A fluorescent cavitand for the recognition of GTP

A new fluorescent cavitand bearing four imidazolium groups as well as four pyrene groups was synthesized for the recognition of GTP through (C-H)⁺-X⁻ hydrogen bond formation.     

New cavitand derivatives bearing four coumarin groups as fluorescent chemosensors for Cu and recognition of dicarboxylates utilizing Cu complex

New cavitand derivatives (1, 2) bearing four coumarin groups were synthesized, and the binding properties of these cavitands towards metal ions were examined through their fluorescent changes. Cavitand 1 effectively recognized the Cu²⁺ ions among the metal ions examined. The recognition of cavitand 1-Cu²⁺ with dicarboxlyates is also described.     

Triphenylamine-based receptor for selective recognition of dicarboxylates

A new triphenylamine-based receptor 1 has been designed and synthesized for the recognition of aliphatic dicarboxylates of various chain lengths. This receptor has been designed to utilize an amide-urea conjugate for binding dicarboxylates. The receptor 1 is found to bind the dicarboxylates with moderate binding strength under a semi rigid, propeller shaped, fluorescent triphenylamine spacer. The binding behavior was studied in CH₃CN using ¹H NMR, fluorescence and UV-vis spectroscopic methods. The conformational behavior of 1 and its complexation modes have been investigated using classical and quantum mechanical theoretical methods. The receptor is found to be selective for long chain suberate.     

Fluorescent imidazolium receptors for the recognition of pyrophosphate

Anthracene and binaphthyl derivatives bearing two imidazolium rings, which strongly bind anions and are particularly selective for pyrophosphate, are examined using fluorescence, ¹H NMR analysis, and density functional calculations.     

Metal-organic frameworks derived from imidazolium dicarboxylates and group I and II salts

A series of coordination polymers containing Group I or II metal ions, connected via an imidazolium-centered dicarboxylate ligand, have been isolated from water and characterized by single crystal X-ray diffraction. All the structures incorporate water molecules that adopt a range of different structural motifs.     

A polymer-bound cavitand

[reaction: see text] An amino-footed cavitand, 1, was attached to an insoluble polystyrene support, and the uptake of organic guest molecules by the resulting polymer 3 from xylene or toluene solutions was achieved.     

Guest recognition in a partially bridged deep cavitand

The synthesis of a new deep cavitand partially bridged via disulfide bonds is described. Its thermodynamic and kinetic complexation parameters are compared with those of an unbridged analogue. The disulfide bridges cause deviations in ΔH and ΔS but result in only small differences in ΔG of complexation. The bridges increase the activation barrier for guest dissociation and lead to complexes with enhanced kinetic stability.     

Design of steroid-based imidazolium receptors for fluoride ion recognition

New deoxycholic acid-based cyclic receptors bearing imidazolium and benzimidazolium moieties bridged with o-xylelene and 1,8-dimethylenenaphthalene groups have been synthesized. Anion binding studies using ¹H NMR revealed that receptors having naphthalenic group as spacer exhibit very high selectivity for fluoride ion over other anions while receptors with o-xylelene group show a preference for the chloride ion.     

A new cavitand ionophore bearing two rigid crown ether groups

A new cavitand (1) bearing two rigid crown ether groups has been synthesized from tetrahydroxycavitand (2). The binding properties of this cavitand towards alkali metal ions as well as ammonium ion were also examined.     

A new tribridged imidazolium cyclo­phane

The new imidazolium cyclo­phane 2,11,13,21,29,31‐hexamethyl‐5,16,24‐tri­aza‐8,19,27‐triazoniahepta­cyclo[10.10.6.1^1,3.­1^5,8.1^10,14.1^16,19.1^24,27]­tritriaconta‐1,3(29),6,8(30),10,­12,14(31),17,19(32),21,25,27(33)‐dodecene tri­bromide dihydrate, C₃₃H₃₉N₆³⁺.3Br^?.2H₂O, belongs to a type of cyl­indrical macrobicyclic salt containing imidazolium groups. It has mirror symmetry, the symmetry surface is the plane of the three 2‐C atoms of imidazoliums. Three bromine anions are associated with two water mol­ecules by hydrogen bonds. The O—H?Br bond lengths are 2.53 (3) and 2.46 (3) Å.     

p-tert-Butylcalix[4]arene-based fluororeceptor for the recognition of dicarboxylates

p-tert-Butylcalix[4]arene-based dipodal receptor has been synthesized in cone conformation. The binding affinity of this receptor was evaluated with some aliphatic diacetates such as malonate, succinate, glutarate, adipate, pimelate, and suberate in CH₃CN. The receptor has the highest binding affinity for pimelate by making a 1:1 complex. This receptor was used to estimate pimelate in the presence of other dicarboxylates.     

Supported imidazolium ionic liquid phases: A new material for solid-phase extraction

This study reports a material that is based on the concept of ionic liquid analogue: a slightly crosslinked polymer-supported imidazolium trifluoroacetate salt (IL-CF₃COO⁻) that favorably combines the properties of ionic liquids (ILs) and the advantages of a solid support.The ionic liquid-supported material was evaluated for the first time as a solid-phase extraction (SPE) sorbent for selectively and quantitatively extracting pharmaceuticals from aqueous samples.The novel IL-CF₃COO⁻ was evaluated under reversed-phase (RP), weak anion exchange (WAX), strong anion exchange (SAX) and strong cation exchange (SCX) SPE procedures, and we found that SAX conditions are the most suitable for investigating the behaviour of the IL-CF₃COO⁻ material. Under SAX conditions, the IL-CF₃COO⁻ material was capable of selectively and quantitatively extracting a group of acidic compounds from aqueous samples, while washing basic analytes that were also present in the sample.The SPE method using IL-CF₃COO⁻ material was used to analyse 1000 ml of different aqueous samples (ultrapure, tap and river) with complete recovery of the acidic compounds studied. Moreover, the method provided clean chromatogram and high recoveries when percolating complex real samples, such as 1000 ml of river water and 250 ml of effluent wastewater from a sewage treatment plant spiked at low levels with the analytes studied.     

A deep cavitand provides a structured environment for the Menschutkin reaction

We report that a synthetic, vase-shaped host molecule forms complexes with quinuclidine and accelerates the Menschutkin reaction in the nanoenvironment that the host provides. Kinetic simulation is used to determine rate constants for reactions of the complex, and these are compared to control reactions in the absence of the host. The efficacy of the host in effecting this supramolecular acceleration is dependent on the structures of the alkylating agent and its leaving group.     

A new imidazolium acridine derivative as fluorescent chemosensor for pyrophosphate and dihydrogen phosphate

A new acridine derivative bearing two imidazolium groups has been synthesized. This chemosensor displayed a large fluorescent quenching effect with pyrophosphate and a unique fluorescent enhancement with H₂PO₄⁻. The strong (C-H)⁺?X⁻ hydrogen bonding between the imidazolium moieties and anions is the key interaction for the recognition. The association constant of 1 with pyrophosphate was calculated as 4.9×10⁷ M⁻¹.     

Synthesis of new chiral imidazolium salts derived from amino acids: their evaluation in chiral molecular recognition

A family of new imidazolium salts derived from natural amino acids has been synthesized and tested for NMR enantiodiscrimination, as chiral shift reagents, of carboxylic acids. These imidazolium receptors contain different structural modifications and the splitting of the signals of the acids, after addition of the corresponding CSRs, depends on these structural variables. Compound 8b exhibited the strongest chiral solvating properties for racemic Mosher acid and was recognized as a suitable CSR for the determination of its enantiomeric composition.     

A facile and general method for the preparation of diaryltellurium dicarboxylates

Diaryltellurium dicarboxylates can be prepared by treatment of the corresponding dichlorides with carboxylic acids in the presence of silver oxide. The conversion of the dichlorides to the carboxylates can also be achieved through a more practical method employing a carboxylate anionic exchange resin. IR and PMR data are given.     

A deep cavitand catalyzes the Diels-Alder reaction of bound maleimides

A deep cavitand catalyzes Diels-Alder reactions of bound maleimides via activation of the dienophile by interaction with the organized hydrogen bonding network at the cavitand rim. Rapid in-out exchange of reactant and product allows efficient turnover. The increase in steric bulk of the reaction product lessens its binding affinity, reducing (and in some cases completely eliminating) product inhibition.     

A new paradigm for pattern recognition of drugs

A new paradigm is suggested for pattern recognition of drugs. The approach is based on the combined application of the 4D/3D quantitative structure-activity relationship (QSAR) algorithms BiS and ConGO. The first algorithm, BiS/MC (multiconformational), is used for the search for the conformers interacting with a receptor. The second algorithm, ConGO, has been suggested for the detailed study of the selected conformers' electron density and for the search for the electron structure fragments that determine the pharmacophore and antipharmacophore parts of the compounds. In this work we suggest using a new AlteQ method for the evaluation of the molecular electron density. AlteQ describes the experimental electron density (determined by low-temperature highly accurate X-ray analysis) much better than a number of quantum approaches. Herein this is shown using a comparison of the computed electron density with the results of highly accurate X-ray analysis. In the present study the desirability function is used for the first time for the analysis of the effects of the electron structure in the process of pattern recognition of active and inactive compounds. The suggested method for pattern recognition has been used for the investigation of various sets of compounds such as DNA-antimetabolites, fXa inhibitors, 5-HT(1A), and alpha(1)-AR receptors inhibitors. The pharmacophore and antipharmacophore fragments have been found in the electron structures of the compounds. It has been shown that the pattern recognition cross-validation quality for the datasets is unity.     

Protein recognition by a self-assembled deep cavitand monolayer on a gold substrate

This paper details the first use of a self-folding deep cavitand on a gold surface. A sulfide-footed deep, self-folding cavitand has been synthesized, and its attachment to a cleaned gold surface studied by electrochemical and SPR methods. Complete monolayer formation is possible if the cavitand folding is templated by noncovalent binding of choline or by addition of space-filling thiols to cover any gaps in the cavitand adsorption layer. The cavitand is capable of binding trimethylammonium-tagged guests from an aqueous medium and can be deposited in 2 × 2 microarrays on the surface for characterization by SPR imaging techniques. When biotin-labeled guests are used, the cavitand:guest construct can recognize and immobilize streptavidin proteins from aqueous solution, acting as an effective supramolecular biosensor for monitoring protein recognition.