Ga Rim You

Fluorescence ‘on–off–on’ chemosensor for the sequential recognition of Hg2+ and cysteine in water

A simple fluorescent chemosensor 1 for the sequential detection of Hg2+ and cysteine was developed by combination of benzene-1,2-diamine and 6-bromopyridine-2-carboxaldehyde. The sensor 1 exhibited an ‘on–off’ fluorescent quenching response in the presence of Hg2+, and could be applied for detection of Hg2+ with a good recovery in water samples. The sensing mechanism of 1 for Hg2+ was supported by theoretical calculations. Moreover, the resulting Hg2+–2·1 complex acted as an efficient ‘off–on’ sensor for cysteine, showing recovery of 1 from Hg2+–2·1 complex. Therefore, the sensor 1 can be employed as a practical fluorescent chemosensor for recognition of Hg2+ and cysteine in aqueous solution.

Chromogenic naked-eye detection of copper ion and fluoride

A bi-functional colorimetric chemosensor 1, based on julolidine moiety and N-(2-aminoethyl)-5-nitropyridin-2-amine, has been synthesized and characterized. The sensor 1 has proven to be highly selective and sensitive to Cu2+ with a color change from colorless to yellow in aqueous solution. The sensing mechanism of 1 for Cu2+ was proposed to be the ligand-to-metal charge-transfer (LMCT), which was explained by theoretical calculations. It was also found that the 1–Cu2+ complex could be recycled simply through treatment with an appropriate reagent such as EDTA. Importantly, the sensor 1 could be used to detect and quantify Cu2+ in water samples. Moreover, 1 showed a selective colorimetric response toward fluoride due to the increase in the intramolecular charge transfer (ICT) band by a deprotonation process without any inhibition from other anions such as CH3COO− and CN−.

Sequential detection of mercury(II) and thiol-containing amino acids by a fluorescent chemosensor

A simple fluorescent chemosensor 1 for the sequential detection of Hg2+ and cysteine or glutathione was developed by combination of thiosemicarbazide and 8-hydroxyjulolidine-9-carboxaldehyde. Sensor 1 exhibited an ‘ON–OFF’ fluorescence quenching response in the presence of Hg2+, which was explained by theoretical calculations. 1 also showed high selectivity in the presence of potential competitors such as Ag+ and Pb2+. Moreover, the resulting Hg2+-2·1 complex acted as an efficient ‘OFF–ON’ sensor for cysteine or glutathione, showing recovery of 2·1 from Hg2+-2·1 complex. Therefore, sensor 1 can be employed as a practical fluorescent chemosensor for recognition of Hg2+ and thiol-containing amino acids in aqueous solution.

Synthesis, Characterization, and Catalytic Activities of A Nickel(II) Monoamido‐Tetradentate Complex: Evidence For NiIII–Oxo and NiIV–Oxo Species

A new mononuclear nickel(II) complex, [NiII (dpaq)Cl] (1), containing a tetradentate monoamido ligand, dpaq (dpaq=2-[bis(pyridin-2-ylmethyl)amino]-N-(quinolin-8-yl)acetamide), has been synthesized and characterized by IR spectroscopy, elemental analysis, and UV/Vis spectroscopy. The structure of the nickel complex has been determined by X-ray crystallography. This nonheme NiII complex 1 catalyzed the epoxidation reaction of a wide range of olefins with meta-chloroperoxybenzoic acid (m-CPBA) under mild conditions. Olefin epoxidation using this catalytic system has been proposed to involve a new reactive NiIV -oxo (4) species, based on the evidence from a PPAA (peroxyphenylacetic acid) probe, Hammett studies, H218 O exchange experiments, and ESI mass spectroscopic analysis. Moreover, the nature of solvent significantly influenced partitioning between heterolytic and homolytic O-O bond cleavage of the Ni-acylperoxo intermediate (2). The O-O bond of 2 proceeded predominantly through heterolytic cleavage in a protic solvent, such as CH3 OH. These results suggest that possibly a NiIV -oxo species is a common reactive intermediate in protic solvents. The two active oxidants, namely NiIV -oxo (3) and NiIII -oxo (4), which are responsible for stereospecific olefin epoxidation and radical-type oxidations, respectively, operate in aprotic solvents.

Distinction between Mn(III) and Mn(II) by using a colorimetric chemosensor in aqueous solution

A new colorimetric chemosensor for Mn(III) and Mn(II) was developed by combination of 2-(aminomethyl)aniline and 4-(diethylamino)-2-hydroxybenzaldehyde. This sensor 1 exhibited an obvious color change from pale yellow to reddish brown in the presence of Mn3+ in aqueous solution (buffer/CH3CN = 7 : 3), which was reversible with the addition of EDTA. Moreover, 1 could be used to detect and quantify Mn3+ in water samples, and as a practical, visible colorimetric test kits for Mn3+. Moreover, 1 could detect Mn2+ via the formation of 1–Mn3+ complex with longer reaction time. The resulting different reaction time of Mn(III) and Mn(II) with 1 was used to differentiate between Mn(III) and Mn(II). Finally, the sensing ability of 1 for Mn3+ was supported by theoretical calculations.

A novel displacement-type colorimetric chemosensor for the detection of Cu2+ and GSH in aqueous solution

A new and simple colorimetric chemosensor 1 was developed for the sequential detection of Cu2+ and glutathione (GSH) in aqueous solution. Receptor 1 detected Cu2+ ions by changing its color from colorless to yellow. Based on UV-vis titrations, Job plot, and ESI-mass spectrometry analysis, the sensing mechanism for Cu2+ was proposed to be the enhancement of the intramolecular charge transfer band, which was further explained by theoretical calculations. The detection limit of 1 for Cu2+ (3.89 μM) was below the World Health Organization (WHO) guideline for drinking water (31.5 μM). Moreover, the resulting 1–Cu2+ complex could sequentially sense GSH, showing recovery of 1 from the complex.