SYNTHETIC ENDEAVOURS TOWARDS
NEW SINGLE MOLECULE MAGNETS and
NEW SINGLE CHAIN MAGNETS
M. Verdaguer,
Emeritus Professor
Chimie Inorganique et Matériaux Moléculaires, C.N.R.S. Unit 7071
Université P. et M. Curie, Paris, France
miv@ccr.jussieu.fr
International Workshop on « Physics on Nanoscale Magnets », Kyoto, 1-4 December 2003
NAREGI Project, Kyoto Garden Palace Hotel
SYNTHETIC ENDEAVOURS TOWARDS
NEW SINGLE MOLECULE MAGNETS and
NEW SINGLE CHAIN MAGNETS
Recents Results, Promises, Problems and Prospects
Coworkers and Collaborators
V. Marvaud1, M. Julve2, F. Villain1, W. Wernsdorfer3
F. Tuyèras1, R. Lescouezec2, J.M. Herrera1, L.T. Marilena2, R. Tiron3
N. Galvez1, R. Garde1, M. Hernandez1
1) CIM2, CNRS Unit 7071, Université Pierre et Marie Curie, Paris, France
2) Departament de Quimica Inorganica, Universitat de Valencia, Burjassot, Spain
3) Laboratoire Louis Néel, CNRS, Grenoble, France
Outline
• Introduction :
- molecular magnetism
- the molecular approach to nanosystems
• What a chemist must & can control ?
• From High Spin Molecules to SSM
- a systematic, rational, approach
- the photomagnetic way …
• Single Chain Magnets
• Conclusions
Chemistry …
A + B
Reactants
C
Products
T, P,
Solvent,
pH …
• Science of matter’s transformation
• A way to transform the world …
M. Noyori, Hanoi, october 2003:
To day
the chemist is able
to synthesize
any molecule
at will
Chemistry …
A + B
How to choose A and B ?
or : which target C ?
C
Chemistry …
A + B
C
which target C ?
-1- to make money … (not
always rewarding
-2- to follow your supervisor …
…)
(not always recommendable …)
-3- to answer questions of physicists ! or others …
… (sometimes amazing and useful)
-4- to achieve a synthetic challenge !
… (difficult but worth of the candle)
-5- Many more …
One possible answer comes from
Molecular Magnetism
a scientific discipline
that conceives
designs
synthesizes
studies
and uses
new molecular magnetic materials …
In a multidisciplinary way …
One of the nests of Molecular Magnetism
« Olivier Kahn was one of those who allowed
to switch from magnetochemistry to molecular magnetism »
D. Gatteschi, Lausanne, 2001
Answering questions of physicists …
the strange and successful story
of Haldane gap …
… Haldane gap
Conjecture
(1983)
Idea
New
ConceptsTheory
Synthesis
New
Materials
New
Properties
Functions
« Dynamic mass generation by the Néel magnon is predicted … »
« Dynamic mass generation by the Néel magnon is predicted … »
Very clear and useful indication for synthesis …
… Haldane gap
« Translation » : Energy Gap in AF Integer spins 1D
Conjecture
(1982)
Idea
Uniform Ni(II), S=1 AF Chains
New
ConceptsTheory
New
Synthesis
Properties
Functions
J.P. Renard et al., Europhys. Letters, 1987
NENP
TMNIN
NINAZ
New
Materials … many others
One of the central questions …
Is it possible to use molecules
(isolated metal complexes)
to build magnets … ?
Achieving a synthetic challenge …
Overcome entropic and kinetics hindrances …
A-L-B-L-[A-L-B]na ferrimagnetic bimetallic
molecule-based magnet
at 4.6 K…
M. Verdaguer et al., Coord. Chem. Reviews, 1998,
Synthetic challenge : feasibility of a bimetallic
molecule-based magnet ?
O
Bimetallic chains
AF Exchange Interaction
between different spins
O
Cu
S
Idea
O
S
2-
O
N
N
O
O
O
O
OH2
O
Cu
ConceptsTheory
2-
O
S
H X
C
New
BUT …
S
MnCu(dto)2•7.5H2O
Synthesis
MnCu(pba)•2H2O
New
Materials
New
Properties
Functions
O
O
Mn
H2 O
O
O
S
S
Cu
S
OH2
S
H
Mn
O
n
O
O
OH2
O
X
C
IT WORKS !
A. Gleizes et al.
JACS 1981 et 1984, 3277
Y. Pei et al. JACS 1986,
OH2
OH2
OH2
O
N
N
Mn
O
O
OH2
O
Mn
Cu
O
OH2
O
O
OH2
O
n
Molecular Engineering vs Crystal Engineering
H OH
C
Bimetallic planes
O
AF between Chains
After Displacement
O
New
NOW …
N
O
O
O
OH2
O
N
Cu
Idea
ConceptsTheory
2-
Cu(pba-OH)
Synthesis
New
Materials
New
Properties
MnCu(pba-OH)•2H2O
Functions
H
X
C
O
Mn
Y. Pei et al., J. Am.Chem.Soc., 1988, 782
N
N
O
O
OH2
O
Mn
Cu
O
OH2
O
O
OH2
O
n
Ferrimagnetic Bimetallic Chains
Molecular Engineering vs Crystal Engineering
Catena µ-[Cu(II)(pba-OH)Mn(II)(H2O)2] Chain
HO
H
C
OH 2
OH 2
O
N
O
O
Mn
Cu
N
O
O
O
Mn
O
O
O
N
Cu
O
N
O
C
H
OH 2
O
Mn
H2 O
OH 2
HO
O
OH 2
O
OH
H
C
O
NH
O
O
Mn
Cu
NH
O
O
O
OH 2
OH 2
Mn
OH 2
O
O
O
NH
Cu
O
O
NH
O
OH 2
Mn
OH 2
CH 3
CH 3
OH 2
C
H
HO
OH
H
C
N
O
O
Mn
OH 2
H2 O
O
Cu
N
O
O
O
Mn
OH 2
O
O
O
N
Cu
OH 2
O
N
O
Mn
OH 2
O
O
Magnet at
TC = 4.6K
C
H
Hydrogen bonding
OH 2
O
OH
Interchain Interactions (af)
Y. Pei et al. J. Am. Chem. Soc. 1988, 110, 782 ;
Ferrimagnetic Bimetallic Chains
Molecular Engineering vs Crystal Engineering
Catena µ-[Cu(II)(pba-OH)Mn(II)(H2O)2] Chain
HO
H
C
OH 2
OH 2
O
N
O
O
Mn
Cu
N
O
O
O
Mn
O
O
O
N
Cu
O
N
O
C
H
OH 2
O
Mn
H2 O
OH 2
HO
O
OH 2
O
OH
H
C
O
NH
O
O
Mn
Cu
NH
O
O
O
OH 2
OH 2
Mn
OH 2
O
O
O
NH
Cu
O
O
NH
O
OH 2
Mn
OH 2
CH 3
CH 3
OH 2
C
H
HO
OH
H
C
N
O
O
Mn
OH 2
H2 O
O
Cu
N
O
O
O
Mn
OH 2
O
O
O
N
Cu
OH 2
O
N
O
Mn
OH 2
O
O
Magnet at
TC = 4.6K
C
H
Hydrogen bonding
OH 2
O
OH
Interchain Interactions (af)
Y. Pei et al. J. Am. Chem. Soc. 1988, 110, 782 ;
Achieving a synthetic challenge …
a confidence problem …
NB : no long range order in 1D
Let us go to 3D …
a brief story of a molecule-based magnet …
at room temperature
M. Verdaguer et al., Coord. Chem. Reviews 1998, 190, 1023 & Phil.Trans.A, 1999, 357, 2959.
Synthetic challenge : feasibility of a room temperature
molecule-based magnet ?
Prussian Blue analogues
Exchange Interaction
(1975, 1976)
Idea
New
ConceptsTheory
Synthesis
V4[Cr(CN)6]8/3•n H2O
… and many others
New
Materials
New
Properties
Functions
TC = 315K
QuickTime™ et un décompresseur
DV - PAL sont requis pour visualiser
cette image.
from magnetochemistry to molecular magnetism …
Blossoming of the discipline …
O. Kahn
Eds. K. Itoh
M. Kinoshita
Eds. J. Miller
M. Drillon
Eds. W. Linert
M. Verdaguer
Switchable Systems
Molecular Magnets
Multifunctional materials
« Single Molecule » Magnets
Single Molecule Magnet
Remains oriented after withdrawing of the field
(slow relaxation of the magnetisation …)
WITHOUT
Interaction between the molecules
Phenomenon strictly molecular !
WHY ?
… Single molecule magnets
Giant Molecular Clusters
High Spin + Anisotropy
∆E = DSz2
Mn12
Fe8
Idea
New
ConceptsTheory
Synthesis
New
Mn4
and many others
Materials
New
Properties
Functions
Top down
3D
Metals
Oxydes
•
•
•
New Physics
Quantum / Classical
Quantum tunneling
Fragments
Threads
Dots
•
Nanosystems •
Nice Chemistry
Single molecule magnets
Giant Molecular Clusters
0D, Molecules
Bottom up
• Applications (far …)
• Recording
• Quantum computing
Nanomagnets : How ?
Molecular Clusters
• No dispersion in size, in • Solubility
shape and in orientation • Biocompatibility
• Systems well
characterised :
structure, magnetic
parameters
• Control of parameters
by synthesis
Single molecule magnets
without interaction between the molecules !
High Spin Anisotropic Molecules
Magnetisation reversal
z
y
x
Anisotropy Barrier
DSz2
and D < 0
Single molecule magnets
z
E
0
Thermal
Activation
y
DSz2
Anisotropy Barrier
x
Tunneling
- Sz
DSz = 400K ?
2
-4 -2 0 +2 +4
|D| = 1K
S = 20
Sz
+Sz
(D < 0)
Remark : if DGS > 0
- Sz
-4 -2 0 +2 +4
+S z Sz
DSz2 D>0
Sz=0
Within the ground state,
Sz=0 state is at the lowest energy
No more SMM behaviour
DGS<0 is necessary for SMM …
Contro also transversal anisotropy E : mixing of M levels
in Fe8 and central for Quantum tunneling
H = DSz2 + E(Sx2 -S2y) + Terms(S4)
E/K
From D. Gatteschi, Florence
Outline
• Introduction : molecular magnetism
- the molecular approach to nanosystems
• What a chemist must & can control ?
• From High Spin Molecules to SSM
- a systematic, rational, approach
- the photomagnetic way …
• Single Chain Magnets
• Conclusions
Outline
• Introduction : molecular magnetism
- the molecular approach to nanosystems
• What a chemist must can control ? & can !
• From High Spin Molecules to SSM
- a systematic, rational, approach
- the photomagnetic way …
• Single Chain Magnets
• Conclusions
For the chemist
Parameters to Control
E
0
S = Spin
D, E = Anisotropy
Thermal
Activation
DSz2
Anisotropy Barrier
Tunneling
- Sz
-4 -2 0 +2 +4
J
J
Sz
+Sz
J’
= Exchange Constant
Intramolecular interaction
zJ’ = Intermolecular interaction
Synthetic “Strategy” in Paris
3-
2+
9+
+ 6
Hexacyanometalate “Heart” Mononuclear Complex
Lewis Base
Lewis Acid
Polynuclear Complex
Flexibility of the Synthetic Parameters :
Metallic Cations, Polydendate ligands, Counter-ions,
Solvents, Stoichiometry …
Valérie Marvaud, A. Scuiller, F.Tuyèras, R. Garde, (T. Mallah)
Control of the ground spin state
• Nuclearity
• Nature of the paramagnetic ions
• Exchange interaction J (F or AF) : Symmetry
Control of the anisotropy
• Molecular (and Crystal) Structure : Symmetry
• Electronic anisotropy (nature of the ions)
Control of the intermolecular interaction J ’
• Bulky ligands
• Charged complexes and counterions
• Dilution in an diamagnetic matrix
Outline
• Introduction : molecular magnetism
- the molecular approach to nanosystems
• What a chemist must & can control ?
• From High Spin Molecules to SMM
- a systematic, rational, approach
- the photomagnetic way …
• Single Chain Magnets
• Conclusions
Control of the ground spin state
• Nuclearity
• Nature of the paramagnetic ions
• Exchange interaction J (F or AF) : Symmetry
Orbital Approach
Hexacyanochromate complex
eg
[CrIII(CN)6]3-
² oct
t2g
Cr(III),
d3
z
t2g
x
Magnetic Strategy :
1) FERROMAGNETISM
M-CN-M'
s
p
Example :
Cr(III) (t2g) 3
2
JF
Ni(II),(e g)
Cr(III)Ni(II)
6
S= 3/2 + 6x1
S = 15/2
Magnetic Strategy :
2) FERRIMAGNETISM
M-CN-M'
p
p
Overlap = antiferromagnetism
Example
Cr(III) (t 2g)3
Cr(III)Mn(II)6
S= |-3/2 + 6 x 5/2|
JAF
Mn(II) (t2g)3
S = 27/2
Heptanuclear Complexes
F
F
CrCu6
S = 9/2
Hexagonal
R -3
a = b = 15,27 Å; c = 78,56 Å
a = b= 90°; g = 120°; V = 4831 Å3
AF
CrNi6
S = 15/2
Hexagonal R -3
a = b = 15,27 Å; c = 41,54 Å
a = b= 90°; g = 120°; V = 8392 Å3
C rM n 6
S = 27/2
Hexagonal R -3
a = b = 23,32 Å; c = 40,51 Å
a = b= 90°; g = 120°; V = 19020 Å3
Marvaud, Chemistry, 2003, 9, 1677 and 1692
N
C
2nd generation
NC
M
NC
CN
= Ni(II)(tetren)
Spin = 1
CN
C
N
= Ni(II)(Rad°)2
Spin = 2
Rad°
1rst generation
N
C
NC
Complex
M
NC
CN
CN
C
N
N
C
NC
M
NC
CN
CN
C
N
K. Vostrikova, P. Rey et al., JACS 2000, 122, 718
S = 14/2
Some examples …
S = 39/2 (AF), 51/2(F)
S = 27/2
Rey, JACS 2000, 122, 718
Decurtins, Angewandte, 2000
Hashimoto, JACS, 2000
Marvaud, Chemistry, 2003, 9, 1677 y 1692
Fe2(Ni-R•2)3
Anisotropy
A rational control is more difficult !
Two aspects :
- Structural
- low symmetry of the cluster
- one anisotropy axis : Cnv, Dnh,…
- Electronic
- local anisotropy of the magnetic ions Di
- exchange anisotropy Di,j
Control of the anisotropy …
• Isolated Ion Anisotropy Di
• Dipolar Interaction
• Anisotropic Exchange Di,j
D = ∑i ci Di + ∑ ci,j D
Can be computed (“Genio” Programme, D. Gatteschi)
i,j
CoCu2
CrNi
CoCo2
CoNi2
CrNi2
7/2
5/2
CoCu3
CoCo3
CoNi3
Marvaud et al., Chemistry, 2003, 9, 1677 and 1692
Ariane Scuiller, Caroline Decroix, Martine Cantuel, Fabien Tuyèras …
CoNi5
Anisotropy
CoCo2
CoCu2
CrNi
CoNi2
7/2
CrNi2
5/2
CoCu3
High spin
CoCo3
CrCo3
CrMn6 27/2
CoMn6
15/2
CrNi6
CoNi3
CrNi3
9/2
CrCu6
CoCu6
CoCo6
CoNi5
CrNi3
V. Marvaud
« CrNi2 » complexes : molecules
+
[CrIII(CN)4{CN-NiII(tetren)}2]+
Cl- or [BF]4-
CrIII, d3, t2g ; NiII , d8, eg
Orthogonality : Ferro
Spin : 2x1 + 3/2 = 7/2
Structural anisotropy
+
S = 7 /2
Anisotropic molecular GdIII …
[CrIII(CN)4{CN-NiII(dienpy2)}2]+
Cl-
One of the most difficult problem :
Control of INTERmolecular interactions J’
i.e. crystal engineering
« CrNi2 » complexes : cell packing
Magnetism : µ-SQUID Measurements
Magnetic Susceptibility
0.4
0.6
0.5
0.3
1/chi (1/T)
1/chi (1/T)
0.4
0.3
0.2
0.2
0.1
0.1
0
0
0
0.5
1
1.5
T (K)
2
Easy axis
F
Coll. W. Wernsdorfer, R. Tiron
2.5
0
0.5
1
T (K)
1.5
2
Hard axis
AF
See R. Tiron et al., Polyhedron, 2002,22, 2247
Simplified scheme of unit cell
[Cr(CN)4{CN-Ni(tetren)}2]Cl
Hysteresis loops vs temperature
1
0.5
0.5
0
M/M
M/M
s
s
1
0.04K
0.4K
0.5K
1K
2K
3K
7K
-0.5
0
0.05K
0.6K
1K
2K
4K
7K
-0.5
-1
-1
-0.6
-0.4
-0.2
0
0.2
µ 0 H (T)
H // easy axis
0.4
0.6
-1.2 -0.8 -0.4
0 0.4
µ 0 H (T)
H // hard axis
0.8
1.2
Hysteresis loops vs direction of H
1
1
1
Happ
Happ
0.5
0.5
-0.5
-1
-0.4
s
-0.5
Happ
-0.2
0
M/M
0
Happ
M/M
M/M
s
s
0.5
0
µ 0 H (T)
0.2
H // easy axis
0.4
-1
-0.4
Happ
0
Happ
Happ
-0.5
-0.2
0
µ 0 H (T)
0.2
Intermediate
0.4
-1
-0.4
-0.2
0
µ 0 H (T)
0.2
0.4
H // hard axis
Hysteresis loops
for 3 samples
H // hard axis
Cr{Ni(tetren)}2
Cr{Ni(tetren)}2 *
[Cr{Ni(dienpy2)}2
Formally, the « same » molecules CrNi2
And slightly different properties …
Two Isomeric Mn12
Mn12(p-MeBz)
Mn12(p-MeBz)H2O
D.N. Hendrickson, G. Christou et al.
(s)
Fe 8with D
Fe 8 standard
1000
Fe 8 with
100
57
Fe
10
1
0.1
0
2
4
6
8
1/T (1/K)
Time necessary to relax 1% of Msat
Fe8D > Fe8st > 57Fe8
10
from D. Gatteschi, R. Sessoli et al.
Exchange-biased quantum tunnelling in a
supramolecular dimer of single-molecule magnets
S = 9/2
QuickTime™ et un décompresseur
Graphique sont requis pour visualiser
cette image.
J
S = 9/2
W. Wernsdorfer, N. Aliaga-Alcalde, D. N. Hendrickson & G. Christou
Nature 416, 406 (28 March 2002)
To get high spin
and anisotropic
molecules :
some work in progress
To get high spin and anisotropic molecules :
some working directions
-I- Tetra or Hexanuclear Complexes
CrNi3, CrNi5
-II- Anisotropic Ions
Co(II), Mn(III)
-III- Heterotrimetallic Complexes
CrNi2Mn4
-IV- Anisotropic Hearts
Fe(II)(phen)(CN)4
Well insulated :
Octacyanometalates
-V- Dilution in a dia/paramagnetic matrix
-VI- Interaction with light
CrNi2 in CoNi2
V. Marvaud
Synthetic Strategy I
Cr(III)Ni(II)3, Tetranuclear Complex, C3v axis
C3v
Caracterisation :
- Isostructural with CoNi3
- Mass Spectrometry : M = 1712.98
Magnetic Properties
• Ferromagnetic Interaction
CrNi3, S=9/2
Hexagonal R 3
a = b = 18,343 Å; c = 23,394 Å
V = 6818 Å3 , Z = 3
• S = 9/2
• J = +9.7 0 cm-1, D = -0.095 cm1
• Hysteresis at 30 mK
V. Marvaud, F. Tuyèras
Synthetic Strategy II
Using Anisotropic Ions, Co(II) and Mn(III) (large D)
Cristallographic Structure
Magnetic Properties
• Antiferromagnetic Interaction
• S = 5/2
• J , D in progress
Cr(III)Mn(III)2
Monoclinic C 2/m
a = 17,821 Å; b = 14,275 Å; c = 8,602 Å
b = 99,206°;
V. Marvaud, F. Tuyèras
Synthetic Strategy III
Hetero tri metallic Complexes , Cr(III)Ni(II)2Mn(II)4
Synthesis
Cristallographic Structure
+
NiII CrIII NiII
S=1 S=3/2 S=1
MnII
S = 5/2
Trigonal R -3
a = b = 23,26 Å; c = 20,35 Å
a = b = 90°; g = 120°; V =9510 Å3
V. Marvaud, F. Tuyèras
CrNi2Mn4 : magnetic properties
Cr-Ni
Cr-Mn
S = (4 x 5/2) - 3/2 - (2 x 1) = 13/2
36
14
34
12
32
10
M (MB)
Chi*T
Hexagonal R -3
a = b = 23,26 Å; c = 20,35 Å
a = b= 90°; g = 120°; V =9510 Å3
30
28
8
6
26
4
24
2
22
F
AF
0
0
50
100
150
T (K)
V. Marvaud, F. Tuyèras
200
250
300
0
1 10 4
2 10 4
3 10 4
4 104
H / Gauss
5 10 4
6 104
Collaboration: R. Sessoli & D. Gatteschi
7 104
CrNi2Mn4 : High Field EPR
0,003
0,002
0,002
0,001
intensité
0,001
0
-0,001
-0,002
-0,003
8,5
9
9,5
10
10,5
11
Champ
CrNi2
V. Marvaud, F. Tuyèras
11,5
0,0015
0,001
0,0005
intensité
0,003
intensité
0,004
8
230 GHz
15K
230 GHz
15 K
285 GHz
10 K
0
-0,001
0
-0,0005
-0,002
-0,001
-0,003
-0,0015
-0,004
-0,002
6
6,5
7
7,5
8
8,5
champ
CrMn6
9
9,5
10
6,5
7
7,5
8
8,5
9
9,5
10
Champ
CrNi2Mn4
Coll.A.L. Barra & D. Gatteschi
CrNi2Mn4 : « Genio » Calculations
D   ciDi   cijDij
i
CrNi2Mn4
ij
CNi = 0,00833
CMn = 0,11096
CCr = 0,025
Looking for the best Hetero-Tri-Metallic Systems
Cr{NiL}2 {NiL’}4 predicted to be a « Single Molecule Magnet »
V. Marvaud
Collaboration: D. Gatteschi
Heterotrimetallic Complexes
+
+
CrNi2Mn4
CrNiMn5
CrNi4 …
And others !
V. Marvaud
Synthetic Strategy IV
Anisotropic “Hearts”
2 - Bidendates TRANS
4 - Tetradendates CIS
3 - Trisdendates FAC y MER
6 - Hexadendates
8 - Octadendates
Polynuclear Complexes with Anisotropic Hearts
Fe(II)(phen)Cu(II)4
Monoclinic P 21/ n
a = 14,581 Å; b = 29,044 Å; c = 18,679 Å
b = 103,708°;
Fe(II), S = 0 !
Fe(III) reduced to Fe(II) …
Fe(II)Cu(II)4
Monoclinic P 21/ a
a = 14,245 Å; b = 14,584 Å; c = 16,261 Å
b = 111,323°;
Ni(II) square planar, S = 0 !
Synthetic Strategy V
Dilution in a dia/paramagnetic matrix
CrNi2 diluted in a CoNi2 matrix
Cr(III) or Co(III)
NB : Co(III), d6, diamagnetic
CrNi2 diluted in a CoNi2 matrix
1
dH/dt = 0.035 T/s
dH/dt = 0.035 T/s
M/M s
M/M s
0.5
0
0.04
0.10
0.12
0.14
-0.5
0
K
K
K
K
0.04
0.10
0.12
0.14
K
K
K
K
-1
-0.8
-0.4
0
µ 0 H (T)
0.4
0.8
Sigmoïdal signal is from matrix
-0.2
-0.1
0
µ 0 H (T)
0.1
0.2
• Quick Relaxation at H=0 ;
• Steeper magnetisation rise at
lower T
Hope : tunneling effect at H = 0 : SMM ?
Heptanuclear Complexes
from octacyanometalate precursors
WIVCuII6
MoIVCuII6
Monoclinic P n
a = 24.89 Å; b = 14,39 Å; c = 30,11 Å
a = g = 90°; b = 108.81°;
WIVNiII6
MoIVNiII6
Monoclinic
a = 22.03 Å; b = 28,39 Å; c = 22,01 Å
a = g = 90°; b =99.48°;
WIVMnII6
MoIVMnII6
Monoclinic C c
a = 25.39 Å; b = 15,22 Å; c = 30,72 Å
a = g = 90°; b = 111.45°;
V. Marvaud, J.M. Herrera, work in progress
Synthetic Strategy V
Interaction with light
Octacyanometalate
Precursors
Heptanuclear
Complexes
WIVCuII6
MoIVCuII6
Monoclinic P n
a = 24.89 Å; b = 14,39 Å; c = 30,11 Å
a = g = 90°; b = 108.81°;
WIVNiII6
MoIVNiII6
Monoclinic
a = 22.03 Å; b = 28,39 Å; c = 22,01 Å
a = g = 90°; b =99.48°;
WIVMnII6
MoIVMnII6
Monoclinic C c
a = 25.39 Å; b = 15,22 Å; c = 30,72 Å
a = g = 90°; b = 111.45°;
V. Marvaud, J.M. Herrera, work in progress
MoIVCuII6 : photomagnetic molecule !
Magnetisation (H=2T) at T= 10K as f(irradiation time)
0.0022
T = 10 K
H = 20 kOe
0.002
Emu
0.0018
M
/ u.a.
0.0016
0.0014
0.0012
0.00
2.00
4.00
6.00
8.00
10.00
Time
/ min.
Time (h.mn)
Photo-excitation
MoIVCu6
6 x (S = 1/2)
hn
MoVCuII5CuI
S = 3
Collaboration: C. Mathonière, ICMC Bordeaux
?
Photo-induced electron transfer
MoIV
hn
MoV
CuII
+5
MoIVCuII6
MoIV, d2 , S=0
No exchange
6 isolated S=1/2
+5
MoVCuI1CuII5
MoV, d1 , S=1/2
Ferro interaction …
S=3
CuI
MoIVCuII6
cMT = f(T) before irradiation
and after irradiation
5
c MT
xT before hv
M
-1
c T / emu mol K
4.5
hn
4
hn (405 nm), 19 h, 5 K
xT after hv
after
3.5
3
before
2.5
280 K
2
0
50
100
150 200
T/K
250
300
MoIVCuII6 : further data
Magnetisation vs H at T= 10K : Experiment and simulation
simulation
M after hv
M before hv
M after cycling T
5
° Before irradiation
-- After cycling at
Room T
4
M / Nb
• After irradiation
-- Simulation (S=3)
3
2
1
0
0
10000 20000 30000 40000 50000
Field / Oe
Fully reversible !
Outline
• Introduction : molecular magnetism
- the molecular approach to nanosystems
• What a chemist must & can control ?
• From High Spin Molecules to SSM
- a systematic, rational, approach
- the photomagnetic way …
• Single Chain Magnets
• Conclusions
Feasibility of « Molecular nanowires » ?
Anisotropic precursor
[Fe(III)(bipy)(CN)4]R. Lescouëzec, M. Julve, Valencia, Spain D. Gatteschi, W. Wernsdorfer
Angewandte Chem. 2003, 142, 1483-6
2 [FeIII(bipy)(CN)4]- + [CoII(H2O)6]2+
Anisotropic precursor
(Structure)
FeIII, d5
bas spin
S = 1/2
Anisotropic assembler
(Electronic Structure)
CoII, d7
haut spin
S = 3/2
Bimetallic Chain ! [{FeIII(bipy)(CN)4 }2CoII(H2O)2• 4H2O]n
Cristallographic Structure (along a axis)
Monoclinic
P21/n
a =7,591Å
b =15,190Å
c =14,714Å
ß =92,92°
J. Vaissermann, Paris
Chain [{FeIII(bipy)(CN)4 }2CoII(H2O)2• 4H2O]n
Perspective View
7.59 Å (a)
J. Vaissermann
Chain catena-µ- [{FeIII(bipy)(CN)4 }2CoII(H2O)2• 4H2O]n
Few and Weak Interchains contacts
Chain catena µ- [{FeIII(bipy)(CN)4 }2CoII(H2O)2• 4H2O]n
View down axis a
Observe the angle between chains
Chain catena µ-[{FeIII(bipy)(CN)4 }2CoII(H2O)2• 4H2O]n
Magnetic Properties (powder)
30
60
Fe(bipy)(CN) Co
Fe(bipy)(CN) , poudre
4
c MT / cm3 mol-1
25
4
50
poudre
1/c
  +18.1 K
40
20
30
15
20
10
10
r = 0.99995 (30 < T < 300 K)
5
0
0
50
100
150
T/K
200
250
300
0
50
100
150
200
T/K
FERROMAGNETIC INTERACTION !
250
300
Orbital interpretation :
Orthogonality of Magnetic orbitals
R. Lescouëzec, J. Cano
Chain catena µ-[{FeIII(bipy)(CN)4 }2CoII(H2O)2• 4H2O]n
FCM plots along crystallographic axes a, b, c (H = 5000 Oe)
16
b
14
12
M / a. u.
10
c
8
a
6
6
7
8
9
10
T/ K
11
12
13
Chain catena µ-[{FeIII(bipy)(CN)4 }2CoII(H2O)2• 4H2O]n
Magnetisation in the bc plane (H = 5000 Oe ; T = 5 K)
1.8
b
1.6
the o
ex p
1.4
M / a. u.
1.2
c
1.0
0.80
0
60
12 0
18 0
a / deg
24 0
30 0
Chain catena µ-[{FeIII(bipy)(CN)4 }2CoII(H2O)2• 4H2O]n
Magnetisation in the bc plane (H = 5000 Oe ; T = 5 K)
m1
Ow
Mb
Fe
Co
m1
o
31
m2
59o
m2
b
c
a
Mc
Chain catena µ-[{FeIII(bipy)(CN)4 }2CoII(H2O)2• 4H2O]n
Single crystal
ac susceptibility
Measurements
(SQUID)
2.0
0.1
1
10
100
1000
1.5
1.0
c" / a . u.
Slow relaxation of
the magnetisation !
0.5
0.0
3
c‘‘ vs. T plots along the b axis.
4
5
6
T/ K
7
8
R. Lescouezec, F. Lloret
Chain catena µ-[{FeIII(bipy)(CN)4 }2CoII(H2O)2• 4H2O]n
Magnetisation on microSQUID (microcrystal)
easy axis
minor species
easy axis
major species
Hy
12°
crystal
-32°
-20°
Hx
50 m
W. Wernsdorfer, LLN Grenoble
Chain catena µ-[{FeIII(bipy)(CN)4 }2CoII(H2O)2• 4H2O]n
MicroSQUID Single crystal measurements // b axis
1
M/M s
0.5
Constant Temperature
Varying Sweeping Rates
2.0 K
H || b
0
0.070 T/s
0.035 T/s
0.017 T/s
0.008 T/s
0.004 T/s
0.002 T/s
0.001 T/s
-0.5
-1
-0.8
-0.4
0
µ 0 H (T)
0.4
0.8
Slow relaxation of the magnetisation
W. Wernsdorfer, Grenoble
Chain catena µ-[{FeIII(bipy)(CN)4 }2CoII(H2O)2• 4H2O]n
MicroSQUID Single crystal measurements // b axis
1
2.0 K
M/M s
0.5
1.5 K
H || b
0
7.0 K
1.1 K
Constant Sweeping Rate
Varying Temperature
-0.5
0.05 K
0.002 T/s
-1
-1.2
-0.8
-0.4
0
0.4
µ 0 H (T)
0.8
1.2
Slow relaxation of the magnetisation
W. Wernsdorfer, Grenoble
Slow relaxation of the magnetisation …
ac: Ea= 142 K, 0 = 6.10-11 s
dc: Ea= 43 K, 0 = 2.10-8 s
The different values of 0
and Ea are attributed to
different relaxation
processes.
1
1.5 K
0.8
M/M s
Both ac and dc
measurements
indicate thermally activated
relaxation of the
magnetisation:
0.6
2.4 K
2.5 K
1.6 K
2.3 K
2.6 K
2.2 K
2.7 K
2.8 K
1.8 K
2.0 K
1.9 K
0.2
0
0.01
1.7 K
2.1 K
0.4
0.1
1
10
t (s)
100
1000
M vs. t plots along the b axis.
W. Wernsdorfer, Grenoble
Slow relaxation of the magnetisation in 1D …
1) New phenomenon
See Gatteschi et al. Angewandte Chemie, 2001
See Miyazaka, J. Am. Chem. Soc. 2002 and this conference
2) Ising slow relaxing chains can be viewed as
1D nanomagnets or nanowires (or single chain magnets) …
3) Prospects :
- mechanisms of the magnetisation reversal
- local origin of the anisotropy (CoII, FeIII, CoII-FeIII ?)
- applications for information storage ?
A flexible chemical system
Substitutions (pure or doped systems) :
• Co(II) by Zn(II) (dia)
• Fe(III) by Co(III) (dia)
Fe(III) / Co(III)
Co(II) / Zn(II)
Slow relaxation of the magnetisation in 1D …
4) Active field in progress …
- Search for quantum tunneling in 1D …
1
2.4 K
0.5
2.1
2 KK
s
M/M
2.3 K
2.2 K
2.0 K
0
1.9 K
1.8 K
1.7 K
1.6 K
1.5 K
-0.5
1.2 K
-1
0
0.2
1.3 K 1.4 K
0.4
µ 0 H (T)
0.6
0.8
Is the regime
becoming
independent
of temperature ?
Outline
• Introduction : molecular magnetism
- the molecular approach to nanosystems
• What a chemist must & can control ?
• From High Spin Molecules to SSM
- a systematic, rational, approach
- the photomagnetic way …
• Single Chain Magnets
• Conclusions
• Introduction :
• What a chemist must & can control ?
• From High Spin Molecules to SSM
- a systematic, rational, approach
- the photomagnetic way …
• Single Chain Magnets
• Conclusions and acknowledgements
Everything possible
in molecular magnetism ?
NO, but …
• Molecular engineering
• Molecules in the solid : molecular engineering
• Subtleties in structures and electronic properties
• But new exciting fields :
- multifunctional materials
- molecular electronics ; quantum computing
• We did the easiest
• The most exciting is coming, for young scientists …
Prospects (short term)
• New chemical systems with larger ∆E
• Improved Instrumentation (microSQUID + …)
Prospects (long term)
• Magnetic storage on ONE single molecule
• Quantum computing
Next « device » ?
Recording on one molecule !
Magnetic Tip
HSM "up"
HSM "down"
Surface
Exciting joint venture between
physicists and chemists
theoreticians and experimentalists
6ème PCRD, NOE
Proposal
Molecular
Approach to
Nanomagnets and
Multifunctional
Materials
D. Gatteschi, Florence
Scientific exchanges …
 To increase and to share new knowledges
 To improve mutual knowledge
 scientific …
 cultural …
 To better understand and respect each other
 To develop friendship and to protect peace
Science for peace …
(V. Balzani, Seeheim 2001)
Fuji-san, November 17, 2002
Hiroshima, November 23, 2002
Acknowledgements
My coworkers
Research groups quoted
French Ministery of Higher Education
C.N.R.S
European TMR Molnanomag and M3D, ESF
Tokyo Institute of Technology
Nagoya University
Organizers of the meeting
Professor Enoki
Professor Awaga
Professor Miyashita et alii
Kyoto November 14, 2002, Tofuku-ji garden
and YOU
for kind
attention
Kyoto November 2002
Imperial Palace Garden
Work partly done in
Pierre & Marie Curie University
Acknowledgements
to my coworkers
Dante Gatteschi
Chaire Blaise Pascal 2001
Valérie
Marvaud
Christophe
Cartier
dit
Moulin
Cyrille
Train
Anne
Bleuzen
Françoise
Villain
R. Lescouëzec
Virginie Escax, Juan Manuel Herrera, Fabrice Pointillart
A. Scuiller
Fabien Tuyèras, Guillaume Champion, Mannan Seuleiman, Hayat Hanouti
S. Ferlay
Cédric Desplanches,Natividad Galvez, Ricardo Moroni, Raquel Garde
V. Gadet