Indole-based Receptor Research Articles

Colorimetric, turn-on fluorescence detection of fluoride ions using simple indole-based receptors in living cells

Herein, an indole-attached fluorescein dye (FI-1) was designed and synthesized as an excellent sensor for fluoride ions.

ANION-BINDING AND SENSING PROPERTIES OF NOVEL RECEPTORS BASED ON N-(INDOL-3-YLGLYOXYLYL)BENZYLAMINE

Indole-based receptors such as biindole, carbazole, and indolocarbazole are regarded as some of the most favorable anion receptors in molecular recognition. This is because indole groups possess N–H groups as hydrogen-bonding donors. The introduction of amide groups in the indole framework can induce strong binding properties and good water solubility. In this study, we designed and synthesized a series of N-(indol-3-ylglyoxylyl)benzylamine derivatives as novel and simple anion receptors. The receptors derived by aryl and aliphatic amines can selectively recognize F– based on a color change from colorless-to-yellow in DMSO. The receptors derived by hydrazine hydrate can recognize F–, AcO–, and H2PO4– by similar color changes in DMSO and can even enable the selective recognition of F– in a DMSO–H2O binary solution by the naked eye. Spectrographic data indicate that complexes are formed between receptors and anions through multiple hydrogen-bonding interactions in dual solutions.

Ratiometric fluorescence detection of fluoride ion by indole-based receptor

A novel artificial receptor 1 containing the indolocarbazole-NH moieties as the recognition sites exhibited high selectivity and sensitivity toward F− over other typical anionic species in DMSO solution. Upon addition of F− into the solution, receptor 1 showed a remarkable ratiometric shift of the fluorescence maximum from 535 to 590nm, and also a prominent color change from light yellow to orange, which was observable by the naked eye. The recognition properties of receptor 1 were investigated by 1H NMR, UV–vis, and fluorescence titration experiments, with the results suggesting a two-step strategy of binding with F−. In addition, the theoretical calculations were carried out to reveal the role of intramolecular charge transfer in the ratiometric fluorescence recognition process.

A turn‐on indole‐based sensor for hydrogen sulfate ion

A simple indole-based receptor 1 was prepared by a simple Schiff-base reaction of 1H-indole-3-carbaldehyde with ethane 1,2-diamine and its fluoroionophoric properties toward anions were investigated. Indole-based receptor 1 acts as a selective turn-on fluorescent sensor for HSO4(-) in methanol among a series of tested anions. Fluorescence spectroscopy, ultraviolet and nuclear magnetic resonance imaging support that the HSO4(-) indeed interacted with imine nitrogen and the proton of nitrogen in indole ring.

ChemInform Abstract: Anion Receptors Containing Heterocyclic Rings

AbstractReview: 79 refs.

Molecular Recognition of Carbohydrates: Evaluation of the Binding Properties of Pyrazole-based receptors and their Comparison with Imidazole- and Indole-based Systems

The aim of the study was to evaluate the potential of pyrazole-based receptors in the complexation of carbohydrates. Representatives of a new series of acyclic pyrazole-based receptors were prepared and their binding properties toward selected mono- and disaccharides evaluated. The results of the binding studies were compared with those obtained for acyclic imidazole- and indole-based receptors. The first binding studies revealed di- vs monosaccharide binding preferences of the new receptors and showed that pyrazole units are useful building blocks for the construction of receptors with interesting binding preferences.

Anion-induced conformational changes in 2,7-disubstituted indole-based receptors

The conformational preorganization and anion-induced conformational changes of indole-based receptors functionalized with an amide group at the 2-position and a variety of amide, urea and thiourea moieties at the 7-position have been studied by the means of NMR spectroscopy. NOE experiments showed that anti-anti orientation across C2-C2alpha and C7-N7alpha bonds is preferred for receptors 1-4 in acetone solution in the absence of anions. Anion-receptor interactions have been evaluated through (1)H and (15)N chemical shift changes. In 2,7-bis-carboxamido functionalized indoles the interaction with chloride and bromide anions primarily occurs at the indole H1 proton. The introduction of urea and thiourea moieties increases the number of hydrogen bond donor sites which manifests itself in a distribution of halide-receptor interactions among the H1, H7alpha and H7gamma protons. Acetate anions also interact strongly with indole and urea NH donor groups, whereas nitrate anions interact solely with H7alpha and H7gamma urea/thiourea protons. NOE enhancements in the presence of anions revealed that anion-receptor complexes favour the syn-syn conformation of the C2 and C7 substituents.