Differential fluorogenic sensing of F− versus CN− based on thiacalix[4]arene derivatives

Fluorometric and colorimetric sensor for selective detection of cyanide anion by dibenzosuberenone-based dihydropyridazine in aqueous solution

A new chemosensory based on deprotonation and intramolecular charge transfer (ICT) was developed to detect cyanide in food samples. Deprotonation was facilitated by increasing the acidity of the NH proton in the dibenzosuberenone-based dihydropyridazine chemosensor Pz3 with -CN substituents. Addition of cyanide to acetonitrile and aqueous acetonitrile solution (1/9) of Pz3 resulted in their significant color change from colorless to purple in visible light, accompanied by a strong red shift in the absorption spectrum. Meanwhile, the near-infrared (NIR) emission (ex. 525 nm, em. 670 nm) of Pz3- resulting from deprotonation showed fluorescence switching behavior to detect the cyanide anion. While the acidic NH protons interact with basic anions as F-, CN-, OAc- and H2PO4- in organic solution (MeCN), just CN ions interact with in aqueous organic solutions (H2O-MeCN 1/9 HEPES pH 7.4). The limit of detection of cyanide from the fluorescence spectrum is 80 nM, which is well below the value determined for drinking water by World Health Organization (WHO). The interference effect of cations and anions showed that Pz3 could play an important role in the determination of waste NaCN. In addition, Pz3 successfully carried out the selective detection of cyanide in food samples such as bitter almonds and sprouting potatoes.

Synthesis, Structure, and Characterization of Thiacalix[4]-2,8-thianthrene

Sulfur-containing macrocycles have attracted substantial interest because they exhibit unique characteristics due to their polygonal ring-shaped skeleton. In this study, a thianthrene-based cyclic tetramer with the sulfur linker, thiacalix[4]-2,8-thianthrene (TC[4]TT), was successfully prepared from a cyclo-p-phenylenesulfide derivative using acid-induced intramolecular condensation. Single crystal X-ray diffraction revealed that TC[4]TT adopts an alternative octagonal form recessed to the inner side. Its internal cavity included small solvents, such as chloroform and carbon disulfide. Due to its polygonal geometry, TC[4]TT laminated in a honeycomb-like pattern with a porous channel. Furthermore, TC[4]TT showed fluorescence and phosphorescence emission in a CH₂Cl₂ solution at ambient and liquid nitrogen temperatures. Both emission bands were slightly redshifted compared with those of the reference compounds (di(thanthren-2-yl)sulfane (TT₂S) and thianthrene (TT)). This work describes a sulfur-containing thiacalixheterocycle-based macrocyclic system with intriguing supramolecular chemistry based on molecular tiling and photophysical properties in solution.

Allosteric binding properties of a 1,3-alternate thiacalix[4]arene-based receptor having phenylthiourea and 2-pyridylmethyl moieties on opposite faces

Thiacalix[4]arene receptors with two thiourea moieties and two 2-pyridyl moieties exhibited a heteroditopic dinuclear receptor with F− and Ag+ ions by a positive allosteric effect.

Elucidating sensing mechanisms of a pyrene excimer-based calix[4]arene for ratiometric detection of Hg(ii) and Ag(i) and chemosensor behaviour as INHIBITION or IMPLICATION logic gates

This article reports the synthesis and characterisation of two lower rim calix[4]arene derivatives with thiourea as spacer and pyrene or methylene-pyrene as fluorophore. Both derivatives exhibit a fluorimetric response towards Hg²⁺, Ag⁺ and Cu²⁺. Only methylene-pyrenyl derivative 2 allows for selective detection of Hg²⁺ and Ag⁺ by enhancement or decrease of excimer emission, respectively. The limits of detection of 2 are 8.11 nM (Hg²⁺) and 2.09 nM (Ag⁺). DFT and TD-DFT computational studies were carried out and used to identify possible binding modes that explain the observed response during fluorescence titrations. Calculations revealed the presence of different binding sites depending on the conformation of 2, which suggest a reasonable explanation for non-linear changes in fluorescence depending on the physical nature of the interaction between metal centre and conformer. INHIBITION and IMPLICATION logic gates have also been generated monitoring signal outputs at pyrene monomer (395 nm) and excimer (472 nm) emission, respectively. Thus 2 is a potential primary sensor towards Ag⁺ and Hg²⁺ able to configure two different logic gate operations.

A new azine derivative colorimetric and fluorescent dual-channel probe for cyanide detection

A novel azine derivative colorimetric and fluorescent dual-channel probe salicylaldehyde hydrazine-3,5-dibromosalicylaldehyde (1) has been designed, synthesized and characterized. The probe 1 is confirmed to have especial selectivity and good sensitivity on detecting CN^- via UV-vis absorption and fluorescence spectrum in aqueous solution (H₂O/DMSO, 1:4, v/v). This colorimetric and fluorescent dual-channel probe response to CN^- owed to the deprotonation process and established the mechanism by using ¹H NMR spectroscopy. Further researches showed that the detection limit of the probe 1 to CN^- anions is 8.01×10^-9M, significantly lower than the maximum level 1.9×10^-6M in potable water from WHO guidelines.

Hydrazine functionalized probes for chromogenic and fluorescent ratiometric sensing of pH and F−: experimental and DFT studies

Two novel hydrazine based sensors, BPPIH (N¹,N³-bis(perfluorophenyl)isophthalohydrazide) and BPBIH (N^1′,N^3′-bis(perfluorobenzylidene)isophthalohydrazide), are presented here.

Colorimetric chemosensor for multiple targets, Cu2+, CN−and S2−

New Schiff-base was developed as colorimetric sensor for Cu²⁺, CN⁻and S²⁻with the detection limits lower than the given guidelines.

Selective colorimetric and “turn-on” fluorimetric detection of cyanide using an acylhydrazone sensor in aqueous media

A simple, highly selective and sensitive fluorescence-enhanced cyanide chemosensor L using an acylhydrazone group as a binding site and a naphthalene group as the fluorescence signal group was designed and synthesized.

Positive and negative allosteric effects of thiacalix[4]arene-based receptors having urea and crown-ether moieties

Allosteric binding behaviors of heteroditopic receptors bearing the 1,3-alternate conformation based thiacalix[4]arene have been evaluated by absorption and ¹H NMR titration experiments.

A selective colorimetric chemosensor with an electron-withdrawing group for multi-analytes CN− and F−

A colorimetric chemosensor with an electron-withdrawing group (–NO₂) 1 for the detection of CN⁻ and F⁻ was developed.

Cyanide detection using a benzimidazole derivative in aqueous media

A novel cyanide selective fluorescent chemosensor S1 based on benzimidazole group and naphthalene group as the fluorescence signal group had been designed and synthesized. The receptor could instantly detect CN(-) anion over other anions such as F(-), Cl(-), Br(-), I(-), AcO(-), H2PO4(-), HSO4(-), SCN(-) and ClO4(-) by fluorescence spectroscopy changes in aqueous solution (H2O/DMSO, 8:2, v/v) with specific selectivity and high sensitivity. The fluorescence color of the solution containing sensor S1 induced a remarkable color change from pale blue to mazarine only after the addition of CN(-) in aqueous solution while other anions did not cause obvious color change. Moreover, further study demonstrates the detection limit on fluorescence response of the sensor to CN(-) is down to 8.8×10(-8)M, which is far lower than the WHO guideline of 1.9×10(-6)M. Test strips based on S1 were fabricated, which could act as a convenient and efficient CN(-) test kit to detect CN(-) in pure water for "in-the-field" measurement. Thus, the probe should be potential applications in an aqueous environment for the monitoring of cyanide.

Design strategies for lab-on-a-molecule probes and orthogonal sensing

This review highlights the currently exploited working concepts of lab-on-a-molecule probes, with a particular focus on what is required for multianalyte detection and quantification in competitive assays. Both, chemosensor and chemodosimeter approaches are considered. The multifaceted design strategies and the orthogonal protocols are evaluated in order to identify and categorise the successful conceptions and to single out unknown territory and challenges for future work.

Rational design of a rapid fluorescent approach for detection of inorganic fluoride in MeCN–H2O: a new fluorescence switch based on N-aryl-1,8-naphthalimide

A desilylation based sensor showed high selectivity and sensitivity to fluoride in MeCN–H₂O media.

A colorimetric chemosensor based on a Schiff base for highly selective sensing of cyanide in aqueous solution: the influence of solvents

A new highly selective colorimetric chemosensor 1 shows exclusive response toward cyanide by a color change in aqueous solution.

A study of allosteric binding behaviour of a 1,3-alternate thiacalix[4]arene-based receptor using fluorescence signal

The allosteric binding behaviour of a receptor L bearing a 1,3-alternate conformation based thiacalix[4]arene has been evaluated by fluorescence and ¹H NMR titration experiments.

Excimer–monomer switch: a reaction-based approach for selective detection of fluoride

Desilylation triggered excimer–monomer switch based on 1,8-naphthalimide was used as a sensing strategy for detection of fluoride.