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

Abstract

The recently developed efficient protocol combining implicit and explicit, accurate quantum mechanical modeling of the condensed state [Katsyuba et al., J. Chem. Phys. 155, 024507 (2021)] is used to describe...

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.…”

“…The DFT simulated IR spectrum of the system matches the corresponding condensed-phase IR experiment better than the theoretical spectrum of the isolated molecule compared to the gas-phase IR spectrum. Application of the above protocol to molecular 8,9 and ionic 10 liquids, and various solutions of structurally flexible compounds, 11 has demonstrated an accuracy of such IR spectra simulations and efficiency of their use for interpretation of the corresponding experimental spectra. Very recently we estimated within the framework of our cluster model a limited number of liquid-state Raman scattering cross sections, σ, of trans - and gauche -conformers of 1,2-dichloroethane.…”

Deciphering and investigating fragment mechanism of quinolones using multi‐collision energy mass spectrometry and computational chemistry strategy

“…Recently, Conformer-Rotamer Ensemble Sampling Tool (CREST) 15 software developed by Grimme et al has gained much attention because of its practicability. CREST invokes another software, Extended Tight Binding (xTB), 16 which supports the novel semiempirical method GFNn-xTB (n = 0, 1, 2), to achieve rapid and relatively accurate computation in conformational search and sampling, [17][18][19] entropy and heat capacity calculation, 20 protonation/deprotonation sites, 21 and tautomerism screening 22 and is suitable for explaining the experimental data using theory principles.…”