Preface

The field of supramolecular chemistry encompasses the study of systems exhibiting molecular recognition or self-assembly modulated by various non-covalent interactions such as hydrogen bonding, π–π stacking, and hydrophobic, electrostatic, and van der Waals interactions. Formation of host–guest complexes via molecular recognition that mimics naturally occurring biomolecular systems, such as enzyme–substrate interactions, has gathered tremendous interest from the scientific community, fuelled by the discovery of various functional macrocyclic host molecules such as crown ethers, cyclodextrins, calixarenes, etc. Among these, cucurbiturils (CB) have risen as a celebrity host molecule in supramolecular chemistry, ever since the initial synthesis of cucurbit[6]uril in 1905 by Behrend, followed by its first structural characterization in 1981 and development of its host–guest chemistry in the subsequent years by Mock, and isolation and characterization of other members of the CB family independently by us and Day in the early 2000s. Despite being a relatively young and emerging field, the CB research community has bloomed at an extraordinary pace over the past decade. The community at present is placed at a vantage point to predict how CB chemistry can outmatch other host–guest systems and explore the unprecedented possibilities of interdisciplinary research. For instance, CB–guest pairs have now begun to assert themselves in the biological sciences where their signature ultra-high affinity binding has allowed them to compete even with well-established biological binding pairs.

At the Gordon Research Conference in January 2006, Lyle Isaacs, Angel Kaifer and I first discussed the possibility of organizing a meeting, solely dedicated to CB inspired by the increasing number of research groups utilizing this unique family of macrocyclic hosts. In 2007, Lyle Isaacs and Angel Kaifer organized the first CB-dedicated workshop held in Maryland, USA, with support from the National Science Foundation (US). With the enthusiastic support from the rapidly growing CB community, I organized the first dedicated CB conference (International Conference on Cucurbiturils) in 2009 at POSTECH in South Korea, which then continued to be held every two years at various locations around the globe, on each occasion, even larger than the last. The growing number of research papers and review articles related to CBs also reflect the growing potential of CB chemistry. Therefore, I felt that editing a book on CBs with the participation of leading scientists in the CB community will inspire new researchers to learn about CBs and generate exciting research ideas. Similarly, I hope that this book will introduce CBs to researchers established in other fields and help them envision novel applications of CBs on their own turf.

The purpose of this book is, therefore, not only to provide a general overview and history of CB chemistry, but also introduce the opportunities within the field to attract new researchers. The book is focused on describing CBs as promising host molecules and highlighting their remarkable guest-binding characteristics, not only in comparison with other synthetic host molecules, but also with natural receptors. It is our belief that this book will inspire new researchers in the arena of supramolecular chemistry and from other research fields to bring in fresh ideas, explore out-of-the box technologies and at the same time, provide easy solutions to the challenges that still persist in the CB field.

While editing this book, it was truly eye-opening for me to find how widely CBs have been used, e.g., in catalysis, sensors, components in self-assembly, porous materials, photonic materials, polymeric materials, soft materials, drug delivery vehicles, amongst others. The overall journey of editing this book was very much an enjoyable endeavor, and also a rewarding experience in many ways including recognizing the directions to which this field is currently heading.

I would like to thank all the authors for their exceptional contributions and participation in this endeavor. Special thanks are due to Roeland Nolte, Sir J. Fraser Stoddart, Vladimir P. Fedin, Hugh I. Kim, Dönüş Tuncel, Adam Urbach and Xi Zhang for their gracious support and valuable comments. Moreover, I greatly appreciate my group members, including Kyeng Min Park, Ilha Hwang, Moon Young Hur, James Murray and Rahul Dev Mukhopadhyay, for their assistance in editing this book. Last but not least, I would like to thank everyone in the CB community for their enthusiastic support and encouragement throughout the editing process, and the Royal Society of Chemistry for their continuous support in materializing this book.

Kimoon Kim