Understanding the absorption spectrum of mesityl oxide dye in solvents of different polarities

Author(s)

Cezar, Henrique M. ^[1] ; Canuto, Sylvio ^[1] ; Coutinho, Kaline ^[1]

Affiliation

^[1] Univ Sao Paulo, Inst Fis, Rua Matao 1371, BR-05508090 Sao Paulo, SP - Brazil

• Document type: Journal article
• Source: JOURNAL OF MOLECULAR LIQUIDS; v. 307, JUN 1 2020.
• Web of Science Citations: 0

Abstract

Understanding the solvent contribution to the UV-Vis absorption spectrum of mesityl oxide (MOx) in different solvents is still challenging because of the interplay between the two possible conformations. The syn:anti relative stability changes according to the solvent polarity. In this work a sequential quantum mechanics/molecular mechanics based on a configuration biased Monte Carlo and the explicit use of solvent molecules is adopted to describe in detail the solvent effects. The contributions of the conformation changes, the polarization effects of the solvent molecules in MOx and the explicit solvation are separated and analyzed. The excitation energies are obtained using time-dependent density functional theory (TDDFT B3LYP/6-311++G(d,p)) calculations on statistically relevant configurations of MOx in acetonitrile, methanol and water solutions. Considering the explicit solvent molecules the calculated solvatochromic shift of -120 cm(-1), -1410 cm(-1) and -2500 cm(-1) are obtained for acetonitrile, methanol and water, respectively. These results are in due agreement with the experimental values. The separated contributions of conformation changes, polarization effects and the explicit solvation add to a consistent description of MOx UV-Vis absorption spectra in solution. The delocalization of the valence orbitals into the solvent region is also considered. The results emphasize the role of the solvent polarity and the limitations of methods that do not include explicit solvent molecules and the thermodynamic condition that characterizes a liquid system. (C) 2020 Elsevier B.V. All rights reserved. (AU)

• FAPESP's process: 14/50983-3 - INCT 2014: complex fluids
• Grantee: Antonio Martins Figueiredo Neto
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 17/11631-2 - CINE: computational materials design based on atomistic simulations, meso-scale, multi-physics, and artificial intelligence for energy applications
• Grantee: Juarez Lopes Ferreira da Silva
• Support Opportunities: Research Grants - Research Centers in Engineering Program