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The effects of different heterocycles and solvents on the ESIPT mechanisms for three novel photoactive mono-formylated benzoxazole derivatives

Abstract

The fluorescence behaviors and properties of three novel photoactive mono-formylated benzoxazole derivatives are found to be affected by different heterocycles and solvents, which were reported in the recent experiment (Rodembusch et al. New J. Chem. 2016, 40, 2785). Unfortunately, the detailed excited-state intramolecular proton transfer (ESIPT) mechanisms of these compounds are lacking. In this work, we used density functional theory (DFT) and time dependent DFT (TDDFT) methods to study the dynamic ESIPT processes of the three compounds A-C in two different surroundings (polar 1,4-dioxane and nonpolar dichloromethane solvents). The calculated absorption and fluorescence spectra were observed to mutually agree with experiment date, which indicated that the TDDFT method we adopted is reliable. In addition, it has been confirmed that the intramolecular hydrogen bonds (HBs) of these compounds were enhanced in the S1 state based on the analysis of bond lengths, angles and IR vibrational spectra in both two solvents, which could promote the ESIPT reactions. Moreover, the frontier molecular orbitals (MOs) and the maps of the electron density difference between the S0 and S1 states displayed the intramolecular charge transfer, which provided the probability of ESIPT reactions for three compounds. Furthermore, recur to the constructed potential energy curves, we revealed detailed dynamical ESIPT mechanisms of the compounds A-C. As a consequence, the ESIPT processes were more likely to take place from A (8.48 kcal/mol) → B (5.36 kcal/mol) → C (0.75 kcal/mol) compounds in polar 1,4-dioxane solvent, while the facility sequence changed to B (4.01 kcal/mol) → A (1.30 kcal/mol) → C (1.15 kcal/mol) in nonpolar dichloromethane solvent. Additionally, it could be determined that the solvent polarity had the tremendous effect on the compound A, whereas the effect on the compound C was the smallest.

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Publication details

The article was received on 05 Apr 2018, accepted on 08 Jun 2018 and first published on 09 Jun 2018


Article type: Research Article
DOI: 10.1039/C8QO00349A
Citation: Org. Chem. Front., 2018, Accepted Manuscript
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    The effects of different heterocycles and solvents on the ESIPT mechanisms for three novel photoactive mono-formylated benzoxazole derivatives

    J. J. Hao and Y. Yang, Org. Chem. Front., 2018, Accepted Manuscript , DOI: 10.1039/C8QO00349A

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