Effects of substitution and conjugation on ESIPT behavior of Schiff base derivatives

Xiaoxiao Li; Qiujie Wang; Liying Song; Jinfeng Zhao; Bing Jin

doi:10.1016/j.saa.2022.121377

Effects of substitution and conjugation on ESIPT behavior of Schiff base derivatives

Spectrochim Acta A Mol Biomol Spectrosc. 2022 Oct 15:279:121377. doi: 10.1016/j.saa.2022.121377. Epub 2022 May 12.

Authors

Xiaoxiao Li¹, Qiujie Wang², Liying Song², Jinfeng Zhao¹, Bing Jin³

Affiliations

¹ Institute of Molecular Sciences and Engineering, Institute of Frontier and Interdisciplinary Science, Shandong University, Qingdao 266237, China; State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China.
² Institute of Molecular Sciences and Engineering, Institute of Frontier and Interdisciplinary Science, Shandong University, Qingdao 266237, China.
³ Institute of Molecular Sciences and Engineering, Institute of Frontier and Interdisciplinary Science, Shandong University, Qingdao 266237, China; State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China. Electronic address: jinbing@sdu.edu.cn.

PMID: 35617834
DOI: 10.1016/j.saa.2022.121377

Abstract

The excited-state proton transfer (ESIPT) behavior of organic fluorophores has been of great interest due to their unique photophysical properties. In this work, we have focused on the excited state kinetic behavior of four Schiff base organic molecules (i.e. CPMP, CPMMP, CPMDP, and CPMN) in acetonitrile solvents. The electron-donating of substituents and conjugation effects on the photophysical properties and ESIPT process of the Schiff base derivatives are investigated by theoretical methods. The results show that the hydrogen bonds are all enhanced in the excited states, which could provide the impetus for the ESIPT process. To further reveal the reaction process of ESIPT, we have scanned the potential energy curves of the ESIPT process and compared the potential barriers. It is found that the stronger the substituents give electrons and the conjugation effects the more favorable the excited state proton transfer (ESIPT). In the meantime, this study paves the way for the development of new Schiff base materials based on ESIPT.

Keywords: Conjugation effect; Electron-giving capacity of the substitution base; Excited state proton transfer; Intramolecular hydrogen bond; Potential energy curve; Schiff base derivatives.