No abstract

In the 25 years since its Nobel Prize in chemistry, supramolecular chemistry based on molecular recognition has been paid much attention in scientific and technological fields. Nanotechnology and the related areas seek breakthrough methods of nanofabrication based on rational organization through assembly of constituent molecules. Advanced biochemistry, medical applications, and environmental and energy technologies also depend on the importance of specific interactions between molecules. In those current fields, molecular recognition is now being re-evaluated. In this review, we re-examine current trends in molecular recognition from the viewpoint of the surrounding media, that is (i) the solution phase for development of basic science and molecular design advances; (ii) at nano/materials interfaces for emerging technologies and applications. The first section of this review includes molecular recognition frontiers, receptor design based on combinatorial approaches, organic capsule receptors, metallo-capsule receptors, helical receptors, dendrimer receptors, and the future design of receptor architectures. The following section summarizes topics related to molecular recognition at interfaces including fundamentals of molecular recognition, sensing and detection, structure formation, molecular machines, molecular recognition involving polymers and related materials, and molecular recognition processes in nanostructured materials.

'Chirality switching' is one of the most important chemical processes controlling many biological systems. DNAs and proteins often work as time-programmed functional helices, in which specific external stimuli alter the helical direction and tune the time scale of subsequent events. Although a variety of organic foldamers and their hybrids with natural helices have been developed, we highlight coordination chemistry strategies for development of structurally and functionally defined metal helicates. These metal helicates have characteristic coordination geometries, redox reactivities and spectroscopic/magnetic properties as well as complex chiralities. Several kinds of inert metal helicates maintain rigid helical structures and their stereoisomers are separable by optical resolution techniques, while labile metal helicates offer dynamic inversion of their helical structures via non-covalent interactions with external chemical signals. The latter particularly have dynamically ordered helical structures, which are controlled by the combinations of metal centres and chiral ligands. They further function as time-programmable switches of chirality-derived dynamic rotations, translations, stretching and shape flipping, which are useful applications in nanoscience and related technology.

Monolayers of the cholesterol-armed cyclen Na+ complex at the air-water interface display a remarkable, surface pressure dependent enantioselectivity of amino acid recognition. Upon compression of the monolayer, the binding constants of amino acids increase accompanying an inversion of chiral selectivity from the d- to l-form in the case of valine.