Analysis Of The Microwave Spectrum, Structure And Internal Rotation Of The Ch3 Group In N-methylimidazole…h2o And 2-methylimidazole…h2o Complexes

Cummings, Charlotte Nicole

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https://hdl.handle.net/2142/116952 Copy

Description

Title

Analysis Of The Microwave Spectrum, Structure And Internal Rotation Of The Ch3 Group In N-methylimidazole…h2o And 2-methylimidazole…h2o Complexes

Author(s)

Cummings, Charlotte Nicole

Contributor(s)

• Walker, Nick
• Heitkämper, Juliane
• Medcraft, Chris
• Gougoula, Eva

Issue Date

2022-06-24

Keyword(s)

Clusters/Complexes

Abstract

The broadband rotational spectra of \emph{N}-methylimidazole…\chem{H_2O} and 2-methylimidazole…\chem{H_2O} have been recorded by Chirped Pulse Fourier Transform Microwave (CP-FTMW) spectroscopy in the frequency range 6.5-18.5 GHz. Each complex was generated by the co-expansion of the methylimidazole isomer and water in an argon backing gas. The spectra of five isotopologues of each complex have been assigned, allowing rotational constants (\emph{A$_{0}$}, \emph{B$_{0}$} and \emph{C$_{0}$}), centrifugal distortion constants (D$_{J}$ and D$_{JK}$), nuclear quadrupole coupling constants (\emph{$\chi$$_{aa}$} and \emph{$\chi$$_{bb-cc}$}) and internal rotation parameters (\emph{V$_{3}$}, $\angle$(\emph{i, b})) to be determined. In both \emph{N}-methylimidazole…\chem{H_2O} and 2-methylimidazole…\chem{H_2O}, a hydrogen bond forms between H$_2$O acting as a hydrogen bond donor and the pyridinic nitrogen of the methylimidazole ring which is the hydrogen bond acceptor. In addition, there is a weak electrostatic interaction between the oxygen atom of \chem{H_2O} and the hydrogen or \chem{CH_3} group attached to the C2 carbon of the methylimidazole ring. The (\emph{V$_{3}$}) barrier to internal rotation of the \chem{CH_3} group has been determined for each complex. For \emph{N}-methylimidazole…\chem{H_2O}, the \emph{V$_{3}$} barrier is essentially unchanged from the monomer. For 2-methylimidazole…\chem{H_2O}, there is a large increase in the barrier height (relative to the \emph{V$_{3}$} of \chem{CH_3} in the 2-methylimdizole monomer) which results from the interaction between the oxygen atom of \chem{H_2O} and the \chem{CH_3} group.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

eng

Handle URL

https://hdl.handle.net/2142/116952

DOI

https://doi.org/10.15278/isms.2022.FD04

Copyright and License Information

Copyright 2022 held by the authors

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