Fluorescence Responses of the Protonation and Deprotonation Processes between Phenolate and Phenol within Rosamine

Abstract

Two rosamine-based pH probes 1a and 1b with pyronine-phenol skeleton were designed and synthesized by a simple one-step reaction. pH titration experiments showed that probes 1a and 1b exhibit near OFF-ON fluorescence responses around 550-750 nm towards the hydrogen ions. The pK a of the probe 1a is 8.29, while that of the probe 1b increases to 12.1 because of the hydrogen bond inside it. Selective and competitive experiments indicated that both common ions and amino acids did not interfere their emission with hydrogen ions. Moreover, confocal fluorescent imaging showed that the probe 1a could be served as mitochondria biomarker in HeLa and Ges-1 cells.

Synthesis of the first 4-oxobutane-1,1,2,2-tetracarbonitriles containing a phenol fragment and their transformation into cyano-substituted pyrrol-2-ones showing three-position molecular switching

“…The presence of a phenolic OH group in the structure of pyrroles 2 and their analogs, as was shown previously, 25,47,48 is promising for the targeted change of optical properties of molecules due to the possibility of phenol/quinoid transformation by the action of bases. The sensitivity of a phenolic hydroxyl group to basic reagents is a routine fact.…”

“…[44][45][46] Also examples of varying the color characteristics of chromophores through involvement of OH groups in an acid-base reaction were reported. 47,48 Thus, it should be noted that one of the most intensively studied areas in OTC chemistry in recent years is the synthesis of pyrrole derivatives 2 (Fig. 1) without a hydroxyl group.…”

Coumarin‐Pyronin Hybrid Dyes: Synthesis, Fluorescence Properties and Theoretical Calculations**

“…The purpose being to assess the possible influence of the protonation state of enol moiety found in the coumarin fragment. For all compounds, only a very weak yellow‐orange fluorescence emission intensity was observed, whatever the substitution pattern of coumarin and pyronin units [3ai] . It prevented us to accurately determine relative fluorescence quantum yields, roughly estimated at less than 1 %.…”

Fluorescent pH Indicators for Neutral to Near-Alkaline Conditions Based on 9-Iminopyronin Derivatives

“…Pyronin derivatives are chemically stable fluorophores that possess high molar absorption coefficients and high fluorescence quantum yields. ,− Many pH sensors exhibiting a high sensitivity in near-alkaline pH suffer from some drawbacks, such as low fluorescence quantum yields, high lipophilicity, or emit only in the blue region of visible light (see the Supporting Information for details, Table S10). Here, we designed and synthesized a library of novel fluorescent 9-iminopyronin derivatives possessing unique and distinct emission properties with the aim of providing optimal sensitivity at neutral to near-alkaline conditions (Supporting Information).…”