A selective chromogenic chemosensor for carboxylate salt recognition

A new heteroditopic chromogenic chemosensor bearing a crown ether substituted at the intraannular position with a nitrophenylthiourea moiety has been synthesized. The binding behavior of this sensor was investigated by (1)H NMR spectroscopy and UV-vis spectroscopy. The receptor binds in a cooperative fashion to both a potassium cation and a carboxylate anion whereas a sodium cation sequesters an anion from the anion-receptor complex. The binding events are confirmed by selective color changes of the chemosensor solution.     

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

A novel colorimetric cation sensor bearing phenol, thiol and HCN groups was designed and synthesized. In a DMSO/H2O (9:1, v/v) solution, the sensor exhibited highly selective recognition of Cu2+ among a range of metal ions tested. In the presence of Cu2+, solutions of the sensor underwent a dramatic color change from colorless to yellow, while the presence of other metal cations such as Zn2+, Pb2+, Cd2+, Ni2+, Co2+, Fe3+, Hg2+, Ag+ and Ca2+ had no effect on the color. The detection limit of the sensor toward Cu2+ is 8.0×10(-7) M and an association constant Ka of 4.3×10(5) M(-1) was measured. The sensing of Cu2+ by this sensor was found to be reversible, with the Cu2+-induced color being lost upon addition of EDTA.     

A novel fluoride selective optical chemosensor based on internal charge transfer signaling

A new internal charge transfer probe, NAPH-1, synthesized by incorporating photoemitive naphthalimide core with an acidic imidazolium ring, offers highly selective colorimetric and ratiometric ‘off-on’ signaling for targeting F⁻, while Cl⁻, Br⁻, I⁻, , SCN⁻, AcO⁻, and do not appreciably perturb the photophysical properties of the probe even at relatively higher concentrations than the F⁻. Deprotonation of the imidazolium ring, supported by the ¹H NMR and theoritical studies, seems to cause the spectral modulations.     

A novel benzothiazole based azocalix[4]arene as a highly selective chromogenic chemosensor for Hg ion: A rapid test application in aqueous environment

A novel calix[4]arene derivative containing benzothiazole azo groups at the upper rim was synthesized as chromogenic chemosensor, and its binding and sensing properties with heavy metal ions (Pb²⁺, Hg²⁺, Ni²⁺, Cd²⁺, Cu²⁺, Zn²⁺, Co²⁺, Fe²⁺, Mn²⁺, Cr³⁺, Ag⁺) were investigated by UV-vis spectroscopy and voltammetric techniques. The results of spectroscopic and voltammetric experiments showed that the chromogenic chemosensor has high selectivity towards Hg²⁺ ion over the other heavy metal ions. Moreover, it was shown that the interaction between Hg²⁺ and the chromogenic chemosensor occurs by means of the benzothiazole azo groups at the upper rim by using differential pulse voltammetry. The stoichiometric ratio and the association constant were determined as 1:1 and (6.1 ± 0.3) × 10⁵ L mol⁻¹ for the complex between Hg²⁺ and the ionophore. Furthermore, we prepared a rapid test kit for early detection of Hg²⁺ in aqueous environment in the concentration range of 1 × 10⁻⁴ to 1 × 10⁻² M.     

A highly selective redox, chromogenic, and fluorescent chemosensor for Hg2+ in aqueous solution based on ferrocene-glycine bioconjugates

The synthesis, electrochemical, optical, and metal-cation-sensing properties of ferrocene-glycine conjugates C(30)H(38)O(8)N(8)Fe (2) and C(20)H(24)O(4)N(4)Fe (3) have been documented. Both compounds 2 and 3 behave as very selective redox (ΔE(1/2) = 217 mV for 2 and ΔE(1/2) = 160 mV for 3), chromogenic, and fluorescent chemosensors for Hg(2+) cations in an aqueous environment. The considerable changes in their absorption spectra are accompanied by the appearance of a new low-energy peak at 630 nm (2, ε = 1600 M(-1) cm(-1); 3, ε = 822 M(-1) cm(-1)). This is also accompanied by a strong color change from yellow to purple, which allows a prospective for the "naked eye" detection of Hg(2+) cations. These chemosensors present immense brightness and fluorescence enhancement (chelation-enhanced fluorescence = 91 for 2 and 42 for 3) following Hg(2+) coordination within the limit of detection for Hg(2+) at 7.5 parts per billion.     

Zinc selective chemosensor based on pyridyl-amide fluorescence

Chemosensors are developed to image zinc ions. Fluorescence enhancement due to Zn²⁺ binding is an excellent way to detect its presence. A chemosensor for Zn²⁺ based on dipicolylamine (DPA) groups connected by a pyridyl amide backbone has been synthesized. Addition of 2-chloroacetyl chloride to 2,6-diaminopyridine affords 2,6-bis(chloroethylamido)pyridine, which is converted to the sensor BADPA-P by 2,2′-dipicolylamine displacement of chlorine. This compound along with two others, the mono-DPA, ADPA-P and the benzyl in place of pyridyl, BADPA-B, present three potential Zn²⁺ sensors. It was found that BADPA-P in the presence of Zn²⁺ shows a large increase in fluorescence, whether in polar organic or aqueous environments. Its fluorescence in the presence of Cd²⁺, unlike with Zn²⁺, is not enhanced when excited at longer wavelengths. Proton NMR measurements, indicate two Zn²⁺ ions bind to BADPA-P. Also, Zn²⁺ enhances fluorescence even when other metal ions are present.     

Azo 8-hydroxyquinoline benzoate as selective chromogenic chemosensor for Hg and Cu

Azo 8-hydroxyquinoline benzoate (2) was synthesized and studied to detect metal ions. Distinct color change was found for compound 2 in the presence of transition metal ions Hg²⁺ or Cu²⁺ in CH₃CN, respectively, which makes it possible for distinguishing Hg²⁺ and Cu²⁺ from other metal ions by the ‘naked eye’.     

A nanoparticle based chromogenic chemosensor for the simultaneous detection of multiple analytes

Quantum Dot-Schiff base conjugate displays selectivity for Cu(2+) and Fe(3+) enabling the simultaneous detection of these ions in semi-aqueous solution; in contrast, the Schiff base itself displayed no selectivity.     

A new fluoride selective fluorescent as well as chromogenic chemosensor containing a naphthalene urea derivative

A new naphthalene derivative containing a urea group at the 1,8-position of naphthalene was synthesized and showed a unique absorption and fluorescence peak with a fluoride ion. Calculations suggested that a new peak was attributed to the increased anion character of urea nitrogen due to the strong interaction of the fluoride and N-H protons.     

A novel fluoride ion colorimetric chemosensor based on coumarin

A novel visible colorimetric sensor (L1) with high selectivity for fluoride ion based on coumarin has been synthesized by a simple modification of our earlier report. The chemosensor L1 shows an obvious color change from yellow to blue upon addition of fluoride ion with a large red shift of 145 nm in acetonitrile, and without interference of other anions such as Cl-, Br-, I-, NO3-, H2PO4-, HSO4-, and AcO-. The investigation of 1H NMR spectrum titration indicates the proposed mechanism is that F- first establishes a hydrogen bonding interaction with L1, and then the formation of [F-H-F]- induces deprotonation.     

A novel selective fluorescent chemosensor for Cu（Ⅱ）

A novel fluorescence enhancement Cu~(2 ) chemosensor derived from coumarin was prepared.Emission study found that it exhibits evident Cu~(2 )-amplified fluorescence prior to Co~(2 ),Pb~(2 ),Mg~(2 ),Mn~(2 ),Ni~(2 ),Zn~(2 ),Fe~(3 ),Ag~ and Cd~(2 ),and the largest emission enhancement factor is about 9 at a ratio of 2:1 (chemosensor 1/Cu~(2 )).     

A selective and sensitive chemosensor for Cu based on 8-hydroxyquinoline

A novel 8-hydroxyquinoline derivative 3 was synthesized. Significant fluorescent quenching was found in the presence of Cu²⁺ and Hg²⁺ with notably higher selectivity for Cu²⁺ than Hg²⁺.     

A highly selective chemosensor for copper ion based on ICT fluorescence

Simple structural compounds 1 to 3 were synthesized.The presence of Cu²⁺ resulted in the fluorescence and absorption spectra change of 1 and 2,which indicated that 1 and 2 showed a highly selective response to Cu²⁺ over other metal ions.However,3 showed no selectivity for metal ions,which means that the compound could bind with several metal ions,such as,Ni²⁺,Zn²⁺,Cd²⁺.Hg²⁺, Pb²⁺,Fe³⁺,Mg²⁺,Ca²⁺,and Co²⁺,except Cu²⁺ and Ag⁺.The different spectral responses were attributed to the difference in binding sites for 1 and 3.     

A novel multisignaling optical-electrochemical chemosensor for anions based on tetrathiafulvalene

[structure: see text] A multisignaling optical-electrochemical receptor for anions based on a triad with anthracene and TTF units was prepared. It showed a unique selectivity for fluoride ion over various anions with dramatic fluorescence enhancement in neutral condition and displayed a special recognition of H2PO4(-) in electrochemical studies with remarkable cathodic displacement of the first oxidation potential E(ox)1 of the TTF unit.     

A selective chromogenic molecular sensor for acetate anions in a mixed acetonitrile-water medium

Quinonehydrazone compound , as a new chromogenic anion sensor, can selectively detect AcO(-) over F(-) and other anions in mixed acetonitrile-water media. The deprotonation of the N-H proton of the sensor is responsible for the drastic color change. An acidic C-H group in the receptor, probably acting as an accessorial binding site, is essential to the selectivity and affinity for sensing the acetate anions.     

A new fluorescent as well as chromogenic chemosensor for anions based on an anthracene carbamate derivative

A new fluorescent as well as chromogenic anion sensor, 1,8-anthradiol bis(N-phenylcarbamate) 2, was synthesized. It exhibits new selective red-shifted absorption and fluorescence bands with F⁻ and AcO⁻, which could be attributed to the anthracene moiety directly involved in the bonding interaction with the anions.     

A selective colorimetric chemosensor for thiols based on intramolecular charge transfer mechanism

Compound 1 as an electron donor-acceptor compound with N,N-dimethylaniline and quinone units was designed for a highly selective colorimetric determination of thiol-containing amino acids and peptides, by making use of the unique reactivity of thiol towards quinone. Compound 1 shows a strong intramolecular charge transfer (ICT) band around 582 nm; but, it decreased after addition of either cysteine (Cys) or glutathione (GSH). Moreover, the ICT band intensity at 582 nm decreased linearly with the increasing concentrations of Cys or GSH. The interference from other amino acids can be neglected. Therefore, compound 1 can be employed as a selective colorimetric visual chemosensor for thiol-containing amino acids and peptides.     

A novel "turn-on" fluorescent chemosensor for the selective detection of Al3+ based on aggregation-induced emission

A water-soluble, 'turn-on' fluorescent chemosensor based on aggregation-induced emission (AIE) has been developed. It exhibits rapid response, excellent selectivity, and sensitivity to Al(3+).     

A ferrocenyl-guanidine derivative as a highly selective electrochemical and colorimetric chemosensor molecule for acetate anions

A highly preorganized chemosensor molecule 1 based on a ferrocenyl-guanidine decorated with a chromogenic aryl azo moiety recognizes the acetate anion in acetonitrile solution. At first, receptor 1 underwent two-step oxidation events. Initially, oxidation of 1 occurs at the Fe(II) centre (E(p) = 440 mV) to form a ferrocenium species, followed by fast electron transfer from the guanidine moiety of the receptor to the Fe(III) centre with concomitant generation of an Fe(II) species with a radical cation centred at the nitrogen atom. In the second step, the radical cation species formed should undergo electrochemical oxidation at higher potential (E(p) = 830 mV). This assumption is supported by spectroelectrochemical studies. A remarkable cathodic shift (182 mV) of the ferrocene/ferrocenium oxidation peak (E(p) = 440 mV) and a progressive red-shift (Δλ = 30 nm) of the low energy band are observed in its absorption spectrum upon complexation of receptor 1 with the acetate anion. This change in the absorption spectrum is accompanied by a colour change from yellow to orange, which can be used for the "naked-eye" detection of this anion. Its monoprotonated form is able to selectively sense the less basic Cl(-), Br(-), NO(3)(-), and HSO(4)(-) anions: the oxidation redox peak at E(p) = 865 mV is cathodically shifted (107-182 mV).