Potential energy functions and conformations of trans-stilbene, 4-methoxy-trans-stilbene, and bicyclo(3.1.0)hexan-3-one in their ground and excited electronic states /
The fluorescence excitation spectra and dispersed fluorescence spectra of trans-stilbene have been recorded and analyzed. Vibrational assignments for the eight low- frequency modes have been made for both the So and SI (ir, 'T') electronic states, and these differ substantially from those...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1994.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=741965021&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The fluorescence excitation spectra and dispersed fluorescence spectra of trans-stilbene have been recorded and analyzed. Vibrational assignments for the eight low- frequency modes have been made for both the So and SI (ir, 'T') electronic states, and these differ substantially from those of previous workers. Two-dimensional kinetic and potential energy calculations were carried out in order to determine the potential energy surfaces for the two phenyl internal rotations, V37 and v48. The function V(01,02) = '/2V2(2+cos2O, +cos2'O2) + V12COs240,cos2O2 + V',2sin2o,sin2(k2 fits the observed data (nine frequencies for So, six for S,) extremely well. The barriers to simultaneous internal rotation of both phenyl groups are given by twice the V2 values. The fundamental frequencies for these torsions are V37=9 cm-' and v4,=118 cm-' for the So state and V37=35 cm-' and V48=110 CM-1 for the SI excited state. The third torsion, P35, which is the internal rotation about the C=C bond, was assigned at 101 cm-' for the So state based on a series of overtone frequencies (202 cm-', 404 cm-', etc.). For SI P35=99 CM-1 based on observed frequencies at 198, 396 cm-', etc. Kinetic energy calculations were also carried out for this mode, and a one- dimensional potential energy function of the form V(O) = 2VI(l -COSO) + '/2V2(l -cos2O) + 1/2V4(l -cos4O) I/ was utilized to reproduce the frequencies for the ground state. For the excited state an additional V8 term was added in order to fit the data for the trans potential energy well. The data indicate that the trans - twist barrier for the SI state is higher than 1400 cm-'. In order to better understand the stilbene system, the fluorescence excitation and dispersed fluorescence spectra of 4-methoxy-trans-stilbene were also recorded and the results were compared to those for transstilbene. The fluorescence excitation spectrum of bicyclo[3. 1. O]hexan-3 -one was also recorded and preliminary results for the carbonyl wagging and ring- puckering vibrations have been obtained. |
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| Item Description: | Vita. "Major Subject: Chemistry". |
| Physical Description: | xvii, 206 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |