Laboratoire National des Champs Magnétiques Pulsés CNRS – INSA

Molecular magnetism
With the recruitment of a Professor in chemistry starting in September 2009 (UJF), ‘Molecular
magnetism’ is now identified as a dedicated theme of the laboratory. During the forthcoming four
years period, the activity on this theme will follow several lines, ranging from chemical synthesis to
physical studies especially with High Field/High Frequency EPR (HFEPR).
Following the important results obtained in enantiomerically pure chiral magnets [Tra08], a first topic
will keep exploring the physical effects related to the simultaneous breaking of space (P) and timereversal
(T) symmetries within the same medium.
Figure 1 : polar paramagnetic heteroleptic tris(bidentate)chrome(III) chiral complexes.
At the molecular level, the coexistence of electric and magnetic dipolar moments within a
chiral molecule can be exploited to probe the Curie-de Gennes conjecture. This conjecture precises
Pasteur's intuition concerning the possibility to obtain an enantiomeric excess (e.e.) from achiral
reactants by applying an external magnetic field: it states that obtaining such an e.e. is indeed possible
by applying simultaneously parallel electric and magnetic fields to the system under reaction in order
to influence the transition energies leading to either enantiomers [Bar94]. In this sense, the
combination of the two external fields acts as a chiral catalyst. We will concentrate on the
interconversion reaction between the two enantiomers of a polar paramagnetic chiral complex. The
synthetic target will be heteroleptic chromium(III) complexes using two different bidentate ligands.
We will focus on the synthesis [Cr(acac)3-x(hfac)x] (acac=acetylacetonate,
hfac=(1,1,1,5,5,5)hexafluoroacetylacetonate; x=1,2) (Figure 1). Given that the effect is expected to be
weak, the interconversion reaction will be studied in collaboration with the Magneto-optic group of G.
Rikken by applying high magnetic field. The experimental demonstration of this effect will
substantiate a possible mechanism to explain the homochirality of life.
In extended structures, the simultaneous breaking of P and T symmetries lead to the formation
of multifunctional magnets that can exhibit, in addition to mere magnetic properties, magnetically
induced Second Harmonic Generation (MFISHG) or ferroelectricity. The latter case corresponds to
multiferroicity, a subject which undergoes an explosive exploration in solid state chemistry [Che07,
Chu08]. In the framework of the Young Researchers ANR program "Ferromol" (leader: C. Train), we
intend to exploit the versatility of molecular chemistry and crystalline engineering to design,
synthesize and assemble polar and paramagnetic building blocks in order to obtain and study
molecular multiferroics. The measurement of ferroelectrical properties will be done in collaboration
with B. Dkhil in Ecole Centrale Paris (Chatenay-Malabry). The interplay between magnetism and
ferroelectricity will be explored by Piezoelectric Force Microscopy in Barthelemy's group at Thales
(Palaiseau) and by measuring the influence of the electric field on the magnetisation by micro-SQUID
at Institut Néel (Grenoble). In parallel with the synthesis of bulk materials, we intend to process them
in nanoporous alumina (M. Woytasik, Institut d'Electronique Fondamentale, Orsay) in order to favour
their integration in devices.
The second topic is the development of coordination chemistry of verdazyl radical [Tra09] in
the framework of the Young Reseachers ANR program "fdp magnets" (leader: V. Robert, Lyon). One
of the synthetic targets will be one dimensional compounds where verdazyl radicals bridge anisotropic
metal ions. The goal is to combine strong single-ion anisotropy with reinforced exchange interaction
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