Issue 25, 2019

Stretching of cis-formic acid: warm-up and cool-down as molecular work-out

Abstract

A new technique to rotationally simplify and Raman-probe conformationally and vibrationally excited small molecules is applied to the cistrans isomerism of formic acid. It quintuples the previously available gas phase vibrational data base on this excited form of a strongly anharmonic planar molecule despite its limited spectral resolution. The newly determined cis-formic acid fundamentals allow for a balanced vibrational benchmark on both rotamers of formic acid. Assuming the adequacy of vibrational perturbation theory, it reveals weaknesses of standard methods for these systems like B3LYP-D3(BJ)/aVQZ VPT2 or PBE0-D3(BJ)/aVQZ VPT2. The functionals ωB97-XD and M06-2X additionally suffer from severe integration grid size and symmetry dependencies. The vibrational benchmark suggests B2PLYP-D3(BJ)/aVQZ VPT2 and MP2/aVQZ VPT2 as partially competitive and in any case efficient alternatives to computationally demanding coupled cluster vibrational configuration interaction calculations. Whether this is due to fortuitous compensation between electronic structure and vibrational perturbation error remains to be explored.

Graphical abstract: Stretching of cis-formic acid: warm-up and cool-down as molecular work-out

Article information

Article type
Edge Article
Submitted
30 Mar 2019
Accepted
15 May 2019
First published
16 May 2019
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2019,10, 6285-6294

Stretching of cis-formic acid: warm-up and cool-down as molecular work-out

K. A. E. Meyer and M. A. Suhm, Chem. Sci., 2019, 10, 6285 DOI: 10.1039/C9SC01555H

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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