Integrative Self-Sorting: One-Pot Synthesis of a Hetero[4]rotaxane from a Daisy-Chain-Containing Hetero[4]pseudorotaxane.

The structural complexity of mechanically interlocked molecules are very attractive to chemists owing to the challenges they present. In this article, novel mechanically interlocked molecules with a daisy-chain-containing hetero[4]rotaxane motif were efficiently synthesized. In addition, a novel integrative self-sorting strategy is demonstrated, involving an ABB-type (A for host, dibenzo-24-crown-8 (DB24C8), and B for guest, ammonium salt sites) monomer and a macrocycle host, benzo-21-crown-7 (B21C7), in which the assembled species in hydrogen-bonding-supported solvent only includes a novel daisy-chain-containing hetero[4]pseudorotaxane. The found self-sorting process involves the integrative recognition between B21C7 macrocycles and carefully designed components simultaneously containing two types of secondary ammonium ions and a host molecule, DB24C8 crown ether. The self-sorting strategy is integrative to undertake self-recognition behavior to form one single species of pseudorotaxane compared with the previous report. This self-sorting system can be used for the efficient one-pot synthesis of a daisy-chain-containing hetero[4]rotaxane in a good yield. The structure of hetero[4]rotaxane was confirmed by 1 H NMR spectroscopy and high-resolution electrospray ionization (HR-ESI) mass spectrometry.

One-pot synthesis of hetero[6]rotaxane bearing three different kinds of macrocycle through a self-sorting process.

In this article, a six-component self-sorting process that involves three types of crown ether macrocycle and three types of cation guest molecule was carefully and thoroughly investigated. The six components include three kinds of crown ether, namely bis(p-phenylene-34-crown-10) (BPP34C10), dibenzo-24-crown-8 (DB24C8) and benzo-21-crown-7 (B21C7), and their corresponding cation guest molecules, namely a 4,4'-bipyridine dication (BPY2+) and dibenzylammonium (DBA) and benzylalkylammonium (BAA) ions, respectively. Based on this well-established highly selective six-component self-sorting process, a hetero[6]rotaxane bearing three different kinds of crown ether macrocycle was designed and successfully synthesized through a facile and efficient one-pot "click" stoppering strategy. Such work is proposed to be a significant advance in the construction of mechanically interlocked molecules with high structural complexity, as well as a good supplement in the areas of multi-component self-sorting and noncovalent self-assembly.

Supramolecular Helical Nanofibers Formed by Achiral Monomers and Their Reversible Sol-Gel Transition.

Well-defined supramolecular helical nanofibers have been constructed by a rationally designed achiral monomer in aqueous solution based on the 1:2 host-guest combination between cucurbit[8]uril and a 4,4'-bipyridin-1-ium chloride (BPY+ ) salt derivative. The formed nanostructures could be adjusted by varying the concentration of monomer from helical nanofibers to a pH-responsive hydrogel.