Benzoates.</subject.lcsh>
<subject.lcsh>Organic compounds - Spectra.</subject.lcsh>
<subject.lcsh>Photochemistry.</subject.lcsh>
<subject.lcsh>Raman spectroscopy.</subject.lcsh>
<subject.lcsh>Time-resolved spectroscopy.</subject.lcsh>
<title>Resonance Raman and time-resolved spectroscopic studies of selected chlorobenzophenone and fluoroquinolones</title>
<type>PG_Thesis</type>
<identifier.hkul>b4807974</identifier.hkul>
<description.thesisname>Doctor of Philosophy</description.thesisname>
<description.thesislevel>doctoral</description.thesislevel>
<description.thesisdiscipline>Chemistry</description.thesisdiscipline>
<description.nature>published_or_final_version</description.nature>
<date.hkucongregation>2012</date.hkucongregation>
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