Table Of ContentNanostructure Science and Technology
Series Editor: David J. Lockwood
Alexey A. Popov Editor
Endohedral
Fullerenes: Electron
Transfer and Spin
Nanostructure Science and Technology
Series editor
David J. Lockwood, FRSC
National Research Council of Canada
Ottawa, Ontario, Canada
More information about this series at http://www.springer.com/series/6331
Alexey A. Popov
Editor
Endohedral Fullerenes:
Electron Transfer and Spin
123
Editor
Alexey A.Popov
LeibnizInstitute for SolidState and
MaterialsResearch
Dresden
Germany
ISSN 1571-5744 ISSN 2197-7976 (electronic)
Nanostructure Scienceand Technology
ISBN978-3-319-47047-4 ISBN978-3-319-47049-8 (eBook)
DOI 10.1007/978-3-319-47049-8
LibraryofCongressControlNumber:2017936031
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Preface
Over the last two decades, the research of endohedral fullerenes has made a dra-
matic progress. Many types of endohedral fullerenes have been discovered, their
production and separation techniques have been substantially improved, and
comprehensive studies of their chemical and physical properties became possible.
Encapsulation into the interior space of the fullerene cage stabilizes unique metal
clusters or single atoms which are not known to exist in the free form. However,
this stabilization isonly partially achieved by theshielding ofthe speciesfrom the
surrounding. Another important factor is that the carbon cage is not “innocent”.
Namely,theelectrontransferbetweentheencapsulatedspeciesandthecarboncage
plays crucial role in the structure and properties of endohedral metallofullerenes.
Unprecedentedmolecularandelectronicstructureofendohedralfullerenesleads
to a plethora of phenomena at the interface between the endohedral atoms and
p-system of the carbon cage. Charge transfer in endohedral metallofullerene
(EMF)moleculescaneitherleaveencapsulatedspeciesintact(i.e.,onlycarboncage
is active as in empty fullerene) or proceed across the metal–cage interface, and
examplesofbothtypesarewelldocumentednowadays.Thelattercaseisespecially
interestingsinceitopensthewaytotunechargestatesofendohedralspecieswhile
keeping a fullerene as a protecting shell around the redox center. Good electron
accepting properties offullerenes made them attractive building blocks for organic
electronics, and multiple studies of the EMF performance in this role have been
carriedout,fromfundamentalphotophysicalstudiesofthedonor–acceptordyadsto
thestudiesofthephotoconversionefficiencyinprototypebulkheterojunctionsolar
cells. High thermal stability of endohedral metallofullerenes allows deposition
of the molecules on various substrates in ultrahigh vacuum conditions and inves-
tigationoftheirelectronicpropertieswithhigh-resolutionscanningprobeandother
surface science methods. Peculiar electronic states and dynamics of fullerene
molecules and endohedral clusters could be investigated with the help of scanning
tunneling microscopy.
Single-electrontransferisinevitablyaccompaniedbythechangeofthespinstate
of the molecule, and here is another unique property of EMFs: the cage can either
keepanunpairedspinitself,oritcantransferthespintotheendohedralcluster,and
v
vi Preface
hence both the cage and the cluster spin states can be altered. Furthermore,
encapsulation of the species with unpaired electrons (e.g., nitrogen or phosphorus
atomsorlanthanide-containingclusters)bringsendohedralfullerenestothefieldsof
molecular magnetism and quantum computing. Electron spin resonance, nuclear
magnetic resonance, magnetometry, and X-ray magnetic circular dichroism have
beenused extensivelytoanalyzespin-related phenomena inendohedralfullerenes.
Finally,well-definedspinstateandlongspincoherencemakeendohedralfullerenes
withnitrogenatom,suchasN@C ,attractiveforthefieldofquantumcomputing.
60
The aim of this book is a concise analysis of the behavior of the interface
between encapsulated atoms and a carbon-based p-system under conditions of the
electron transfer and description of the spin-based phenomena caused by the
shielding of endohedral spins by the fullerene cage. In Chap. 1 we introduce the
reader into the world of endohedral fullerenes by describing the basics of their
synthesis, separation, and molecular structure elucidation. Chapter 2 gives an
overview of electrochemical studies of EMFs supported by the molecular orbital
analysis.Chapter3bySamoylovaandStevensondescribesthedevelopmentinthe
non-chromatographic separation techniques, which benefit from the difference of
reductionandoxidationpotentialsofdifferenttypesofEMFsandemptyfullerenes.
Chapter4byBoltalinareviewsthestudiesoftheionsofEMFsinthegasphaseby
varioustypesofmassspectrometryandfocusesontheionmolecularreactivityand
determination of the electron affinities. In Chap. 5, Zhen, Liu, and Yang give an
account on the photoexcitation behavior of EMF in molecular and supramolecular
dyads with donors and acceptors and describe possible applications of EMFs in
photovoltaics. Chapter 6 by Feng and Petek reviews the studies of the EMFs by
low-temperature scanning tunneling microscopy with a focus on superatom elec-
tronic state and switching of the molecular geometry by tunneling currents.
Chapters 7–9 are devoted to the studies of EMFs by electron spin resonance
spectroscopy (ESR). In Chap. 7, Wang and Wang describe ESR studies of Sc and
Y-basedEMFs.Chapter8byKatoreviewsESRspectroscopyoflanthanideEMFs,
including those with large spin moments exceeding 1/2. In Chap. 9, we describe
EPRstudiesofionradicalsofEMFsinsolution.MagneticpropertiesofEMFswith
endohedral lanthanides are described in Chaps. 10 and 11. Chapter 10 reviews the
studies by paramagnetic NMR in solution and describes the use of pNMR for the
analysis of molecular structure and dynamics of EMFs as well as for the analysis
of the magnetic anisotropy of lanthanide ions in nitride clusterfullerenes. Chapter
11 by Westerström and Greber provides extended introduction into the magnetism
of EMF and in particular into single-molecule magnetism of EMFs in bulk and in
molecular layers on surfaces. In Chap. 12, Lawler reviews nonmetal endohedral
fullerenes with emphasis on dihydrogen-containing fullerenes, their molecular
dynamics, and nuclear spin chemistry. Chapter 13 by Zhou and Porfyrakis gives a
detailed account of the synthesis and separation of C with nitrogen atom in its
60
center, N@C , its studies by ESR spectroscopy, and chemical derivatization for
60
the use in quantum computing. In Chap. 14, Harneit describes general concepts of
quantum information processing and shows how pnictide endohedral fullerenes,
and especially N@C , can be used in this field. We hope that this collection of
60
Preface vii
chapterspreparedbythescientistswithdiverseexpertiseandsummarizingthevast
developmentofourunderstandingofthechargetransferandspin-relatedproperties
ofendohedralfullereneswillbringtheinformation aboutthefascinatingproperties
ofthesemoleculestothebroaderaudienceandinspirefurtherprogressinthisfield.
Dresden, Germany Alexey A. Popov
Contents
1 Synthesis and Molecular Structures of Endohedral
Fullerenes. .... .... .... ..... .... .... .... .... .... ..... .... 1
Alexey A. Popov
2 Electrochemistry and Frontier Molecular Orbitals
of Endohedral Metallofullerenes.... .... .... .... .... ..... .... 35
Alexey A. Popov
3 Non-Chromatographic Separation of Endohedral
Metallofullerenes by Utilizing Their Redox Properties.. ..... .... 63
Nataliya Samoylova and Steven Stevenson
4 Ions of Endometallofullerenes in the Gas Phase... .... ..... .... 81
Olga V. Boltalina
5 Photoexcitation in Donor–Acceptor Dyads Based on Endohedral
Fullerenes and Their Applications in Organic Photovoltaics.. .... 103
Jieming Zhen, Qing Liu and Shangfeng Yang
6 Scrutinizing the Endohedral Space: Superatom States
and Molecular Machines. ..... .... .... .... .... .... ..... .... 123
Min Feng and Hrvoje Petek
7 Electron Spin Resonance Studies of Metallofullerenes .. ..... .... 159
Taishan Wang and Chunru Wang
8 Electron Spin Resonance of Lanthanide EMFs.... .... ..... .... 169
Tatsuhisa Kato
9 Ion Radicals of Endohedral Metallofullerenes Studied
by EPR Spectroscopy ... ..... .... .... .... .... .... ..... .... 183
Alexey A. Popov
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x Contents
10 Nuclear Magnetic Resonance Spectroscopy of Endohedral
Metallofullerenes with Paramagnetic Metal Ions: Structure
Elucidation and Magnetic Anisotropy ... .... .... .... ..... .... 199
Alexey A. Popov
11 Magnetic Properties of C Endofullerenes... .... .... ..... .... 213
80
Rasmus Westerström and Thomas Greber
12 Nonmetallic Endofullerenes and the Endohedral Environment:
Structure, Dynamics, and Spin Chemistry.... .... .... ..... .... 229
Ronald G. Lawler
13 Preparation and Chemistry of N@C ... .... .... .... ..... .... 265
60
Shen Zhou and Kyriakos Porfyrakis
14 Spin Quantum Computing with Endohedral Fullerenes. ..... .... 297
Wolfgang Harneit
Index .... .... .... .... .... ..... .... .... .... .... .... ..... .... 325
Contributors
Olga V. Boltalina Department of Chemistry, Colorado State University, Fort
Collins, CO, USA
Min Feng Department of Physics and Astronomy and Pittsburgh Quantum
Institute, University of Pittsburgh, Pittsburgh, PA, USA; School of Physics and
Technology, Wuhan University, Wuhan, Hubei, China
Thomas Greber Physik-Institut, University of Zürich, Zürich, Switzerland
Wolfgang Harneit Fachbereich Physik, Universität Osnabrück, Osnabrück,
Germany
Tatsuhisa Kato Institute for Liberal Arts and Sciences, Kyoto University,
Sakyoku, Kyoto, Japan
Ronald G. Lawler Department of Chemistry, Brown University, Providence, RI,
USA
QingLiu HefeiNationalLaboratoryforPhysicalScienceatMicroscale,CASKey
Laboratory of Materials for Energy Conversion, Department of Materials Science
and Engineering, University of Science and Technology of China (USTC), Hefei,
China
Hrvoje Petek Department of Physics and Astronomy and Pittsburgh Quantum
Institute, University of Pittsburgh, Pittsburgh, PA, USA
Alexey A. Popov Leibniz Institute for Solid State and Materials Research,
Dresden, Germany
Kyriakos Porfyrakis Department of Materials Science, University of Oxford,
Oxford, UK
Nataliya Samoylova Leibniz Institute for Solid State and Materials Research,
Dresden, Germany
xi
