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Table 2.3: Vertical triplet pp electronic excitation energies (DE, in eV) of the HBDI
anion in the gas phase.
Basis set CIS SOS-CIS(D)
cc-pVDZ 2.03 1.91
aug-cc-pVDZ 2.02 1.88
cc-pVTZ 2.03 1.86
solute. For example, dipole moment of water in bulk water is about 30% larger than in
the gas phase. More polar charge distribution in the ground state in solvent is clearly
seen from the respective NBO charges (see Table 2.5). Thus, for the difference of dipole
moments of two states one may anticipate an enhanced effect.
Triplet pp state
The vertical excitation energies at the RI-MP2/cc-pVTZ geometry of the lowest triplet
state are summarized in Table 2.3. The analysis of the wave function confirms that the
triplet is derived from the transitions between the same orbitals as the singlet (Fig. 2.3).
As expected, all methods consistently place the triplet considerably below the singlet.
The variations between the methods are smaller for the triplet state. Our best value
(SOS-CIS(D)/cc-pVTZ) is 1.86 eV. The 0.76 eV gap between the singlet and the triplet
does not suggest efficient intersystem crossing at this geometry. The triplet state is
0.3–0.4 eV below VDE and is, therefore, a bound electronic state. Thus, much longer
lifetime is expected for this state (as compared to the singlet), not only because the
radiationless relaxation to the ground state is a spin-forbidden process, but also because
the autoionization channel is absent.
60
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 70 |
| Contributing entity | University of Southern California |
| Repository email | cisadmin@lib.usc.edu |
| Full text | Table 2.3: Vertical triplet pp electronic excitation energies (DE, in eV) of the HBDI anion in the gas phase. Basis set CIS SOS-CIS(D) cc-pVDZ 2.03 1.91 aug-cc-pVDZ 2.02 1.88 cc-pVTZ 2.03 1.86 solute. For example, dipole moment of water in bulk water is about 30% larger than in the gas phase. More polar charge distribution in the ground state in solvent is clearly seen from the respective NBO charges (see Table 2.5). Thus, for the difference of dipole moments of two states one may anticipate an enhanced effect. Triplet pp state The vertical excitation energies at the RI-MP2/cc-pVTZ geometry of the lowest triplet state are summarized in Table 2.3. The analysis of the wave function confirms that the triplet is derived from the transitions between the same orbitals as the singlet (Fig. 2.3). As expected, all methods consistently place the triplet considerably below the singlet. The variations between the methods are smaller for the triplet state. Our best value (SOS-CIS(D)/cc-pVTZ) is 1.86 eV. The 0.76 eV gap between the singlet and the triplet does not suggest efficient intersystem crossing at this geometry. The triplet state is 0.3–0.4 eV below VDE and is, therefore, a bound electronic state. Thus, much longer lifetime is expected for this state (as compared to the singlet), not only because the radiationless relaxation to the ground state is a spin-forbidden process, but also because the autoionization channel is absent. 60 |
