What quantum chemical simulations tell us about the infrared spectra, structure and interionic interactions of a bulk ionic liquid

Abstract

The recently developed efficient protocol to explicit quantum mechanical modeling of structure and IR spectra of liquids and solutions [Katsyuba et al., J. Phys. Chem. B, 2020, 124, 6664-6670] is...

Computational analysis of the vibrational spectra and structure of aqueous cytosine

“…In other words, we demonstrated that the vibrational modes and derivatives of the polarizability of a solute are mainly locally influenced by its immediate environment, while the effect of bulk water is rather modest. This is in parallel with the outcome of our liquid-state IR spectra simulations, 6,[8][9][10][11][12] which showed that the dipole moment derivatives of a solute are mainly locally influenced by its immediate surroundings. This knowledge not only improves our understanding of solute-solvent interactions, but also allows minimization of the computational costs of QM simulations of the liquid-state Raman spectra.…”

“…Initially 6 we calculated the IR spectrum of any system, modeled within the framework of our cluster approach, as a thermodynamic average of the individual spectra computed for each complete cluster at the DFT level. Nevertheless, further studies [8][9][10][11][12] have shown that the difference between the spectrum of the lowest-energy cluster and that averaged from all clusters in the final ensemble is negligible, and hence the averaging was avoided to minimize computational expenses. The same turned out to be true for the present case, which is clearly seen in Fig.…”

“…In this work, an explicit modeling has been used to evaluate the structure of aqueous cytosine, and vibrational frequencies and relative IR and Raman intensities of bands in its spectra. Similarly to the broader tested case of liquid-state IR spectra simulations, 6,[8][9][10][11][12] it was sufficient to take into account mainly the first solvation shell of the solute to reproduce experimental Raman spectra for this strongly H-bonded system. Successful computations of not only the positions of the experimental Raman and IR bands, but also their relative intensities for both cytosine and deuterated cytosine in aqueous solutions, means that we were able to correctly model not only the potential energy surface, but also the derivatives of the dipole moments and polarizability of these systems.…”

“…In previous studies 6,[8][9][10] it has been suggested that vibrational modes and dipole moment derivatives are mainly influenced by their immediate local surroundings, which also holds for strongly hydrogen bonded systems. The inclusion of the first solvation shell is deemed to be sufficient to simulate solution phase IR spectra with similar accuracy to individual molecules in a vacuum.…”

Synthesis and computationally assisted spectroscopic study of tautomerism in 3-(phenyl(2-arylhydrazineylidene)methyl)quinoxalin-2(1H)-ones

“…55 In previous studies 56 it has been suggested that vibrational modes and dipole moment derivatives are mainly influenced by their immediate local surroundings, which also holds for hydrogen bonded systems like ethanol, 57 aqueous and methanolic solutions of methyl lactate, 58 and ionic liquids. 59 The inclusion of the first solvation shell is deemed to be sufficient to simulate solution phase IR spectra with similar accuracy as for individual molecules in a vacuum. To simulate the dichloromethane clusters of solvated tautomers/conformers, 19 to 44 CH 2 Cl 2 molecules were added to each of the solute geometries.…”