Solvent-induced Stokes' shift in DCJTB: Experimental and theoretical results

Abstract

The solvent-induced Stokes' shift, which describes the response at different solvents (acetonitrile, chloroform, dichloromethane, 1,4-dioxane, N,N-dimethylformamide, ethanol, heptanol, tetrahydrofuran, and toluene) to a sudden change in the charge distribution of excited 4-(Dicyanomethylene)-2-tert-butyl-6- (1,1,7,7-tetramethyljulolidin-4-yl-vinyl)-4H-pyran (DCJTB) molecule, was studied through absorption and emission spectra and TD-DFT calculations; the solvent effect was studied trough the IEF-PCM model. The application of IEF-PCM model with TD-DFT methods to obtain the absorption energies provided excellent match with the experimental results. The results observed, for solvents effects on the positions of maxima absorption and emission between experimental data and theoretical calculations, have average absolute deviations of only 0.03 eV and 0.22 eV, respectively. A systematic error was observed by comparing the theoretical and experimental maxima for the emission energies. However, the application of the Lippert-Mataga and Bilot-Kawski equations to the TD-DFT-simulated Stokes' shifts values resulted in excellent correlation coefficients: Lippert-Mataga, R-2 = 0.9982, Bilot-Kawski, R-2 = 0.9908 and R-2 = 0.9795. (C) 2019 Elsevier B.V. All rights reserved.