Pillar[n]arene-calix[m]arene hybrid macrocyclic structures.

To reserve planar chirality, enhance molecular recognition, and build advanced self-assemblies, hybrid macrocyclic hosts containing rigid pillar[n]arene and flexible calix[m]arene were designed, prepared and investigated for interesting applications. This review summarizes and discusses different synthetic strategies for constructing hybrid macrocyclic structures. Pillar[n]arene dimer with rigid aromatic double bridges provided the possibility of introducing calix[m]arene cavities, where the planar chirality was reserved in the structure of pillararene. The capacity for molecular recognition was enhanced by hybrid macrocyclic cavities. Interestingly, the obtained pillar[n]arene-calix[m]arene could self-assemble into "channels" and "honeycomb" in both the solid state and solution phase as well as donate the molecular architecture as the wheel for the formation of mechanically interlocked molecules, such as rotaxane. In addition, the pillar[n]arene and calix[m]arene could also be coupled together to produce pillar[n]arene embeded 1,3-alternate and cone conformational calix[m]arene derivatives, which could catalyze the oxidative polymerization of aniline in aqueous solutions. Except for building hybrid cyclophanes by covalent bonds, weak supramolecular interactions were used to prepare pillar[n]arene-calix[m]arene analogous composites with other pillar-like pillar[n]pyridiniums and calix-like calix[m]pyrroles, exhibiting reasonable performances in enhancing molecular recognition and trapping solvent molecules.

Fullerene-containing pillar[n]arene hybrid composites.

The construction and application of fullerene-containing pillar[n]arene organic-inorganic hybrid composites/systems has been discussed and summarized. Both supramolecular interactions and covalent bonds were involved during the preparation process. By using supramolecular interactions, pillar[n]arenes mainly donate the hydrophobic and electron-rich cavity for complexing fullerene and its derivatives. The "bigger-sized" unmodified pillar[10]arene could directly include C60 in a stoichiometry of 1/1 via host-guest interaction, while the perfunctionalized "smaller-sized" pillar[5]arene with an enlarged channel-like structure could further interact with "size-fixed" fullerene. Additionally, recognition site-containing modified fullerene could integrate with the pillararene cavity for fabricating the functional supramolecular system, which could be further used for applications in photodevices. By forming stable covalent bonds, coupled pillar[n]arene and fullerene hybrid composites could be synthesized via either the modification of pillar[n]arenes with the fullerene subunits, or the utilization of fullerene as the partial structural skeleton for building pillar[n]arenes, in which diverse classic organic synthesis reactions were involved. Interestingly, those fullerene-containing pillar[n]arenes with free cavities could further participate in the formation of hierarchical architectures, such as mechanically interlocked molecules, by cooperating with the "dumbbell" molecule.