Themed collection Form and Function of Molecular Cups and Capsules

Welcome to this CrystEngComm themed issue entitled “Form and Function of Molecular Cups and Capsules”.

Based on designed constructions of cavity networks and arrays, macroscopic mechanical motions can lead to cavity manipulations for drug delivery and molecular capture. From biomedical applications to mechanical cavity manipulation, the potential and possibilities of cavity nanoarchitectonics are demonstrated in this highlight.

The synthesis, the single-crystal X-ray structure, and a metal-exchange study of a zinc-seamed C-hexylpyrogallol[4]arene/PgC₆Zn dimer are reported.

The cocrystallization between diminazene and cucurbit[6]uril succeeds only after thorough purification of the macrocycle from the acid. Otherwise, the drug molecule undergoes acid-catalyzed hydrolysis with formation of 4-aminobenzamidine.

“Russian doll”-like complexes based on a triptycene-derived macrotricyclic host with paraquat derivative and polycyclic aromatic hydrocarbons in the solid state were described.

A cyclotriveratrelyne–acetonitrile inclusion complex is shown to undergo a single-crystal-to-single-crystal transformation upon desolvation to an intermediate phase and it is furthermore demonstrated that the preparation conditions may introduce polymorphism of the apohost.

A supramolecular polymer as well as a dimeric capsule, both constructed from a combination of a tetra-carboxylic acid functionalized cavitand and a suitable N-heterocyclic ‘linker’, have been crystallographically characterized.

In the solid state, a larger resorcin[6]arene self-assembles in twin capsules able to host solvent molecules.

Interaction of a symmetrical α,α′,δ,δ′-tetramethyl-cucurbit[6]uril (TMeQ[6]) with a series of lanthanide cations (Ln³⁺) was investigated in neutral water and acidic solution.

Anion induced capsular and non-capsular assembly of polyammonium tripodal receptors into supramolecular network and formation of side-cleft recognition of a sulfate–water cluster are reported.

Three novel calix[4]arene semitubes having two alkyl bridging spacers of different lengths were synthesized and used as homoditopic hosts for small neutral acidic molecules and N-alkylpyridinium salts.

Heterometallic cubes, assembled in a modular fashion from a [CrL₃] metalloligand and simple M^II salts, display interesting encapsulation and magnetic behaviours.

The regioselective host-to-guest proton transfer readily triggers the formation of overall-neutral supramolecular capsules.

Four new cationic cage type compounds have been synthesized and characterized. Their compounds successfully removed perchlorate ions from aqueous solutions. The solvent dependent anion inclusion of the cationic cage is described.

Selected alkaline earth ions interact with a symmetric octamethyl-cucurbituril in the presence of polychlorido cadmium(II) anions to yield new porous coordination polymers that reversibly adsorb common volatile liquid vapours.

Non-covalent interactions drive enantioselective self-recognition in racemic calixsalens.

A series of lanthanide (Tb, Gd and Eu) based p-sulfonatocalix[4]arene have been synthesized, and screened for their anti-proliferation activity; all complexes exhibited low CC₅₀ values.

The solvothermal reactions of p-tert-butylsulfonylcalix[4]arene (H₄BSC4A), phosphonic acid and neodymium chloride have resulted in three novel high-nuclearity neodymium coordination compounds.

Direct meta-dimercuration can be used for subsequent bridging of a calix[4]arene skeleton to form an unprecedented, rigid and highly distorted cavity.

Two isomeric diphosphonate cavitands (ABii and ACii) were probed for the molecular recognition of L-lactic acid in solution via NMR spectroscopy and in the solid state via crystal structure determination. The interactions involved in the recognition event are a combination of hydrogen bonding and CH–π interactions.

4-Substituted pyridine N-oxides due to cavity misfit form a C_2v boat conformer and give 1-D tubular chains, while 2- and 3-methylpyridine N-oxides give in-cavity complexes with a C_4v crown conformation.

A series of octanuclear p-cymene ruthenium and pentamethylcyclopentadienyl rhodium and iridium metalla-assemblies has been prepared from tetrapyridyl porphyrin panels. All assemblies possess IC₅₀ values around 0.1 μM, and induce apoptosis in cancer cells.

Exo-cavity binding into resorcinarene based inverted molecular cups creates 1-D and 2-D silver coordination polymers with argentophilic interactions.

Two kinds of calixarene-based metal–organic coordination cages, a tetrahedral one and a truncated octahedral one, were obtained with the same precursors at different pH values.

Multi-component materials having supermolecules made up of mono- or bis-imidazolium cations shrouded by two p-sulfonated calix[4]arenes essentially form molecular capsules as part of the extended structure, with their formation mediated by Gd(III), which is incorporated only in complex I.