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Two structurally simple and easily synthesized luminescent anion receptors featured with an amide-type anion binding site and rhenium(I) tricarbonyl pyridine signaling units have been developed, and they display outstanding sensitivity and selectivity toward a variety of anionic species. These complexes are highly emissive in solution. Upon anion binding, the emission intensity was significantly quenched. The sensitivities of these complexes are so high that the emission intensity can be effectively quenched by as much as 10% even in the presence of only 10(-8) M cyanide or fluoride anions. The ability of formation of intramolecular hydrogen bonding between the amide protons and central pyridine is believed to be responsible for the observed high selectivity.

Recently, 4-(pyrrol-1-yl)pyridine has been found to act as a supramolecular chemodosimeter, sensing nitrite ions in an aqueous solution with naked eye detection and a low limit of detection of 0.330 ppm. This work explores the anion-sensing properties of related derivatives, 4-(2,5-dimethyl-pyrrol-1-yl)pyridine and 4-(2,4-dimethyl-pyrrol-1-yl)pyridine, and provides a comparison with the parent compound. These molecules are determined to be effective sensors for nitrite ions with limits of detection of 1.06 ppm and 1.05 ppm, respectively. The high sensitivity and selectivity to nitrite remain even in the presence of competing anions such as SO32−, NO32−, PO43−, SO42−, Cl−, F−, I−, Br−, AcO−, and CN−. Analogous to the 4-(pyrrol-1-yl)pyridine system, the sensing mechanism appears to be the result of changes in the supramolecular aggregate system upon the interaction of an anion; this is further explored through dynamic light scattering, the Tyndall effect, and NMR spectroscopy. The two methylated derivative systems reported herein, 4-(2,5-dimethyl-pyrrol-1-yl)pyridine and 4-(2,4-dimethyl-pyrrol-1-yl)pyridine, are shown to affect the size of the supramolecular system and provide further insight into the unique mechanism of action. [ABSTRACT FROM AUTHOR]

Two structurally simple and easily synthesized luminescent anion receptors featured with an amide-type anion binding site and rhenium(I) tricarbonyl pyridine signaling units have been developed, and they display outstanding sensitivity and selectivity toward a variety of anionic species. These complexes are highly emissive in solution. Upon anion binding, the emission intensity was significantly quenched. The sensitivities of these complexes are so high that the emission intensity can be effectively quenched by as much as 10% even in the presence of only 10[sub -8] M cyanide or fluoride anions. The ability of formation of intramolecular hydrogen bonding between the amide protons and central pyridine is believed to be responsible for the observed high selectivity. [ABSTRACT FROM AUTHOR]

Abstract: This article describes our recent research results on several rhenium(I) carbonyls complexes with polarized N–H recognition motifs as anion receptors. Structurally simple and easily synthesized luminescent anion receptors containing an amide-type anion binding site and a rhenium(I) tricarbonyl pyridine signaling unit have been developed, and they display outstanding sensitivity and selectivity toward a variety of anionic species. Moreover, thioamides and thiourea derivatives of 2,6-pyridinedicarbonyl dichloride, isophthaloyl dichloride and terephthaloyl dichloride have been synthesized. These ligands have been incorporated in dinuclear rhenium(I) diimine tricarbonyl complexes and provide anion recognition properties in these complexes. Furthermore, the related rhenium(I) complex featuring sulfonamide interacting sites that incorporate the highly chromophoric π-conjugated quinoxaline moiety has been prepared, characterized, and its photophysical properties were also studied. [Copyright &y& Elsevier]

Abstract: A simple and easily synthesized colorimetric anion sensor, based on a thiourea moiety as a binding subunit on a 1,2-cyclohexane backbone and a p-nitrophenyl group as a signaling unit, has been synthesized in a one step procedure. The selective sensing of anions, particularly cyanide, has been investigated in DMSO by UV–vis titration, 1H NMR titration techniques and through ‘naked eye’ observation experiments. [ABSTRACT FROM AUTHOR]

Transition-metal complexes for anion recognition and sensing have attracted increasing attention due to their rich spectroscopic and luminescent properties upon interacting with anions. In this review, we summarize the recent progress made with transition-metal complexes for anion sensing purposes. We focus on ruthenium(II), rhenium(I) and iridium(III) polypyridyl complexes with different polarized N H recognition motifs acting as the anion receptors. [ABSTRACT FROM AUTHOR]

Abstract: Thioamides, urea and thiourea derivatives of 2,6-pyridinedicarbonyl dichloride, isophthaloyl dichloride and terephthaloyl dichloride have been synthesized. These ligands have been incorporated in dinuclear rhenium(I) diimine tricarbonyl complexes and the anion recognition properties of these complexes have been studied by luminescence, UV–Vis and 1H NMR spectroscopic methods. The complexes act as receptors for anions via hydrogen bonding and electrostatic interactions. The anion sensing properties of the complexes are compared to earlier amide-based dinuclear rhenium(I) tricarbonyl complexes. [Copyright &y& Elsevier]

Review: 113 refs. [ABSTRACT FROM AUTHOR]