New chemistry of the cyclic molecular host cyclotriveratrylene (CTV) includes applications such as in sensors and separations; in self-organised materials such as gels, liquid crystals, dendritic systems, and self-assembled monolayers; and in metallo-supramolecular chemistry. This tutorial review covers aspects of CTV chemistry interest to supramolecular, coordination and host-guest chemists as well as those interested in self-organised systems.

Crystals of -and 4-hexanitrohexaazaisowurtzitane (-and 4-HNIW, space group P2 1 /n for both crystals) have been investigated in the 100±298 K temperature range using single-crystal X-ray diffraction techniques. Temperature-dependent changes of their crystal lattices have been evaluated from the second-rank thermal expansion tensors. Both lattices undergo anisotropic thermal expansion, that of -HNIW being more anisotropic than that of the 4 phase. Comparison with previously reported predictions from molecular dynamics calculations indicates signi®cant differences. Although there are many short (less than van der Waals) intermolecular interactions in both polymorphs, there is no obvious relationship between the short distances and the difference in thermal expansion behavior. Non-linear temperature dependence of the atomic displacement parameters is indicative of anharmonicity of the crystal mean ®eld potential.

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Icosahedral and cuboctahedral arrangements of calixarenes, a nanometer-scale, spheroidal assembly of 12 calixarene molecules, can be manipulated in a highly controlled fashion. Previously, such assemblies were observed to favor placement of the calixarenes at the vertexes of an icosahedron. A supramolecular constraint is employed in order to enforce molecular alignment and produce a cuboctahedral arrangement. The internal volume of the cuboctahedron is approximately 30% greater than that of the icosahedron. Furthermore, in stark contrast to that of the icosahedral Platonic solid, the shell of the cuboctahedral Archimedean solid is porous.

The focus of this perspective is the self assembly in aqueous solutions (pH < 3.5) of the synthons sodium p-sulfonatocalix[4]arene and 18-crown-6, or related macrocycles, into globular superanions or ionic capsules, for example {Na ؉ ʚ(18-crown-6)(OH 2 ) n }ʚ{(p-sulfonatocalix[4]arene(4Ϫ)) 2 } 7؊ , n ‫؍‬ 0 or 2. These can crystallise, often selectively, polynuclear hydrolytic metal(III) cations [M 2 (OH) 2 (H 2 O) 8 ] 4؉ , [M 3 (OH) 4 (H 2 O) 10 ] 5؉ , [M 4 (OH) 6 -(H 2 O) 12 ] 6؉ , M ‫؍‬ Cr or Rh, or [Al 13 O 4 (OH) 24 (H 2 O) 12 ] 7؉ , depending on the pH and other synthetic parameters, which are established using a combinatorial approach. These superanions are ambivalent; two calixarenes shroud a crown ether with a central sodium ion bound also by two trans-water molecules or two oxygen centres of sulfonate groups from each of the calixarenes. Electrostatic repulsion between the negatively charged calixarenes is compensated by the large polynuclear cations interacting with the negatively charged hydrophilic equatorial region of the capsule, and some protonation of the sulfonate groups. Similarly, protonated cyclam forms a capsule with two calixarenes and crystallises [Cr 2 (OH) 2 (H 2 O) 8 ] 4؉ . Lanthanide(III) ions form a range of complexes at specific pH in the presence of the calixarene and crown ether, including complexes containing the capsule [{18-crown-6}ʚ {(M(H 2 O) 7 3؉ ) 1.33 (p-sulfonatocalix[4]arene(4؊))} 2 ], for the smaller lanthanides, or the ferris wheel type structure [{La 3؉ ʚ(18-crown-6)(OH 2 ) 3 }ʝ{(p-sulfonatocalix[4]arene-(4؊) ؉ 2H ؉ )}] ؉ , for the larger lanthanide. Only some of the continuous structures have an up-down bilayer arrangement of calixarenes.

Metallosupramolecular chemistry relies on self-assembly processes in which complicated species form through labile dative-covalent interactions. Two remarkable areas of this chemistry are the synthesis of topologically complicated threaded assemblies and of three-dimensional (3D) polyhedral assemblies. Very few polyhedral 3D metallosupramolecular assemblies show threaded motifs within them. Here we report an example of a new type of threaded 3D metallosupramolecular assembly built from four organic ligands and four palladium ions, a Pd(4)L(4) so-called 'Solomon's cube' in which interweaving and twisting of the ligands form both Solomon's links and figure-of-eight ring motifs. In the solid state, six of these Pd(4)L(4) tetramers assemble into a hollow spheroid that closely resembles a stellated truncated hexahedron.

Control over the conformational flexibility of p-sulfonatocalix[6]arene in the solid state is possible in the presence of varied stoichiometric amounts of [18]crown-6 and selected lanthanide(III) chlorides. Complexes 1 and 2 have the calixarene in the elusive up-up double cone conformation, whilst complex 3 has the calixarene in the centrosymmetric up-down double partial cone conformation, whereby it acts as a divergent receptor. Complex 1 has a double molecular capsule arrangement which is composed of two p-sulfonatocalix[6]arenes shrouding two [18]crown-6 molecules, also with both coordinated and homoleptic aquated lanthanide ions around the hydrophilic sulfonate rims of the calixarenes. Complex 2 has a ferris wheel arrangement with one lanthanide metal centre coordinated to a sulfonate group and another coordinated to the crown ether whilst tethered to a sulfonate group of the calixarene. Complex 3 forms from a solution with large excess of [18]crown-6, and possesses a crown ether molecule in each of the partial cones and has homoleptic aquated lanthanide ions involved in a complicated hydrogen-bonding regime within the extended structure.

1,2-Dicarbadodecaborane(12) (o-carborane) and bowl-shaped cyclotriveratrylene (CTV) self-assemble through bifurcated C ± H carborane´´´( O) 2 hydrogen bonds into infinite arrays with two-dimensional (2D) hexagonal grid or helical chain topologies. The in-built shape-specific receptor sites bind o-carborane or fullerene C 70 . The structures of two such supramolecular systems in the solid state were established: (ocarborane) 2 (CTV) features hydrogenbonded carborane´´´CTV hexagonal grids as well as CTV´´´carborane host ± guest interactions, while a helical hydrogen-bonded carborane´´´CTV chain is formed in the quaternary system (C 70 )(o-carborane)(CTV)(1,2-dichlorobenzene) in addition to CTV´´´C 70 host ± guest interactions. The bifurcated C ± H carborane´´´( O) 2 hydrogen bonding interaction common to both these structures was studied on the model system (o-carborane)(1,2-dimethoxybenzene) using ab initio calculations and found to be energetically favoured by 5.48 kcal mol À1