Pd 0 -mediated Tsuji-Trost reaction is a practical strategy to design fluorescent probes for carbon monoxide (CO) sensing, and in such reaction CO can reduce Pd 2+ to Pd 0 in-situ and remove allyl groups on fluorophores. In most of these probes, esters are commonly used to link allyl on fluorophores. We found that the ester groups could be hydrolyzed by esterase activity of fetal bovine serum (FBS), while FBS is a requisite in cell culture, and the hydrolysis could interfere the Pd 0 -mediated Tsuji-Trost reaction. In this study, we synthesized a fluorescent probe (Cou-CO) using allyl ether as reaction site rather than allyl ester. Cou-CO is non-fluorescence, and could react with CO under the presence of Pd 0 to form Cou with strong fluorescence, and the maximum excitation and emission wavelengths of Cou are 464 nm and 495 nm respectively. Cou-CO shows excellent selectivity to CO and could avoid the effect of FBS with the limit of detection for CO is 78 nm. Finally, Cou-CO was successfully applied for imaging of CO in living cells.
A fluorescent probe based on the Tsuji–Trost reaction was developed for detecting palladium species of all the typical oxidation states (0, +2, +4). In this probe, a novel fused four-ring quinoxalinamine was firstly designed as the fluorophore. The probe displayed high selectivity towards palladium with a distinct color change in aqueous media. Non-toxic and water-soluble PEG400 was used to replace the phosphine ligands and the reducing agents. In the absence of PEG400, the probe could discriminate Pd(0) from Pd(II) and Pd(IV) in solutions. The actual water sample detection and bio-imaging results indicated the probe's great potential for palladium detection in both solutions and living systems.
Ting Yu,Guoxing Yin,Peng Yin,Ying Zeng,Haitao Li,Youyu Zhang,Shouzhuo Yao
We have synthesized a novel long-wavelength fluorescent probe MFC for detection of palladium (Pd0). This probe not only shows high selectivity for palladium, but also could quickly discriminate different palladium species (Pd0, Pd2+, Pd4+) in phosphate buffered solution. After the reaction with Pd(PPh3)4, the UV absorption of the probe MFC shifts from 334 nm to 594 nm within a few minutes. The probe MFC conjugated with alkyl carbamate, which destroys the principle of intramolecular charge transfer (ICT) and shows weak fluorescence. Based on the Pd0-catalyzed Tsuji–Trost deallylation reaction, the fluorogen was released and the fluorescence intensity at 612 nm was observed with 13-fold enhancement along with an obvious color change from yellow to purple with low detection limit.
A near-infrared chemosensor for palladium based on the Tsuji–Trost reaction was developed. It displayed specific and ratiometric fluorescent responses toward palladium with a distinct color change from green to blue in aqueous media. PEG400 was employed as the reducing agent and palladium ligand instead of water-insoluble triphenylphosphine. The chemosensor's bioimaging potential was demonstrated by in vitro and in vivo experiments.
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