Vibrational spectroscopy is a useful technique for probing chemical environments. The development of models that can reproduce the spectra of nitriles and azides is valuable because these probes are uniquely suited for investigating complex systems. Empirical vibrational spectroscopic maps are commonly employed to obtain the instantaneous vibrational frequencies during molecular dynamics simulations but often fail to adequately describe the behavior of these probes, especially in its transferability to a diverse range of environments. In this paper, we demonstrate several reasons for the difficulty in constructing a general-purpose vibrational map for methyl thiocyanate (MeSCN), a model for cyanylated biological probes. In particular, we found that electrostatics alone are not a sufficient metric to categorize the environments of different solvents, and the dominant features in intermolecular interactions in the energy landscape vary from solvent to solvent. Consequently, common vibrational mapping schemes do not cover all essential interaction terms adequately, especially in the treatment of van der Waals interactions. Quantum vibrational perturbation (QVP) theory, along with a combined quantum mechanical and molecular mechanical potential for solute–solvent interactions, is an alternative and efficient modeling technique, which is compared in this paper, to yield spectroscopic results in good agreement with experimental FTIR. QVP has been used to analyze the computational data, revealing the shortcomings of the vibrational maps for MeSCN in different solvents. The results indicate that insights from QVP analysis can be used to enhance the transferability of vibrational maps in future studies.
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14 March 2022
Research Article|
March 11 2022
Origin of thiocyanate spectral shifts in water and organic solvents
Special Collection:
Time-resolved Vibrational Spectroscopy
Ruoqi Zhao;
Ruoqi Zhao
1
Institute of Theoretical Chemistry, Jilin University
, Changchun, Jilin Province 130023, China
2
Institute of Systems and Physical Biology, Shenzhen Bay Laboratory
, Shenzhen 518055, China
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Joseph C. Shirley
;
Joseph C. Shirley
3
Department of Chemistry, University of Texas
, Austin, Texas 78712, USA
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Euihyun Lee
;
Euihyun Lee
3
Department of Chemistry, University of Texas
, Austin, Texas 78712, USA
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Adam Grofe
;
Adam Grofe
a)
1
Institute of Theoretical Chemistry, Jilin University
, Changchun, Jilin Province 130023, China
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Hui Li
;
Hui Li
1
Institute of Theoretical Chemistry, Jilin University
, Changchun, Jilin Province 130023, China
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Carlos R. Baiz
;
Carlos R. Baiz
b)
3
Department of Chemistry, University of Texas
, Austin, Texas 78712, USA
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Jiali Gao
Jiali Gao
b)
2
Institute of Systems and Physical Biology, Shenzhen Bay Laboratory
, Shenzhen 518055, China
4
School of Chemical Biology and Biotechnology, Peking University Shenzhen Graduate School
, Shenzhen 518055, China
5
Department of Chemistry and Supercomputing Institute, University of Minnesota
, Minneapolis, Minnesota 55455, USA
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a)
Present address: Department of Chemistry, University of Washington, Seattle, WA 98195, USA.
Note: This paper is part of the JCP Special Topic on Time-Resolved Vibrational Spectroscopy.
J. Chem. Phys. 156, 104106 (2022)
Article history
Received:
December 20 2021
Accepted:
February 17 2022
Citation
Ruoqi Zhao, Joseph C. Shirley, Euihyun Lee, Adam Grofe, Hui Li, Carlos R. Baiz, Jiali Gao; Origin of thiocyanate spectral shifts in water and organic solvents. J. Chem. Phys. 14 March 2022; 156 (10): 104106. https://doi.org/10.1063/5.0082969
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