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Effects of the protonation and the polar solvation on the molecular properties of methyl orange: A density functional theory study
Ist Teil von
Bulletin of the Korean Chemical Society, 2023, 44(6), , pp.523-527
Ort / Verlag
Weinheim: Wiley‐VCH Verlag GmbH & Co. KGaA
Erscheinungsjahr
2023
Link zum Volltext
Quelle
Wiley Online Library
Beschreibungen/Notizen
Methyl orange (MO) and its protonated derivatives were investigated at the density functional theory (DFT) level using CAM‐B3LYP functional and 6‐311 + G(d,p) basis sets; their absorption spectra in aqueous solution were simulated, their relative stabilities in both the gas phase and the polar solutions were calculated, and the activation energy barrier for the cis‐to‐trans isomerization in both phases were computed. Except the protonation at the amino group, all the protonated isomers show a bathochromic shift of the most intense absorption peak. In the gas phase, the sulfonate unit turns out to be the most favorable proton acceptor. In the polar solutions, however, azo groups are more effective to accept the proton. The protonation at the azo N atom next to the phenyl‐sulfonate group significantly reduces the energy barrier for the cis‐to‐trans conversion in the aqueous solution, which suggests a swift conversion in the ground state.
A density functional theory (DFT) study was carried out to unveil the effect of the protonation and the solvation on the molecular properties of methyl orange (MO) anion. In the gas phase, the sulfonate is the strongest proton acceptor and shows the least energy barrier for the cis‐to‐trans isomerization, while the protonation at azo N atom is the most stable in both the equilibrium and transition states in the aqueous solution.