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A new coumarin derivative containing both imine bond and amide moiety was synthesised. It was used as a reaction‐based pH probe and was sensitive to pH changes in the intervals 1.50–4.10 and 10.20–12.86. In the pH range 1.50–4.10, the ultraviolet‐visible (UV‒vis) absorption band of the probe gradually shifted from 353 nm to 340 nm with decrease in the pH value. The colour changed from pale yellow fluorescence at pH 4.10 to blue fluorescence at pH 1.50. Meanwhile the fluorescence emission band at 501 nm gradually shifted to 560 nm accompanying a gradual enhancing in the emission intensity. This pH response is caused by the hydrolysis of the imine bond in the probe under acidic conditions (pH 1.50–4.10). The colourless probe solution turned yellow at pH range 10.20–12.86. Bathochromic shift of the fluorescence band from 501 nm gradually to 550 nm was observed with the increase of pH value from 10.20 to 12.86 accompanying a gradual enhancement of the fluorescence emission intensity, indicating that the new compound serves as a fluorescent pH probe at pH range 10.20–12.86 through a deprotonation process. Under strongly alkaline conditions with pH larger than 12.86, hydrolysis of the lactone structure in the probe occurred to produce non‐fluorescent species. [ABSTRACT FROM AUTHOR]

Graphical abstract A coumarin-based multifunctional sensor has been developed for colorimetric and fluorogenic dual-signal sensing of arginine, lysine and Cu2+ and fluorescent detection of Al3+. Its Cu2+ complex serves as colorimetric and fluorometric probe for highly selective and sensitive detection of cysteine, homocysteine and glutathione over other common amino acids. Highlights • A coumarin-based multifunctional chemosensor has been developed. • It is useful for chromogenic and fluorogenic detection of Arg and Lys. • It serves as colorimetric and fluorimetric probe for selective detection of Cu2+. • It can be utilized for fluorescent sensing of Al3+. • Its Cu2+ complex exhibits colorimetric and fluorimetric response to Cys, Hcy and GSH. Abstract A new chemosensor L1 based on coumarin was synthesized straightforward. It serves as a colorimetric and fluorescent probe for selective and sensitive detection of Arg and Lys over other common amino acids Cys, Hcy, GSH, Phe, His, Met, Gly, Val, Tyr, Glu and Leu. Among various metal ions L1 is able to detect Cu2+ ion by the naked eye with high selectivity and sensitivity. The probe L1 can be utilized for fluorescent sensing of Cu2+ and Al3+ ion with the detection limit of 8 μM and 2 μM, respectively. The ' in situ ' formed L1 –Cu2+ ensemble may be used for colorimetric and fluorescent recognition of Cys, Hcy and GSH over other common amino acids including Phe, His, Met, Gly, Val, Tyr, Glu, Arg, Lys and Leu. The detection limit of the ensemble L1 –Cu2+ toward Cys, Hcy and GSH reached 10 μM, 10 μM and 16 μM, respectively. Possible sensing mechanism of L1 toward Arg/Lys and Cu2+/Al3+ ions and the ensemble L1 –Cu2+ toward the biothiols is proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • A fluorescent probe with dual recognition sites for Hg2+ was developed. • Addition of Hg2+ induced fluorescence enhancement of the probe by 70 fold. • The probe turned from colorless to blackish brown upon addition of Hg2+ ion. • The probe showed low LOD of 0.12 μM for sensing of Hg2+ ion. • It was used for bioimaging and determination of Hg2+ concentrations in real water samples. A novel thionocarbonate-coumarin-thiourea triad-based probe with dual recognition sites for sensing mercury (Hg2+) ion was developed. The synthesized probe possessed both fluorogenic ("off-on") and chromogenic (from colorless to blackish brown) sensing performance towards Hg2+ ions. The fluorescence intensity was increased by 70 fold after the addition of Hg2+. As expected, the probe exhibited excellent selectivity and sensitivity for Hg2+ compared to other common competitive metal ions. The fluorescence intensity of the probe improved linearly with the increase of the concentration of Hg2+ (0–40 μM). Also, the minimum limit of detection (LOD) of the synthesized probe was 0.12 μM. Considering the importance of test feasibility in the harsh environment, the developed probe was applicable for detecting Hg2+ ions over a broad working pH range of 3–11. It is reliable and qualifies for the quantitative determination of Hg2+ concentrations in actual water samples. Finally, the probe achieved the bioimaging performance of Hg2+ in living cells and plants with good biocompatibility. [ABSTRACT FROM AUTHOR]

Abstract: A series of novel coumarin dyes (3–12) were designed and synthesized. The structures of the dyes were characterized by IR, 1H NMR, 13C NMR, 19F NMR, MS and single crystal X-ray diffraction. 3-(2-Benzoylhydrazonotrifluoroethyl)-7-(N,N-diethylamino)coumarin (11) could recognize Cu2+ and Ni2+ selectively in aqueous solution. Upon addition of Cu2+ or Ni2+ to 11 a blue shift or a bathochromatic shift of the absorption band was observed while the emission band blue-shifted with decrease in the fluorescence intensity. Upon addition of Cu2+ the color of the solution of 11 changed from orange to red. The results showed that 11 could be used as an optical chemosensor of Cu2+ and Ni2+. [Copyright &y& Elsevier]

Abstract A fluorescent and colorimetric probe L1 based on a simple coumarin derivative for detection of Hg2+ and F− ions was developed. Upon addition of Hg2+ and F− ions, L1 underwent desulfurization and desilylation, respectively, to induce marked increase in the fluorescence intensity and sharp color change from light yellow to dark purple and light brown, respectively. Probe L1 could be used for sensing and for quantitative measurement of Hg2+ and F− ions by both UV–vis and fluorescence spectra. The bifunctional probe exhibited a high selectivity over other competitive cations and anions and could be used in both organic and aqueous media over a wide pH range. Graphical Abstract A novel bifunctional fluorescent and colorimetric probe for detection of Hg2+ and F− ions was synthesized. The probe exhibited a high selectivity over other competitive cations and anions and could be used in both organic and aqueous media over a wide pH range. Unlabelled Image Highlights • A coumarin-based fluorescent and colorimetric probe for Hg2+ and F− was synthesized. • The probe can be used for quantitative measurement of Hg2+ and F− by UV–vis and fluorescence spectra. • The probe exhibited a high selectivity over other competitive cations and anions. • The probe can be used in both organic and aqueous media over a wide pH range. [ABSTRACT FROM AUTHOR]

[Display omitted] • A near-infrared fluorescent probe for sensing Cu2+ and GSH was developed. • The probe responded to Cu2+ and GSH, respectively in different medium. • The detection limit was calculated to be 37 nM for Cu2+ and 20 nM for GSH. • The sensing mechanism was verified by spectral analysis and DFT calculations. • The probe was applicable for detection of real water samples and bioimaging. A novel near-infrared Schiff base fluorescent probe was synthesized. The probe displayed medium-dependent selectivity and could specifically recognize Cu2+ in EtOH/H 2 O (9:1, v/v) while respond to glutathione (GSH) in THF/H 2 O (9:1, v/v). Addition of Cu2+ to the probe solution caused obvious fluorescence quenching and color change. The detection limit was calculated to be 37 nM. The probe could specifically detect GSH through fluorescence turn-on in THF/H 2 O (9:1, v/v) medium based on GSH-induced hydrolysis of the probe, with the detection limit as low as 20 nM. The sensing mechanism of the probe was verified by spectral analysis and density functional theory (DFT) calculations. Application of the probe to real water samples analysis and bioimaging was achieved. [ABSTRACT FROM AUTHOR]

[Display omitted] • A coumarin-derived fluorescent probe was developed for specific sensing of Arg. • The probe emitted at 642 nm and exhibited a large Stokes shift of 272 nm. • The probe displayed a low detection limit 0.78 μM and rapid response to Arg in 10 s. • The probe was applicable for Arg imaging in living L929 cells. The development of fluorescent probes for prompt and accurate arginine (Arg) detection with high selectivity and sensitivity is in great demand due to the critical roles and implications of Arg for health. In this paper, a new coumarin-derived fluorescent probe, CL, was designed and synthesized. It was efficient for the rapid and specific detection of Arg in MeCN/H 2 O (6:4, v/v), with a low detection limit of 0.78 μM and a short response time of less than 10 s. Probe CL was stable at pH 3–10 and exhibited excellent anti-interference from competitive amino acids, including lysine, histidine, cysteine, homocysteine, glutathione, glycine, glutamic acid, valine, tyrosine, tryptophan, leucine, phenylalanine, aspartic acid and methionine. Density-functional theory (DFT) calculations investigated and verified the sensing mechanism. Considering that probe CL features multiple advantages, including high specificity, emission at a long wavelength of 642 nm with a massive Stokes shift of 272 nm, fast response and a broadly applicable pH range, this study provides a new idea for the development of susceptible and selective detection method for Arg. [ABSTRACT FROM AUTHOR]

A novel coumarin dye was synthesized, which acts as a chemosensor for selective detection of Ag + and Ce 3+ ions in aqueous solution. Upon addition of Ag + to the sensor solution a new absorption band centered 580 nm was observed and the color of the solution changed from pale yellow to brown while other metal ions (Cu 2+ , Hg 2+ , Zn 2+ , Li + , Na + , Al 3+ , Fe 3+ , Co 2+ , Ni 2+ , K + and Cr 3+ ) did not cause distinct change. The coumarin dye can also be used as a fluorescence turn-on chemosensor for selective detection of Ce 3+ over other metal ions including common trivalent metal ions Al 3+ , Fe 3+ and Cr 3+ as well as lanthanide metal ions Pr 3+ , Yb 3+ , Nd 3+ and La 3+ . Investigation on changes in the intensity of the fluorescence emission band at around 350 nm with the equivalent ratio of Ce 3+ /sensor (0–1.1) reveals an approximate linear relationship, from which the concentration of Ce 3+ ion may be estimated. The detection limit of Ce 3+ ion by the sensor is estimated to be 2.07 × 10 –7 M. [ABSTRACT FROM AUTHOR]

A fluorescent sensor based on coumarin-maleimide conjugate was developed for efficient discrimination of Cys from Hcy and GSH in both organic and aqueous solution. Addition of Cys to the non-fluorescent sensor solution in DMF induced bright blue fluorescence and enhanced the fluorescence intensity by 320-fold while other amino acids and biothiols (Gly, Hcy, GSH, Glu, Val, Tyr, Arg, Trp, Lys, His, Leu, Phe, Asp and Met) did not bring about remarked change. The sensor responds to Cys extremely rapidly. If Cys was added to the sensor solution, the fluorescence intensity increased by 170-fold immediately and attained the maximum value in 5 min. A linear relationship was observed between Cys concentration within 2–20 μM and the fluorescence intensity of the sensor solution. The detection limit of the sensor toward Cys is as low as 4.7 nM. The sensor is also effective for specific detection of Cys in aqueous (DMF/H 2 O = 9:1, v/v) solution. Practical application of the sensor to drug analysis and bioimaging of living Hela cells has been verified. Possible sensing mechanism of the sensor toward Cys has been proposed. A coumarin-maleimide conjugate was synthesized for fluorescence turn-on discriminating Cys from Hcy and GSH in both organic and aqueous media. The sensor is superior in respect of its low LOD (4.7 nM), rapid response (several sec‒5 min), extraordinary fluorescence enhancement (320-fold), and facile synthesis and is applicable in drug analysis and bioimaging of living cells. [Display omitted] • A coumarin-maleimide conjugate-based fluorescent sensor was synthesized facilely. • The sensor can discriminate Cys from Hcy and GSH in both organic and aqueous media. • The sensor shows low LOD of 4.7 nM and rapid response (less than 5 min) in DMF. • Addition of Cys induces fluorescence enhancement by 320-fold in DMF. • The sensor is applicable in drug analysis and bioimaging of living cells. [ABSTRACT FROM AUTHOR]