A highly selective fluorescent sensor for dual detection of Zn2+ and F− based on a new diarylethene

Solvent-directed multiple correspondence fluorescent probe for highly selective and sensitive detection of Cu2+ and Mg2

A solvent-directed, new Schiff base multiple correspondence fluorescent probe, (E)-2-(2-hydroxybenzylidene) hydrazine-1-carboxamid (L), was synthesized for selective sensing of Cu2+ and Mg2+ ions. L showed excellent selectivity and high sensitivity toward Cu2+ in "turn off" mode with a detection limit of 40.5 nM in 10 mM, pH = 7.0 PBS buffer. Contrary to that, when acetonitrile was used as the solvent, L exhibited highly selective and sensitive fluorescence sensing ability for Mg2+ in "turn on" mode with a detection limit of 9.5 nM. L can coordinate to Cu2+ and Mg2+ in a 1:1 molar ratio, respectively, evidenced by Job's plot analysis. Their binding modes were investigated by NMR, IR and XPS spectroscopies. Moreover, the satisfied results were obtained when L was used to detect Cu2+ and Mg2+ in real water samples.

Coumarin functionalized molecular scaffolds for the effectual detection of hazardous fluoride and cyanide

Fluoride and cyanide contamination in drinking water imposes detrimental impacts on human health above their permissible limits. Hence, the quantitative detection of these colourless water-soluble toxins has attracted attention. Even though a plethora of chemosensors have been reported so far for the detection of fluoride and cyanide from various matrices, still their applicability is limited to a few examples. Nevertheless, recent advances in the syntheses of coumarin derivatives have shown significant impact on fluoride and cyanide detection. Therefore, this present review provides a brief overview of the application of coumarin-coupled molecular scaffolds towards the detection of perilous fluoride and cyanide along with their sensing mechanisms in order to develop more innovative, simple, sensitive, real-time responsive and cost-effective coumarin-based supramolecular chemosensors to promote next generation approaches towards the ultra-trace quantitative detection of these toxic anions.

Detection of toxic fluoride ion via chromogenic and fluorogenic sensing. A comprehensive review of the year 2015-2019

Fluoride ion (F^-) contamination can be accumulated along the water and the food chain and cause serious risk to public health. It is of the greatest importance that selects the suitable chromophores and fluorophores for the design and synthesis of outstanding selective, sensitive chromogenic and fluorogenic probes for detection of fluoride ion. In this review is mainly focused on the current progress of fluoride ion detection according to their receptors into several categories like anthracene, azo, benzothiazole, BODIPY, calixarene, coumarin, imidazole, diketopyrrolopyrrole, hydrazone, imidazole, naphthalene, naphthalimide, quantum dots, Schiff base and urea group sensing in the year 2015-2019.

Coumarin-Based Small-Molecule Fluorescent Chemosensors

Coumarins are a very large family of compounds containing the unique 2H-chromen-2-one motif, as it is known according to IUPAC nomenclature. Coumarin derivatives are widely found in nature, especially in plants and are constituents of several essential oils. Up to now, thousands of coumarin derivatives have been isolated from nature or produced by chemists. More recently, the coumarin platform has been widely adopted in the design of small-molecule fluorescent chemosensors because of its excellent biocompatibility, strong and stable fluorescence emission, and good structural flexibility. This scaffold has found wide applications in the development of fluorescent chemosensors in the fields of molecular recognition, molecular imaging, bioorganic chemistry, analytical chemistry, materials chemistry, as well as in the biology and medical science communities. This review focuses on the important progress of coumarin-based small-molecule fluorescent chemosensors during the period of 2012-2018. This comprehensive and critical review may facilitate the development of more powerful fluorescent chemosensors for broad and exciting applications in the future.

A novel bifunctional fluorescent and colorimetric probe for detection of mercury and fluoride ions

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.

A highly sensitive fluorescent sensor for Zn2+ based on diarylethene with an imidazole unit

A new sensitive sensor for Zn²⁺ based on diarylethene with an imidazole unit has been synthesized. Its photochromic and fluorescent behaviors have been systematically investigated by the stimulation of UV/vis lights and Zn²⁺ ion in THF solution. It displayed a dual-mode with a "turn on" fluorescence and color response to Zn²⁺. With the addition of Zn²⁺, the emission intensity enhanced 26-fold, accompanied by the fluorescent color changed from dark red to bright yellow. The 1:1 stoichiometry between the sensor and Zn²⁺ was verified by Job's plot and MS. The LOD for Zn²⁺ was determined to be 6.12 × 10^-9 mol L^-1. Furthermore, a logic circuit was designed by using the fluorescence at 578 nm as output and the combinational stimuli of UV/vis and Zn²⁺/EDTA as inputs.

A Photoswitchable Colorimetric Sensor for Fluoride Based on a Dithienylethene Unit

A novel dithienylethene amide-based photoswitchable anion receptor was synthesised by amidation of 4,4′-(cyclopent-1-ene-1,2-diyl) bis(5-methylthiophene-2-carboxylic acid) with 4-nitroaniline in 56% yield under mild conditions; its structure was confirmed by NMR, MS and elemental analysis. Investigation of its photochromic properties indicated that 4,4′-(cyclopent-1-ene-1,2-diyl)bis[5-methyl-N-(4-nitrophenyl) thiophene-2-carboxamide] had good reversibility and excellent fatigue resistance upon irradiation with UV or visible light and can serve as a colorimetric sensor for fluoride, resulting in a significant change in the absorption spectrum.

A naphthalene benzimidazole-based chemosensor for the colorimetric and on-off fluorescent detection of fluoride ion

A novel naphthalene benzimidazole (NBI)-based chemosensor (D2) was developed for fluoride ion (F^-) detection. The absorption spectrum of D2 changed dramatically from yellow to blue in the visible region accompanied with a 225nm red shift of its absorption maximum upon the addition of F^- in DMSO. D2 also exhibited a fluorescence turn-off response towards the fluoride ion. The emission intensity of D2 decreased drastically along the increasing F^- concentration and the detection limit for F^- was as low as 3.2×10^-9mol/L. ¹H NMR and HRMS-ESI results indicated that the formation of NBI-O^- through the desilylation reaction of F^- with NBI-OSi was responsible for the spectral changes. Overall, this kind of NBI-type molecules represent a new type chemosensor for the spectral detection of fluoride ion in solution.