A novel 5-mercapto triazole Schiff base as a selective chromogenic chemosensor for Cu2+

Highly Sensitive and Selective Spiropyran-Based Sensor for Copper(II) Quantification

The metal-binding capabilities of the spiropyran family of molecular switches have been explored for several purposes from sensing to optical circuits. Metal-selective sensing has been of great interest for applications ranging from environmental assays to industrial quality control, but sensitive metal detection for field-based assays has been elusive. In this work, we demonstrate colorimetric copper sensing at low micromolar levels. Dimethylamine-functionalized spiropyran (SP1) was synthesized and its metal-sensing properties were investigated using UV-vis spectrophotometry. The formation of a metal complex between SP1 and Cu²⁺ was associated with a color change that can be observed by the naked eye as low as ≈6 μM and the limit of detection was found to be 0.11 μM via UV-vis spectrometry. Colorimetric data showed linearity of response in a physiologically relevant range (0-20 μM Cu²⁺) with high selectivity for Cu²⁺ ions over biologically and environmentally relevant metals such as Na⁺, K⁺, Mn²⁺, Ca²⁺, Zn²⁺, Co²⁺, Mg²⁺, Ni²⁺, Fe³⁺, Cd²⁺, and Pb²⁺. Since the color change accompanying SP1-Cu²⁺ complex formation could be detected at low micromolar concentrations, SP1 could be viable for field testing of trace Cu²⁺ ions.

Unusual absence of FRET in triazole bridged coumarin-hydroxyquinoline, an active sensor for Hg2+ detection

A triazole-bridged coumarin conjugated quinoline sensor has been 'click'-synthesized by Cu(i) catalyzed Huisgen cycloaddition, and it exhibited high selectivity for toxic Hg2+. Surprisingly, no evidence of energy transfer from the quinoline moiety to coumarin has been found, substantiated by time-resolved fluorescence study. The possible binding mode of this sensor to Hg2+ has been established via NMR study, steady-state and time-resolved fluorescence spectroscopy, which is further supported by TDDFT calculations. The sensor has been found to be cell membrane permeable and non-toxic, and hence is suitable for intracellular Hg2+ detection.

Rationally designed phenanthrene derivatized triazole as a dual chemosensor for fluoride and copper recognition

A 1,2,3-triazole chemosensor containing phenanthrene and phenol moieties (PhTP) was efficiently synthesized via copper (I)-catalyzed azide-alkyne cycloaddition, "click chemistry". PhTP is a dual analyte sensor for fluoride and copper (II) ions in homogeneous medium. Deprotonation of the phenolic OH proton by the fluoride ion is responsible for a change in fluorescence color from blue (PhTP) to yellowish-orange (PhTP-fluoride adduct), while a charge transfer between the triazole nitrogen of the chemosensor and Cu²⁺ revealed a turn-off fluorescence output. The detection capability of PhTP was analyzed with a series of anions (F^-, Cl^-, Br^-, I^-, H₂PO₄^-, ClO₄^-, OAc^-, BF₄^-) and cations (Fe³⁺, Fe²⁺, Cu²⁺, Ag⁺, Cr³⁺, Al³⁺, Co²⁺, Ni²⁺, Cd²⁺, Zn²⁺). With anions, competitive fluorescence responses under UV lamp were observed for acetate and dihydrogen phosphate anions, but maximum response from fluoride ion was substantiated from steady state absorption and fluorescence experiments. With cations, PhTP displayed a selective and sensitive recognition towards Cu²⁺ ion through spectral modulation in absorption spectroscopy and a turn-off fluorescence response. Nuclear magnetic resonance (NMR) spectroscopic titration studies supported the results obtained through photophysical studies and provided evidence for the ion-binding sites on the probe.

A benzimidazole-based chemodosimeter for the fluorometric detection of Zn and Cu via 1,5 proton shifts and C–N bond cleavage

The new probe APBHN that we designed has been successfully used for the detection of Zn²⁺and Cu²⁺in both (1 : 1) and (1 : 2) ratios chemically as well as biologically in liver carcinoma cellsvia1,5 proton shifts and C–N bond cleavage.

Oxaazamacrocycles incorporating the quinoline moiety: synthesis and the study of their binding properties towards metal cations

Nitrogen- and oxygen-containing macrocycles with an endocyclic quinoline moiety synthesized via Pd(0)-catalyzed amination were found to be prospective fluorescent chemosensors for Cu(ii).

Highly sensitive and selective “naked eye” sensing of Cu(ii) by a novel amido–imine based receptor: a spectrophotometric and DFT study with practical application

Synthesis of (E)-bis-N'-((1H-pyrrol-2-yl)-methylene)-pyridine-2,6-carbohydrazide and its sensing ability towards copper(ii) ion in aqueous medium by color change, the sensing limit being 4.0 × 10⁻⁹ M.

A colorimetric “naked-eye” Cu(ii) chemosensor and pH indicator in 100% aqueous solution

A highly selective and sensitive colorimetric Cu²⁺-chemosensor and pH probe for practical use in water has been developed.

Synthesis and evaluation of simple naked-eye colorimetric chemosensors for anions based on azo dye-thiosemicarbazones

A series of novel, highly selective azo dye-thiosemicarbazones based anion sensors (3e-f) have been synthesized from the condensation reaction between thiosemicarbazide and six different azo salicylaldehydes. The structure of the sensors was confirmed by spectroscopic methods. The selectivity and sensitivity in the recognition for acetate anion over other anions such as fluoride, chloride, iodide and dihydrogenphosphate anions were determined by naked-eyes and UV-vis spectra. The color of the solution containing sensor had an obvious change from light yellow to orange only after the addition of acetate anion in aqueous solution (water/dimethylsulfoxide, 7:3, v/v) while other anions did not cause obvious color change. The anion recognition property of the receptor via proton-transfer is monitored by UV-vis titration and (1)H NMR spectroscopy. Under condition in aqueous solution of sensor 3e (water/dimethylsulfoxide, 7:3, v/v), linearity range for the quantification of acetate anion was 1-22 μM and limit of detection (LOD) of acetate anion was 0.71 μM.

Highly selective colorimetric sensing of Cu(II) ions in aqueous solution via modulation of intramolecular charge transfer transition of aminonaphthoquinone chemosensor

An aminonaphthoquinone based colorimetric chemosensor has been developed and demonstrated for the highly selective detection of Cu(II) ions in aqueous solution. The intramolecular charge transfer (ICT) transition exits in amine moiety directly attached to the quinone ring is modulated by the d-d transition of a square planar Cu(II)-receptor complex resulting in a change of color from yellow to blue. No significant color change was observed upon addition of other selected metal ions. The sensing property has been investigated using various spectral techniques (UV-Vis, fluorescence) and product analysis (Elemental analysis, magnetic moment, UV-Vis, FT-IR, EPR).

Mercapto thiadiazole-based sensor with colorimetric specific selectivity for AcO- in aqueous solution

A novel acetate selective anion sensor 3 based on azophenol and mercapto thiadiazole had been designed and synthesized. Sensor 3 behaves a single selectivity and sensitivity in the recognition for AcO(-) anion over other anions such as F(-), Cl(-), Br(-), I(-), H(2)PO(4)(-), HSO(4)(-) and ClO(4)(-) by naked-eyes and UV-vis spectra changes in aqueous solution (H(2)O/DMSO, 5:5, v/v). The color of the solution containing sensor 3 had an obvious change from colorless to orange only after the addition of AcO(-) in aqueous solution while other anions did not cause obvious color change. (1)H NMR titration results revealed that the binding process includes two steps: (i) hydrogen bonding interactions (for small quantities of acetate) and (ii) proton transfer between the sensor 3 and the coordinated anion (for high quantities of acetate). The association constant K(a) was 7.35×10(3) M(-1). The detection limitation of AcO(-) with the sensor 3 was 1.0×10(-6) mol L(-1).