Selective colorimetric sensing of fluoride ion and its use for insitu cyclization of the sensor

Design and synthesis new colorimetric receptors for naked-eye detection of biologically important fluoride and acetate anions in organic and arsenite in aqueous medium based on ICT mechanism: DFT study and test strip application

Novel three colorimetric anion receptors R1, R2 and R3 have been designed and synthesized via condensation reaction and characterized using IR, MS, and NMR spectroscopic techniques. Anion sensing properties were studied using colorimetric, UV-vis titration, ¹H NMR titration, and Cyclic Voltammetric Studies. Comparing the UV-visible titration data of the receptors R1 and R2, R2 showed high redshift (∆λ_max) in the mixed competitive solution (DMSO: H₂O, 9: 1; v/v) of about 155 nm, 157 nm, 169 nm for Na⁺F^-, Na⁺AcO^-, and Na⁺AsO₂^- ions with LOD of 0.23 ppm, 0.18 ppm, and 0.30 ppm, respectively. The observed spectral change of receptor R2 is due to the anion-induced deprotonation of the OH proton, which is confirmed by UV-vis titration, ¹HNMR titration, and cyclic voltammetric studies. Theoretical studies via DFT calculation were carried for R1 and R2 to optimize the structure and to explain the anion-binding mechanism. The application of designed receptor R2 was successfully demonstrated for the detection of F^- and AsO₂^- ions using a test strip. The receptors R1 and R2 proved itself to be potentially useful for real-life application by sensing F^- and AcO^- ions in real samples like toothpaste, mouthwash, vinegar and seawater in a complete aqueous medium.

Novel nitro-substituted formazan derivatives: selective ratiometric and colorimetric chemosensors for fluoride anion sensing detectable by the naked eye

This study is the first report of formazan derivatives designed as chemosensors for fluoride anion recognition.

Harnessing a pyrimidine based molecular switch to construct reversible test strips for F-/AcO- with respect to Al3+: A colorimetric approach

We report novel compound 4-nitro-2-((pyrimidin-2-ylamino) methyl) phenol (1) synthesized by the condensation of 5-nitro salicylaldehyde with 2-amino pyridine. Compound 1 serves as a dual signalling chromogenic receptor for F^-/AcO^- and Al³⁺ ions. The chromogenic response of 1 towards the aforementioned analytes is reversible with respect to either Al³⁺/X (=F/AcO)^- or X(F/AcO)^-/Al³⁺. The limit of detection of 1 for F^- and AcO^- are 1.0025×10^-7M and 0.79×10^-7M, respectively. The optical switching has been rationalized on the basis of UV-Vis titrations and ¹H NMR titrations respectively. The optical switching has been successfully use by constructing reversible paper strips for detecting Al³⁺ as well as F^-/AcO^-.

A selective chemosensor for fluoride ion and its interaction with Calf Thymus DNA

The amido-Schiff base 1 (N¹, N³-bis (2-nitrobenzylidene)benzene-1,3-dicabohydrazide) containing a CONH group and CHN linkage has been synthesized by the condensation between isophthalic acid dihydrazide and o-nitrobenzaldehyde. This molecule can act as a fluoride ion sensor with high selectivity and sensitivity. Presence of nitro group in the phenyl ring may be responsible for the detection of fluoride ion visually with a dramatic color change from colorless to deep red in aqueous dimethyl sulphoxide solution. This Schiff base can be used as test kit for sensing of fluoride ion in the solid state. Compound 1 can detect fluoride also in commercially available toothpaste. As the compound has adequate solubility in DMSO-water mixture (7:93, v/v) and having some hydrogen bond donor and acceptor centers, we have investigated its nature of binding with Calf Thymus-DNA (CT-DNA) using theoretical molecular modelling and other experimental methods like UV-vis spectroscopy, circular dichroic and thermal melting studies. Thermodynamic parameters have been obtained using the well known Van't Hoff's equation. From both theoretical and experimental findings it has been observed that it can interact effectively with CT-DNA with binding energy -7.55kcal/mol to -7.50kcal/mol.

Selective chromo-fluorogenic molecular sensor for dual channel recognition of Cu2+and F−: effect of functional group on selectivity

The amido-Schiff base (3-hydroxy-naphthalene-2-carboxylic acid(4-cyano-benzylidene)-hydrazide) shows dual mode sensibility towards Cu²⁺and F⁻. It can detect Cu²⁺in HEK 293 cells and F⁻in tooth paste and in solid state.