Theoretical insights into the excited-state single and double proton transfer processes of DEASH in water

• Published in: Chemical physics Vol. 570; p. 111882
• Main Authors: Xin, Xin, Shi, Wei, Zhao, Yu, Zhao, Guijie, Li, Yongqing
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.06.2023
• Subjects: ESIDPT; ESISPT; Intramolecular hydrogen bond; Potential energy surface; Potential energy surface; Intramolecular hydrogen bond; ESISPT; ESIDPT
• ISSN: 0301-0104
• DOI: 10.1016/j.chemphys.2023.111882

Recently, a new fluorescent chromophore 6,6′-((1E,1′E)-hydrazine-1,2-diylidenebis(methanylylidene))bis(3-(diethylamino)phenol) (DEASH) with double intramolecular hydrogen bonds (IHBs) was synthesized and could be used as an effective indicator of hydrazine. The experimental results showed that DEASH could emit bright green fluorescence due to the excited state intramolecular proton transfer (ESIPT) induced by IHBs. [Dyes Pigments, 2022, 197, 109880.] However, the underlying mechanism of the ESIPT process for DEASH is still unclear. In this paper, we investigate excited-state intramolecular single (ESISPT) and double (ESIDPT) proton transfer processes of DEASH by density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods. Through the theoretical analyses for the constructed potential energy surfaces (PESs), excited hydrogen bond strengthening and photophysical properties of the molecule, we finally come to the conclusion that ESIDPT process of the DEASH in water solution is inclined to a stepwise process.