Published:16 Aug 2021
Since the advent of supramolecular chemistry in the 1970s, studies of chemical reactivity within confined spaces have been among the most vital strands in this field. Work on encapsulation chemistry has taken place in a space that the 1987 Nobel Prize in Chemistry has helped to define, and in particular in the shadow of pioneering work by one of its laureates, the late Donald Cram. Cram was among the first to explore systematically the inner phases (a term he coined) of container molecules such as spherands, which are capable of binding metal cations with 1010 M−1 affinity, and carcerands, which crucially extended encapsulation chemistry to neutral molecules. Such landmark results were achieved as the stabilisation and spectroscopic characterization of the fleeting molecule cyclobutadiene.
Upon these foundations were built a wide range of new molecular containers and confined spaces. A profusion of soluble cages and metal–organic frameworks have been reported in recent years, as diverse groups develop the art of defining new molecular voids and examine how molecules react within them. Their reactivity may differ markedly from what is observed in solution, as this book explores.
A newcomer to the field may be intimidated by the many new container molecules and framework materials and by the new encapsulation-related behaviours that have been described in recent years. This book aims to provide a path through these new discoveries, furnishing a resource of knowledge, data and information to allow both experienced and more junior investigators to work on applications and novel science surrounding reactivity in confined spaces. It seeks to highlight connections between separated studies that are related but not often, if at all, grouped into the same book, journal, conference or scientific community.
As a practitioner of molecular encapsulation, I strongly support the efforts of Ross and Gareth in bringing this collection of authors and ideas together. Enzymes show us how remarkable transformations can be achieved through molecular confinement within hosts composed of only 20 amino acid building blocks. Structures built using similar precepts but with a vastly expanded range of subcomponents would thus seem certain to enable a cornucopia of new and useful synthetic chemistry. This book seeks to open the door to the discovery of these new hollow structures.
Jonathan R. Nitschke
University of Cambridge