A Microwave Spectroscopic Study Of Methylated Indoles: Internal Rotation And Nuclear Quadrupole Coupling

Gurusinghe, Ranil

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https://hdl.handle.net/2142/51116 Copy

Description

Title

A Microwave Spectroscopic Study Of Methylated Indoles: Internal Rotation And Nuclear Quadrupole Coupling

Author(s)

Gurusinghe, Ranil

Contributor(s)

Tubergen, Michael

Issue Date

2014-06-19

Keyword(s)

Large amplitude motions, internal rotation

Abstract

The barrier to methyl internal rotation of an asymmetric two ring system depends on the position of the methyl substitution. A cavity based Fourier transform microwave spectrometer was used to record rotational spectra of different methyl substituted indoles in the range of 10.5 - 20 GHz. About 160 hyperfine components arising from about 30 rotational transitions were assigned for each 1- and 3-methylindole. The program XIAM$^{a}$ was used to fit the rotational constants, distortion constants, nuclear quadrupole coupling constants and barrier to internal rotation to the measured transition frequencies of the A and E internal rotation states.\\ The best fit values for the rotational constants are A = 2651.12(2) MHz, B = 1305.266(2) MHz, C = 879.800(2) MHz for 1-methylindole and A = 2603.7224(5) MHz, B = 1268.7886(1) MHz, C = 857.8091(1) MHz for 3-methylindole. The different values observed for the barrier to internal rotation, 279.8(3) \wn for 1-methylindole and 433(1) \wn for 3-methylindole, may be due to the different rotor axis lengths and differences in local $\pi$-electron density.\\ Progress on the assignment of additional methylated indoles will also be presented.\\ $^{a}$H. Hartwig and H. Dreizler, Z. Naturforsch, 51a, 923 - 932.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

Permalink

http://hdl.handle.net/2142/51116

DOI

https://doi.org/10.15278/isms.2014.RJ03

Copyright and License Information

Copyright 2014 by the authors. Licensed under a Creative Commons Attribution 4.0 International License. http://creativecommons.org/licenses/by/4.0/

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