An Excited State Intramolecular Proton Transfer-Based Fluorescent Probe with a Large Stokes Shift for the Turn-on Detection of Cysteine: A Detailed Theoretical Exploration

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

doi:10.1021/acsomega.0c02393

An Excited State Intramolecular Proton Transfer-Based Fluorescent Probe with a Large Stokes Shift for the Turn-on Detection of Cysteine: A Detailed Theoretical Exploration

ACS Omega. 2020 Jul 31;5(31):19695-19701. doi: 10.1021/acsomega.0c02393. eCollection 2020 Aug 11.

Authors

Sha Ding^{1

2}, Aixiang Xu³, Aokui Sun¹, Yong Xia^{1

4}, Yuejun Liu¹

Affiliations

¹ School of Packaging and Materials Engineering, Hunan University of Technology, Zhuzhou 412007, PR China.
² Hunan Key Laboratory of Biomass Fiber Functional Materials, Hunan University of Technology, Zhuzhou 412007, PR China.
³ School of Civil Engineering, Hunan University of Technology, Zhuzhou 412007, China.
⁴ College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China.

Abstract

DFT and TDDFT calculations are adopted to study the sensing mechanism of a turn-on-type cysteine fluorescent probe (2-(1-phenyl-imidazo[1,5-α]pyridine-3-yl)phenyl acrylate, denoted as MZC-AC). The photoinduced electron transfer (PET) process of MZC-AC and the excited state intramolecular proton transfer (ESIPT) process of MZC have been investigated in detail. We demonstrate that the fluorescence quenching of MZC-AC is ascribed to the PET mechanism and the large Stokes shift fluorescence emission of MZC is the result of the ESIPT mechanism. The results have been cross-validated by geometries, frontier molecular orbital analysis, and potential energy curve scanning. As a result, our calculations completely reproduce the experimental results and give powerful evidence for the sensing mechanism of MZC-AC for cysteine.