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Fullerene-Based Materials: Structures and Properties 109 Structure and Bonding Series Editor: D. M. P. Mingos Fullerene-Based Materials Structures and Properties Volume Editor: K. Prassides Springer Berlin Heidelberg New York The series Structure and Bonding publishes critical reviews on topics of research concerned with chemical structure and bonding. The scope of the series spans the entire Periodic Table. It focuses attention on new and developing areas of modern structural and theoretical chemistry such as nanostructures, molecular electronics, designed molecular solids, surfaces, metal clusters and supramolecular structures. Physical and spectroscopic techniques used to determine, examine and model structures fall within the purview of Structure and Bonding to the extent that the focus is on the scientific results obtained and not on specialist information concerning the techniques themselves. Issues associated with the development of bonding models and generalizations that illuminate the reactivity pathways and rates of chemical processes are also relevant. As a rule, contributions are specially commissioned. The editors and publishers will, however, always be pleased to receive suggestions and supplementary information. Papers are accepted for Structure and Bonding in English. In references Structure and Bonding is abbreviated Struct Bond and is cited as a journal. Springer WWW home page: http://www.springeronline.com Visit the SB content at http://www.springerlink.com ISSN 0081-5993 (Print) ISSN 1616-8550 (Online) ISBN-13 978-3-540-20106-9 DOI 10.1007/b84247 Springer-Verlag Berlin Heidelberg 2004 Printed in Germany Series Editor Volume Editor Professor D. Michael P.Mingos Professor Kosmas Prassides Principal University Sussex St. Edmund Hall Department of Chemistry Oxford OX1 4AR, UK Falmer E-mail: michael.mingos@st-edmund-hall. Brighton BN1 9QJ, UK oxford.ac.uk E-mail: [email protected] Editorial Board Prof. Allen J. Bard Prof. Herbert W. Roesky Department of Chemistry and Biochemistry Institute for Inorganic Chemistry University of Texas University of Göttingen 24th Street and Speedway Tammannstrasse 4 Austin, Texas 78712,USA 37077 Göttingen, Germany E-mail: [email protected] E-mail: [email protected] Prof. Peter Day, FRS Prof.Jean-Pierre Sauvage Director and Fullerian Professor of Chemistry Faculté de Chimie The Royal Institution of Great Britain Laboratoires de Chimie 21 Albemarle Street Organo-Minérale London WIX 4BS, UK Université Louis Pasteur E-mail: [email protected] 4, rue Blaise Pascal 67070 Strasbourg Cedex, France Prof. James A. Ibers E-mail: [email protected] Department of Chemistry North Western University Prof. Fred Wudl 2145 Sheridan Road Department of Chemistry Evanston, Illinois 60208-3113, USA University of California E-mail: [email protected] Los Angeles, CA 90024-1569, USA E-mail: [email protected] Prof.Thomas J. Meyer Associate Laboratory Director for Strategic and Supporting Research Los Alamos National Laboratory PO Box 1663 Mail Stop A 127 Los Alamos, NM 87545, USA E-mail: [email protected] Preface The fullerene family represents a new molecular form of pure carbon, which has proven to be of remarkable interest for both its chemical and physical properties. Following the serendipitous discovery of C60 (a quasi-spherical molecule with di- mensions of ~1 nm) and the production of bulk crystalline samples of fullerenes from arc-processed carbon, research on the solid-state properties of fullerene- based nanostructures and nanonetworks has proceeded at an exhilarating pace. Novel carbon materials like the nanotubes, the buckyonions and the endohedral metallofullerenes have been subsequently discovered, while fullerene derivatives show a plethora of interesting properties, ranging from superconductivity to fer- romagnetism and promise future applications in batteries, transistors, solar cells and sensors among others. The present volume contains contributions from both theorists and experimentalists and attempts to highlight some of the interdisci- plinary issues, presently at the forefront of fullerene research. I hope the reader will benefit from the range of topics covered in this volume and find the issues stimulating and possibly able to generate new ideas and approaches to these fas- cinating materials. I warmly thank all the authors who enthusiastically contributed their out- standing work for this volume. Brighton,January 2004 Kosmas Prassides Contents Organofullerene Materials N. Tagmatarchis, M. Prato . 1 Electronic Structure and Energetics of Fullerites, Fullerides, and Fullerene Polymers S. Saito, K. Umemoto, T. Miyake . 41 Charge Density Level Structures of Endohedral Metallofullerenes by the MEM/Rietveld Method M. Takata, E. Nishibori, M. Sakata, M. Shinohara . 59 Polymeric Fullerene Phases Formed Under Pressure B. Sundqvist . 85 Structural and Electronic Properties of Selected Fulleride Salts S. Margadonna,Y.Iwasa, T. Takenobu, K. Prassides . 127 NMR Studies of Insulating, Metallic, and Superconducting Fullerides: Importance of Correlations and Jahn–Teller Distortions V. Brouet, H. Alloul, S. Gàràj, L. Forrò . 165 Charge Transfer and Bonding in Endohedral Fullerenes from High-Energy Spectroscopy M.S. Golden, T. Pichler, P.Rudolf . 201 The Jahn–Teller Effect and Fullerene Ferromagnets D. Arčon, R. Blinc . 231 Author Index 101–109 . 277 Subject Index . 281 Structure and Bonding,Vol. 109 (2004): 1–39 DOI 10.1007/b94377HAPTER 1 Organofullerene Materials Nikos Tagmatarchis · Maurizio Prato Università di Trieste, Dipartimento di Scienze Farmaceutiche, Piazzale Europa 1, 34127 Trieste, Italy E-mail: [email protected]; [email protected] Abstract The most significant developments of recent years on organofullerene materials are presented in this comprehensive review. With selected examples chosen from the current literature, original and well-established synthetic protocols utilizing mainly addition and cy- cloaddition reactions that have been successfully applied to fullerenes, are discussed. Among these, 1,3-dipolar cycloadditions, Bingel cyclopropanations, and various [2+2], [3+2], and [4+2] cycloadditions are the most useful reactions and have been widely applied for the construction of novel organofullerene materials. Emphasis is also given to the applications of these materi- als in diverse fields varying from nano- to biotechnological areas, and from the construction of plastic solar cells and optical limiting glasses to DNA photocleavage, magnetic resonance imaging (MRI) agents, and quantum computing. Keywords Fullerenes · Materials · Applications · Nanotechnology · Biotechnology 1Introduction . 2 2Fulleropyrrolidine Materials . 3 3Methanofullerene Materials . 4 4Cycloadded Organofullerene Materials . 6 4.1 [2+2] Cycloadditions . 6 4.2 [3+2] Cycloadditions . 8 4.3 [4+2] Cycloadditions . 9 5Miscellaneous Organofullerene Materials . 10 6Functionalized Endohedral Metallofullerene Materials . 12 7Technological Applications . 14 7.1 Plastic Solar Cells (Photovoltaics) . 14 7.2 Donor–Acceptor Systems . 15 7.2.1 Porphyrins . 18 7.2.2 Tetrathiafulvalenes . 21 7.2.3 Ferrocenes . 22 7.2.4 Miscellaneous Hybrids . 23 7.3 Optical Limiting . 26 © Springer-Verlag Berlin Heidelberg 2004 2 N. Tagmatarchis · M. Prato 8Biotechnological and Medicinal Applications . 27 8.1 Empty Fullerenes . 27 8.2 Endohedral Metallofullerenes . 29 9 Quantum Computing . 30 10 References . 32 1 Introduction An important field of organic chemical investigation emerged soon after the remarkable discovery [1] and macroscopic production [2, 3] of fullerenes, a new allotrope form of carbon after diamond and graphite. As by definition organic chemistry deals with the chemistry of carbon, the progress in this field by ex- ploring fullerene organic transformations was rapid. Twelve years after the first isolation and preparation of synthetically useful amounts of fullerenes, the exo- hedral covalent functionalization of C60 is continuing unabated. The main ad- vantage gained upon functionalization of fullerenes is the solubility enhance- ment of the so-produced organofullerene derivatives. The difficult processibility of fullerenes due to their poor solubility in most organic solvents is surmounted with the aid of functionalization and the construction of novel organofullerene materials. Therefore, organic functionalization of fullerenes puts them in pole position in the run for applying envisioned innovative uses. In general, C60 is the most abundant, least expensive and therefore, most thoroughly studied member of these all-carbon hollow-cluster materials. The overall fullerene structures can be imagined as fused 1,3,5-cyclohexatrienes and [5]radialenes, with alternation of single and double bonds. The latter are located exclusively between two six-membered rings (6,6-bonds) with a bond length of 1.38 Å, while the bonds between five- and six- membered rings (5,6- bonds) are essentially single with a length of 1.45 Å. The energy cost for intro- ducing one double bond between a five- and a six-membered ring has been cal- culated as approximately 8.5 kcal mol–1 [4]. In addition, a large amount of strain energy exists within the cage due to the highly pyramidalized sp2 hybridized carbon atoms [5]. The substantial curvature of fullerenes is reflected by an average sp2.278 and a fractional s-character of the p-orbitals of 0.085 [6]. A closed-shell electronic configuration for C60 consisting of 60 p-electrons [7] gives rise to a completely full HOMO (highest occupied molecular orbital) that is energetically located approximately 1.8 eV lower than the corresponding
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