Synthesis, photochemical stability and photo-stabilizing efficiency of probes based on benzothioxanthene chromophore and Hindered Amine Stabilizer

Investigation of the K4[Fe(CN)6]-Mediated Mono- and Bis-Palladium-Catalyzed Cyanation of the Benzothioxanthene Core

The pallado-catalyzed cyanation of benzothioxanthene imide (BTXI) derivatives is explored herein. Once optimized on the monobromo BTXI, mild reaction conditions were successfully applied to the dibromo derivative affording two regioisomers that have been isolated and structurally solved. Additional hydrogen-deuterium exchange experiments were carried out to support a proposed mechanism involving the formation of a five-membered palladacycle intermediate in the bay area. As well as impacting the structural, photo physical and electrochemical properties of the BTXI core, nitrile moieties were successfully used as orthogonal protecting groups, thus opening doors to new design principles.

Novel fluorene-based fluorescent probe with excellent stability for selective detection of SCN- and its applications in paper-based sensing and bioimaging

SCN- is one of the most important anions in metabolic processes. However, the investigation of SCN- in living systems is restricted by the lack of stable functional molecular tools. Herein, the first fluorene-based polymer fluorescent probe V1 was synthesized through rational design. Compared with small molecule fluorescent probes, V1 exhibited excellent fluorescence stability in bovine serum albumin (BSA) solution. Furthermore, the V1-based paper sensor was highly selective toward SCN- in aqueous solution. Significantly, these merits of the probe V1 enable the detection of SCN- in different living cell lines and zebrafish.

Preparation and spectral characterization of fluorescence probes based on 4-N,N-dimethylamino benzoic acid and sterically hindered amines

The adducts of simple chromophore 4-N,N-dimethylamino benzoic acid with 2,2,6,6-tetrametyl-4-hydroxy- or 4-amino-piperidine were examined as fluorescence probes (spin double sensors) to monitor radical processes. The links in the adducts were either an ester or amide group, and the sterically hindered amines were in the form of -NH, -NO• and -NOR. The spectral properties of the three related derivatives (esters or amides) were quite similar. The maxima of the absorption spectra were in the range of 295-315 nm, and the maximum of fluorescence was located in the range of 330-360 nm, depending on the polarity of the solvent. In polar solvents, a red-shifted fluorescence band at 460-475 nm was observed. The fluorescence of these derivatives was rather weak as compared to anthracene under the same conditions. The Stokes shift was large, as high as 6,000 cm(-1), indicating the formation of a twisted intra-molecular charge transfer (TICT) state. No large differences in Stokes shifts were observed in polymer matrices of poly(methyl methacrylate), polystyrene and poly(vinyl chloride). The extent of intramolecular quenching was expressed as Φ(NX)/Φ(NO) (X = H, NOR) and was in the range of 1-3 in solution and as high as 8 in polymer matrices. The low efficiency of intramolecular quenching limits the application of these new adducts as fluorescence probes for the monitoring of radical processes in solution but favors their application in polymer matrices.