Rotationally Resolved Electronic Spectra of 2- and 3-Methylanisole in the Gas Phase: A Study of Methyl Group Internal Rotation
| Autor: | John T. Yi, David W. Pratt, Leonardo Alvarez-Valtierra |
|---|---|
| Rok vydání: | 2006 |
| Předmět: |
Chemistry
Substituent Rotation Molecular physics Spectral line Surfaces Coatings and Films chemistry.chemical_compound Computational chemistry Excited state Materials Chemistry Rigid rotor Physics::Chemical Physics Physical and Theoretical Chemistry Conformational isomerism Molecular beam Methyl group |
| Zdroj: | The Journal of Physical Chemistry B. 110:19914-19922 |
| ISSN: | 1520-5207 1520-6106 |
| DOI: | 10.1021/jp062050h |
| Popis: | Rotationally resolved fluorescence excitation spectra of several torsional bands in the S1-- S0 electronic spectra of 2-methylanisole (2MA) and 3-methylanisole (3MA) have been recorded in the collision-free environment of a molecular beam. Some of the bands can be fit with rigid rotor Hamiltonians; others exhibit perturbations produced by the coupling between the internal rotation of the methyl group and the overall rotation of the entire molecule. Analyses of these data show that 2MA and 3MA both have planar heavy-atom structures; 2MA has trans-disposed methyl and methoxy groups, whereas 3MA has both cis- and trans-disposed substituents. The preferred orientations (staggered or eclipsed) in two of the conformers and the internal rotation barriers of the methyl groups in all three conformers change when they are excited by light. Additionally, the values of the barriers opposing their motion depend on the relative positions of the substituent groups, in both electronic states. In contrast, no torsional motions of the attached methoxy groups were detected. Possible reasons for these behaviors are discussed. |
| Databáze: | OpenAIRE |
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