Substituent effect on ESIPT and hydrogen bond mechanism of N-(8-Quinolyl) salicylaldimine: A detailed theoretical exploration

Sha Ding; Aixiang Xu; Aokui Sun; Yong Xia; Yuejun Liu

doi:10.1016/j.saa.2020.118937

Substituent effect on ESIPT and hydrogen bond mechanism of N-(8-Quinolyl) salicylaldimine: A detailed theoretical exploration

Spectrochim Acta A Mol Biomol Spectrosc. 2021 Jan 15:245:118937. doi: 10.1016/j.saa.2020.118937. Epub 2020 Sep 11.

Authors

Sha Ding¹, Aixiang Xu², Aokui Sun³, Yong Xia⁴, Yuejun Liu³

Affiliations

¹ School of Packaging and Materials Engineering, Hunan University of Technology, Zhuzhou 412007, China; School of Civil Engineering, Hunan University of Technology, Zhuzhou 412007, China; Hunan Key Laboratory of Biomass Fiber Functional Materials, Hunan University of Technology, Zhuzhou 412007, China.
² School of Civil Engineering, Hunan University of Technology, Zhuzhou 412007, China.
³ School of Packaging and Materials Engineering, Hunan University of Technology, Zhuzhou 412007, China.
⁴ School of Packaging and Materials Engineering, Hunan University of Technology, Zhuzhou 412007, China; Hunan Key Laboratory of Biomass Fiber Functional Materials, Hunan University of Technology, Zhuzhou 412007, China; College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China. Electronic address: [email protected].

PMID: 32977109
DOI: 10.1016/j.saa.2020.118937

Abstract

The effects of substituent on excited-state intramolecular proton transfer (ESIPT) and hydrogen bonding of N-(8-Quinolyl) salicylaldimine (QS) have been studied by theoretical calculation with DFT and TDDFT. The representative electron-withdrawing nitryl and electron-donating methoxyl were selected to analyze the effects on geometries, intramolecular hydrogen bond interaction, absorption/fluorescence spectra, and the ESIPT process. The configurations of the three molecules (QS, QS-OMe and QS-NO₂) were optimized in the ground and excited states. The structure parameters, infrared spectra, hydrogen bond interactions, frontier molecular orbitals, absorption/fluorescence spectra, and potential curves have cross-validated the current results. The results show that the introduction of substituent results in a bathochromic-shift of the absorption and fluorescence spectra with large Stokes shift, and is more beneficial to the ESIPT process. The current work will be beneficial to the improvement of ESIPT properties and deepen understanding of the mechanism of ESIPT process.

Keywords: Absorption and fluorescence spectra; ESIPT; Hydrogen bond; Substituent effect; TDDFT.