A novel near-infrared fluorescent probe with large stokes shifts for sensing extreme acidity and its application in bioimaging was written by Gong, Jin;Liu, Chang;Jiao, Xiaojie;He, Song;Zhao, Liancheng;Zeng, Xianshun. And the article was included in Spectrochimica Acta, Part A: Molecular and Biomolecular Spectroscopy in 2020.Name: 6-Methoxyquinoxaline This article mentions the following:
The authors reported a novel near-IR (NIR) fluorescent probe RQNN (I) with large Stokes shift (98 nm) for monitoring pH under extremely acidic conditions. For the preparation of this probe, a 1,4-diethylpiperazine moiety was introduced in rhodamine scaffold to tune the electron-donating character, and an o-phenylenediamine was introduced in spironolactone to provide larger steric hindrance. The deprotonated-protonated equilibrium between RQNN, RQNN-H+ and RQNN-H2+ were evaluated in different pH by absorption and emission spectra. As expected, RQNN exhibited lower pka values (pka1 = 4.83, pka2 = 2.99), indicating that the probe can be used in extremely acidic pH. Moreover, RQNN possessed highly selective response to H+ over essential metal ions and biol. related redox mols., high photo-stability, rapid response time, and excellent reversibility. Importantly, the probe had excellent cell membrane permeability and was further applied successfully to monitor pH fluctuations in live cells. In the experiment, the researchers used many compounds, for example, 6-Methoxyquinoxaline (cas: 6639-82-3Name: 6-Methoxyquinoxaline).
6-Methoxyquinoxaline (cas: 6639-82-3) belongs to quinoxaline derivatives. Quinoxalines are important class of heterocyclic compounds, associated with wider pharmacological applications. Quinoxalines are used in the treatment of bacterial, cancer, and HIV infections. Moreover, varenicline, a clinical drug is used for treating nicotine addiction, also contains quinoxaline moiety.Name: 6-Methoxyquinoxaline
Referemce:
Quinoxaline – Wikipedia,
Quinoxaline | C8H6N2 | ChemSpider