Suk-Kyu Chang

Coumarin-derivative-based off–on catalytic chemodosimeter for Cu2+ ions

In this study, a new coumarin derivative is shown to be a highly effective turn-on fluorescent sensor that is catalytically hydrolyzed by Cu2+, and the catalytic process induces a large increase in the fluorescence intensity, due to amplification of the fluorescence signal.

Chromogenic and Fluorogenic Signaling of Sulfite by Selective Deprotection of Resorufin Levulinate

A new sulfite-selective probe system based on resorufin was investigated. Levulinate of resorufin exhibited a prominent chromogenic and turn-on type fluorogenic signaling toward sulfite ions in aqueous media based on the selective deprotection of the levulinate group. The sulfite-selective signaling was possible in the presence of commonly encountered anions.

Hydrazine-Selective Chromogenic and Fluorogenic Probe Based on Levulinated Coumarin

Chemosignaling of hydrazine by selective deprotection of levulinated coumarin was investigated. In the presence of hydrazine, levulinated coumarin was selectively deprotected, resulting in chromogenic and fluorescent turn-on type signaling. The selective naked-eye detectable signaling of hydrazine was possible in the presence of representative metal ions and common anions in an aqueous environment.

Dual signaling of hydrazine by selective deprotection of dichlorofluorescein and resorufin acetates

The highly selective chemosignaling behaviors for hydrazine by a reaction-based probe of dichlorofluorescein and resorufin acetates were investigated. Hydrazinolysis of latent dichlorofluorescein and resorufin acetate fluorochromes caused prominent chromogenic and fluorescent turn-on type signals. The probes selectively detected hydrazine in the presence of commonly encountered metal ions and anions as background. Dichlorofluorescein and resorufin acetates selectively detected hydrazine with detection limits of 9.0 × 10(-8) M and 8.2 × 10(-7) M, respectively. Furthermore, hydrazine was selectively detected over other closely related compounds, such as hydroxylamine, ethylenediamine, and ammonia. As a possible application of the acetate probes, hydrazine signaling in tap water was tested.

Selective Perborate Signaling by Deprotection of Fluorescein and Resorufin Acetates

The acetate derivatives of fluorescein and resorufin exhibited a prominent turn-on type signaling behavior toward BO(3)(-) ions over other common anions. Signaling is based on the selective deprotection of acetate groups by perborate, which resulted in significant chromogenic and fluorogenic signaling. Compound 1 also exhibited a pronounced perborate selectivity over other commonly used oxidants in 90% aqueous acetonitrile solution.

New metal cation-selective ionophores derived from calixarenes: their syntheses and ion-binding properties

Various derivatives (ethoxycarbonylmethyl, carboxymethyl, and ethoxyethyl, etc.) of calix[4]arene, calix[6]arene, and calix[8]arene have been synthesized and their ion-binding properties investigated by solvent extraction, ion-transport through liquid membranes, and u.v. spectroscopy. The extraction of various metal ions (as picrate salts) from the aqueous phase into dichloromethane by the calixarene derivatives showed that the ethoxycarbonylmethyl derivatives exhibited markedly increased extraction efficiency compared with their unsubstituted phenol analogues, and the efficiency was in general comparable to those of crown ethers. The most notable feature was the selectivities exhibited by their ethoxycarbonylmethyl derivatives; calix[4]arene for Na+, calix[6]arene for Cs+, and calix[8]arene for K+. A liquid membrane study with a water–chloroform–water system also indicated that the ion-transport efficiencies exhibited by calixarenes were found to be in accordance with their extraction abilities, confirming the strong participation of the ester carbonyl oxygen in this function. However, the ester derivative of calix[4]arene was an exception in that inefficient carrier activity was observed in spite of high extraction efficiency. The pronounced Cs+ selectivity exhibited by the calix[6]arene ester was further confirmed by the changes in the u.v. spectrum of the ester from 277 and 270 nm to 275 and 267 nm upon interaction with Cs+ ion in methanol.

Ratiometric Signaling of Hypochlorite by the Oxidative Cleavage of Sulfonhydrazide-Based Rhodamine-Dansyl Dyad.

A reaction-based probe 1 for hypochlorite signaling was designed by the conjugation of two fluorophores, rhodamine and dansyl moieties, by the reaction of rhodamine B base with dansylhydrazine. Probe 1 exhibited pronounced hypochlorite-selective chromogenic and fluorescent signaling behavior over other oxidants used in practical applications, such as hydrogen peroxide, peracetic acid, and ammonium persulfate, as well as commonly encountered metal ions and anions. Signaling was attributed to the hypochlorite-induced oxidative cleavage of the sulfonhydrazide linkage of the probe. In particular, favorable ratiometric fluorescence signaling was possible by utilizing the emissions of the two fluorophores. A detection limit of 1.13 × 10(-6) M (0.058 ppm) was estimated for the determination of hypochlorite. A paper-based test strip was prepared and was used as a semiquantitative indicator for the presence of hypochlorite in aqueous solutions. The probe was also successfully applied for the determination of hypochlorite in practical tap water samples.

A new fluorogenic benzothiazolyl ionophore based upon calix[4]arene-crown-5 ether for calcium determination in aqueous media

A new benzothiazolyl functionalized ionophore based upon the calix[4]arene-crown-5 ether has been prepared and its fluoroionophoric properties toward Ca2+ ions were investigated. The compound exhibited a pronouncedly selective fluoroionophoric behavior toward Ca2+ ions among the surveyed physiologically important metal ions of Na+, K+, and Mg2+. Detection limit for Ca2+ ions was found to be 9×10−5 M in dioxane–water (80:20, v/v) solution.

Electrochemical behavior of calix[4]arenediquinones and their cation binding properties

Abstract The redox and cation-binding properties of three quinone-functionalized calix[4]arenes have been studied in acetonitrile. Cation-bound calix[4]arenediquinone produces a new set of redox peaks at positively shifted potentials. Thus, the association constant between cation and calix[4]arenediquinone is found to be enhanced by the electrochemical reduction of the receptor molecule. The enhancement is dependent on the charge and size of cations. The magnitude of the potential shift can be explained on the basis of stabilization due to the transition of binding characteristics from ion-dipole to ion-ion interaction by an electron transfer reaction. Substituents in the lower rim exert considerable influence on the redox behavior of the complex. NH + 4 produces extraordinary voltammetric behavior due to the fact that only NH + 4 can form hydrogen bondings with calix[4]arenes, in contrast to other metal ions.

A new Hg2+-selective chromoionophore based on calix[4]arenediazacrown ether

A new azophenol type chromogenic ionophore based on the p-tert-butylcalix[4]arenediazacrown ether was prepared: the ionophore exhibited a pronouncedly selective chromogenic behaviour toward Hg2+ ions among the surveyed guests of alkali, alkaline earth, transition and heavy metal ions in liquid-liquid extraction experiments.