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.

Ship in a breakable bottle: fluoride-induced release of an organic molecule from a Pr(iii)-linked molecular cage.

A 3-dimensional networked molecular cage, , has been synthesized. This macrocycle-based framework was prepared from a solvothermal reaction involving a flexible organic building block, calix[4]pyrrole dibenzoic acid (H2), and Pr(NO3)3·6H2O. A unique feature of is that it retains free calix[4]pyrrole molecules in the framework pores. Treatment with a fluoride anion source serves to destroy the network and allows release of the organic guest. The net result is a 'molecular ship' in a 'breakable bottle'.

A phthalazine-based two-in-one chromogenic receptor for detecting Co(2+) and Cu(2+) in an aqueous environment.

A new multifunctional and highly selective chemosensor for Co(2+) and Cu(2+) was designed and synthesized. could simultaneously detect both Co(2+) and Cu(2+) by changing its color from pale yellow to pink and to orange in a near-perfect aqueous solution. The binding modes of to Co(2+) and Cu(2+) were determined to be a 2 : 1 complexation stoichiometry through Job's plot, ESI-mass spectrometry analysis and (1)H NMR titration. The detection limits (1.5 and 2.1 µM) of for Co(2+) and Cu(2+) were lower than the DEP guidelines (1.7 µM for Co(2+)) and the WHO guidelines (31.5 µM for Cu(2+)) for drinking water. The chemosensor could be used to quantify Co(2+) and Cu(2+) in water samples. Moreover, could be used as a practical, visible colorimetric test kit for both Co(2+) and Cu(2+). The sensing mechanisms of Co(2+) and Cu(2+) by were supported by theoretical calculations.

A colorimetric sensor for the sequential detection of Cu(2+) and CN(-) in fully aqueous media: practical performance of Cu(2+).

A new highly selective colorimetric chemosensor 1 (E)-9-(((5-mercapto-1,3,4-thiadiazol-2-yl)imino)methyl)-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-8-ol was designed and synthesized for the sequential detection of Cu(2+) and CN(-). This sensor 1 exhibited an obvious color change from yellow to orange in the presence of Cu(2+) in a fully aqueous solution. The detection limit (0.9 µM) of 1 for Cu(2+) is far lower than the WHO limit (31.5 µM) for drinking water. In addition, the resulting Cu(2+)-2· 1 complex can be further used to detect toxic cyanide through a color change from orange to yellow, indicating the recovery of 1 from Cu(2+)-2·1. Importantly, chemosensor 1 could be used to detect and quantify Cu(2+) in water samples, and a colorimetric test strip of 1 for the detection of Cu(2+) could be useful for all practical purposes.

A new multifunctional Schiff base as a fluorescence sensor for Al³âº and a colorimetric sensor for CN⁻ in aqueous media: an application to bioimaging.

A multifunctional fluorescent and colorimetric receptor 1 ((E)-N'-((8-hydroxy-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinolin-9-yl)methylene)benzohydrazide) for the detection of both Al(3+) and CN(-) in aqueous solution has been developed. Receptor 1 exhibited an excellent selective fluorescence response toward Al(3+). The sensitivity of the fluorescent based assay (0.193 µM) for Al(3+) is far below the limit in the World Health Organization (WHO) guidelines for drinking water (7.41 µM). In addition, receptor 1 showed an excellent detection ability in a wide pH range of 4-10 and also in living cells. Moreover, receptor 1 showed a highly selective colorimetric response to CN(-) by changing its color from colorless to yellow immediately without any interference from other anions.

A single molecule that acts as a fluorescence sensor for zinc and cadmium and a colorimetric sensor for cobalt.

A new metal ion sensor that contains quinoline and pyridylaminophenol has been synthesized. In acetonitrile and in the presence of Zn(2+), the sensor fluoresces. In contrast, in aqueous solutions the sensor fluoresces in the presence of Cd(2+). The fluorescence of the molecule is selective for Zn(2+) or Cd(2+) and shows no fluorescence with other metal ions. The crystal structure of the Cd(2+) complex shows coordination through the amide and phenol oxygens, as well as the amine nitrogen of the sensor. The sensor also acts as a colorimetric sensor for Co(2+) by changing color from colorless to yellow. The color change is selective for Co(2+) and is not observed with other metal ions. The unique combination of pyridine and phenol groups with quinoline results in the properties of this sensor.