BARRIERS TO INTERNAL ROTATION AND MOLECULAR GEOMETRIES OF COMPLEXES FORMED BETWEEN ISOMERS OF METHYLTHIAZOLE AND WATER STUDIED BY MICROWAVE SPECTROSCOPY

Cummings, Charlotte

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https://hdl.handle.net/2142/122367 Copy

Description

Title

BARRIERS TO INTERNAL ROTATION AND MOLECULAR GEOMETRIES OF COMPLEXES FORMED BETWEEN ISOMERS OF METHYLTHIAZOLE AND WATER STUDIED BY MICROWAVE SPECTROSCOPY

Author(s)

Cummings, Charlotte

Contributor(s)

• Walker, Nick
• Nguyen, Ha Vinh Lam
• Song, Wentao

Issue Date

2023-06-19

Keyword(s)

• Large amplitude motions
• internal rotation

Abstract

The (V₃) barriers to internal rotation of many five-membered heteroaromatic rings have been investigated using microwave spectroscopy. The rotational spectra of 2-methylthiazole···H₂O, 4-methylthiazole···H₂O and 5-methylthiazole···H₂O were recorded over the frequency range 7.0-18.5 GHz using Chirped Pulse Fourier Transform Microwave (CP-FTMW) spectroscopy. The complexes were generated in a supersonic expansion containing low concentrations of a methylthiazole isomer and water in an argon buffer gas. In total spectra of five isotopologues of each complex have been assigned and analysed. The fitting of observed A-species transition frequencies to Watson’s S-reduced Hamiltonian within PGOPHER gave “effective” fits of each complex. Global fits (simultaneous fitting of both A- and E- species transitions) have been performed using XIAM allowing the determination of rotational constants (A₀, B₀, C₀), centrifugal distortion constants (DJ, DJK, d₁, d₂) and nuclear quadrupole coupling constants (χₐₐ(N) and χbb(N) - χcc(N)) as well as the V₃ barrier to internal rotation. The monohydrate complexes are formed by a non-linear hydrogen bond between H₂O acting as the hydrogen bond donor and the nitrogen atom of the methylthiazole ring which is the hydrogen bond acceptor. The influence formation of the monohydrate complex on the V₃ barrier will be discussed.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

Text

Language

eng

Handle URL

https://hdl.handle.net/2142/122367

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