Unprecedented multi-stable spin crossover molecular material with two thermal memory channels

Article abstract of DOI:10.1002/chem.201300394

Two in one: A new iron(II) complex with short alkyl substituents exhibits an unprecedented bimodal behavior governed by the coexistence of three phases: two structurally different low-spin phases and one high-spin phase. The compound features two distinct well-separated strong cooperative spin-crossover transitions by varying the scan rate (see graphic). Copyright

Full text of DOI:10.1002/chem.201300394

COMMUNICATION
DOI: 10.1002/chem.201300394
Unprecedented Multi-Stable Spin Crossover Molecular Material with Two
Thermal Memory Channels
[
a, b]
[c]
[d]
[a]
Maksym Seredyuk,
M. Carmen MuÇoz, Miguel Castro, Tania Romero-Morcillo,
[a] [a]
Ana B. Gaspar, and Jose Antonio Real*
Iron(II) spin crossover (SCO) compounds represent one
of the most important examples of switchable molecular ma-
terials. They can be reversibly switched through a perturba-
tion by temperature, light, or pressure between the diamag-
netic (S=0) low-spin state (LS) and the paramagnetic
duce different molecular isomers and/or different packing
patterns of structurally equivalent molecules in the crystal
lattice giving polymorphs, which strikingly influence the
SCO properties.
[6]
Soft molecular materials made up of metal complexes
functionalized with long alkyl substituents (metallomeso-
gens) constitute an exception of the generalization made
above. They exhibit a melting associated with the ability of
ACHTUNGTRENNUNG( S=2) high-spin state (HS) with corresponding variation of
magnetic, dielectric, and optical responses. These properties
have created important expectations for the construction of
[1]
[7]
sensory and memory devices based on SCO compounds.
the alkyl chains to induce a disordered quasi-liquid state.
The spin-state switch is strongly coupled with structural
changes primarily involving the size and shape of the SCO
centre (FeꢀN bond lengths and angles). In discrete solid-
This controllable behavior has provided well-documented
evidence about the influence of structural changes associat-
ed with crystal to liquid-crystal PTs on the SCO in iron(II)
[8]
state SCO compounds, these structural changes propagate
cooperatively from one SCO centre to another through elas-
tic interactions mediated by intermolecular contacts, which
determine the nature of the spin crossover behavior, that is,
gradual, abrupt, hysteresis, steps, etc. In special cases, the
SCO is accompanied by additional structural order–disorder
compounds. Furthermore, solid to solid structural PTs of
crystalline metallomesogens has enabled the observation of
highly cooperative SCO transitions for a lipid layerlike ar-
ranged SCO complex of iron(II) with an alkylated Schiff-
[9]
base ligand and the so-called “reverse” SCO in several
[10]
homo ACHUTNGRNEUNGl ogues of cobalt(II) terpyridine-based compounds.
[
2]
[3]
[2c,4]
(
of anions, solvents, ligands moieties
) and/or symme-
Thus, crystalline alkylated SCO compounds can unite the
conformational lability of the alkyl chains able to induce a
solid to solid structural PT and can satisfy the requirements
necessary for the propagation of cooperative interactions.
Herein, we report on the first case of a SCO complex dis-
playing two separate cooperative SCO behaviors coupled
with an isostructural PT involving substantial conformation-
al change of the alkyl substituents and intermolecular reor-
ganization.
[5]
try breaking-phase transitions (PTs). The appearance of
structural PTs is, in general, rather unpredictable and usual-
ly associated to subtle structural changes. They often pro-
[
a] Dr. M. Seredyuk, T. Romero-Morcillo, Dr. A. B. Gaspar,
Prof. Dr. J. A. Real
Institut de Ciꢀncia Molecular (ICMol)
Departament de Quꢁmica Inorgꢂnica
Universitat de Valꢀncia
The title compound [Fe ACTHUNGTRENN(UNG nBu-im) AHCUTGNRNTEUNG( tren)] ACHNTUGTRENNUNG( PF ) (1) was ob-
3 6 2
tained in the form of well-shaped red crystals by reacting
C/Catedrꢃtico Josꢄ Beltrꢃn Martꢁnez, 2
4
6980 Paterna (Valencia) (Spain)
E-mail: jose.a.real@uv.es
[
b] Dr. M. Seredyuk
Permanent address:
Taras Shevchenko National University
Department of Physical Chemistry
Volodymyrska Str. 64, Kyiv 01601 (Ukraine)
[
c] Prof. Dr. M. C. MuÇoz
Departament de Fꢁsica Aplicada,
Universitat Politꢀcnica de Valꢀncia,
Camino de Vera s/n, 46022, Valencia (Spain)
[
d] Prof. Dr. M. Castro
Instituto de Ciencia de Materiales de Aragꢅn
FeCl ·4H O with the n-buthylated 1H-imidazol-2-aldehyde
2
2
(
CSIC-Universidad de Zaragoza)
(
nBu-im) and tris(2-ethylamino)amine (tren) in the presence
Departamento de Ciencia y Tecnologꢁa de Materiales y Fluidos
Campus Rio Ebro, Edificio Torres Quevedo
C/Maria de Luna, 3, 50018 Zaragoza (Spain)
ꢀ
of PF6 anions (see the Experimental Section). The magnet-
ic properties of 1 in the form of the c T product versus T in
M
both cooling and heating modes are shown in Figure 1 (cM is
the molar magnetic susceptibility and T is temperature). At
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201300394.
Chem. Eur. J. 2013, 19, 6591 – 6596
ꢆ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
6591

M
Figure 1. Thermal variation of the c T as a function of T for 1 at 4 (&)
ꢀ
1
and 0.1 Kmin (*).
3
ꢀ1
2
00 K, c T is equal to 3.3 cm Kmol , a value consistent
M
with the HS state of iron(II), whereas at temperatures
below 100 K, c T approximates zero, which is typical for the
M
iron(II) in the LS state. The cooling and heating modes per-
ꢀ
1
formed at 4 Kmin show an abrupt cooperative change of
c T between the HS state and a LS state (denoted LS1)
M
fl
›
with critical temperatures T =115 and T =129 K (corre-
c
c
sponding to the temperature for which 50% of the transi-
tion has been produced) for descending and ascending
branches, respectively, involving a hysteresis loop DT =
c
14 K wide, and revealing a first-order character for the spin
transition (Figure 1). Paradoxically, a decrease of the scan
rate leads to an increase of the width of the hysteresis loop,
whereas the opposite tendency is usual for first-order PTs.
ꢀ
1
Indeed, at a scan rate of 0.1 Kmin the compound trans-
forms between the HS state and a second LS state (denoted
fl
›
LS2) with critical temperatures T =135, T =176, and
c
c
DT =41 K (Figure 1).
c
The lower critical temperatures observed in the “fast-
cooling” experiment suggest the occurrence of a tempera-
ture lag due to the “freeze in” of the HS state during the
HS!LS conversion. Indeed, this metastable HS phase re-
laxes to the “slow-cooling” phase in the interval 130–150 K,
ꢀ
1
confirming that the hysteresis loop observed at 0.1 Kmin
is stationary (Figure 2). The rate constants kHL(T) were esti-
mated from the fitting of the experimental relaxation curves
[11]
to the Avrami equation (see Table S1 and Figure S1 in the
Supporting
Information).
An
activation
energy
factor
ꢀ1
E =38.32 kJmol
and
a pre-exponential
a
10
ꢀ1
A=3.6·10
s
have been obtained from the corresponding
Arrhenius plot (see Figure S2 in the Supporting Informa-
tion). Interestingly, for intermediate scan rates (2, 1,
ꢀ
1
0
.25 Kmin ), coalescence of the two hysteresis loops is ob-
served with a partial transition LS1!HS!LS2 starting at
Figure 2. Thermal variation of the c
cated scan rates. Symbol & corresponds to temperature dependence of
the c T value of the metastable HS1* and HS2* phases generated from
LS1 or LS2 phases, respectively, at 10 K by the LIESST effect. Symbol *
M
T as a function of T for 1 at the indi-
approxiately 127 K upon heating (Figure 2).
From magnetic data it follows that the transformation be-
tween both LS phases is unidirectional taking place when
moving from the LS1 to the LS2 phase but not in the re-
verse sense. Worth noting, however, that once the LS1
M
corresponds to the stationary values of c
HS!LS2 (see in text).
M
T evaluated from relaxation
ꢀ
1
phase is generated upon cooling at 4 Kmin , it does not
6592
www.chemeurj.org
ꢆ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 6591 – 6596

Unprecedented Multi-Stable Spin Crossover Molecular Material
COMMUNICATION
convert into the LS2 phase up to a critical temperature of
approximately 127 K (see Figure S3 in the Supporting Infor-
mation). Thus, the LS1 phase can be photoexcited to a
metastable HS1* phase at 10 K upon irradiation with green
[
12]
light (532 nm) over 3 h (LIESST effect;
Figure 2,
ꢀ
1
4
Kmin ). Once the photostationary regime is attained and
upon further heating at 0.3 Kmin in the dark, a T
ꢀ
1
LS1
LIESST
[13]
equal to 81 K is observed.
A
significantly smaller
=53 K was observed for the HS2* phase generated
LS2
T
LIESST
upon application of the same procedure to the LS2 phase
ꢀ
1
(
Figure 2, 0.1 Kmin ). The difference between both T
LIESST
temperatures of 28 K is consistent with the difference of
average critical temperatures for the two spin-crossover
ꢀ
1
av
›
fl
modes at 4 and 0.1 Kmin (Tc =(T +T )/2), as expected
c
c
[12]
from the inverse energy-gap law.
In Figure 3 the thermal variation of d AHCTUNGTERNNGNU( c T)/dT and the
M
excess of heat capacity, DCP , at different scan rates is
shown. The extrema of both closely coincide. In the differ-
ential scan calorimetry profile upon cooling/heating at
ꢀ
1
4
Kmin , only one peak corresponding to the transition
HS$LS1 is observed associated with an average change of
enthalpy of DH=5.5ꢁ0.4 kJmol and entropy of DS=
5.8ꢁ3 JK mol typically observed for iron(II) spin cross-
over complexes. A heating starting in the LS1 phase per-
ꢀ
1
ꢀ
1
ꢀ1
14]
4
[
ꢀ
1
formed at 0.25 Kmin shows the generation of the LS2
phase leading to a DC versus T profile with three peaks.
P
The first peak at approximately 125 K, also observed at
ꢀ
1
rates 4 and 1 Kmin , corresponds to the onset of transition
›
0.25
ꢀ1
›0.25
LS1!HS
(DH1
=2.9ꢁ0.4 kJmol ,
DS1
=23.2ꢁ
ꢀ
1
ꢀ1
3
JK mol ) immediately followed by a broad exothermic
peak at 132 K corresponding to the relaxation of the HS
›
0.25
state to the new LS2 phase (vide infra) (DH
=ꢀ4.5ꢁ
2
ꢀ
1
›0.25
ꢀ1
ꢀ1
0.4 kJmol , DS2
=ꢀ34.1ꢁ3 JK mol ). Finally, at
1
72 K an endothermic peak corresponding to the LS2!HS
›
0.25
ꢀ1
conversion
is
observed
(DH
=6.8ꢁ0.4 kJmol ,
3
DS3› =39.5ꢁ3 JK mol ). Similar qualitative behavior
0.25
ꢀ1
ꢀ1
ꢀ
1
P M
Figure 3. Variation of the DC and of the derivative d AHCTNURTEGNNNU(G c T)/dT as a func-
tion of T for 1 at the indicated scan rates. In the case of the calorimetric
can be observed for the measurement at 1 Kmin , but with
different enthalpy and entropy contents due to the combina-
tion of the higher scan rate and the relaxation process.
If the cooling from the HS state is performed at a lower
measurements, all the heating processes were performed after cooling
ꢀ1
the sample at 4 Kmin
.
ꢀ1
scan rate of 0.25 Kmin , two peaks in the calorimetric pro-
file are present in agreement with the magnetic measure-
since there are a higher number of short C···F contacts in
the LS2 phase with respect to the LS1 one (vide infra).
By using the entropy and enthalpy parameters obtained
from the calorimetric measurements at 0.25 and 4 Kmin ,
simulation of the hysteresis loops shows a substantial in-
crease of the parameter accounting for the intermolecular
fl0.25
ments. The first broad one centered at 130 K (DH
=
1
ꢀ
1
fl0.25
ꢀ1
ꢀ1
3
.0ꢁ0.4 kJmol , DS
=23.4ꢁ3 JK mol ) corresponds
1
ꢀ
1
to a gradual decrease of the susceptibility, and the second
well-defined peak at 120 K (DH2
DS2
abrupt drop of the susceptibility. The total variation DH
and DST
fl0.25
ꢀ1
=4.3ꢁ0.4 kJmol ,
fl0.25
ꢀ1
ꢀ1
=35.8ꢁ3 JK mol ) corresponds to
a
further
fl0.25
[15]
ꢀ1
ꢀ1
interactions, G, from 2.7 (4) to 4.2 kJmol (0.1 Kmin )
(see Figure S4 in the Supporting Information). This result is
supported by the analysis of the reorganization of intermo-
lecular interactions observed in the cycle HS!LS1!LS2!
HS (vide infra).
T
fl0.25
ꢀ1
ꢀ1
ꢀ1
is 7.3ꢁ0.4 kJmol and 59.2ꢁ3 JK mol , re-
›
4
ꢀ1
›4
spectively. If DH =5.2ꢁ0.4 kJmol
and DS =41.6ꢁ
ꢀ
1
ꢀ1
3
JK mol can be considered as the thermodynamic pa-
›
0.25
rameters for the LS1!HS transition and DH
=6.8ꢁ
3
ꢀ
1
›0.25
ꢀ1
ꢀ1
0
.4 kJmol and DS
=39.5ꢁ3 JK mol for the LS2!
The crystal structure of 1, determined at 110, 130 K upon
heating and at 150 K upon cooling, retains the same space
3
HS, the comparison reveals that there is a noticeable excess
of DH of about 30% in favor of the LS2!HS, whereas the
DS values are equal considering the estimated errors. This
fact should be associated with the different crystal packing
¯
group P1 whatever the temperature (see Tables S2 and S3 in
the Supporting Information). The unit cell consists of two
crystallographically identical complex cations of opposite
Chem. Eur. J. 2013, 19, 6591 – 6596
ꢆ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
6593

J. A. Real et al.
ꢀ
chirality and four PF6 counterions (two crystallographically
distinct sites) balancing the charge (Figure 4a). The iron(II)
ion is surrounded by three n-buthyl-1H-imidazol-2-ylimino
moieties defining a pseudooctahedral [FeN ] coordination
6
environment with FeꢀN average bond lengths typical for the
LS state, FeꢀN=1.989(6) (LS1) and 1.972(4) ꢇ (LS2) at 110
and 130 K, respectively. At 150 K, the average FeꢀN bond
length, 2.193(2) ꢇ, indicates that the iron(II) ion is in the
HS state. The average FeꢀN bond length variation, approxi-
[1]
mately 0.2 ꢇ, suggests the occurrence of a complete SCO.
The angles of the [FeN ] coordination sphere change accord-
6
ingly with the spin state. The average trigonal distortion
[
16]
[17]
F
and (S) parameters are 5.97 (52.50), 5.50 (58.69), and
.568 (103.358) for 110, 130, and 150 K, respectively. These
parameters reflect higher distortion of the coordination
polyhedron in the HS state. There is also a marked displace-
9
ACHTUNGTRENNUNG
ment of the nitrogen atom (N7) of the tertiary amine upon
SCO. This nitrogen atom, located at 3.425(6)
ACHTUNGTRENNUNG( LS1)/3.334(4) ꢇ (LS2) from the iron(II) ion, approaches to
it until a value of 3.019(3) ꢇ in the HS state is obtained.
Figure 4b displays the minimized overlay of the complex
cation at 110 and 130 K in the LS1 and LS2 states, respec-
tively. It shows significant differences in the conformations
of two alkyl substituents (C18–C20, C28–C30) as well as in
ꢀ
the relative position of both PF6 counterions while the
inner surrounding of the LS iron(II) ion, composed of imi-
dazole and imino groups, closely coincides in both phases as
evidenced by the corresponding FeꢀN bond distances, F,
and S parameters. These remarkable structural differences
at the periphery of the [FeN ] core between the two LS
6
phases strongly contrast with the moderate structural modi-
fications observed when moving from the LS1 (110 K) phase
to the HS (150 K) phase. They are mostly ascribed to the
change of the [FeN ] bond lengths and angles and concomi-
6
tant displacement of molecular moieties and counterions
while, except for the fragment C8–C10, the conformation of
the alkyl chains remains unchanged (Figure 4c). Consistent
with these facts, the LS2 (130 K) and HS (150 K) structures
strongly differ from each other. Indeed, apart from the
structural differences associated with the distinct spin state,
similar divergences to those found between LS1 (110 K) and
LS2 (130 K) phases are observed, namely, significant confor-
mational changes of the alkyl groups (fragments C8–C10,
C18–C20, and C28–C30) and displacement and rotation of
ꢀ
PF6 anions (Figure 4d).
The displacive behavior experienced by the PF6 anions
ꢀ
and the periphery of the complex cations provokes dramatic
changes in the crystal packing, which are dominated by
Figure 4. a) Projection of the cation of 1 with atom numbering scheme
(
110 K). Displacement ellipsoids are shown at the 30% probability level.
Hydrogen atoms are omitted for clarity. b) Minimized overlay of cation
and anions in LS1 (black) and LS2 phases (gray). c) Minimized overlay
of cation and anions of LS1 (black) and HS phases (gray). d) Minimized
overlay of cation and anions of LS2 (black) and HS (gray) phases.
Dashed ellipses outline fragments for which a change of the conforma-
tion or a large displacement is observed.
6594
www.chemeurj.org
ꢆ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 6591 – 6596

Unprecedented Multi-Stable Spin Crossover Molecular Material
short C···F contacts between the complex cation and the
COMMUNICATION
determine the cooperative nature of each SCO mode. Our
magnetic, photomagnetic, calorimetric, and structural stud-
ies consistently support this conclusion.
The results reported here show an unprecedented exam-
ple of multi-stability in which kinetics of an isostructural PT
can be used to segregate two well-differentiated hysteretic
SCO modes characterized by distinct long-range-order struc-
tural reorganization.
ꢀ
PF6 group. Considering only the C···F contacts below the
[18]
van der Waals radii (3.17 ꢇ ), only one discrete interac-
tion, d[C24···F2(P1)]=3.052(4) ꢇ, is operative in the HS
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
state, in contrast to the extended supramolecular assemblies
formed in the LS1 and LS2 states. More precisely, in the
ꢀ
LS1 state each P(1)F6 anion connects two adjacent cat
A
H
U
G
E
N
N
(
d
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
[C24···F2]=2.924(9),
d AHCTUNETGRNNUN[G C5···F5]=3.055(9),
ii
d[C5 ···F6]=3.092(8) ꢇ) defining single chains running
along the [010] direction (Figure 5a). In the LS2 state both
Experimental Section
Details of the syntheses, crystallographic studies, magnetic and calorimet-
ric measurements, and LIESST experiments can be found in the Support-
ing Information.
Acknowledgements
This work was supported by the Spanish Ministerio de Ciencia e Innova-
ciꢅn (MICINN) (presently Ministerio de Economꢁa y Competitividad
(
MINECO)) and FEDER funds (CTQ2010–18414, MAT2007–61621,
MAT2011–24284, Consolider Ingenio CSD 2007–00010), the Generalitat
Valenciana through PROMETEO/2012/049 and ACOMP2012/233. M.S.
thanks the EU for a Marie Curie fellowship (IIF-253254). T.R.M. thanks
the MICINN for a predoctoral (FPI) grant. We thank Dr. C. Enachescu
for help in performing preliminary FORC analysis of the hysteresis
loops.
Keywords: intermolecular interactions · iron · LIESST
effect · molecular materials · phase transitions
Figure 5. Supramolecular organization of
1 in the LS1 (a) and LS2
phases (b). Dashed lines correspond to short C···F contacts.
[1] See, for example: a) P. Gꢈtlich, H. A. Goodwin, Eds. :, Top. Curr.
Chem. 2004, Vols. 233–235; b) J. A. Real, A. B. Gaspar, M. C.
MuÇoz, Dalton Trans. 2005, 2062–2079; c) M. A. Halcrow, Polyhe-
dron 2007, 26, 3523–3576; d) M. Nihei, T. Shiga, Y. Maeda, H.
Oshio, Coord. Chem. Rev. 2007, 251, 2606–2621; e) P. Gamez, J.
Sꢃnchez-Costa, M. Quesada, G. Aromꢁ, Dalton Trans. 2009, 7845–
7853; f) J. Olguꢁn, S. Brooker, Coord. Chem. Rev. 2011, 255, 203–
240; g) A. Bousseksou, G. Molnꢃr, L. Salmon, W. Nicolazzi, Chem.
Soc. Rev. 2011, 40, 3313–3335.
ꢀ
ꢀ
P(1)F6 and P(2)F6 participate in the supramolecular or-
ganization defining a double chain running along the [100]
ꢀ
direction (Figure 5b). P(1)F6 connects three adjacent cat-
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
ions (d[C17···F11]=3.033(6),
d AHCTUNGRETNNUN[G C14···F7]=3.120(6), and
ꢀ
d
ACHTUNGTRENNUNG[ C6···F1]=3.124(6) ꢇ), whereas P(2)F located at the pe-
6
[
2] a) E. Kçnig, G. Ritter, S. K. Kulshreshtha, S. M. Nelson, Inorg.
Chem. 1982, 21, 3022; b) J. M. Holland, J. A. McAllister, Z. B. Lu,
C. A. Kilner, M. Thornton-Pett, M. A. Halcrow, Chem. Commun.
2001, 577; c) G. S. Matouzenko, A. Bousseksou, S. A. Borshch, M.
Perrin, S. Zein, L. Salmon, G. Molnar, S. Lecocq, Inorg. Chem.
riphery of the double layer displays only one discrete inter-
action d[C24···F2]=3.015(5) ꢇ (see Figure S5 and Table S4
ACHTUNGTRENNUNG
in the Supporting Information).
In summary, the title compound displays two well-differ-
entiated SCO behaviors characterized by large hysteresis
loops, which critically depend on the sweeping rate of tem-
2
004, 43, 227; d) V. A. Money, J. Elhaik, I. R. Evans, M. A. Halcrow,
J. A. K. Howard, Dalton Trans. 2004, 65; e) G. A. Craig, J. Sꢃnchez
Costa, O. Roubeau, S. J. Teat, G. Aromꢁ, Chem. Eur. J. 2011, 17,
ꢀ
1
perature. For rate 4 Kmin , the SCO is characterized by an
3
120.
av
average critical temperature Tc =122 K with a hysteresis
[3] a) M. Mikami, M. Konno, Y. Saito, Chem. Phys. Lett. 1979, 63, 566;
b) D. Chernyshov, M. Hostettler, K. W. Tçrnroos, H. B. Bꢈrgi,
Angew. Chem. 2003, 115, 3955; Angew. Chem. Int. Ed. 2003, 42,
loop 14 K wide (mode 1). In contrast, for rates below
ꢀ
1
av
0
.1 Kmin the SCO takes play at Tc =156 K and the hys-
3
825; c) M. Hostettler, K. W. Tçrnroos, D. Chernyshov, B. Vangdal,
teresis loop widens up to a value of 41 K (mode 2). There is
a scan rate threshold to initialize each SCO mode, which ap-
parently is linked to the kinetics of a structural PT taking
place between two LS state phases that share the same HS
state. This kinetically controlled PT involves a remarkable
reorganization of the intermolecular interactions leading to
two well-differentiated stable phases LS1 and LS2, which
H. B. Bꢈrgi, Angew. Chem. 2004, 116, 4689; Angew. Chem. Int. Ed.
2004, 43, 4589; d) K. W. Tçrnroos, M. Hostettler, D. Chernyshov, B.
Vangdal, H. B. Bꢈrgi, Chem. Eur. J. 2006, 12, 6207; e) D. Cherny-
shov, N. Klinduhov, K. W. Tçrnroos, M. Hostettler, B. Vangdal, H. B.
Bꢈrgi, Phys. Rev. B 2007, 76, 014406; f) D. Chernyshov, B. Vangdal,
K. W. Tornroos, H. B. Burgi, New J. Chem. 2009, 33, 1277.
[
4] a) G. S. Matouzenko, D. Luneau, G. Molnar, N. Ould-Moussa, S.
Zein, S. A. Borshch, A. Bousseksou, F. Averseng, Eur. J. Inorg.
Chem. Eur. J. 2013, 19, 6591 – 6596
ꢆ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
6595

J. A. Real et al.
Chem. 2006, 2671; b) S. Lakhloufi, P. Guionneau, M. Lemꢄe-Cail-
leau, P. Rosa, J. F. Lꢄtard, Phys. Rev. B 2010, 82; c) T. M. Ross, B.
Moubaraki, K. S. Wallwork, S. R. Batten, K. S. Murray, Dalton
Trans. 2011, 40, 10147.
5] Because of space limitation only some references have been select-
ed: a) D. Boinnard, A. Bousseksou, A. Dworkin, J. M. Savariault, F.
Varret, J. P. Tuchagues, Inorg. Chem. 1994, 33, 271; b) J. F. Lꢄtard, P.
Guionneau, E. Codjovi, O. Lavastre, G. Bravic, D. Chasseau, O.
Kahn, J. Am. Chem. Soc. 1997, 119, 10861; c) A. L. Thompson, A. E.
Goeta, J. A. Real, A. Galet, M. C. MuÇoz, Chem. Commun. 2004,
c) M. Seredyuk, A. B. Gaspar, V. Ksenofontov, Y. Galyametdinov, J.
Kusz, P. Gꢈtlich, Adv. Funct. Mater. 2008, 18, 2089; d) M. Seredyuk,
A. B. Gaspar, V. Ksenofontov, Y. Galyametdinov, M. Verdaguer, F.
Villain, P. Gꢈtlich, Inorg. Chem. 2008, 47, 10232; e) M. Seredyuk,
A. B. Gaspar, V. Ksenofontov, Y. Galyametdinov, M. Verdaguer, F.
Villain, P. Gꢈtlich, Inorg. Chem. 2010, 49, 10022; f) M. Seredyuk,
Inorg. Chim. Acta 2012, 380, 65; g) A. B. Gaspar, M. Seredyuk, P.
Gꢈtlich, Coord. Chem. Rev. 2009, 253, 2399.
[
[9] S. Schlamp, B. Weber, A. D. Naik, Y. Garcia, Chem. Commun. 2011,
47, 7152.
1
390; d) S. Bonnet, M. A. Siegler, J. S. Costa, G. Molnar, A. Bous-
seksou, A. L. Spek, P. Gamez, J. Reedijk, Chem. Commun. 2008,
619; e) I. Krivokapic, C. Enachescu, R. Bronisz, A. Hauser, Chem.
[10] a) S. Hayami, Y. Komatsu, T. Shimizu, H. Kamihata, Y. H. Lee,
Coord. Chem. Rev. 2011, 255, 1981.
[11] C. N. R. Rao, K. J. Rao, Phase transitions in solids, McGraw-Hill,
New York, 1978.
[12] A. Hauser, Comments Inorg. Chem. 1995, 17, 17–40.
[13] J. F. Lꢄtard, J. Mater. Chem. 2006, 16, 2550–2559.
[14] M. Sorai, M. Nakano, Y. Miyazaki, Chem. Rev. 2006, 106, 976.
[15] C. P. Slichter, H. G. Drickamer, J. Chem. Phys. 1972, 56, 2142.
5
Phys. Lett. 2008, 455, 192; f) V. Martꢁnez, A. B. Gaspar, M. C.
MuÇoz, G. V. Bukin, G. Levchenko, J. A. Real, Chem. Eur. J. 2009,
1
5, 10960; g) N. Brefuel, H. Watanabe, L. Toupet, J. Come, N. Mat-
sumoto, E. Collet, K. Tanaka, J.-P. Tuchagues, Angew. Chem. 2009,
21, 1; Angew. Chem. Int. Ed. 2009, 48, 1; h) A. Kaiba, H. J. Shep-
1
2
4
herd, D. Fedaoui, P. Rosa, A. E. Goeta, N. Rebbani, J. F. Lꢄtard, P.
Guionneau, Dalton Trans. 2010, 39, 2910; i) C. J. Adams, M. C.
MuÇoz, R. E. Waddington, J. A. Real, Inorg. Chem. 2011, 50, 10633;
j) N. F. Sciortino, K. R. Scherl-Gruenwald, G. Chastanet, G. J.
Halder, K. W. Chapman, J. F. Lꢄtard, C. J. Kepert, Angew. Chem.
Int. Ed. 2012, 51, 10154; k) K. Bhar, S. Khan, J. S. Costa, J. Ribas, O.
Roubeau, P. Mitra, B. K. Ghosh, Angew. Chem. Int. Ed. 2012, 51,
[16] F is defined here as Si (60ꢀq
i i
)/24, with q the angle generated by
superposition of two opposite faces of the octahedron (there are
four pairs of such superpositions with six q values for each one).
The following references are relevant concerning the trigonal distor-
tion: H.-R. Chang, J. K. McCusker, H. Toftlund, S. R. Wilson, A. X.
Trautwein, H. Winkler, D. N. Hendrickson, J. Am. Chem. Soc. 1990,
112, 6814–6827 and K. F. Purcell, J. Am. Chem. Soc. 1979, 101,
5147.
2
142; l) J. B. Lin, W. Xue, B. Y. Wang, J. Tao, W. X. Zhang, J. P.
Zhang, X. M. Chen, Inorg. Chem. 2012, 51, 9423.
6] J. Tao, R. J. Wei, R. B. Huang, L. S. Zheng, Chem. Soc. Rev. 2012,
[17] S represents octahedron distortion defined as the sum of deviations
from 908 of the 12 cis-N-Fe-N angles in the coordination sphere S=
[
1
2
4
1, 703.
Si (jfꢀ90j): M. G. B. Drew, C. J. Harding, V. McKee, G. G.
i
[
[
7] J. L. Serrano, Metallomesogens, Wiley-VCH, Weinheim, 1996.
8] a) M. Seredyuk, A. B. Gaspar, V. Ksenofontov, S. Reiman, Y. Galya-
metdinov, W. Haase, E. Rentschler, P. Gꢈtlich, Chem. Mater. 2006,
Morgan, J. Chem. Soc. Chem. Commun. 1995, 1035.
[18] A. Bondi, J. Phys. Chem. 1964, 68, 441.
1
8, 2513; b) M. Seredyuk, A. B. Gaspar, V. Ksenofontov, Y. Galya-
Received: January 31, 2013
metdinov, J. Kusz, P. Gꢈtlich, J. Am. Chem. Soc. 2008, 130, 1431;
Published online: April 9, 2013
6596
www.chemeurj.org
ꢆ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2013, 19, 6591 – 6596