A macrocyclic fluorescent probe for the detection of citrate

We present a macrocyclic fluorescent probe for the detection of citrate. This receptor binds citrate through hydrogen-bonding interactions in aqueous solutions, and exhibits a turn-on in fluorescence in response to binding. The presence of common biologically relevant dicarboxylate species does not significantly impact the fluorescence response. We have demonstrated the utility of this probe with the staining of murine splenocytes, and identified different basal levels of citrate present in immune cell subsets via flow cytometry analysis.

Preparation of a Multicarbazole-Based Nanocapsule Capable of Largely Modulating Guest Spectroscopic Properties in Water

A nanocapsule composed of multiple carbazole panels (ca. 12 panels) was quantitatively generated from bent carbazole-based amphiphiles in water. Unlike previously reported macrocycles and coordination cages bearing several carbazole panels, the resultant nanocapsule displays enhanced emissivity and improved electrochemical stability as compared with the monomeric amphiphile. The spectroscopic properties of substituted coumarin and boron-dipyrromethene dyes can be modulated upon encapsulation by the nanocapsule in water. In the cavity, a highly blue-shifted absorption band is observed from largely twisted coumarin dyes and two absorption bands are found from boron-dipyrromethene dimers stacked in an unusual L-shaped fashion. Moreover, the encapsulated dimers exhibit unique excimer-like emission.

N-Bromosuccinimide (NBS)-Catalyzed C-H Bond Functionalization: An Annulation of Alkynes with Electron Withdrawing Group (EWG)-Substituted Acetyl Indoles for the Synthesis of Carbazoles

An N-bromosuccinimide-catalyzed intermolecular annulation of acetyl indoles with alkynes was developed, allowing for regioselective formation of valuable carbazoles through direct C-H bond functionalization. The readily available catalyst, wide substrate scope, gram scale synthesis, and mild conditions make this method practical. Mechanistic investigations indicate that the bromination of acetyl indole takes place to generate a bromide intermediate, followed by coupling with an alkyne and intramolecular cycloaromatization to furnish carbazole products.

Anion binding of a neutral bis(cyclopeptide) in water-methanol mixtures containing up to 95% water

Anion receptor 2b was designed and synthesized, which was structurally derived from a previously described bis(cyclopeptide) 2a comprising two covalently linked cyclic hexapeptide rings with alternating L-proline and 6-aminopicolinic acid subunits. Solubilizing groups attached to the aromatic cyclopeptide subunits of 2b cause a substantial improvement of water solubility with respect to 2a, but have negligible effects on anion binding properties. Thus, anion affinity of 2b could be evaluated in aqueous solvent mixtures in which 2a is not sufficiently soluble, namely in water–methanol with a water content of up to 95 vol%. The solvent-dependent characterization of anion binding showed that the logKa values of the iodide and sulfate complexes of 2b decrease linearly with increasing water content while the individual contributions of complexation enthalpy and entropy correlate with the solvent composition in a more complex manner. The obtained results provide insight into the factors that control anion affinity and selectivity of these neutral receptors in aqueous media. In addition, they show that substantial anion affinity can be expected even in 100% water.

Binding studies and anion-selective electrodes with neutral isophthalamide-based receptors

The incorporation of neutral and structurally simple isophthalamide-based receptors into plasticised polymeric membrane anion-selective electrodes has afforded devices with a good sensing ability.

Coumarin-based supramolecular gelator: a case of selective detection of F− and HP2O73−

Coumarin-based small molecular gelator 1 forms stable, fluorescent gel from CHCl₃–petroleum ether (1 : 1, v/v). The gel is selectively disintegrated in the presence of F⁻ and hydrogen pyrophosphate.

Highly sensitive and selective detection of the pyrophosphate anion biomarker under physiological conditions

Self-assembled monolayers on gold of a multidentate adsorbate bearing a bis(carbazolyl)urea unit are prepared and used as a surface resonance plasmon sensor for the detection of hydrogen pyrophosphate anions under physiological conditions.

Bis(carbazolyl)ureas as selective receptors for the recognition of hydrogenpyrophosphate in aqueous media

Recognition properties of the novel bis(carbazole) tris-ureidic-based receptors 1 and 2 toward different anions have been studied by (1)H NMR and absorption and emission spectroscopy, as well as by DFT calculations. Receptor 1, in which the two urea-functionalized arms are decorated with p-nitrophenyl rings, behaves as a highly selective chromogenic molecular probe for hydrogenpyrophosphate anion in a competitive medium (acetonitrile/water, 70/30). Receptor 2, bearing two urea arms decorated with photoactive pyrenyl rings, acts as a highly selective fluorescent molecular probe for hydrogenpyrophosphate anion in either acetonitrile or an aqueous mixture (acetonitrile/water, 85/15). Receptor 2 exhibits a dual monomer-excimer emission spectrum and undergoes a remarked ratiometry in acetonitrile in the presence of hydrogenpyrophosphate: the excimer band disappears, whereas the monomer band is slightly increased. However, in the aqueous mixture, a strong increase of the excimer emission band was observed, while the monomer emission bands remained almost unaffected. The resulting binding modes and spectroscopic features are explained by suitable structures of model complexes for both receptors. In such complexes, a peripheral cooperative effect was found, alleviating the excess of negative charge in the guest toward the outer surface of the host, as well as the required enlargement on its internal cavity.