Molecular manipulation based on allosteric crown-appended units and related systems

Synthesis of many potentially useful molecular units by chemists promotes the development of methods for constructing supramolecular architectures. Indeed, programmed supramolecular interactions play crucial roles in the preparation of well-defined nanoscale assemblies. This review highlights successful approaches in designing for specific functions systematically. The incorporation and synergistic communication of conformation-switchable segments into molecules bears great promise. Allostery, which is often observed in naturally occurring proteins, provides a hint for molecular manipulation. In supramolecular chemistry crown ethers can serve not only as substrate-binding sites but also as function-tuning sites. With the combination of synthetic versatility and well-tailored design, diverse capabilities (molecular recognition, catalytic properties, chirality, actuation, and so on) become possible at the molecular or mesoscopic level. The synthetic preparation of advanced molecular units allows the systems to become smarter, and promise nanosystems with programmable functions. This review considers mainly the use of crown ethers which act as anchoring as well as allosteric sites, from the standpoint of design for molecular manipulation. It also gives a brief discussion of recent progress in molecular manipulation, based on related systems. The "synthetic systems" described in the present review should contribute to not only to more elaborate "chemical systems", but also to the evolving field of "molecular machinery", that can utilize these systems.