Structures, Energetics, and Spectra of (NH) and (OH) Tautomers of 2-(2-Hydroxyphenyl)-1-azaazulene: A Density Functional Theory/Time-Dependent Density Functional Theory Study

Asmaa B El-Meligy; Safinaz H El-Demerdash; Mohamed A Abdel-Rahman; Mohamed A M Mahmoud; Tetsuya Taketsugu; Ahmed M El-Nahas

doi:10.1021/acsomega.2c00866

Structures, Energetics, and Spectra of (NH) and (OH) Tautomers of 2-(2-Hydroxyphenyl)-1-azaazulene: A Density Functional Theory/Time-Dependent Density Functional Theory Study

ACS Omega. 2022 Apr 15;7(16):14222-14238. doi: 10.1021/acsomega.2c00866. eCollection 2022 Apr 26.

Authors

Asmaa B El-Meligy¹, Safinaz H El-Demerdash¹, Mohamed A Abdel-Rahman², Mohamed A M Mahmoud³, Tetsuya Taketsugu^{4

5}, Ahmed M El-Nahas¹

Affiliations

¹ Chemistry Department, Faculty of Science, Menoufia University, Shebin El-Kom 32512, Egypt.
² Chemistry Department, Faculty of Science, Suez University, Suez 41522, Egypt.
³ Basic Sciences Department, Tanta Higher Institute of Engineering and Technology, Tanta 31511, Egypt.
⁴ Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan.
⁵ Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Sapporo 060-0810, Japan.

Abstract

Tautomerization of 2-(2-hydroxyphenyl)-1-azaazulene (2OHPhAZ) in the gas phase and ethanol has been studied using B3LYP, M06-2X, and ωB97XD density functional theory (DFT) with different basis sets. For more accurate data, energies were refined at CCSD(T)/6-311++G(2d,2p) in the gas phase. Nuclear magnetic resonance (NMR), aromaticity, Fukui functions, acidity, and basicity were also calculated and compared with experimental data. Time-dependent density functional theory (TDDFT)-solvation model based on density (TDDFT-SMD) calculations in acetonitrile have been utilized for the simulation of UV-vis electronic spectra. In addition, electronic structures of the investigated system have been discussed. The results reveal that the enol form (2OHPhAZ) is thermodynamically and kinetically stable relative to the keto tautomer (2OPhAZ) and different rotamers (2OHPhAZ-R1:R3) in the gas phase and ethanol. A comparison with the experiment illustrates a good agreement and supports the computational findings.