Photochromism is a phenomenon where two isomers with markedly different absorption spectra are interconverted by a reversible photochemical reaction. The photochromism of 1’,3’,3’-trimethyl-6-nitrospiro[2H-1]-benzopyran-2,2’-indoline (NSP) and 1,2-bis(2,4-dimethyl-5-phenyl-3-thienyl)-3,3,4,4,5,5-hexafluoro-1-cyclopentene) (DAE) was studied in aqueous solutions containing NaCl and the bile salts sodium cholate (NaC), sodium deoxycholate (NaDC) or sodium taurocholate (NaTC).
Bile salts are amphiphilic compounds that aggregate in water. These aggregates can solubilize hydrophobic organic compounds in water and affect the reactivity of the bound compounds. NSP and DAE are photochromic compounds that can be switched between a colored and a colorless isomer. The colored isomer of DAE can only be transformed into the colorless form by irradiation of light, while the colored isomer of NSP is also converted into the colorless form by a dark reaction.
The dark reaction rate constant of NSP increases at high concentrations of bile salt and NaCl. The bile salt structure also affects the dark reaction rate constant, which is smaller in NaTC and approximately the same in NaC and NaDC. The activation energy for the reaction in all conditions studied is similar to the value reported for polar organic solvents.
A method that employs HPLC was developed to determine the molar absorptivity coefficients of photochromic compounds. The values obtained were important to determine the quantum yields for photocoloration (ΦAB) and photodecoloration (ΦBA). Quantum yield values were determined by a photokinetic method that employs irradiation at a single wavelength and numerical analysis. The values of ΦAB and ΦBA for DAE in bile salts are the same as the values in cyclohexane. For NSP, ΦAB is dependent on the structure of the bile salt and increases in the order NaTC < NaC < NaDC. / Graduate
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/3555 |
| Date | 06 September 2011 |
| Creators | da Silva Santos, Cerize |
| 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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