Quantitative characterisation of the ring normal modes. Pyridine as a study case

E Benassi; H Fan

doi:10.1016/j.saa.2020.119026

Quantitative characterisation of the ring normal modes. Pyridine as a study case

Spectrochim Acta A Mol Biomol Spectrosc. 2021 Feb 5:246:119026. doi: 10.1016/j.saa.2020.119026. Epub 2020 Oct 3.

Authors

E Benassi¹, H Fan²

Affiliations

¹ School of Chemistry and Chemical Engineering, Shihezi University, Shihezi 832003, China. Electronic address: ebenassi3@gmail.com.
² Chemistry Department, School of Sciences and Humanities, Nazarbayev University, Nur-Sultan City 010000, Kazakhstan.

PMID: 33070012
DOI: 10.1016/j.saa.2020.119026

Abstract

In the present work, the vibrational normal modes (NM) of pyridine were revisited. Quantum Chemical calculations were performed to help understand the true nature of some ring related vibrational normal modes (RNM) and how they may be correlated with the electronic structure on the ring. The 27 vibrational normal modes were decomposed into the molecular internal coordinates, and the interest was focused on 7 of them, involving the in-plane ring motion. The electronic structure was analysed through frontier Molecular Orbitals (MO), maps of Molecular Electrostatic Potential surfaces (MEPs) and Natural Bond Orbital (NBO) analysis in a dynamic manner, wherein, each vibration was scanned. The present investigation is aimed to provide the Reader with a quantitative characterisation of the RNMs of pyridine.

Keywords: Anharmonicity; Dynamic natural bond orbital analysis; Ring related normal modes.