Prologue

Research on molecular recognition became a fashionable topic for physical organic chemists in the 1980s. At the time there was growing disenchantment with the nonclassical ion controversy, and orbital symmetry fatigue was taking hold in the community. But the discovery of crown ethers by Pedersen in 1962 ignited the study of their complexes with ions, and macrocyclic polyethers dominated the scene for decades. The weak intermolecular interactions of these complexes gave rise to the concepts of molecular recognition: complementarity of sizes, shapes and chemical surfaces. The culmination of this activity was the award of the Nobel Prize in Chemistry to Pedersen, Cram and Lehn in 1987 for establishing host–guest chemistry and, on a grander scale, supramolecular chemistry…