Molecular Magnetic Materials E-Book
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- Herausgeber: Wiley-VCH Verlag GmbH & Co. KGaA
- Kategorie: Fachliteratur
- Sprache: Englisch
A comprehensive overview of this rapidly expanding interdisciplinary field of research.
After a short introduction to the basics of magnetism and molecular magnetism, the text goes on to cover specific properties of molecular magnetic materials as well as their current and future applications. Design strategies for acquiring molecular magnetic materials with desired physical properties are discussed, as are such multifunctional materials as high Tc magnets, chiral and luminescent magnets, magnetic sponges as well as photo- and piezo-switching magnets.
The result is an excellent resource for materials scientists, chemists, physicists and crystal engineers either entering or already working in the field.
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Veröffentlichungsjahr: 2016
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Table of Contents
Cover
Title Page
Copyright
List of Contributors
Preface
Chapter 1: Magnetism
1.1 Origin of Magnetism
1.2 Macroscopic Approach
1.3 Units in Magnetism
1.4 Ground State of an Ion and Hund's Rules
1.5 An Atom in a Magnetic Field
1.6 Mechanisms of Magnetic Interactions
1.7 Collective Magnetic State
1.8 Applications and Research
References
Chapter 2: Molecular Magnetism
2.1 Introduction
2.2 Birth of the Topic: Exchange-Coupled Clusters
2.3 Evolution of the Topic: Molecule-Based Magnets
2.4 Burgeoning Topics: Single-Molecule Magnets
2.5 Single-Chain Magnets
2.6 Spin Crossover Complexes
2.7 Charge Transfer-Induced Spin Transitions
2.8 Multifunctional Materials
2.9 Future Perspectives
References
Chapter 3: High-Spin Molecules
3.1 Introduction
3.2 Strategies for High-Spin Molecules
3.3 High-Spin Molecules based on d-Metal Ions
3.4 High-Spin Molecules Based on f-Metal Ions
3.5 High-Spin Molecules Based on d–f Metal Ions
3.6 Conclusions and Perspectives
References
Chapter 4: Single Molecule Magnets
4.1 Introduction
4.2 Measurement Techniques
4.3 Rational Design of SMMs
4.4 Family of SMMs
4.5 Conclusions and Perspectives
References
Chapter 5: Magnetic Molecules as Spin Qubits
5.1 Introduction
5.2 Molecular Qubits
5.3 Schemes for Two-Qubit Gates
5.4 Conclusions and Perspectives
Appendix: The Basics
List of Acronyms
References
Chapter 6: Single-Chain Magnets
6.1 Introduction
6.2 The Very Basics
6.3 Synthetic Endeavors Toward SCMs
6.4 Theoretical Modeling
6.5 New Directions
6.6 Conclusions and Perspectives
References
Chapter 7: High-Tc Ordered Molecular Magnets
7.1 Introduction
7.2 TCNE-Based Molecule-Based Magnets
7.3 Prussian Blue Analogs
7.4 Hepta- and Octacyanido-based Molecule-based Magnets
7.5 Conclusions and Perspectives
References
Chapter 8: Thin Layers of Molecular Magnets
8.1 Introductory Remarks
8.2 Thin Layers of Single-Molecule Magnets
8.3 Thin Layers of Antiferromagnetic Spin Clusters
8.4 Thin Layers of High-Spin Cages
8.5 Thin Layers of Molecular Magnets with Extended Networks
8.6 Conclusions and Perspectives
Acknowledgments
References
Chapter 9: Spin Crossover Phenomenon in Coordination Compounds
9.1 Introduction
9.2 Spin Crossover in the Solid and Liquid States
9.3 Multifunctionality in Spin Crossover Compounds
9.4 Spin Crossover Phenomenon in Soft Matter
9.5 Spin crossover Phenomenon at the Nanoscale
9.6 Charge Transport Properties of Single-Spin Crossover Molecules
9.7 Conclusion
References
Chapter 10: Porous Molecular Magnets
10.1 Introduction
10.2 PMMs with Spin-State Switching
10.3 PMMs with Slow Relaxation of Magnetization
10.4 PMMs with Long-Range Magnetic Ordering
10.5 PMMs with Switching Between Ferromagnetism and Antiferromagnetism
10.6 PMMs with the Magnetism-Modified Through Postsynthetic Process
10.7 Conclusions and Perspectives
References
Chapter 11: Molecular Magnetic Sponges
11.1 Introduction
11.2 The First Molecular Magnetic Sponge Systems
11.3 CN-Bridged Molecular Magnetic Sponges
11.4 Molecular Magnetic Sponges with Bridging Ligands Other Than Cyanide
11.5 Conclusions and Perspectives
References
Chapter 12: Non-Centrosymmetric Molecular Magnets
12.1 Introduction
12.2 Synthetic Strategies Toward Non-centrosymmetric Magnets (NCM)
12.3 Physicochemical Properties of Non-centrosymmetric Magnets
12.4 Conclusion
Acknowledgment
References
Chapter 13: Molecular Photomagnets
13.1 Introduction
13.2 Photomagnetic Coordination Networks based on [
M
(CN)
x
] (
x
= 6 or 8)
13.3 Photomagnetic Polynuclear Molecules Based on [
M
(CN)
x
] (
x
= 6 or 8)
13.4 Conclusions and Perspectives
References
Chapter 14: Luminescent Molecular Magnets
14.1 Introduction
14.2 Electronic Structure of Lanthanide Ions
14.3 Luminescence of Lanthanide Ions
14.4 Magnetism of Lanthanide Ions
14.5 Synthetic Strategies to Obtain Luminescent SMMs
14.6 Luminescent Lanthanide Single Molecule Magnets
14.7 NIR Luminescent-Prolate Lanthanides
14.8 Conclusions and Perspectives
References
Chapter 15: Conductive Molecular Magnets
15.1 Introduction
15.2 Design of Metal Complexes with TTF-Containing Ligands
15.3 Hybrid Arrangements of Magnetic Layers and Conducting Stacked Layers
15.4 Conductive Magnetic Coordination Frameworks
15.5 Purely Organic Systems
15.6 Conclusions and Perspectives
References
Chapter 16: Molecular Multiferroics
16.1 Multiferroicity
16.2 Classification of Multiferroic Materials
16.3 Classification of Molecular Multiferroics
16.4 Metal–Organic Framework Compounds and Hybrid Perovskites
16.5 Charge Order Multiferroics
16.6 Conclusions and Perspectives
References
Chapter 17: Modeling Magnetic Properties with Density Functional Theory-Based Methods
17.1 Introduction
17.2 Theoretical Analysis of Spin Crossover Systems
17.3 DFT Methods to Evaluate Exchange Coupling Constants
17.4 DFT Methods to Calculate Magnetic Anisotropy Parameters
17.5 DFT Approaches to Calculate Transport Through Magnetic Molecules
References
Chapter 18: Ab Initio Modeling and Calculations of Magnetic Properties
18.1 Introduction
18.2
Ab Initio
Calculations
18.3 Spin Hamiltonian Calculations
References
Index
End User License Agreement
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Guide
Cover
Table of Contents
Preface
Begin Reading
List of Illustrations
Chapter 1: Magnetism
Figure 1.1 An elementary magnetic moment d
μ
=
I
d
S
due to an elementary current loop (a). An electron in a hydrogen atom orbiting with velocity
v
around the nucleus (a single proton) giving rise to the magnetic moment
μ
antiparallel to its orbital angular momentum
l
(b).
Figure 1.2
S
,
L
, and
J
for (a) 3d and (b) 4f ions according to Hund's rules (
n
is the number of electrons in the corresponding subshell).
Figure 1.3 Spatially symmetric bonding orbital of a diatomic molecule with antiparallel spins and spatially antisymmetric antibonding molecular orbital.
Figure 1.4 Superexchange interaction between metal ions mediated by the oxygen ligand. Dependent on the M1OM2 angle, the resulting coupling is antiferromagnetic (a) or weak ferromagnetic (b).
Figure 1.5 (a) Collinear antiferromagnet in case of symmetric exchange; (b) canted moments with weak net magnetization in case of Dzyaloshinsky–Moriya antisymmetric exchange.
Figure 1.6 RKKY coupling of localized moments mediated by the conduction electrons. The interaction shows an oscillatory behavior.
Figure 1.7 (a) Density of states
g
(
E
) for itinerant electrons: at
H
≠ 0, the spin sub-bands split, giving rise to Pauli paramagnetism. (b) Relationship between the exchange constant and ratio of the
r
ab
interatomic distance to the radius of the 3d shell.
Figure 1.8 Arrangements of magnetic moments in (a) ferromagnet, (b) antiferromagnet, (c) spin glass, (d) helical structure, and (e) spiral structure.
Figure 1.9 Temperature dependence of the relative magnetization
M
/
M
s
for different values of total angular momentum
J.
Figure 1.10 Three forms of the Curie–Weiss law for paramagnets: (a) magnetic susceptibility χ, (b) reciprocal susceptibility 1/χ, (c) χ
T
. Data of noninteracting moments (θ = 0), ferromagnetic (FM, θ =
T
t
> 0), and antiferromagnetic (AFM, θ = −
T
t
< 0) interaction are shown. Transition to the long-range order occurs at the temperature
T
t
, only paramagnetic region is shown.
Figure 1.11 (a) Temperature dependence of the magnetic susceptibility for an antiferromagnet (see text). (b) Different types of magnetization curves for an antiferromagnet;
H
a
is an anisotropy field,
H
c
is a critical field to reach saturation.
Figure 1.12 Magnetic coupling in ferrimagnetic Fe
3
O
4
.
Figure 1.13 (a) Schematic Sherrington–Kirkpatrick phase diagram; (b)
H–T
mean field phase diagram for spin glass showing the freezing lines of longitudinal and transverse spin components (for details, see text).
Figure 1.14 (a) Schematic shape of a hysteresis loop:
M
s
– magnetization of saturation,
M
R
– remanence, and
H
c
– coercivity; (b) approximate market share of the main types of applied magnetic materials.
Chapter 2: Molecular Magnetism
Figure 2.1 Crystal structure of [Cu
2
(OAc)
4
(H
2
O)
2
].
Figure 2.2 Diagrams of interactions between magnetic orbitals of transition metal ions in Prussian blue analogs, Ni
3
[Cr(CN)
6
]
2
·9H
2
O, KV[Cr(CN)
6
]
2
·2H
2
O, Cs
2
Mn[V(CN)
6
], and Cr
3
[Cr(CN)
6
]
2
·10H
2
O.
Figure 2.3 Molecular structure of [Mn
12
O
12
(OAc)
16
(H
2
O)
4
].
Figure 2.4 (a) Magnetization versus applied magnetic field for Mn
12
. (Thomas
et al
. [16]. Reproduced with permission of Nature Publishing Group.). (b) Out-of-phase magnetic susceptibility versus temperature for (PPh
4
)[Mn
12
O
12
(O
2
CPh)
16
(H
2
O)
4
]·8CH
2
Cl
2
at different frequencies of applied field. (Aubin
et al
. [23]. Reproduced with permission of American Chemical Society.)
Figure 2.5 Crystal structure of the [Mn
4
O
3
Cl
4
(O
2
CEt)
3
(py)
3
] “dimer.” Dashed lines represent intermolecular contacts.
Figure 2.6 Energy of magnetic states of the (Mn
4
)
2
dimer of SMMs as a function of applied magnetic field (a) and magnetic hysteresis loops recorded at 0.04 K and different sweep rates (b). (Wernsdorfer
et al
. [57]. Reproduced with permission of Nature Publishing Group.)
Figure 2.7 Crystal structure of [Co(hfca)
2
(NITPhOMe)] (a). Packing along
a
-axis (b). Packing along
c
-axis (c). For the sake of clarity, H-atoms were omitted.
Figure 2.8 Crystal structure of [Mn
2
(saltmen)
2
Ni(pao)
2
(py)
2
](ClO
4
)
2
(a). Packing along
b
-axis (b). H-atoms are omitted for clarity.
Figure 2.9 Energy diagram of the ground and excited states of the d
6
metal ion, showing the excitation and relaxation pathways that lead to the LIESST effect.
Figure 2.10 The {[Mn
II
Cr
III
(oxalate)
3
]
−
}∞ anionic layer responsible for ferromagnetism and the layer of columns of (BEDT-TTF
•
)
0.33+
radical cations responsible for conductivity (left) and the stacking of these layers (right) in the crystal structure of the multifunctional material, (BEDT-TTF)
3
[MnCr(oxalate)
3
]·CH
2
Cl
2
.
Chapter 3: High-Spin Molecules
Figure 3.1 Strategies for ferromagnetic interactions: (a) the strictly orthogonal approach between the
orbital of Cu
II
ion and the d
xy
orbital of V
IV
ion in [CuVO{(fsa)
2
en}(MeOH)] (the magnetic orbitals of other atoms were omitted for clarity); (b) the strictly orthogonal approach between the σ orbitals of Ni
II
ion (Only the
orbital is shown here) and the π
*
orbital of the semiquinone radical in [Ni(CTH)(DTBSQ)]
+
cation; (c) the accidental orthogonality achieved by the topological orthogonality in [Cu
3
(dcadpz)
2
(pz)(ClO
4
)
2
]
2+
cation. The magnetic orbitals φ
Cu
were rotated by 45°; (d) the orthogonal arrangement of two bidentate radicals by using the tetrahedral coordination geometry of Cu
I
for accidental orthogonality in [Cu(immepy)
2
]; (e) the spin polarization mechanism based on the 1,3,5-trihydroxybenzene bridging unit in [Cu
3
(talen)].
Figure 3.2 Schematic diagram of the influence of blocking ligand on the magnetic interaction.
Figure 3.3 Views of the {Mn
7
} (
4
) (a), {Mn
6
} (
11
) (b), and {Mn
19
} (
25
) (c) cores.
Figure 3.4 Perspective view of {Ho
2
} (
73
). The arrow represents the calculated directions of the magnetic moments of Ho
III
ions.
Figure 3.5 Plots of
J
versus dihedral angle. The solid line represents the fitting for the data in Table 3.9.
Chapter 4: Single Molecule Magnets
Figure 4.1 (a) Illustration of the double-well potential, in which the
S
= 10 state is split into
M
s
levels, thus causing a barrier to relaxation, shown as Δ
E
. Arrows represent the spins. (b) Illustration of the adiabatic process of quantum tunneling of the magnetization (QTM) and nonadiabatic process (direct process). See details in the main text. (c) Temperature and constant-field sweep-rate dependences. Magnetic hysteresis loops for single crystals of Mn
12
-
t
BuAc SMMs.(d) Left figure is an enlarged view of (c), and right figure is for Mn
12
-Ac SMMs. Hysteresis loop measurements at several temperatures reveal a fine structure of steps due to thermally assisted and pure QTM, which is due to the dominate energy level crossings. All step positions can be modeled by using a simple spin Hamiltonian.
Figure 4.2 (a) Temperature (
T
) dependence of χ
M
T
for an Mn
III
SIM. (b) Field dependence of
M
for an Mn
III
SIM. The solid lines in (a) and (b) were simultaneously analyzed by using the appropriate spin Hamiltonian. (Vallejo 2013 [21]. Reproduced with permission of Wiley.) (c) Magnetization versus
H
for [Mn
4
]
2
determined by using a micro-SQUID:
T
dependence in on top and the sweep rate dependence is on the bottom. (Wernsdorfer 2002 [22]. Reproduced with permission of Nature Publishing Group.) (d) Time decay of the magnetization of [Mn
12
] measured in the remanent state at different values of
T
.
Figure 4.3 (a) Temperature (
T
) dependence of the in-phase (χ′) (
T
) and out-of-phase components (χ″) of χ for (NBu
n
4
)[Mn
12
O
12
(O
2
CPh)
16
(H
2
O)
3
] at the frequencies (ν) indicated and (b) a plot of the natural logarithm of the inverse of the relaxation rate, ln(1/τ), versus
T
−1
using the χ″ versus
T
data from (a). Solid lines were fitted by using the Arrhenius equation (Eq. (4.20)). (Tasiopoulos 2005 [23]. Reproduced with permission of American Chemical Society.) (c) ν dependence of χ″ for K[(tpaMes)Fe] (
3
) and (d) Cole–Cole plot. The solid lines were simultaneously analyzed by using the generalized Debye model (Eqs. (4.17)(4.18)(4.19)), and (e) Arrhenius plot constructed from data from (c). The dashed lines represent data fitted for Orbach, direct, and Raman processes. The solid line represents a simultaneous fit of three processes.
Figure 4.4 (a) ESR spectra of a powdered sample of [Mn
12
] (
1
) recorded at different wavelengths (λ). (Caneschi 1991 [27]. Reproduced with permission of American Chemical Society.)
55
Mn NMR spectra of
1
at 1.4 K in an
H
of zero. (Furukawa 2001 [29]. Reproduced with permission of American Physical Society.) (c) Inelastic neutron scattering spectra of a deuterated [Fe
8
] (
2
) at 4.8 and 9.6 K. (Caciuffo 1998 [30]. Reproduced with permission of American Physical Society.) (d)
T
dependence of the asymmetry of
1
in a muon (μ) beam. The inset is the corresponding
T
dependence of the proton relaxation rate.
Figure 4.5 (a) Quadrupole approximations of the 4f-shell electron distribution for Ln
III
ions [39]. (b) The
6
H
15/2
ground state of Dy
III
ions split into the 2
J
+ 1 sublevels with quantum numbers of
M
J
caused by spin–orbit coupling and ligand field. (Feltham 2014 [40]. Reproduced with permission of Elsevier.). (c) Illustration of the ligand field (LF: yellow) that puts pressure on the 4f ions in the oblate (left; such as Tb
III
and Dy
III
) and prolate (right; such as Er
III
and Yb
III
) electron density (blue). The green arrows represent the orientations of the spin angular momentum coupled to the orbital moment.
Figure 4.6 Molecular structures of
1–6
. (a)
1
. (Cornia 2011 [41]. Reproduced with permission of Royal Society of Chemistry.) (b)
2
. (Gatteschi 2000 [42]. Reproduced with permission of Royal Society of Chemistry.) (c)
3
. (Harman 2010 [26]. Reproduced with permission of American Chemical Society.) (d)
4
, (e)
5
. (Demir 2012 [43]. Reproduced with permission of American Chemical Society.) (f)
6
.
Chapter 5: Magnetic Molecules as Spin Qubits
Figure 5.1 Magnetic field dependence of the four lowest-lying energy levels of the [CeEr] complex studied in [57]. The antiferromagnetic interaction between the two qubits is of the order of a few gigahertz. For an applied field of 470 mT, X-band photons (9.5 GHz) are resonant with the |00⟩ → |01⟩ transition, but not with the |10⟩ → |11⟩ transition, thus providing realization of a CNOT gate, where the left qubit acts as control. Inset: structure of the [CeEr] complex. (Aguilà
et al
. [57]. Reproduced with permission of American Chemical Society.)
Figure 5.2 (a) Schematic illustration of a possible setup for a pair of Cr
7
Ni qubits as proposed in [15]. Larger circles represent Ni ions. The
a
1
,
a
2
coefficients are single-ring properties and have opposite signs. The effective qubit–qubit exchange
J
eff
tends to zero as the permanent
j
1
and
j
2
couplings come close to a ratio
j
1
/
j
2
= −
a
2
/
a
1
. (b), (c) A possible setup for a register made of an ABAB… array of slightly inequivalent triangular MNMs [16]. If the B triangle is in the (computational) ground doublet (b), one has
a
1
=
a
2
= 0, and therefore
J
eff
= 0 independently of the ratio
j
1
/
j
2
. If the B triangle is in the (noncomputational) first-excited doublet (c),
J
eff
≠ 0. The dashed ellipse indicates that the enclosed spins form a nonmagnetic singlet. (d) Structure of the low-energy sector of the spectrum for noninteracting (left and right) and interacting (center) triangles. The dashed box in (d) encloses the logical states of the AB dimer,
together with the excited states
exploited in the C-gate. (Carretta
et al
. [16]. Reproduced with permission of American Physical Society.)
Figure 5.3 (a) Mapping of a spin-1 target Hamiltonian
onto an equivalent spin-1/2 Hamiltonian
, and encoding of
into the spin-qubit chain ABAB… (b) Mapping of the Hubbard model onto the spin-1/2 Hamiltonian
. (Santini
et al
. [62]. Reproduced with permission of American Physical Society.)
Figure 5.4 (a) Scheme of a pair of Cr
7
Ni rings, which encode two qubits, linked by a Ni
2+
complex. Two-qubit gates are performed by a selective excitation/de-excitation of the Ni ion, conditioned to the state of the qubits. The effective Ni–ring couplings are linear combinations of the Ni–Cr and Ni–Ni couplings,
J
Ni
and
J
Cr
. (b) Molecular structure of a variant where the two Cr
7
Ni qubits are inequivalent, as the planes of the two rings are not parallel. The black arrow indicates the principal anisotropy axis (
z
) of the central Ni spin, determined by diagonalization of the zero-field-splitting tensor calculated
ab initio
. H atoms and CH
3
groups on the rings are not shown, O are red, F are yellow, C are gray, N are blue, Cr are green, and Ni are violet. (c) The plots map the modulus of exemplary orbitals for the Ni ion (red surface) and the ring (blue surface), providing large contributions to the ring–Ni exchange couplings
J
Cr
(left) and
J
Ni
(right). In this variant, the principal anisotropy axis of the central Ni spin points toward a ring. (Chiesa
et al
. [68]. Reproduced with permission of Nature Publishing Group.)
Figure 5.5 Simulated experiment where a pulse sequence is applied to a crystal of Cr
7
Ni–Ni–Cr
7
Ni molecules to reproduce
, where
is the two-site transverse-field Ising model (
). The plots show the time oscillations of the longitudinal average magnetization that characterize the evolution from a starting ferromagnetic state, corresponding to molecules thermally initialized in
. The exact result (continuous line) corresponding to 10 Trotter–Suzuki steps is well reproduced by the simulation, which is based on a master equation formalism accounting for decoherence of rings and switch.
Figure 5.6 Plot illustrating the effect of the external electric potential on the polyoxometalate MNM [PMo
12
O
40
(VO)
2
]q
−
. If the number of electrons delocalized on the core is even (low
V
g
), then their spins pair antiferromagnetically into a singlet state (open circle), and the two vanadyl spins are nearly decoupled. If an electron is injected into the core (high
V
g
), the resulting unpaired spin 1/2 and the two vanadyl spins are subject to exchange interactions that produce a three-spin evolution ψ
123
(
t
). By appropriately choosing the duration of the potential pulse, one can produce a variation of the qubit state corresponding to a
gate.
Chapter 6: Single-Chain Magnets
Figure 6.1 Concepts of SCM physics illustrated by a chain of ferromagnetically coupled Ising spins: (a) definition of the correlation length ξ with the position of the domain walls (DW), (b) spin-flip adjacent to a chain defect (purple cross) that generates a DW in the finite regime. (c) Hysteresis loops for [Mn
2
(5-MeOsaltmen)
2
Ni(pao)
2
(phen)](PF
6
)
2
obtained on a single-crystal measured along the easy axis of magnetization (d
H
/d
t
= 280 mT s
−1
). (d) Field dependence of the single-crystal susceptibility obtained from magnetization measurements at 2.9 K (dots). The susceptibility deduced from relaxation data after normalization is also shown (squares). The inset shows the magnetic susceptibility data of a polycrystalline sample at three different applied fields. The straight line gives the activation energy, here Δ
ξ
/
k
B
= 18 K. (Coulon 2009 [5]. Reproduced with permission of American Physical Society.)
Figure 6.2 Selection of conceptually different SCMs discussed in the main text. (a) [Co(hfac)
2
(NITPhOMe)] (F atoms omitted for clarity), (b) [Mn
III
(TMAMsaltmen)(TCNQ)]-(ClO
4
)
2
(trimethylammonio groups omitted for clarity); (c) [Dy(hfac)
3
{NIT(C
6
H
4
OPh)}], (d) [Mn
2
(saltmen)
2
Ni(pao)
2
(py)
2
]-(ClO
4
)
2
; (e) (DEA)
4
Fe
II
Re
IV
Cl
4
(CN)
2
; (f) {[(tptz)Mn
II
(H
2
O)Mn
III
(CN)
6
]
2
Mn
II
(H
2
O)
2
}
n
·4
n
MeOH·2
n
H
2
O (g) {[U
V
O
2
(salen)py][Mn(py)
4
]}NO
3
; (h) [Fe(ClO
4
)
2
{Fe(bpca)
2
}](ClO
4
); (i) [Mn(TPP)O
2
PHPh]·H
2
O; color codes: U, pale green; Dy, turquoise; Re, pale blue; Ni, blue green; Co, purple; Fe, orange; Mn, pink; Cl, pale green; P, yellow; F, pale green; O, red; N, blue; C, gray. Hydrogen, co-crystallized solvent molecules and noncoordinated counterions are omitted for clarity.
Figure 6.3 (a) Qualitative energy landscape,
H
(θ) =
DS
2
cos
2
(θ), with a reference thermal energy
k
B
T
smaller than the total anisotropy barrier Δ
A
. Horizontal segments indicate the corresponding levels for a quantum spin
S
= 3. (b) Unitary sphere representing the configurations along which a classical spin can point; in the presence of uniaxial anisotropy, the spin spends most of its time in the neighborhood of the “north” and “south” pole, highlighted in grey.
Figure 6.4 (A) Schematic view of the magnetization reversal from one ground-state (GS) configuration (a) to the energetically degenerate one (f); time is thought to evolve from (a) to (f). Intermediate configurations represent the nucleation of a DW (b), its step-by-step propagation (b–e), and final annihilation (e–f). Each process is a stochastic event and typically implies to overcome of an energy barrier (e.g., c to d) if |
D
| > 4
J
/3 (sharp DWs). (B) The diffusion of a sharp DW occurring by thermally activated steps is schematized with an effective potential consisting of peaks (Δ
A
being the difference of energy between peak and valleys). The energy associated with each spin configuration in the left panel is marked with a bullet on the schematized potential
V
(
x
). It is worth noting that the potential at the segment edges is simply schematized and not calculated from a model. (C) Scheme of a broad DW (a) with the associated flat potential (b), illustrating that the diffusion coefficient does not obey an activated law in the |
D
| < 4
J
/3 limit.
Figure 6.5 (a) Scheme of two domains in the canted antiferromagnetically coupled spin chain, [Mn(TPP)O
2
PHPh]·H
2
O giving rise to opposite magnetization along the
b
crystallographic axis. (b) Semilogarithmic plot of the temperature dependence of the correlation length along the
b
and
c
eigendirections of the magnetization, superimposed to the χ′
b
T
product measured along
b
(vertically rescaled for a better comparison). (Bernot 2008 [23]. Reproduced with permission of American Chemical Society.)
Figure 6.6 X-ray near-edge absorption (XANES) and the derived dichroic signals, rescaled as percentage of the absorption in the continuum, where the measured XANES signal is equal to 1, at the metal K-edge of [Co(hfac)
2
(NITPhOMe)] (a) and [Mn(hfac)
2
(NITPhOMe)] (b). The color lines correspond to the spectra recorded on the
P
3
1
crystals while the gray lines are those of the enantiomeric
P
3
2
crystals. The temperature is 5 K and the applied magnetic field is 3 T. (Sessoli 2015 [74]. Reproduced with permission of Nature Publishing Group.)
Chapter 7: High-Tc Ordered Molecular Magnets
Figure 7.1 Structural formula of TCNE (a). Atomic spin distribution of [TCNE]
•−
, determined from the single-crystal-polarized neutron diffraction. The unit of the distribution is
μ
B
Å
−2
. Views to the plane (b) and edge (c) of [TCNE]
•−
. (Miller [2]. Reproduced with permission of Elsevier.)
Figure 7.2 (a) Idealized possible structural model of V
II
[TCNE]
•−
z
[TCNE]
2−
1−
z
/2
for the limiting case (
z
= 1). (Miller [27]. Reproduced with permission of Elsevier.) (b) Field-cooled and zero-field-cooled magnetization plots. (Miller [2]. Reproduced with permission of Elsevier.)
Figure 7.3 Schematic crystal structures of Prussian blue analogs: (a) M
A
II
[M
B
III
(CN)
6
]
2/3
·
z
H
2
O and (b) A
I
M
A
II
[M
B
III
(CN)
6
]. (Tokoro and Ohkoshi [4]. Reproduced with permission of Royal Society of Chemistry.)
Figure 7.4 Photograph of a polycrystalline sample of nominal K
0.058
V
II
0.57
V
III
0.43
–[Cr
III
(CN)
6
]
0.79
·(SO
4
)
0.058
·0.93H
2
O composition being attracted to a Teflon-covered magnet in air at room temperature (a) and the field-cooled magnetization curves for this magnet (b). (Hatlevik
et al
. [47]. Reproduced with permission of Wiley.)
Figure 7.5 Powder X-ray diffraction pattern (a) and temperature dependence of the zero-field-cooled magnetization (b) of KV
II
[Cr
III
(CN)
6
]·2H
2
O·0.1KOTf. (Holmes and Girolami [46]. Reproduced with American Chemical Society.)
Figure 7.6 Three-dimensional network of Mn
II
2
[Mo
III
(CN)
7
]·(pym)
2
·2H
2
O ferrimagnet with
T
c
= 47 K (a) and magnetic properties, including magnetization versus temperature curve at 10 G, and magnetization versus applied magnetic field plot at 2 K of the isostructural V
II
2
[Mo
III
(CN)
7
]·(pym)
2
·4.5H
2
O ferrimagnet with
T
c
= 110 K (b). (Tomono
et al
. [61]. Reproduced with permission of American Chemical Society.)
Figure 7.7 (a) Field-cooled magnetization curves under an external magnetic field of 10 Oe for K
0.10
V
II
0.54
V
III
1.24
[Nb
IV
(CN)
8
]·(SO
4
)
0.45
·6.8H
2
O (
T
c
= 138 K). (Kosaka
et al
. [63]. Reproduced with permission of American Chemical Society.) (b) K
0.59
V
II
1.59
V
III
0.41
[Nb
IV
(CN)
8
]·(SO
4
)
0.50
·6.9H
2
O (
T
c
= 210 K). (Imoto
et al
. [64]. Reproduced with permission of Wiley.) (c) Together with the schematic structural model valid for both compounds. Triangle symbols in (b) show the zero-field-cooled magnetization, while the circle symbols relate to the remnant magnetization.
Chapter 8: Thin Layers of Molecular Magnets
Figure 8.1 Molecular structure of magnetic molecules treated in this chapter: (a) Fe
4
H, (b) Fe
4
C5, (c) Fe
4
Ph, (d) TbPc
2
, (e) Er(trensal), (f) Dy
2
Sc@C80, (g) Cr
7
Ni, (h) Fe
14
bta, and (i) Gd
4
Ni
8
. The heterometal site in (g) is represented at an arbitrary position, but is actually disordered. Hydrogen atoms are omitted.
Figure 8.2 (a) Electronic transitions from the spin–orbit split 2p core level to the spin-polarized 3d band of a magnetized materials probed by X-rays with helicity parallel (μ
+
) or antiparallel (μ
−
) to the sample magnetization (
L
2,3
edges). (b) XAS and XMCD at the
L
2,3
edges of Co. (van der Laan and Figueroa [112]. Reproduced with permission of Elsevier.)
Figure 8.3 (a) STM topographic image of Fe
4
Ph (0.8 ML) sublimated onto Au(111), measured at 3.5 V bias, 10 pA, and 30 K. (b) Field-dependent XMCD signal at the maximum of Fe
L
3
edge for a 0.5-ML sample of Fe
4
Ph sublimated onto Au(111), measured at 0.68 K with magnetic field at 0° and 45° from the surface normal (the full hysteresis loop was measured in about 90 min). Data recorded with increasing (decreasing) field are indicated as solid (empty) symbols. (Malavolti
et al
. [91]. Reproduced with permission of American Chemical Society.) STM topographic images of Fe
4
H deposited by ESD on h-BN/Rh(111) at different coverages ranging from isolated molecules (c,d) to islands (e,f) to an almost complete ML (h,i). The regular hexagonal pattern with periodicity of about 3.2 nm is the moiré superstructure of the monoatomic layer of h-BN. The height profile along the dashed line in (f) is shown in (g). All scans have been performed with 2.5-V bias, at 5 pA and 6.7 K in (c,d) and at 10 pA and 1.9 K in (e–i). (Erler
et al
. [102]. Reproduced with permission of American Chemical Society.)
Figure 8.4 (a,b) Field-dependent magnetization curves (500 Oe s
−1
) recorded by XMCD at the maximum of Tb
M
5
edge on an ML of functionalized TbPc
2
on silicon at the given temperatures and angles between the magnetic field and the surface normal. Data for a bulk sample are also presented in (b) for comparison. (c) Absolute value of the difference between upfield and downfield magnetization values plotted in (b), highlighting the larger hysteresis opening in the ML. (Mannini
et al
. [81]. Reproduced with permission of Nature Publishing Group.)
Figure 8.5 Artistic view of Cr
7
Ni rings anchored on HOPG surface covered by an ML of anionic surfactants (by courtesy of C. Muryn, University of Manchester).
Figure 8.6 Entropy variation between 6 and 0 T estimated for TFs and MLs of Gd
4
Zn
8
and Gd
4
Ni
8
single-molecule coolers by low temperature XMCD experiments. Data obtained by traditional magnetometry on microcrystalline powder samples are also given for comparison. (Corradini
et al
. [185]. Reproduced with permission of Wiley.)
Figure 8.7 Scheme of Langmuir–Blodgett film deposition and how it can be used to build up films of 2D cyanometallate networks.
Figure 8.8 Sequential assembly of {Fe(pz)[M(CN)
4
]} (M = Ni, Pd, or Pt) thin films displaying room-temperature spin crossover and host–guest properties. (Bousseksou
et al
. [218]. Reproduced with permission of Royal Society of Chemistry.)
Chapter 9: Spin Crossover Phenomenon in Coordination Compounds
Figure 9.1 (a) Schematic illustration of the spin-state switching in iron(II) coordination compounds. Switching takes place between the paramagnetic
5
T
2g
HS state and the diamagnetic
1
A
1g
LS state induced by a variation of temperature, application of pressure, or light irradiation. Both states are characterized by exhibiting different magnetic, dielectric, optical (color), and structural (volume) properties. (b)
State-of-the-art
laboratory prototypes for storage and display information based on iron(II) SCO compounds. The writing and erasing of information takes place by an input of temperature, pressure, or light. The information is displayed as a change of color.
Figure 9.2 Example for an iron(II) spin crossover complex with thermal hysteresis loop. For this amphiphilic complex, the up to 50-K-wide hysteresis is due to a rotation of the axial pyridine ligand and associated changes in the hydrogen bond network between the polar head groups. The volume change upon spin transition is negligible for this system. The steps are due to a disorder of one pyridine and one of the alkyl chains in the HS state. (Schlamp 2011 [35]. Reproduced with permission of Royal Society of Chemistry.)
Figure 9.3 (a) Magnetic properties in the form of
χ
M
T
versus
T
for the 3D clathrate [Fe(dpe)Pt(CN)
4
]·G (G = naphthalene, anthracene, phenazine). Schematic illustration of the porous polymer emphasizing the guest clahtration. (Muñoz-Lara 2012 [86]. Reproduced with permission of Wiley.) (b) Color change detection of the adsorption/desorption of guest molecules in the SCO 3D polymer {Fe
3
(tr
2
ad)
4
[Au(CN)
2
]
2
}[Au(CN)
2
]
4
·8H
2
O. Pink and brown indicate the LS and HS states, respectively. (Muñoz-Lara 2012 [88]. Reproduced with permission of American Chemical Society.)
Figure 9.4 (a) Schematic illustration of the structure of compounds [Fe(C
n
-tba)
3
]X
2
and [Fe(II)(4-octadecyl-1,2,4-triazole)
3
](tosylate)
2
·2H
2
O. (Seredyuk 2006 [94]. Reproduced with permission of American Chemical Society.). Representation of the columnar mesophase of compounds [Fe(C
n
-tba)
3
]X
2
in the liquid crystalline state. (b) Change of color in the [Fe(C
n
-tba)
3
]X
2
SCO LC films around 60 °C and in the [Fe(II)(4-octadecyl-1,2,4-triazole)
3
](tosylate)
2
·2H
2
O gel in decane. (Roubeau 2004 [97]. Reproduced with permission of Wiley.)
Figure 9.5 Illustration of the synthetic methods used to obtain nano-objects exhibiting spin crossover properties.
Figure 9.6 (a) Magnetic properties in the form of (χ
M
T
) molar magnetic susceptibility versus temperature (
T
) for nanocrystals and bulk compound [Fe(pz)Pt(CN)
4
] pz = pirazine. (b) Change of color upon spin transition in the nanocrystals, red (LS) and yellow (HS). (c) TEM image of the nanocrystals showing the regular square morphology. (Boldog 2008 [116]. Reproduced with permission of Wiley.)
Chapter 10: Porous Molecular Magnets
Figure 10.1 (a) Scheme of a molecular magnet, whose overall magnetism can range from that of a metal ion/cluster to that characteristic of a 3D magnetic ordering depending on the magnetic interactions. (b) The guest/coordinated molecule-triggered magnetism alterations essentially arise from the effect of guest/coordinated molecule on the ligand field strength, coordination number, and magnetic coupling of the metal ions.
Figure 10.2 (a) [Fe{M
II
(CN)
4
}(pz)] framework featuring 2D [Fe{M
II
(CN)
4
}] grids pillared by pz ligands. (b) Interaction between pz guest molecule and two pz-bridges. (c) CS
2
guest molecule involved in interacting with both pz bridges and Pt
II
centers. (d) Quasi-reversible interconversion between anhydride and maleic acid within the framework.
Figure 10.3 (a) Triakis tetrahedral [Co
8
(μ
4
-O)Q
12
]
2+
cluster and the resulting 3D
dia
framework via π–π interactions between two Q
−
ligands. (b) [Co
8
(μ
3
-OH)
4
(SO
4
)
2
(H
2
O)
4
]
8+
cluster of MCF-32 and the corresponding (3,12)-connected 3D framework.
Figure 10.4 Schematic presentations of pillared-layer magnets with flexible (a) and rigid (b) pillars, as exemplified by chdc
2−
and ina
−
ligands, respectively.
Figure 10.5 (a) 3D framework of [Co
3
(OH)
2
(C
4
O
4
)
2
] view along the chain direction. (b) Antiferromagnetic structure of Co1 sublattice observed at 1.8 K for the hydrated form. (c) Spin “idle” phase of Co1 observed at 6.0 K for both of hydrated and dehydrated forms. (d) Ferromagnetic structure of Co1 sublattice found at 1.8 K for the dehydrated form.
Figure 10.6 (a) Construction of 3D robust double-wall framework by linking magnetic rods via pybz linkers. (b) Scheme of intra- and interchain magnetic couplings and their effects on the magnetic properties of the bulk material.
Chapter 11: Molecular Magnetic Sponges
Scheme 11.1 Concept of the self-assembly of a molecular magnetic sponge system from a solution of the preorganized paramagnetic building blocks (a). Solvent-induced polymerization of the 1D molecular magnetic sponge (b) into a coordination layer/double chain (c). Paramagnetic building blocks – large gray squares, solvent – small squares, bridging ligands – small squares attached to large squares.
Figure 11.1 Suggested structural changes and the related magnetic properties in the two-step transformation of [Co
II
Cu
II
(obbz)(H
2
O)
4
]·2H
2
O (a) into [Co
II
Cu
II
(obbz)(H
2
O)
3
] (b) and [Co
II
Cu
II
(obbz)(H
2
O)] (c). The dotted lines show the hydrogen bonds between the coordinated H
2
O and O
COO
−
. The solid lines show the new coordination bonds in the second dehydrated phase. (Kahn 1999 [2]. Reproduced with permission of Wiley.)
Figure 11.2 (a) Reversible structural changes between hexanuclear Fe
III
4
Fe
II
2
molecules and 1D chiral chains. (b) Magnetic properties at
H
DC
= 1 kOe (main) and
T
= 2 K (inset). (Zhang 2009 [41]. Reproduced with permission of American Chemical Society.)
Figure 11.3 Reversible structural changes from the 2D [Mn
II
(NNdmenH)(H
2
O)][Cr
III
(CN)
6
]·H
2
O to the 3D [Mn
II
(NNdmenH)][Cr
III
(CN)
6
] including (a) the scheme of the decorating ligand, (b) crystal packing, and (c) topochemical reaction. Cr, pink; C
CN
, purple; Mn, green; N
CN
, dark green; H
2
O, orange;
N
,
N
-dmenH, gray. The red-orange arrows show the direction of the additional bridge formation upon dehydration.
Figure 11.4 Structural transformation in {[Mn
II
(dpop)]
3
[Mn
II
(dpop)(H
2
O)][Mo(CN)
7
]
2
}·13.5H
2
O. Crystal packing diagram along the 1-nm channels (a) and formation of new Mn–NC–Mo linkage (b) (dpop omitted in (b) for clarity).
Figure 11.5 Solvent-sensitive magnets Cu
II
3
[W
V
(CN)
8
]
2
(pym)
2
·8H
2
O and Cu
II
3
[W(CN)
8
]
2
(pym)
2
·3/2PrOH·9/4H
2
O: crystal packing of
7
(a), reversible structural transformations (b), and magnetic properties of
7
and
7solv
(c). (Ohkoshi 2007 [45]. Reproduced with permission of American Chemical Society.)
Figure 11.6 Reversible structural transformation between {[Mn
II
2
(imH)
2
(H
2
O)
4
[Nb
IV
(CN)
8
]}·4H
2
O and {[Mn
II
2
(imH)
2
[Nb
IV
(CN)
8
]}. (Pinkowicz 2008 [47]. Reproduced with permission of American Chemical Society.)
Figure 11.7 Structural transformation in the {[Mn
II
(pydz)(H
2
O)
2
][Mn
II
(H
2
O)
2
][Nb
IV
(CN)
8
]·2H
2
O}
n
molecular magnetic sponge.
Figure 11.8 Reversible structural changes upon dehydration of [{Mn
II
(HL)(H
2
O)}
2
Mn
II
{Mo(CN)
7
}
2
]·2H
2
O: the structural formula of the decorating ligand HL (a), structural diagram along the channels of the pristine and dehydrated forms (b), and side view of the organization of H
2
O molecules in the channel (c).
Chapter 12: Non-Centrosymmetric Molecular Magnets
Figure 12.1 Crystal classes and new expected physicochemical effects arising from the interaction between properties that might exist in non-centrosymmetric materials [2] and long-range magnetic order.
Figure 12.2 Different strategies toward non-centrosymmetric systems.
Figure 12.3 A one-dimensional non-centrosymmetric compound obtained by using a chiral radical bridging ligand (a); [22] An octacyanido-based two-dimensional non-centrosymmetric compound obtained by using a chiral coligand (b) [23].
Figure 12.4 Enantioselective self-assembly of oxalate-bridged compounds.
Figure 12.5 MSHG (a) and magnetochiral dichroism (b) in oxalate-based systems [40, 51].
Figure 12.6 Scheme of a ferroelectric (a), ferromagnetic (b), and single-phase multiferroic and magnetoelectric system (c) with the corresponding orders and symmetry properties (adapted from [74]).
Figure 12.7 Structure (a), ferromagnetic (b), and ferroelectric (c) properties of an oxalate-based system. (Pardo 2014 [18]. Reproduced with permission of Wiley.)
Chapter 13: Molecular Photomagnets
Scheme 13.1 (a) Schematic energy diagram of a photomagnetic system. IC corresponds to intersystem crossing and Δ is the thermal energy barrier. (b) Spin crossover in a Fe
II
complex and electron transfer in the bimetallic cyanide-bridged Co/Fe pair.
Figure 13.1 Photoinduced magnetic pole inversion in (Fe
0.40
Mn
0.60
)
1.5
Cr(CN)
6
·7.5H
2
O. (a) Schematic of the crystal structure and superexchange interactions (Ohkoshi 1997 [38]. Reproduced with permission of American Institute of Physics.). (b) Saturation magnetizations for (Fe
x
Mn
1–
x
)
1.5
Cr(CN)
6
as a function of
x
. Calculated (line) and experimentally observed (circle). (c) Magnetization versus temperature before (black circles), after irradiating with light (white circles), and thermal treating (triangles) (Ohkoshi 1999 [39]. Reproduced with permission of American Chemical Society.).
Figure 13.2 Photomagnetic phenomenon in Rb
x
Mn[Fe(CN)
6
]
(
x
+2)/3
·
z
H
2
O. (a) Magnetization versus temperature curves (upper) and magnetization versus irradiation time plot at 3 K (lower). Before irradiating (open squares), after irradiating with 532-nm light (black circles), after irradiating with 410-nm light (open circles), and after thermal treating (black squares). (b) Schematic illustration of the mechanism, crystal structure, and spin arrangement. (Tokoro 2008 [51]. Reproduced with permission of American Chemical Society.)
Figure 13.3 Visible light-induced reversible photomagnetism in Cu
2
[Mo(CN)
8
]·8H
2
O. (a) Schematic of the crystal structure. (b) Magnetization versus temperature curves before (black line) and after irradiating with 473 nm light (gray line), and after irradiating with 658, 785, or 840 nm light (bold line). (c) Mechanism of the photoinduced charge transfer in a class II mixed-valence complex.
E
h
ν1
and
E
h
ν2
indicate the photon energy of 473-nm and 658-, 785-, or 840-nm lights, respectively. (Ohkoshi 2012 [5]. Reproduced with permission of American Chemical Society.)
Figure 13.4 Photomagnetic phenomenon in {[Co(tmphen)
2
]
3
[Fe(CN)
6
]
2
}. (a) Scheme of the crystal structure. (b) Temperature dependence of the χ
T
measured in the dark (dark circles) and after 1 h of white light irradiation (white circles) under 1 T. (Funck 2011 [70]. Reproduced with permission of American Chemical Society.)
Figure 13.5 Photomagnetic properties in {[(pzTp)Fe
III
(CN)
3
]
4
[Co
II
(TpOH)]
4
[ClO
4
]
4
}·13DMF·4H
2
O (a) Schematic view of the crystal structure. (b) χ
T
versus temperature plots before (white circles), after irradiating (gray circles), and after thermal quenching (black circles). (Li 2008 [81]. Reproduced with permission of American Chemical Society.)
Figure 13.6 Photomagnetic properties in [(Tp)Fe
III
(CN)
3
Co
II
(PY5Me
2
)][OTf] (a) Schematic view of the crystal structure. (b) χ
T
versus temperature plots before (white circles), after irradiating (gray circles). (Koumousi 2014 [90]. Reproduced with permission of American Chemical Society.)
Chapter 14: Luminescent Molecular Magnets
Figure 14.1 Energy diagram of the electronic structure of lanthanide ions.
Figure 14.2 Illustration of the photophysical mechanisms, which can be involved in the sensitization by antenna effect of the lanthanide luminescence. ic, Internal conversion; isc, intersystem crossing.
Figure 14.3 (a) Molecular structure of [Zn(NO
3
)(
L
1
)Dy(NO
3
)
2
(H
2
O)] (
1
) [Color codes: gray, C; blue, N; red, O; H atoms are removed for clarity]. (b) Components of the
4
F
9/2
→
6
H
15/2
transition arising from the first (cyan) and second (pink)
4
F
9/2
sublevels to the
6
H
15/2
multiplet. (c) Molecular structure of [Tb{ZnBr(
L
2
)}
2
(MeOH)]
−
(
2
) [Color codes: gray, C; blue, N; red, O; brown, Br; H atoms and counterions are removed for clarity]. (d) Summarized energy level diagram of
J
z
sublevels estimated from the emission fine structure (black sticks) and the calculations based on the anisotropic Hamiltonian (red sticks).
Figure 14.4 (a) Structure of the ligand H
2
L
3
(center) and corresponding derivatives obtained by varying the synthetic conditions (i) H
2
L
3
/Zn(OAc)
2
·2H
2
O/Ln(NO
3
)
3
·
n
H
2
O, 1 : 1 : 1, in MeOH (Ln = Tb, Dy, Er, Yb). (ii) H
2
L
3
/Zn(NO
3
)
2
·6H
2
O/Ln(NO
3
)
3
·
n
H
2
O, 1 : 1 : 1, in MeOH (Ln = Er, Nd). (iii) H
2
L
3
/Zn(NO
3
)
2
·6H
2
O/Ln(NO
3
)
3
·
n
H
2
O/9-An/Et
3
N. 1 : 1 : 1 : 1 : 1, in CH
3
CN (Ln = Tb, Dy, Er, Yb). (iii) Using the same conditions as in part i and recrystallization in CH
3
CN (Ln = Yb). (iv) The same conditions as in part iii (Ln = Nd). (v) H
2
L
3
/Zn(ClO
4
)
2
·6H
2
O/Nd(NO
3
)
3
·6H
2
O//9-An/Et
3
N, 1 : 1 : 1 : 1 : 1, in MeOH (Ln = Nd). (b) (top) Molecular structure of one of the dinuclear complexes
R
,
R
-
16
and
S
,
S
-
17
, showing their enantiomeric relationship. (bottom) View of the packing arrangement of the dinuclear complexes along the
b
crystallographic axis, emphasizing the two crystallographically independent complexes shown in black and gray.
Figure 14.5 View of the molecular structure of (a) LnDOTA (Ln-
L
4
) along the pseudo-
C
4
axis; (b) Ln(trensal) (Ln-
L
5
) along the crystallographically imposed
C
3
axis (carbon atoms are without labels).
Figure 14.6 (a) Molecular structure of [Er(
L
8
)(H
2
O)]ClO
4
·3H
2
O (
9
) [Color codes: gray, C; blue, N; red, O; orange, P; H atoms, counterions and solvent molecules of crystallization are removed for clarity]. (b) The NIR emission spectrum of the
4
I
13/2
→
4
I
15/2
transition with the experimental decompositions. The
M
J
states are obtained from fitting dc magnetic susceptibility (green), ac magnetic susceptibility (orange) and photoluminescence (PL, purple). (c) Molecular structure of [Yb(
L
9
)
3
]·11H
2
O (
10
) [Color codes: gray, C; blue, N; red, O; H atoms and solvent molecules of crystallization are removed for clarity]. (d) Solid-state luminescence spectrum of
10
in the NIR spectral range at 77 K (λ
ex
= 400 nm, 25 000 cm
−1
) with experimental decompositions and scheme of the energy diagram as extracted from spectroscopic measurement (PL) calculated from crystal field fitting of the magnetic susceptibility using Stevens parameters (dc) and from dynamic magnetic susceptibility (ac). (e) Molecular structure of [Yb(tta)
2
(
L
10
)(
L
11
)]
2
(
11
) [Color codes: gray, C; blue, N; red, O; yellow, S; green, F; H atoms and solvent molecules of crystallization are removed for clarity]. (f) Energy splitting of the
m
J
level of the
2
F
7/2
ground state multiplet determined from the dc fit (Δ = 3 cm
−1
) (dc), ac fit (Δ = 14 cm
−1
) (ac) and the luminescence spectrum (Δ = 16 cm
−1
) (PL).
Figure 14.7 (a) Molecular structure of [Yb
2
(hfac)
6
(
L
12
)
2
] (
12
) [Color codes: gray, C; blue, N; red, O; yellow, S; light green, F; H atoms are removed for clarity]. Splitting of the fundamental
2
F
7/2
Yb centered level calculated with the Stevens technique. On the right, the solid-state 77 K emission spectrum is represented with an appropriate shift of the energy scale. (b) Molecular structure of [Yb(hfac)
3
(
L
13
)] (
13
) [Color codes: gray, C; blue, N; red, O; yellow, S; light green, F; H atoms are removed for clarity]. Energy splitting of the fundamental
2
F
7/2
Yb centered level calculated with the Stevens technique from the dc data (on the left), by CASSCF/RASSI-SO calculations (on the middle). On the right, the solid-state 77 K emission spectrum is represented with an appropriate shift of the energy scale.
Chapter 15: Conductive Molecular Magnets
Figure 15.1 Several representative electron donor and acceptor molecules.
Figure 15.2 Several structural arrangements for the design of conductive molecular magnets: (i) hybrid (alternating) arrangements of magnetic layers and conducting stacked layers, (ii) the construction of conductive magnetic frameworks with donor/acceptor building blocks, and (iii) the framework design based on a perpendicular arrangement of magnetically ordering pathway and conducting pathway.
Figure 15.3 TTF-containing ligands, where the groups (a)–(f) are classified by chemical spacers linking coordination sites (groups) and the TTF skeleton: (a) alkylthio, (b) amide, (c) ethenyl, (d) ethynyl, (e) imine, and (f) direct or fused connection.
Figure 15.4 Molecular structures of discrete metal complexes (a–h) and polymeric metal complexes (i–m) with TTF-containing ligands:
trans-
[Cu
II
(hfac)(TTF-CHCH-4-py)
2
] [18] (a),
cis
-[Cu
II
(hfac)
2
(TTF-CHN-2-py)] [19] (b), [Co
II
(CH
3
CN)(Me
2
-TTF-bis-PPh
2
)
2
]
2+
[18, 20] (c), [Ru
III
(salen)(PPh
3
)(TTF-CHCH-4-py)] [21] (d), [Co
II
2
(C
6
H
5
COO)
4
(Me
3
-TTF-CHCH-4-py)
2
] [22] (e), [Co
II
2
Mn
II
(C
6
H
5
COO)
6
(TTF-CHCH-4-py)
2
] [19, 23] (f), [Fe
III
2
(O)(TTF-salphen)
2
] [18, 24] (g), [Cu
II
2
(LH)
2
(TTF-CHCH-4-py)(H
2
O)] [21, 25] (h), [Mn
II
(μ-Cl)Cl(EDT-TTF-S-4-py)]
n
[26] (i),
trans
-[Cu
II
Cl
2
(BP-TTF)]
n
[27] (j),
trans
-[Cu
II
Cl
2
(pyra-TTF)]
n
[28] (k), [Cu
II
(BMT-TTF-bis-COO)(2,2′-bpy)]
n
[29] (l), and [Mn
II
(BMT-TTF-bis-COO)(4,4′-bpy)]
n
(m) [29].
Figure 15.5 Representative examples of hybrid structures of magnetic layer/conducting layer, (BEDT-TTF)
3
[MnCr(C
2
O
4
)
3
]. (Coronado 2000 [102]. Reproduced with permission of Nature Publishing group.) SMM/conducting layer, [{Mn
II
2
Mn
III
2
(hmp)
6
(MeCN)
2
}{Pt(mnt)
2
}
4
][Pt(mnt)
2
]
2
[103], and spin crossover complex/conducting layer, [Fe
III
(qnal)
2
][Pd(dmit)
2
]
5
·acetone [[104, 102]].
Figure 15.6 (a) Structure of [{Co
II
((
R
)-pabn)}{Fe
III
(tp)(CN)
3
}]BF
4
·MeOH·2H
2
O, where green, Fe; blue, Co; pink, B; gray, C; and purple, N. (b) Temperature dependence of the dc conductivity (red) and magnetic susceptibility (blue) of [{Co
II
((
R
)-pabn)}{Fe
III
(tp)(CN)
3
}]BF
4
·H
2
O. (Hoshino 2012 [150]. Reproduced with permission of Nature Publishing Group.)
Figure 15.7 Packing diagrams of [{Ru(O
2
CCF
3
)
4
}
2
(TCNQF
4
)]·3(
p
-xylene) projected along the
c
axis (a) and the
b
axis (b), where the solvent molecules (three
p
-xylene molecules) were omitted for the sake of clarity [160, 161], and normalized resistivity (ρ
1
) of the complex as a function of temperature measured at several frequencies by terahertz-time-domain spectroscopy, where the dashed line represents
T
N
= 95 K estimated by the magnetic data. (Miyasaka 2010 [161]. Reproduced with permission of American Chemical Society.)
Figure 15.8 Organic systems: benzo-annulated TTF-based donor radicals, ETBN, ESBN, and TSBN (a) and BTBN (b); schematic representation of the generation of triplet ground state of ESBN upon one-electron oxidization process (c); structural representations of spiro-biphenalenyl systems: (d) spiro-bis(1,9-disubstituted-phenalenyl)boron neutral radicals, (e) its diaminophenalenyl system, and (f) its oxygen-functionalized form; resonance structures of bisdithiazolyl/bisthiaselenazolyl radicals (g); structural representation of oxobenzo-bridged bisdithiazolyl radicals (h).
Chapter 16: Molecular Multiferroics
Figure 16.1 Representation of magnetoelectric and multiferroics by the classification of Eerenstein
et al
. (Eerenstein 2006 [2]. Reproduced with permission of Nature Publishing Group.)
Figure 16.2 Block of [(CH
3
)
2
NH
2
]Mn(HCOO)
3
abbreviated as DMMF. The DMA cation (A) is at the center of corner-linked MnX
6
octahedra, consisting of manganese (B) and formate (X) ions, forming a cavity. (Jain 2009 [19]. Reproduced with permission of American Chemical Society.)
Figure 16.3 Temperature dependence of the dielectric constant (a) and heat capacity (b) of [(CH
3
)
2
NH
2
]Zn(HCOO)
3
. (Jain 2008 [14]. Reproduced with permission of American Chemical Society.)
Figure 16.4 X-ray structure of C[MnCr(ox)
3
(CH
3
CH
2
OH)]. (C
+
= 1-(hydroxyethyl)-4-(
N
,
N
-dimethylamino)pyridinium; ox
2−
= C
2
O
4
2−
) at 110 K. (a) Anionic network in the ac plane. (b) Packing of the cations between the corrugated planes. The Cr and Mn atoms are depicted as green and purple polyhedra, respectively. Oxygen, hydrogen, and nitrogen atoms are indicated in red, pink, and blue, respectively. The hydrogen bonds are indicated by dashed lines. (Pardo 2012 [15]. Reproduced with permission of Wiley.)
Figure 16.5 Temperature dependence of (a) the remnant electric polarization (left) and the dc resistivity (right) and (b) the dielectric permittivity
ϵ
′ (left) and the dielectric losses tan(δ) (right) of C[MnCr(ox)
3
(CH
3
CH
2
OH)]. (C
+
= 1-(hydroxyethyl)-4-(
N
,
N
-dimethylamino)pyridinium; ox
2−
= C
2
O
4
2−
) at different frequencies. (Pardo 2012 [15]. Reproduced with permission of Wiley.)
Figure 16.6 Crystal structure of CuCl
4
(C
6
H
5
CH
2
CH
2
NH
3
)
2
determined by single crystal X-ray diffraction at 100 K. (Polyakov 2012 [36]. Reproduced with permission of American Chemical Society.)
Figure 16.7 Side view (a) and top view (b) representations of the buckling of the CuCl
6
octahedra in the CuCl
4
(C
6
H
5
NH
3
)
2
organic–inorganic hybrid, causing cooperative hydrogen bond ordering. (Polyakov 2012 [36]. Reproduced with permission of American Chemical Society.)
Figure 16.8 Temperature dependence of the buckling angle for CuCl
4
(PEA)
2
hybrid (a) and of the polarization (b) obtained by integration of the pyroelectric current over time. (Polyakov 2012 [36]. Reproduced with permission of American Chemical Society.)
Figure 16.9 (a) Ball-and-stick model of [CH
3
CH
2
NH
3
]Mn(HCOO)
3
in the centric (λ = 0) (left) and polar (λ = 1) (right) phases. The most important polar displacements are highlighted by closed lines and arrows. Yellow, red, green, blue, and black balls refer to manganese, oxygen, carbon, nitrogen, and hydrogen atoms, respectively. (b) Spatial ordering of the A-group dipole moments in the centric structure: by symmetry, the dipoles are parallel to the
ab
plane and antiparallel on nearest planes along the
c
-axis, leading to a zero net polarization. (c) Same as for (b) but in the polar structure the dipole moments do not cancel along
c
-axis because of molecular bending. (Sante 2013 [38]. Reproduced with permission of American Chemical Society.)
Figure 16.10 Representation of the charge order-induced multiferroicity.
Chapter 17: Modeling Magnetic Properties with Density Functional Theory-Based Methods
Figure 17.1 Periodic DFT optimization of the Fe
4
single-molecule magnet on Au(111) surface using the TPSS functional with a hybrid Gaussian/plane-wave basis set. The magnetization is perpendicular to the Fe
4
plane (blue arrow) has an angle of 35° with the normal to the surface in perfect agreement with the experimental data obtained X-ray natural linear dichroism. (Mannini 2010 [20]. Reproduced with permission of Nature Publishing Group.)
Figure 17.2 (a) Model structure of the gold electrodes and the
trans
bis(3-(2-pyridyl)(1,2,3)triazolo(1-5)pyridine)bis(isothiocyanato)iron(II) complex. (b) Projected DOS and transmission spectra calculated (alpha-green and yellow-beta) at DFT-NEGF level for the high- (above) and low-spin (below) states. (Aravena 2012 [227]. Reproduced with permission of American Chemical Society.)
Chapter 18: Ab Initio Modeling and Calculations of Magnetic Properties
Figure 18.1 Schematic representation of the action of the four-spin ring exchange operator.
Figure 18.2 (a) Fictitious molecule with the structure of an icosahedron and nearest-neighbor antiferromagnetic interactions along the edges. (b): Low-lying energy eigenvalues for single-spin quantum number
s
= 1. The energy levels are characterized by their total spin quantum number as well as the irreducible representations of the icosahedral group.
Figure 18.3 (a): Low-lying part of the energy spectrum of the ferric wheel Fe
10
, in which 10Fe
(III)
ions with spin 5/2 interact via nearest-neighbor antiferromagnetic interactions. (b): Low-field magnetic susceptibility – data given by symbols and theoretical calculation given by the curve.
Figure 18.4 (a): Low-lying part of the pseudo-energy spectrum of an icosidodecahedron of 30 spins 1/2 with antiferromagnetic nearest-neighbor interactions. Circles are centered at Krylov energy eigenvalues and possess a radius that reflects the respective weight. (b): Low-field magnetic susceptibility of the molecule {W
72
V
30
}; experimental data are given by symbols, and the theoretical FTLM calculation is given by the blue curve.
Figure 18.5 (a): Structure of the centered ring molecule Gd
7
superimposed with a snowflake. (b): Isentropes of Gd
7
(curves) compared to the isentropes of a paramagnet (straight lines).
Figure 18.6 (a): Structure of the magnetic core of Mn
12
-Ac, red balls mark Mn
(IV)
, blue balls Mn
(III)
. (b): Effective magnetic moment calculated for various parameterizations of Heisenberg Hamiltonians, data provided by Mark Murrie and Roberta Sessoli.
Figure 18.7 (a): Effective magnetic moment calculated with the Heisenberg part as well as the full anisotropic Hamiltonian of [63]. (b): Calculated magnetization for the full anisotropic Hamiltonian of [63] as powder average and for a direction close to the tetragonal axis as well as perpendicular [68].
List of Tables
Chapter 1: Magnetism
Table 1.1 Units in the SI system and cgs emu system
Table 1.2 Occurrence (+) or absence (−) of the long-range order at
T
≠ 0 for dimensions of the lattice and order parameter; ⊗ − Berezinsky–Kosterlitz–Thouless transition
Chapter 3: High-Spin Molecules
Table 3.1 Structural and magnetic parameters for selected {Mn
6
} complexes
Table 3.2 Selected manganese oxoclusters with
S
t
> 10
Table 3.3 Selected manganese clusters with oxo- and halide-bridging ligands
Table 3.4 Selected manganese clusters with oxygen and azido bridging ligands
Table 3.5 Selected iron clusters with ground spin state
S
t
> 10
Table 3.6 Selected hetero-metal high-spin molecules with ground spin state
S
t
> 10
Table 3.7 Magnetostructural data for selected gadolinium(III) complexes with ferromagnetic interactions
Table 3.8 Structural data for selected dysprosium(III) complexes with ferromagnetic interactions
Table 3.9 Selected magneto structural data for dinuclear Cu
II
–Gd
III
complexes with two
μ
-oxo bridges
Chapter 4: Single Molecule Magnets
Table 4.1 The energy eigenvalues with ZFS for the case of
S
= 1
Chapter 7: High-Tc Ordered Molecular Magnets
Table 7.1 Molecule-based magnets constructed of TCNE and its derivatives with
T
c
exceeding the temperature of boiling nitrogen
Table 7.2 Hexacyanidometallate-based magnets with
T
c
exceeding the temperature of boiling nitrogen
Table 7.3 Hepta- and octacyanidometallate-based magnets with
T
c
exceeding the temperature of boiling nitrogen
Chapter 17: Modeling Magnetic Properties with Density Functional Theory-Based Methods
Table 17.1 Jacob's ladder classification of the exchange correlation functionals proposed by Perdew
Table 17.2
J
values (cm
−1
) for the Cu
II
acetate calculated using some of the methods discussed in the text [62, 98–100]
Table 17.3 Total spin
S
and
D
values (cm
−1
) for some polynuclear complexes calculated by Pederson and coworkers [182] using the procedure described in the text (Eqs. ((17.22)–(17.24)) or (17.27)) with PBE functional
Table 17.4
D
values (cm
−1
) for the family of Mn
II
complexes, [Mn(tpa)X
2
] (tpa = tris-2-picolylamine) and X = I, Br, and Cl [186]
Chapter 18: Ab Initio Modeling and Calculations of Magnetic Properties
Table 18.1 Isotropic exchange interaction parameters (millielectronvolt) as suggested by various authors. The spin labels correspond to Figure 18.6a
