Chiral Recognition by Supramolecular Porphyrin-Hemicucurbit[8]uril-Functionalized Gravimetric Sensors.

Enantiorecognition of a chiral analyte usually requires the ability to respond with high specificity to one of the two enantiomers of a chiral compound. However, in most cases, chiral sensors have chemical sensitivity toward both enantiomers, showing differences only in the intensity of responses. Furthermore, specific chiral receptors are obtained with high synthetic efforts and have limited structural versatility.

Self-Assembly of Chiral Cyclohexanohemicucurbit[]urils with Bis(Zn Porphyrin): Size, Shape, and Time-Dependent Binding.

In order to investigate the ability of bis(zinc octaethylporphyrin) () to discriminate cyclohexanohemicucurbit[n]urils () of different shapes and sizes, the self-assembly of barrel-shaped chiral with was studied by various spectroscopic methods (absorption, fluorescence, circular dichroism (CD), and NMR). While the binding of 6-membered induced a tweezer-like conformation followed by the formation of form of upon further addition of , the interaction of 8-membered is more complex and proceeds through the featured -to- conformational change of and further intermolecular self-assembly via multiple noncovalent associations between and . Whilst bis-porphyrins are known to be effective chemical sensors able to differentiate various guests based on their chirality via induced CD, their ability to sense small differences in the shape and size of relatively large macrocycles, such as chiral and , is scarcely examined.

Cyclohexanohemicucurbit[8]uril Inclusion Complexes With Heterocycles and Selective Extraction of Sulfur Compounds From Water.

Solid-phase extraction that utilizes selective macrocyclic receptors can serve as a useful tool for removal of chemical wastes. Hemicucurbiturils are known to form inclusion complexes with suitably sized anions; however, their use in selective binding of non-charged species is still very limited. In this study, we found that cyclohexanohemicucurbit[8]uril encapsulates five- and six-membered sulfur- and oxygen-containing unsubstituted heterocycles, which is investigated by single-crystal X-ray diffraction, NMR spectroscopy, isothermal titration calorimetry, and thermogravimetry.

Binding Between Cyclohexanohemicucurbit[]urils and Polar Organic Guests.

Inherently chiral, barrel-shaped, macrocyclic hosts such as cyclohexanohemicucurbit[]urils (cycHC[]) bind zinc porphyrins and trifluoroacetic acid externally in halogenated solvents. In the current study, we tested a set of eighteen organic guests with various functional groups and polarity, namely, thiophenols, phenols, and carboxylic and sulfonic acids, to identify a preference toward hydrogen bond-donating molecules for homologous cycHC[6] and cycHC[8]. Guests were characterized by Hirshfeld partial charges on acidic hydrogens and their binding by H and F NMR titrations.

Supramolecular chirogenesis in zinc porphyrins by enantiopure hemicucurbit[n]urils (n = 6, 8).

Chiral cyclohexanohemicucurbit[n]urils (n = 6, 8) (cycHCs) are able to bind guests through multiple "outer surface interactions", which in the case of planar zinc porphyrins leads to induction of chirality. Crystal structures of complexes of complementary sized hosts revealed social self-sorting, while in the solution phase one cycHC can accommodate up to three porphyrin molecules with log Ktotal 9.

Propanediurea-Based Molecular Clips Bind Halide Anions: An Insight into the Mechanism of Cucurbituril Formation.

The synthesis and supramolecular properties of the first methylene-bridged propanediurea-based dimers are described. These dimers, bearing an aromatic sidewall, have the shape of molecular clips. Unlike glycoluril-based dimers, these clips neither dimerize nor accept any organic guests, due to their small cavities.

A Cucurbituril Derivative That Exhibits Cation-Modulated Self-Assembly.

Cucurbiturils are the most potent artificial receptors known for many organic molecules in water. However, little is known about their supramolecular chemistry in organic solvents. Here we present a new cucurbituril derivative, 1, and investigate its supramolecular properties in methanol.

Pressocucurbit[5]uril.

A novel macrocycle, decamethylpressocucurbit[5]uril (Me10prCB[5]), was synthesized by acid-catalyzed condensation of propanediurea and paraformaldehyde. This macrocycle binds methane with higher affinity than cucurbit[5]uril and its permethylated derivative.