Stilbene-Bridged tert-Butylcalix[4]arene as Photoswitchable Molecular Receptors

Controlled binding of organic guests by stimuli-responsive macrocycles

Synthetic supramolecular chemistry pursues not only the construction of new matter, but also control over its inherently dynamic behaviour.

Constructing bridged multifunctional calixarenes by intramolecular indole coupling

2,2′-Bisindole bridges can be easily created at (thia)calixarene cores providing the molecules with multiple functionalities for application in supramolecular chemistry.

Fluorescent phenylethynylene calix[4]arenes for sensing TNT in aqueous media and vapor phase

The upper-rim of calix[4]arene is modified with phenylacetylene derivatives via Sonogashira coupling reaction to produce a wider cavity for entrapping TNT.

Photochemical Cycloisomerizations via 7-exo-dig Reactions on a Calix[4]arene Scaffold

Narrow-rim 1,3-bis(phenylethynyl)-p-tert-butylcalix[4]arenes were found to be photolabile, producing unprecedented seven-membered oxacyclic systems formed via 7-exo-dig cyclizations and a new [3.2.1]bicyclic system via subsequent 1,8-H shifts. The calixarene provided a scaffold for these unprecedented photochemical reactions to occur.

Diazocinones: synthesis and conformational analysis

1,2,4,5-Tetrazines (prepared from aryl nitriles) condense with isoxazolylcyclobutanones (prepared from 3-benzenesulfonyl-3-vinylcyclobutanol) in methanolic KOH to give conformationally restricted 6-isoxazol-5-yl-6,7-dihydro-5H-[1,2]diazocin-4-ones. The solution 1H NMR spectra of dihydrodiazocinone 1a with phenyl moieties at C3 and C8 reveal two conformations of the eight-membered heterocycle that are non-interconverting on the NMR time scale at ambient temperature. The kinetics of the conversion process, followed by 1H NMR between 21 and 70 degrees C in DMSO solution, yield an activation energy of approximately 21 kcal/mol relative to the kinetic conformer and show an equilibrated ratio of approximately 5:1 of the thermodynamic to the kinetic conformers. The electronic structure calculations on a model dihydrodiazocinone predict geometries for the two conformations. One of these geometries agrees with the X-ray crystallographic analysis of the thermodynamic conformation of 1a.

Rational Design of New Polymerizable Oxyanion Receptors

We report the synthesis of a library of new polymerizable functional monomers designed for complexing with the oxyanionic moiety of the chemotherapeutic drug methotrexate. The 1H NMR and ITC binding studies allowed for the selection of receptors possessing the best association parameters. Subsequently, the design of a broad library of polymerizable moiety-specific binding monomers for the imprinting of dicarboxylate containing drugs was accomplished. Di(ureidoehylenemethacrylate)stilbene possesses the highest association properties and shows potential to act as a monomer in the molecularly imprinting technique to obtain photoswitchable cavities.

Pyridyl thioureas as switchable anion receptors

The binding selectivity of simple pyridyl thioureas in acetonitrile can be completely switched by protonation; hence the neutral thiourea binds acetate, but not chloride or bromide, whereas the protonated thiourea binds strongly to chloride or bromide, but is deprotonated by acetate.