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Figure 3.7: Infrared spectra of the anionic and cationic forms of deprotonated
HBDI computed with RI-MP2/cc-pVTZ.
computed IR spectra of anionic and cationic deprotonated HBDI. The anion spectrum is
dominated by a band at 1691 cm1, which is an asymmetric CO stretch strongly coupled
with an asymmetric bridge vibration. In the cation, this mode changes its character to an
almost pure bridge vibration, loses intensity and is blue-shifted. Instead, those modes
gain intensity that involve the imidazolin moiety hosting a positive charge. The two
most intense bands are predominantly CH3 vibrations at 1534 and 1435 cm1, followed
by lower frequency bands involving skeletal imidazolin vibrations.
3.4 Chapter 3 conclusions
We characterized changes in the electronic structure of the deprotonated HBDI anion
due to one- and two-electron oxidation processes. One-electron oxidation produces
a doublet radical with strongly blue-shifted absorption, whereas the absorption in the
cation is red-shifted by almost 0.6 eV with respect to the anion. From the electronic
structure point of view, the cation has a closed-shell singlet ground state, and is expected
to be relatively stable chemically.
99
Object Description
| Title | Development of predictive electronic structure methods and their application to atmospheric chemistry, combustion, and biologically relevant systems |
| Author | Epifanovskiy, Evgeny |
| Author email | epifanov@usc.edu; epifanov@usc.edu |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Chemistry |
| School | College of Letters, Arts and Sciences |
| Date defended/completed | 2011-03-21 |
| Date submitted | 2011 |
| Restricted until | Unrestricted |
| Date published | 2011-04-28 |
| Advisor (committee chair) | Krylov, Anna I. |
| Advisor (committee member) |
Wittig, Curt Johnson, Clifford |
| Abstract | This work demonstrates electronic structure techniques that enable predictive modeling of the properties of biologically relevant species. Chapters 2 and 3 present studies of the electronically excited and detached states of the chromophore of the green fluorescent protein, the mechanism of its cis-trans isomerization, and the effect of oxidation. The bright excited ππ∗ state of the chromophore in the gas phase located at 2.6 eV is found to have an autoionizing resonance nature as it lies above the electron detachment level at 2.4 eV. The calculation of the barrier for the ground-state cis-trans isomerization of the chromophore yields 14.8 kcal/mol, which agrees with an experimental value of 15.4 kcal/mol; the electronic correlation and solvent stabilization are shown to have an important effect. In Chapter 3, a one-photon two-electron mechanism is proposed to explain the experimentally observed oxidative reddening of the chromophore. Chapter 4 considers the excited states of uracil. It demonstrates the role of the one-electron basis set and triples excitations in obtaining the converged values of the excitation energies of the nπ∗ and ππ∗ states. The effects of the solvent and protein environment are included in some of the models.; Chapter 5 describes an implementation of the algorithm for locating and exploring intersection seams between potential energy surfaces. The theory is illustrated with examples from atmospheric and combustion chemistry. |
| Keyword | electronic structure theory; coupled clusters theory; equation of motion theory; organic chromophore; green fluorescent protein; uracil |
| Language | English |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m3801 |
| Contributing entity | University of Southern California |
| Rights | Epifanovskiy, Evgeny |
| Repository name | Libraries, University of Southern California |
| Repository address | Los Angeles, California |
| Repository email | cisadmin@lib.usc.edu |
| Filename | etd-Epifanovskiy-4557 |
| Archival file | uscthesesreloadpub_Volume14/etd-Epifanovskiy-4557.pdf |
Description
| Title | Page 109 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | Figure 3.7: Infrared spectra of the anionic and cationic forms of deprotonated HBDI computed with RI-MP2/cc-pVTZ. computed IR spectra of anionic and cationic deprotonated HBDI. The anion spectrum is dominated by a band at 1691 cm1, which is an asymmetric CO stretch strongly coupled with an asymmetric bridge vibration. In the cation, this mode changes its character to an almost pure bridge vibration, loses intensity and is blue-shifted. Instead, those modes gain intensity that involve the imidazolin moiety hosting a positive charge. The two most intense bands are predominantly CH3 vibrations at 1534 and 1435 cm1, followed by lower frequency bands involving skeletal imidazolin vibrations. 3.4 Chapter 3 conclusions We characterized changes in the electronic structure of the deprotonated HBDI anion due to one- and two-electron oxidation processes. One-electron oxidation produces a doublet radical with strongly blue-shifted absorption, whereas the absorption in the cation is red-shifted by almost 0.6 eV with respect to the anion. From the electronic structure point of view, the cation has a closed-shell singlet ground state, and is expected to be relatively stable chemically. 99 |
