This book introduces the role of cation interactions in chemistry, biology, and polymer materials science. Since the cation interaction was defined in 1990, its importance has been recognized in a variety of fields due to its relatively significant interaction energy. A number of examples are introduced in which the contribution of cation- interactions was evidenced by X-ray structures, spectroscopies, computations, and other means. The latest developments in these areas are remarkable; therefore, many recent examples are included.As this book covers the basic aspects of the applications of cation interactions it is useful for students and researchers in a wide variety of scientific fields. In addition, the book will not only facilitate understanding of the phenomena occurring in various systems but also provides insights into the design of new catalysts, reactions, and materials.

Shinji Yamada received his Ph.D. degree from Hokkaido University in 1986 and was a JSPS research fellow from 1985 to 1987. From 1987 to 1990, he worked for the KAO Corporation, then in 1990 he joined the faculty of the Department of Chemistry at Kanagawa University as an assistant professor. In 1993 and 1994 he worked with Professor Charles J. Sihs group at the University of Wisconsin (USA) as a research fellow. In 1995 he became an associate professor in the Faculty of Science at Ochanomizu University and was promoted to professor in 2003. Dr. Yamada has published more than 100 articles including many in Chemical Reviews and has contributed to three books. His current research interests are applications of a cation interaction to various organic reactions and systems in both solution and solid-state.

1. Introduction.- 2. Nature of Cation-pi Interaction.- 3. Structure of Cation-pi Complexes.- 4. Synthetic Application to Various Organic Reactions.- 5. Supramolecular and Biomimetic Catalysis in Organic Reactions.- 6. The role of cation-pi interactions in Biology.- 7. Application to Materials Sciences.- 8. Conclusions.