The condensation reaction between p-tert-butylphenol and formaldehyde leads in a single step to good yields of cyclic oligomers in which, depending on the reaction conditions, either four, six, or eight phenol units are joined by methylene bridges. The beakerlike shape of the most stable conformation of the tetramer has led to their being given the name “calixarenes” (calix = chalice). Resorcinol can undergo condensation in a similar manner with a variety of aldehydes to afford cyclic tetramers with the same basic structure (the resorcarenes). In both cases the reaction does not require the use of dilution techniques, so that large quantities of product can be readily obtained. In addition, the parent compounds can be modified in various ways, in particular at the phenolic hydroxy groups or the phenyl residues; these approaches can be used separately or in combination. Calixarenes are thus ideal starting materials for the synthesis of various types of host molecules and can also act as building blocks for the construction of larger molecular systems with defined structures and functions. Their potential applications range from use as highly specific ligands for analytical chemistry, sensor techniques and medical diagnostics to their use in the decontamination of waste water and the construction of artificial enzymes and the synthesis of new materials for non-linear optics or for ultrathin layers and sieve membranes with molecular pores.

Calixarenes, Macrocycles with (Almost) Unlimited Possibilities

Crown ethers: sensors for ions and molecular scaffolds for materials and biological models.

Fulgides for Memories and Switches.

Recent progress in phosphonate and sulfonate MOFs is reviewed with an emphasis on open frameworks. These two ligating functionalities are paired due to their structural analogy but the review will show that their differences likely outweigh their similarities when it comes to their framework structures and properties. Examples that are highlighted focus on new routes to open structures, demonstrations of porosity and functionality, and examples with dynamic structures. This critical review is geared to researchers interested in designing open framework solids (134 references).

Phosphonate and sulfonate metal organic frameworks.

Pillar[5]arenes are [1(5)]paracyclophane derivatives consisting of 1,4-disubstituted hydroquinones linked by methylene bridges in the 2,5-positions. The first report of these novel macrocycles was in 2008, when 1,4-dimethoxypillar[5]arene was prepared in 22% yield, and subsequent improvements in synthetic methods have allowed the number of derivatives to expand significantly. In addition to D(5) symmetric pillar[5]arenes, asymmetric pillar[5]arenes with two different substituents in the 1- and 4-positions and copillar[5]arenes consisting of two different repeat units in a 4 : 1 ratio have been synthesised. Crystallographic, computational and spectroscopic studies are starting to shed light on the compounds' unusual inclusion phenomena, from gelation and transportation of water through nanotubes to the formation of chromogenic rotaxanes. Applications as molecular sensors are starting to appear with a focus on guest detection by fluorescence quenching. This tutorial review will provide a summary of research into the pillar[5]arenes since their recent discovery.

/pdf/pillar-5-arenes-fascinating-cyclophanes-with-a-bright-future-4ww9jsmycl.pdf

Pillar[5]arenes: fascinating cyclophanes with a bright future

Novel Layer Structure of Sodium Calix[4]arenesulfonate Complexes—a Class of Organic Clay Mimics?

The reaction of HCl(g), H 2 O, and 18-crown-6 in toluene gives [H 3 O•18-crown-6] [Cl−H−Cl]•3.6 tol (tol=toluene), from which crystals of [H 3 O•18-crown-6] [Cl−H−Cl] are isolated: space group P2 1 /c. The liquid clathrate dissolves KCl, and upon standing, the solution affords crystals of [K•18-crown-6] [Cl−H−Cl]: space group P2 1 /c. In a similar fashion, the liquid clathrate dissolves MgCl 2 and yields [Mg•18-crown-6] [Cl−H−Cl]2: space group Pbca. The [Br−H−Br] − anion is produced by the reaction of HBr(g), H 2 O, and 18-crown-6 in toluene

Synthesis of salts of the hydrogen dichloride anion in aromatic solvents. 2. Syntheses and crystal structures of [K.cntdot.18-crown-6][Cl-H-Cl], [Mg.cntdot.18-crown-6][Cl-H-Cl]2, [H3O.cntdot.18-crown-6][Cl-H-Cl], and the related [H3O.cntdot.18-crown-6][Br-H-Br]

The interaction of the oxonium ion, H/sub 3/O/sup +/, with polar solvents has been extensively reviewed in the broader context of hydrogen bonding The first report of a complex of H/sub 3/O/sup +/ and a macrocycle was an infrared spectroscopic study in 1972 More recently several reports have appeared This has proved to be a method of isolation of H/sub 3/O/sup +/ from higher hydrated species, H/sub 3/O/sup +/ coordinated to macrocycles have been reported, one which lends strong support for pyramidal H/sub 3/O/sup +/, and one which may be interpreted in terms of planar H/sub 3/O/sup +/ In the extensive literature of the oxonium ion, evidence for the species in aromatic solution has not bee presented Here the authors report that the oxonium ion coordinated to 18-crown-6 does indeed have a stable existence in aromatic media

The oxonium cation in aromatic solvents. Synthesis, structure, and solution behavior of [H3O+.cntdot.18-crown-6][Cl-H-Cl]

Le compose du titre cristallise dans le groupe d'espace P2 1 /n. Affinement de la structure jusqu'a 0,088

Interaction of aluminum trichloride with tetrahydrofuran. Formation and crystal structure of dichlorotetrakis(tetrahydrofuran)aluminum(1+) tetrachloroaluminate(1-)

Stabilization of the [AlMe2]⊕ Cation by Crown Ethers

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