Preface The unique molecular architecture of calixarenes makes them a suitable platform for constructing host molecules that can selectively bind a variety of guest substrates that range from cations and anions to fullerenes. Substrates can be bound within the hydrophobic bowl-cavity of the calixarenes through noncovalent interactions or outside the cavity by introducing suitable ligand systems on the upper or lower rim. Also, the self-assembly of some calixarene derivatives via non-covalent interactions leads to a new class of encapsulation agents, inclu-sion complexes, and molecular networks. The fascinating conformational and chemical reactivity of the calixarene systems has led to their use in a variety of applications that range from de-velopment of efficient separation systems, specific sensors, and molecular switches to a new generation of catalysts. The scientific interest in the applications of this class of molecules to solve separation problems is demonstrated by the number of recent publications as well as the award of numerous patents that utilizes the chemistry of calixarenes. These patents include the use of calixarenes as extraction agents for separations, such as recovering uranyl ion from sea water and removing cesium from nuclear wastes. Calixarenes are also being used as selective agents for metal ion transport through supported liquid membranes. It is important to point out that efficient chemical separations are now integral not only to manu-facturing processes, but also for compliance with subsequent industrial waste-discharge requirements. This book is the outcome of a recent symposium titled "Calixarene Molecules for Separations" that was held at the 217 American Chemical Society (ACS) National Meeting in Anaheim, California, March 23-25, 1999. Although a number of other books and reviews on calixarenes have appeared, they have not focused on the development of calixarene host-guest systems that have ap-plications to important challenges in the field of separations chemistry. Topics that are covered in this book include (1) synthetic methodology relevant to the development of calixarene-based receptors, (2) recent developments in the use of calixarenes for separations involving cations and anions, many of them important for radioactive waste remediation, and (3) binding of cations, anions, and neutral molecules by calixarenes and related molecules. The chapters pertaining to selec-tive metal ion extraction and coordination chemistry of some of the calixarene de-rivatives provide highly relevant discussions regarding the characterization of ligand-metal complexes using strategies such as molecular dynamics simulation, nuclear magnetic resonance spectroscopy, and electrospray mass spectroscopy. In addition, some of the chapters in this book address related systems such as heterocalix[3]arenes, thiacalixarenes, and calixpyrroles and their binding prop-erties. The assembly of calixarenes through non-covalent interactions to form deep cavities and capsules for encapsulation of target substrates is another area of discussion. This book will be useful for a th
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wide range of scientists whose interests vary from the chemistry of calixarenes to the area of host-guest complexation, coordination chemistry, separation technologies, and environmental remediation. Acknowledgments
We gratefully acknowledge the Donors of The Petroleum Research Fund, ad ministered by the ACS, for support of the Calixarenes for Separations Symposium held in Anaheim, California. The financial support of the Separation Science and Technology Subdivision of the ACS Division of Industrial and Engineering Chem-istry, Inc. for the symposium is also acknowledged. We thank all the participants of this symposium and the authors and reviewers of the manuscripts published in this book for their cooperation and valuable contributions. Our sincere thanks to David Gutsche for his introductory review (Chapter 1) that gives the reader a broad picture of the exciting field of calixarenes. Finally, we thank the ACS for their encouragement and support in the publication of this book. GREGG J. LUMETTA
Pacific Northwest National Laboratory P.O. Box 999 Richland, WA 99352 ROBIN D. ROGERS
Department of Chemistry The University of Alabama Tuscaloosa, AL 35487 ARAVAMUDAN S. GOPALAN
Department of Chemistry and Biochemistry New Mexico State University Las Cruces,NM88003
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