Published: February 4, 2011 r2011 American Chemical Society 2672 dx.doi.org/10.1021/ja109462j | J. Am. Chem. Soc. 2011, 133, 2672–2690 ARTICLE pubs.acs.org/JACS Poly(perfluoroalkylation) of Metallic Nitride Fullerenes Reveals Addition-Pattern Guidelines: Synthesis and Characterization of a Family of Sc 3 N@C 80 (CF 3 ) n (n =2-16) and Their Radical Anions Natalia B. Shustova, ‡ Dmitry V. Peryshkov, ‡ Igor V. Kuvychko, ‡ Yu-Sheng Chen, § Mary A. Mackey, z Curtis E. Coumbe, z David T. Heaps, z Bridget S. Confait, z Thomas Heine, ^ J. Paige Phillips,* ,z Steven Stevenson,* ,z Lothar Dunsch,* ,† Alexey A. Popov,* ,† Steven H. Strauss,* ,‡ and Olga V. Boltalina* ,‡ ‡ Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States § ChemMatCARS Beamline, University of Chicago Advanced Photon Source, Argonne, Illinois 60439, United States z Department of Chemistry and Biochemistry, University of Southern Mississippi, Hattiesburg, Mississippi 39406, United States ^ School of Engineering and Science, Jacobs University, D-28759 Bremen, Germany † Department of Electrochemistry and Conducting Polymers, Leibniz Institute for Solid State and Materials Research, D-01069 Dresden, Germany b S Supporting Information ABSTRACT: A family of highly stable (poly)perfluoroalky- lated metallic nitride cluster fullerenes was prepared in high- temperature reactions and characterized by spectroscopic (MS, 19 F NMR, UV-vis/NIR, ESR), structural and electro- chemical methods. For two new compounds, Sc 3 N@C 80 - (CF 3 ) 10 and Sc 3 N@C 80 (CF 3 ) 12, single crystal X-ray structures are determined. Addition pattern guidelines for endohedral fullerene derivatives with bulky functional groups are formulated as a result of experimental ( 19 F NMR spectroscopy and single crystal X-ray diffraction) studies and exhaustive quantum chemical calculations of the structures of Sc 3 N@C 80 (CF 3 ) n (n = 2-16). Electrochemical studies revealed that Sc 3 N@C 80 (CF 3 ) n derivatives are easier to reduce than Sc 3 N@C 80 , the shift of E 1/2 potentials ranging from þ0.11 V (n = 2) to þ0.42 V (n = 10). Stable radical anions of Sc 3 N@C 80 (CF 3 ) n were generated in solution and characterized by ESR spectroscopy, revealing their 45 Sc hyperfine structure. Facile further functionalizations via cycloadditions or radical additions were achieved for trifluoromethylated Sc 3 N@C 80 making them attractive versatile platforms for the design of molecular and supramolecular materials of fundamental and practical importance. 1. INTRODUCTION More than a decade ago, a new class of endohedral metallo- fullerenes (or endometallofullerenes, EMFs) was discovered, metallic nitride cluster fullerenes (MNFs). 1 Due to later ad- vances in synthetic routes, 2-6 large-scale synthesis, and isolation techniques, 2-6 these compounds have been actively studied by scientists from a wide range of research disciplines (for recent reviews see refs 7-9). Besides an obvious fundamental interest, MNFs show promise in various areas of practical importance such as biomedical research 10,11 and energy conversion. 12-14 In the latter, the development of organic photovoltaic (OPV) devices based on the use of fullerenes as electron acceptor materials has recently led to the fabrication and testing of the OPV devices with an MNF acceptor blended with the donor polymer P3HT. Due to a better separation between LUMO level of the acceptor and HOMO level of the donor, these devices showed high power conversion efficiency, rivaling that of PCBM/P3HT-based devices. 15 Among several critical issues that have to be solved before MNF-based OPV devices become commercially viable are the improvements in processability (which involves improved solubility of MNFs and higher stability of the films and solutions), optimization of the morphology of the blends, and optimization of the electronic properties of the donor and fullerene acceptor, i.e., bandgap engineering (to ensure the most efficient exciton separation and light harvest- ing). In the biomedical field, 10,11 precisely controlled derivati- zation of MNFs is one of the keys to successful advancements toward practical applications that may result in new concepts such as “bio-shuttle” systems. Overall, innovative methods of functionalization of MNFs need to be developed to satisfy the needs of emerging technological applications. In contrast to the well-developed mono-cycloadditions to MNFs and to less Received: October 30, 2010