Open AccessToward Fully Unsupervised Anharmonic Computations Complementing Experiment for Robust and Reliable Assignment and Interpretation of IR and VCD Spectra from Mid-IR to NIR: The Case of 2,3-Butanediol and trans-1,2-Cyclohexanediol
Author(s) -
Lorenzo Paoloni,
Giuseppe Mazzeo,
Giovanna Longhi,
Sergio Abbate,
Marco Fusè,
Julien Bloino,
Vincenzo Barone
Publication year - 2020
Publication title -
the journal of physical chemistry. a/the journal of physical chemistry. a.
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.756
H-Index - 235
eISSN - 1520-5215
pISSN - 1089-5639
DOI - 10.1021/acs.jpca.9b11025
Subject(s) - anharmonicity , computation , spectral line , scaling , interpretation (philosophy) , vibrational circular dichroism , density functional theory , harmonic , amplitude , molecule , chemistry , molecular physics , computational chemistry , computational physics , statistical physics , physics , algorithm , computer science , quantum mechanics , mathematics , geometry , programming language
The infrared (IR) and vibrational circular dichroism (VCD) spectra of 2,3-butanediol and trans -1,2-cyclohexanediol from 900 to 7500 cm -1 (including mid-IR, fundamental CH and OH stretchings, and near-infrared regions) have been investigated by a combined experimental and computational strategy. The computational approach is rooted in density functional theory (DFT) computations of harmonic and leading anharmonic mechanical, electrical, and magnetic contributions, followed by a generalized second-order perturbative (GVPT2) evaluation of frequencies and intensities for all the above regions without introducing any ad hoc scaling factor. After proper characterization of large-amplitude motions, all resonances plaguing frequencies and intensities are taken into proper account. Comparison of experimental and simulated spectra allows unbiased assignment and interpretation of the most interesting features. The reliability of the GVPT2 approach for OH stretching fundamentals and overtones is confirmed by the remarkable agreement with a local mode model purposely tailored for the latter two regions. Together with the specific interest of the studied molecules, our results confirm that an unbiased assignment and interpretation of vibrational spectra for flexible medium-size molecules can be achieved by means of a nearly unsupervised reliable, robust, and user-friendly DFT/GVPT2 model.