Table Of ContentWolfgang Linert
Michel Verdaguer (eds.)
Molecular Magnets
Recent Highlights
Springer-Verlag Wien GmbH
Dr. Wolfgang Linert
Institute of Applied Synthetic Chemistry, Vienna University of Technology
Vienna, Austria
Dr. Michel Verdaguer
"Chimie Inorganique et Materiaux MoIeculaires" Laboratory, Pierre et Marie Curie University
Paris, France
Chairman of the "Molecular Magnets" Programme
of the European Science Foundation
This work is subject to copyright.
All rights are reserved, whether the whole or part of the material is concemed, specifically
those of translation, reprinting, re-use of illustrations, broadcasting, reproduction by photo
copying machines or similar means, and storage in data banks.
Product Liability: The publisher can give no guarantee for all the information contained in this
book. This does also refer to information about drug dosage and application thereof. In every
individual case the respective user must check its accuracy by consulting other pharmaceutical
literature. The use of registered names, trademarks, etc. in this publication does not imply, even
in the absence of a specific statement, that such names are exempt from the relevant protective
laws and regulations and therefore free for general use.
© 2003 Springer-Verlag Wien
Originally published by Springer-Verlag Wien New York in 2003
Softcover reprint of the hardcover 1s t edition 2003
Cover illustration:
V. Marvaud et al, "High Spin ... ", Fig. 2, page 18, this volume
Typesetting: Thomson Press Ltd., Chennai, India
Printing: Manz Cross media, A-I051 Wien
Binding: Papyrus, A-lIOO Wien
Printed on acid-free and chlorine-free bleached paper
SPIN: 10896440
With 106 Figures and Tables
CIP data applied for
Special Edition of
Monatshefte für Chemie/Chemical Monthly Vol. 134, No.2, 2003
ISBN 978-3-7091-7300-8 ISBN 978-3-7091-6018-3 (eBook)
DOI 10.1007/978-3-7091-6018-3
Editorial: Molecular Magnets
Between magnetochemistry which was measuring magnetism of chemicals with
the hope to discover their structures, to molecular magnetism which can be defined
as a discipline which conceives, realizes, studies, and uses new molecular materials
bearing new but predictable magnetic (and other) physical property, a few decades
took place.
Instead of going to the laboratory shelves to study the magnetic properties of
already existing chemicals, chemists are now designing new (supra)molecular sys
tems to get low density, transparent, biocompatible magnets, bistability, single
molecule magnet behaviour, materials whose properties can be changed by tem
perature, pressure or light, or still molecular objects combining several physical
functions (magnetism and conductivity, magnetism and optics ... ).
This new field is blossoming in many countries, in North America, in Japan,
and in Europe. Different European networks (including a Molecular Magnets pro
gramme of the European Science Foundation) were recently very active and pro
duced major results. It is our pleasure to welcome in this volume some of the actors
of this scientific saga, which is on the way to transform molecules in useful
devices.
Our volume opens by a brief and lively historical overview of the domain by
one of the leaders in the field, Prof. Dante Gatteschi, a chemist who received in
2002 with four other colleagues, chemists and physicists, the Agilent Technologies
Prize of the European Physical Society: this fact alone demonstrates how the field
is indeed multidisciplinary. The content of the volume is another illustration of the
diversity of the scientists engaged hand in hand in molecular magnetism: quantum
chemists and physicists, computing more and more accurately the properties of
molecules and solids and opening astonishing prospects in the field of electronic
quantum computing; chemists and physicists using large instruments (neutrons and
synchrotron radiation sources) to extract unique information unavailable by other
techniques and then comparing to theoretical models. Some of the synthetic chem
ists present here, tailor spin cross-over systems which present a fascinating
bistability between two states with different magnetic properties and colours, open
ing the way to the use in display devices. Others assemble molecules bearing very
large spins, which do not exist "naturally" in the elements of the periodic table;
anisotropy will confer to these systems the ability to store magnetic information at
the molecular level, to reach the highest, ultimate storage density of information;
some transform the beautiful C60 fullerene molecule in a molecule-based magnet;
some others combine cleverly the power and the fiexibilities of organic and
inorganic molecular chemistry to get multifunctional materials, magnetic and
VI Editorial
conducting, magnetic and optically active .... All of them provide the physicists
community with wonderful new objects to study and the engineers with new func
tions to be used tomorrow in useful devices.
The field is not only multidisciplinary but also more and more international:
many of the contributions imply various laboratories belonging to different
countries, each of them having a unique expertise which is shared when necessary.
Active international cooperation is indeed at work here.
We hope that the reader will enjoy the volume as much as we enjoyed ourselves
and that the book will help in developing more rapidly the exchange of ideas and
experience in this exciting new scientific area, molecular magnetism.
Wolfgang Linert
Michel Verdaguer
Issue Editors
Foreword: Molecular Magnetism,
an Interdisciplinary Field
Molecular magnetism is a relatively recent scientific field which originated from the
transformation of magnetochemistry in an interdisciplinary area where chemists and
physicists started to collaborate very closely with the stated goal of designing,
synthesizing, and characterizing the magnetic properties of molecular based materi
als. The idea of using molecules, rather than the ionic and metallic lattices of typical
magnets, stems from the rapid development of functional molecular materials which
started in the second half of the last century. The transition from magnetochemistry
to molecular magnetism required some time, because in order to develop efficiently
a deeper understanding of the magnetic phenomena was needed than that available
at that time in chemistry. The interaction with some physicists who were curious to
see the developments which might be associated with the exotic objects provided by
molecules was the event which officially determined the birth of the area. A testi
mony of this is given by the book "Structural-Magnetic Correlations in Exchange
Coupled Systems" edited in 1983 by Roger Willett, the late Olivier Kahn, and
myself. The title itself gives an indication of the efforts the chemists were making
at that time to understand how structural differences gave rise to different magnetic
properties. The book reports the proceedings of a NATO ASI which was extremely
stimulating. The contributions from chemists were based on simple dinuclear or
oligonuclear species, while those of physicists started from infinite arrays, with a
bias towards one dimensional materials which were extremely popular at that time.
That ASI was the start of attempts of the two communities of using similar lan
guages and it allowed chemists to dare to tackle more complex materials, and con
vinced the physicists that it was indeed possible to observe new types of magnetic
phenomena using molecular based materials.
The development of molecular magnetism has been rapid. I would like to quote
some of the milestones in the development of the area. Kahn and Verdaguer
reported the first example of molecular ferrimagnet based on copper(II)-manga
nese(II) derivatives, while Miller and Epstein reported the first example of molecular
ferromagnet containing organic building blocks like TCNE. Perhaps the most
important development was the discovery of Kinoshita that purely organic matter
can indeed order ferromagnetic ally after the elegant work of Itoh and Iwamura who
showed how extremely strong ferromagnetic coupling can be observed in polycar
benes. The subsequent discoveries of higher critical temperatures in the work of
Rassat, Wudl, Mihailovic, Rawson, and Palacio confirmed the vitality of this area,
the last ones describing organic weak ferromagnets ordering at temperatures as
VIII Foreword
high as 35 K. The rush to room temperature was won by Miller and Epstein again
who showed that V(TCNEh is a disordered ferrimagnet above room temperature.
Verdaguer opened the saga of Prussian blue derivatives, finally reporting a ferri
magnet comprising chromium(III), vanadium(II), and vanadium(III) which orders
above room temperature.
Nowadays the attempts to prepare molecular magnets which can be used at room
temperature are continuing but at the same time there are many attempts to synthe
sise molecular magnets which have properties which are difficult to be met in inor
ganic magnets. Day reported an organic superconductor coexisting in the same
lattice of a molecular paramagnet, while more recently Coronado reported a mole
cular ferromagnet hosting in the lattice an organic conductor. This is an example of
ferromagnetic conductor in which the active electrons, namely conducting and mag
netic, are separated. Many efforts are currently done to investigate chiral magnets
and to use light to influence the magnetic properties of the materials.
One of the fields where the interdisciplinary approach has produced much
success is that of zero-dimensional magnets. By this I mean systems which com
prise a finite number of interacting magnetic centres. Chemists are learning how to
make either in a rational or in a serendipitous way large clusters with different spin
topologies. The fortunate case has been that these systems have proved to be
extremely timely, because physicists were looking for small magnetic particles,
all identical to each other, in order to test theories that suggested that it was
possible to observe quantum effects in magnets. The main difficulty was just that
of obtaining assemblies of identical particles, because the quantum effects are
expected to scale exponentially with the size of the particles. Further it is manda
tory to be able to minimise the magnetic interactions between particles. Several
different approaches were used in order to reach this goal, including attempts to use
iron loaded ferritin, but no unambiguous evidence was reached. Finally, as p.eE.
Stamp wrote in a "News and Views" in Science magazine "Then the chemists
came .... ". In fact it was discovered that in a cluster comprising twelve manga
nese ions, characterised by a ground spin S = 10 state possessing a huge Ising type
magnetic anisotropy, the magnetisation relaxes very slowly at low temperature,
following a thermally activated behaviour with a barrier of ca. 65 K and a pre
exponential factor of 2 x 10-7 s. This means that at 2 K the relaxation time of the
magnetisation becomes of the order of months and magnetic hysteresis of molec
ular origin is observed. This discovery showed that indeed single molecules may
behave as tiny magnets and they were called single molecule magnets, SMM. Soon
it was realised that these molecules were providing the long looked for magnetic
particles which could show quantum effects. In fact molecules are all identical to
each other, allowing to measure a large ensemble and collecting the individual
response. In 1996 two teams (Friedman, Sarachik, Tejada, and Ziolo on one side,
Thomas, Lionti, Barbara, Sessoli, and Gatteschi on the other side), almost at the
same time, discovered that the hysteresis curves of oriented polycrystalline pow
ders or single crystals show a stepped behaviour which is the signature of quantum
tunnelling effects. Finally, it was possible to test the theories of quantum relaxation
in meso scopic magnets with the experimental properties of real objects! Other
clear evidence of quantum size in magnets came later with the observation
of temperature independent relaxation time of the magnetisation in a cluster
Foreword IX
comprising eight iron(III) ions, Fe8. Wernsdoifer and Sessoli later showed that
quantum interference effects were observed in the same compound in the presence
of an applied field along the hard axis. Again this was the evidence that the so
called Berry phase could be observed in magnets, as long theoretically predicted.
The importance of this research has been publicly recognised by the European
Physical Society by awarding the Agilent Technology Europhysics Prize 2002 to
Bernard Barbara, Jonathan Friedman, Dante Gatteschi, Roberta Sessoli, and
Wolfgang Wernsdoifer "for developing the field of quantum dynamics of nano
magnets including the discovery of quantum tunnelling and interference in
dynamics of magnetisation". I find extremely significant that the Prize has been
awarded to three physicists and two chemists, recognizing the interdisciplinary
nature of the field. I think that this is the official acknowledgement of the coming
of age of molecular magnetism, showing that indeed the effort of using exotic
materials, exploiting large organic moieties, is worth to be done, because it affords
new physics. Indeed, the dreams of the pioneers of the field, among whom I always
like to indicate the forward dreamer Olivier Kahn, have become true.
Dante Gatteschi
Firenze
October 2002
Contents
Invited Reviews
Clement R., Decurtins S., Gruselle M., Train C
Polyfunctional Two- (2D) and Three- (3D) Dimensional Oxalate
Bridged Bimetallic Magnets ................................................. .
Mihailovic D.
Ferromagnetism in Metallocene-Doped Fullerenes 21
Marvaud v., Herrera i. M., Barilero T., Tuyeras F., Garde R., Scuiller A.,
Decroix C, Cantuel M., Desplanches C
High Spin and Anisotropic Molecules Based on Polycyanometalate Chemistry 33
Letard i.-F., Chastanet G., Nguyen 0., Marcen S., Marchivie M.,
Guionneau P., Chasseau D., Giitlich P.
Spin Crossover Properties of the [Fe(PM-BiAh(NCShl
Complex - Phases I and II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
van Koningsbruggen P. i., Grunert M., Weinberger P.
Spin Transition of lD, 2D and 3D Iron(II) Complex Polymers
The Tug-of-War between Elastic Interaction and a Shock-Absorber Effect. . . . . . . . . . . . . . . . . 67
Boca R., Linert W
Is There a Need for New Models of the Spin Crossover? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
Leuenberger M. N., Meier F., Loss D.
Quantum Spin Dynamics in Molecular Magnets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
Ressouche E., Schweizer i.
Ab Initio Calculations Versus Polarized Neutron Diffraction
for the Spin Density of Free Radicals ......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
Contributions
Stassen A. F., Ferrero E. M., Gimenez-Saiz C, Coronado E.,
Haasnoot i. G., Reedijk i.
A New Layered Compound Containing [PMoI204o]3-and Both 5- and
6-Coordinated Homoleptic (1-(2-Chloroethyl)tetrazole )Copper(II) Cations. . . . . . . . . . . . . . . . . 139
Gerbier P., Ruiz-Molina D., Domingo N., Amabilino D. B., Vidal-Gancedo i.,
Tejada i., Hendrickson D. N., Veciana i.
Synthesis and Characterization of a [Mn120n(02CRh6(H20)4] Complex
Bearing Paramagnetic Carboxylate Ligands. Use of a Modified
Acid Replacement Synthetic Approach .......................................... 149
XII Contents
Champion G., Arrio M.-A., Sainctavit P., Zacchigna M., Zangrando M.,
Finazzi M., Parmigiani F., Villain F., Mathoniere C, Cartier dit Moulin C
Size Effect on Local Magnetic Moments in Ferrimagnetic Molecular Complexes:
An XMCD Investigation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
Gaspar A. B., Munoz M. C, Moliner N., Ksenofontov v., Levchenko G.,
Giitlich P., Real J. A.
Polymorphism and Pressure Driven Thermal Spin Crossover Phenomenon
in [Fe(abpth(NCX)2] (X = S, and Se): Synthesis, Structure and
Magnetic Properties ........................................................ 169
Paulsen H., Duelund L., Zimmermann A., Averseng F., Gerdan M.,
Winkler H., Toftlund H., Trautwein A. X.
Substituent Effects on the Spin-Transition Temperature in Complexes
with Tris(pyrazolyl) Ligands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
Rodrfguez-Fortea A., Ruiz E., Alemany P., Alvarez S.
Magneto-Structural Correlations in Trinuclear Cu(II) Complexes:
A Density Functional Study .................................................. 191
Massobrio C, Ruiz E.
Localized Orbitals vs. Pseudopotential-Plane Waves Basis Sets:
Performances and Accuracy for Molecular Magnetic Systems. . . . . . . . . . . . . . . . . . . . . . . . .. 201
