Acid‐Induced Shift of Intramolecular Hydrogen Bonding Responsible for Excited‐State Intramolecular Proton Transfer. Issue 13 (30th May 2018)

• Record Type: Journal Article
• Authors: Wang, Qin; Niu, Yahui; Wang, Rong; Wu, Haoran; Zhang, Yanrong
• Is Part Of: Chemistry, an Asian journal. Volume 13:Issue 13(2018)
• Page Start: 1735
• Page End: 1743
• Publication Date: 2018-05-30
• Subjects: density functional calculations -- fluorescence -- hydrogen bonds -- protonation -- theoretical calculations; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/asia.201800457
• Languages: English
• ISSNs: 1861-4728

Abstract

Abstract: The significant progress recently achieved in designing smart acid‐responsive materials based on intramolecular charge transfer inspired us to utilize excited‐state intramolecular proton transfer (ESIPT) for developing a turn‐on acid‐responsive fluorescent system with an exceedingly large Stokes shift. Two ESIPT‐active fluorophores, 2‐(2‐hydroxyphenyl)pyridine (HPP) and 2‐(2‐hydroxyphenyl)benzothiazole (HBT), were fused into a novel dye (HBT‐HPP) fluorescent only in the protonated state. Moreover, we also synthesized three structurally relevant control compounds to compare their steady‐state fluorescence spectra and optimized geometric structures in neutral and acidic media. The results suggest that the fluorescence turn‐on was caused by the acid‐induced shift of the ESIPT‐responsible intramolecular hydrogen bond from the HPP to HBT moiety. This work presents a systematic comparison of the emission efficiencies and basicity of HBT and HPP for the first time, thereby utilizing their differences to construct an acid‐responsive smart organic fluorescent material. As a practical application, red fluorescent letters can be written using the acid as an ink on polymer film. Abstract : Red‐letter day : An acid‐induced excited‐state intramolecular proton transfer (ESIPT) was used to activate an intramolecular hydrogen‐bonding shift from a 2‐(2‐hydroxyphenyl)pyridine fluorophore to a 2‐(2‐hydroxyphenyl)benzothiazole moiety. As a practical application, red fluorescent letters can be written using the acid as an ink on polymer film (see figure).