Cyanide-bridged [Fe8M6] clusters displaying single-molecule magnetism (M=Ni) and electron-transfer-coupled spin transitions (M=Co)

Article abstract of DOI:10.1002/chem.201101404

Cyanide-bridged metal complexes of [Fe₈M₆(μ-CN) ₁₄(CN)₁₀ (tp)₈(HL)₁₀(CH ₃CN)₂][PF₆]₄·nCH ₃CN·mH₂O (HL=3-(2-pyridyl)-5-[4-(d

Full text of DOI:10.1002/chem.201101404

DOI: 10.1002/chem.201101404
Cyanide-Bridged [Fe8M6] Clusters Displaying Single-Molecule Magnetism
(M=Ni) and Electron-Transfer-Coupled Spin Transitions (M=Co)
Kiyotaka Mitsumoto, Emiko Oshiro, Hiroyuki Nishikawa, Takuya Shiga,
Yasuhisa Yamamura, Kazuya Saito, and Hiroki Oshio*[a]
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FULL PAPER
Abstract: Cyanide-bridged metal com-
high-spin (HS) MII ions (M=Ni and
Co), all of which are bridged by cya-
nide ions, to form a crown-like core
structure. Magnetic susceptibility mea-
AHCTUNGTRENNsGUN urements revealed that intramolecular
ferro- and antiferromagnetic interac-
sample of 2, respectively. Ac magnetic
plexes
of
[Fe8M
N
susceptibility measurements of
1
(tp)8(HL)
10A(CH3CN)2]-
showed frequency-dependent in- and
out-of-phase signals, characteristic of
single-molecule magnetism (SMM),
while desolvated samples of 2 showed
thermal- and photoinduced intramolec-
ular electron-transfer-coupled spin
transition (ETCST) between the [(LS-
[PF6]4·nCH3CN·mH2O (HL=3-(2-pyr-
idyl)-5-[4-(diphenylamino)phenyl]-1H-
pyrazole), tpÀ =hydrotris(pyrazolylbo-
rate), 1: M=Ni with n=11 and m=7,
and 2: M=Co with n=14 and m=5)
were prepared. Complexes 1 and 2 are
isomorphous, and crystallized in the
monoclinic space group P21/n. They
have tetradecanuclear cores composed
of eight low-spin (LS) FeIII and six
tions are operative in 1 and in a fresh
Keywords: cluster compounds · cy-
anide · magnetic properties · single-
FeII)
(LS-FeIII)
R
(LS-CoIII)3]
3ACHTUNGTRENNUNG
and the [(LS-FeIII)
(HS-CoII)6] states.
molecule magnets
metals
·
transition
Introduction
in our systems; electron-transfer-coupled spin transition
(ETCST). It should be noted that such discrete ETCST sys-
tems are expected to switch between their low- and high-
spin states by light irradiation, and such a photoinduced
high-spin phase may be an SMM.[3b] However, metal ions in
multinuclear complexes are assembled by bridging ligands,
and weak intramolecular interactions such as hydrogen
bonds can be used to stabilize unique and unexpected mo-
lecular structures.[5] To take advantage of intramolecular hy-
drogen bonds in the construction of unique structures, a new
ligand (HL=3-(2-pyridyl)-5-[4-(diphenylamino)phenyl]-1H-
pyrazole) with acidic protons was prepared. The HL ligand
has a proton donor site on the pyrazole moiety that can
form intramolecular hydrogen bonds, while its bulky triaryl
amine substituent is expected to separate molecules by hin-
dering intermolecular hydrogen bonds. Herein we report the
syntheses and magnetic properties of two novel heterometal
Cyanide ions are useful tools in the assemblies of metal ions
into complexes; from zero-dimensional clusters up to three-
dimensional arrays. Cyanide bridges propagate magnetic
and electronic interactions, and indeed some Prussian blue
analogues[1] have shown magnetic ordering[1a–c] and multi-
functional magnetic properties, such as photomagnetism,[1d]
multiferroics,[1f] and ionic conductivity in molecular mag-
nets.[1g] Cyanide-bridged discrete molecules have been syn-
thesized in a wide range of shapes and arrangements such as
squares,[2] cubes,[3] and trigonal bipyramids.[4] These have
also been afforded considerable attention for their physical
properties, such as multistep redox,[2a,3c] spin crossover,[2b]
single-molecule magnetism (SMM),[3a,4a] and charge-transfer-
induced spin transitions (CTIST).[2d,3b,4b,c] It should be men-
tioned that the term “charge transfer” is often used to de-
scribe both cases in which a fraction of the charge is shared
between two sites or when a complete transfer of charge has
occurred with no electron delocalization. The latter case
may simply be termed “electron transfer”. Photoinduced
CTIST follows a multistep pathway; firstly charge transfer
clusters,
[Fe8M6(CN)24(tp)8(HL)10ACHTGNUTERNNU(G CH3CN)2]-
AHCUTNTGERG[NNUN PF6]4·nCH3CN·mH2O (1: M=Ni, n=11, m=7 and 2: M=
Co, n=14, m=5; tpÀ =hydrotris(pyrazolylborate)), which
exhibit SMM and ETCST behaviors, respectively.
from the [(LS-FeII)(LS-CoIII)] to the [(LS-FeIII)(LS-CoII)]
ACHTUNGTRENNUG CAHTUNGTRENNUGN
state, meaning that the valence electron is delocalized both
on the iron and cobalt sites. Secondly, the low-spin CoII ion
with an S=1/2 undergoes spin transition to reach the HS
Results and Discussion
Structure descriptions: Complexes 1 and 2 were prepared by
the reactions of HL, MACHTNGUTERN[NUG BF4]2·6H2O (M=Ni for 1, and M=
state of [(LS-FeIII)
G
becomes localized on the CoII ion.[1h] The thermally induced
process is, on the other hand, an entropy-driven phenome-
Co for 2) with nBu4N[Fe(CN)3(tp)][2e] and nBu4NPF6 in
CH3CN. The structure of 24+ at 93 K is shown in Figure 1.
Complexes 1 and 2 are isostructural and crystallize in the
monoclinic space group of P21/n. Cations of both complexes
are located on the crystallographic inversion center, and
charge balance, coordination bond lengths, and Mçssbauer
data (Figure S1 and S2) suggest that the complex cations are
composed of eight low-spin (LS) FeIII and six NiII (or CoII)
ions, abbreviated as [(LS-FeIII)8(Ni(or HS-CoII))6]. The core
structure of 24+ can be recognized as a twelve-membered
crown with an alternating arrangement of six FeIII and six
CoII ions, cyanide bridged to form a ring motif, with two ad-
ditional terminal FeIII ions that are linked to the crown-like
ACHTUNGTRENNUNGnon, and occurs in one step, that is, electron transfer does
not “induce” the spin transition. Thus, we use a term which
applies equally to the thermal- and light-induced processes
[a] K. Mitsumoto, E. Oshiro, Prof. Dr. H. Nishikawa, Dr. T. Shiga,
Dr. Y. Yamamura, Prof. Dr. K. Saito, Prof. Dr. H. Oshio
Graduate School of Pure and Applied Sciences
University of Tsukuba, Tennodai 1-1-1, Tsukuba 305-8571 (Japan)
Fax : (+81)29-853-4238
E-mail: oshio@chem.tsukuba.ac.jp
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201101404.
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9613

H. Oshio et al.
and 2, respectively. In both complexes, six intramolecular
hydrogen bonds are found between the uncoordinated cya-
nide nitrogen atoms and six protons of the pyrazole nitrogen
atoms, supporting the large structures with a diameter of
about 3 nm.
Magnetic properties: The dc magnetic susceptibility data of
1 were collected in the temperature range of 1.8–300 K, and
the cmT versus T plot is shown in Figure 2. The cmT value at
300 K is 11.12 emumolÀ1 K, which is close to the value
(12.08 emumolÀ1 K) expected for eight uncorrelated LS-Fe
III
(S=1/2, gFe =2.7) and six NiII ions (S=1 and gNi =2.1).
Relatively large gFe values have been previously reported
for cyanide-bridged LS-FeIII complexes.[2c,d,6] The cmT values
gradually increased as the temperature was lowered and
reached the maximum value of 46.18 emumolÀ1 K at 1.8 K.
This suggests the occurrence of ferromagnetic interactions
between the LS-FeIII and NiII ions, for which Curie and
Weiss constants of C=10.54 emumolÀ1 K and q= +10.73 K
were obtained. The magnetic data were analyzed by MAG-
PACK[7] and fitted with a spin Hamiltonian of H=À2J-
ACHTNURTGE[GNNUN SNi1·(SFe1+SFe4)+SNi1#·(SFe1#+SFe4#)+SNi2·(SFe1+SFe2 +SFe3)+
SNi2#·(SFe1#+SFe2# +SFe3#)+SNi3·(SFe2#+SFe4)+SNi3#·(SFe2+SFe4#)],
supposing the same isotropic exchange coupling constant (J)
between the FeIII and NiII pairs. The solid curve in Figure 2
was drawn using parameters of J= +9.0 K and g=2.2. The
occurrence of ferromagnetic interactions can be understood
by the orthogonal magnetic orbitals of the LS-FeIII (dp spin)
and NiII (ds spin) ions. The ac magnetic susceptibility mea-
AHCTUNGTREGsNNNU urements for 1 were performed in a 3 Oe ac field (Figure 2,
inset). Both in- and out-of-phase signals showed frequency-
dependence, suggesting that 1 is an SMM. At fixed tempera-
tures from 1.80 to 2.05 K, Cole–Cole plots exhibited semicir-
cles, which could be fitted to the extended Debye model,[8]
yielding a values of 0.09–0.18. The a parameter is the width
of the distribution of the magnetic relaxation processes, and
such small values correspond to a single relaxation process
for 1 (Figure 3).
Figure 1. Structures of the cation 24+ at 93 K and its cyanide bridged
core. Dotted red lines represent the hydrogen bonds which support the
core. Symmetry operation key: #=1Àx, y, z.
core by cyanide bridges. The six coordination sites of each
FeIII ions in the crown are occupied by three nitrogen atoms
from the tridentate tpÀ ligand and the remaining facial posi-
tions are filled by the three cyanide carbon atoms. The ter-
minal FeIII ions are coordinated by three nitrogen atoms
from the tpÀ ligand and three cyanide ions—one of these cy-
anide ions bridges to a CoII center and the remaining two
act as monodentate ligands. The octahedral coordination en-
vironments of the Co1 and Co3 ions consist of N6 donor sets
from two bidentate ligands (HL) and two cyanide nitrogen
atoms. The Co2 atom also has an octahedral coordination
environment, but is connected to three cyanide nitrogen
atoms, one HL ligand, and one CH3CN molecule. The coor-
dination bond lengths of the NiII and CoII ions in 1 and 2 at
93 K are in the range of 2.072(8)–2.082(8) and 2.116(5)–
2.122(5) ꢁ, respectively, characteristic of divalent metal ions
Figure 2. cmT versus T plot of 1 measured in an applied magnetic field of
500 Oe. The inset displays plots of out-of-phase AC susceptibility signals
vs. temperature for 1. The solid line was calculated by the parameters
given in the text.
À
in the high-spin state. The Fe C bond lengths are in the
range of 1.872(12)–1.947(11) and 1.873(4)–1.949(7) ꢁ for 1
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Cluster Compounds
FULL PAPER
Storage of sample 2 at ambient temperature resulted in
drastic changes in its magnetic behavior up to 18 days after
which time no further change was observed (Figure 4).
After 18 days of storage was formulated as
2
[Fe8Co6(CN)24(tp)8(HL)10A(CH3CN)2]ACHTNGUTERN[NUG PF6]4·5H2O (Figure 4,
G
filled circles; henceforth termed desolvated 2) from elemen-
tal analysis and TGA data, and showed an almost constant
cmT value (9.4–9.8 emumolÀ1 K) in the temperature range of
20–180 K. A sigmoidal increase in cmT value began at
170 K, reaching cmT=20.0 emumolÀ1 K at 250 K. The cmT
value of 9.4 emumolÀ1 K at 20 K corresponds to the value
(10.86 emumolÀ1 K) expected for the [(LS-FeII)
(LS-FeIII)5-
3ACHTUNGTRENNUNG
A
CHTUNGTRENNUNG
spectroscopic measurements, and the value at 250 K is the
same as that for the fresh sample 2. It is, therefore, assumed
that three electrons were transferred from the [(LS-FeII)3-
Figure 3. Cole–Cole diagrams of 1. The solid lines represent least-square
fits of the data to the Debye model.
AHCTUNGTERNUNGN 5ACHUTNGTRENNUG 3ACHTUNGERTNNUNG 8ACHTUNGTRENNUNG(HS-
(LS-FeIII) (HS-CoII) (LS-CoIII)3] to the [(LS-FeIII)
CoII)6] states upon the temperature increase. Note that no
hysteresis was observed for desolvated 2. When the sample
was dried under vacuum for four days, only gradual increase
of cmT values was observed from 13.7 emumolÀ1 K at 10 K
to 17.7 emumolÀ1 K at 250 K, suggesting the absence of the
electron transfer (see Figure S3 in the Supporting Informa-
tion). Differential scanning calorimetry (DSC) measure-
ments of desolvated 2 were performed (Figure S4 in the
Supporting Information) and no peak was observed, indicat-
ing that negligibly small cooperativity exists in this transi-
tion. This agreed with the absence of hysteresis in the mag-
netic susceptibility data.
Thermogravimetric analysis (Figure S5 in the Supporting
Information), elemental analysis, and 57Fe Mçssbauer spec-
tral measurements were conducted to study the effect of
storage and thermal treatment on 2. The TGA of 2 displays
a weight loss of 7.5% upon heating from 40 to 738C, which
correspond to the release of 14 acetonitrile molecules
(calcd. 6.9%). It is suggested that desolvated 2 has the for-
Magnetic susceptibility measurements of 2 showed tem-
perature profiles dependent upon the sample treatment
(Figure 4). All measurements began at 1.8 K and the tem-
peratures were increased. The fresh sample (open circle)
showed rapidly increasing cmT values from 1.8 to 11.6 K, fol-
lowed by a gradual increase to the cmT value of 21.34 emu
molÀ1 K at 300 K; the value at 300 K is close to the Curie
constant (20.34 emumolÀ1 K) obtained by summing the un-
correlated spins of eight LS-FeIII (S=1/2) and six CoII ions
(S=3/2) with the gFe =2.7 and gCo =2.3,[2d,3b] corresponding
with the cluster in the [(LS-FeIII)
G
netic susceptibility data suggested that antiferromagnetic in-
teractions between the FeIII and CoII ions were operative
and the notable change of the cmT values in the low and in-
termediate temperature ranges might be due to the orbital
contribution from the metal ions.
mula [Fe8Co6(CN)24(tp)8(HL)10ACTHNUTGRENNUG(CH3CN)2]AHCTUGNTREN[NGUN PF6]4·5H2O. The
single crystal of desolvated 2 could not be obtained, and the
powder XRD measurement for desolvated 2 was, therefore,
performed and the result was depicted in Figure 5. The
Figure 5. a) Powder XRD pattern of desolvated 2. The solid line repre-
sent least-square fits of the data by using the parameters; a=22.186(8),
b=26.406(5), c=35.91(1) ꢁ, b=93.35(2)8. Rp =0.090, Rwp =0.235. b) The
diffraction data generated using single-crystal structure analyses data.
Figure 4. cmT versus T plots for 2 collected as a function of storage and
light irradiation at 808 nm.
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H. Oshio et al.
Le Bail method[9] was applied to estimate the lattice con-
stants for the desolvated 2, and the least-square calculation
yielded similar lattice constants of a=22.186(8), b=
26.406(5), c=35.91(1) ꢁ, b=93.35(2)8, close to those for the
fresh sample of 2, with the same monoclinic space group,
and Rp and Rwp residuals were 0.090 and 0.235, respectively.
The result suggests that desolvated 2 retained a crystal struc-
ture similar to 2.
0.64/0.36) and magnetic susceptibility data, three of the
eight LS-FeIII ions in the high-temperature (HT) phase
8A
the low-temperature (LT) phase ([(LS-FeII)
3A
CoII) (LS-CoIII)3]); that is, three electrons were transferred
(LS-FeIII)
3ACHUTGNENRNUG 5ACHTUNGTRENNUNG(HS-
CTHUNGTRENNUNG
from the FeII to CoIII sites followed by spin transition to the
HS state on the CoII sites. Note that no hysteresis was ob-
served in the temperature dependence of the Mçssbauer
spectra. Thermodynamic parameters accompanying the tran-
sition were estimated by the temperature dependence of the
LS-FeIII fractions, assuming identical recoil free fractions of
LS-FeIII and LS-FeII species. The results gave enthalpy and
entropy changes for the three-electron transfer process of
DH=17.5 kJmolÀ1 and DS=85.2 JKÀ1 molÀ1 with Tc =205 K
(Figure S6 in the Supporting Information).
Variable-temperature 57Fe Mçssbauer spectra: 57Fe Mçssba-
uer spectra of 1, and fresh and desolvated 2 were measured
at several temperatures (Figures S1 and S2 in the Supporting
Information and Figure 6). The Mçssbauer spectra of 1 at
20 K, and the fresh sample of 2 at 20 and 298 K all showed a
single doublet, which were fitted with Mçssbauer parame-
ters (relative to iron steel) of d=0.05 and DEQ =
1.20 mmsÀ1, d=À0.05 and DEQ =0.93 mmsÀ1, and d=0.02
and DEQ =1.06 mmsÀ1, respectively, characteristic of LS-
FeIII species. Desolvated 2 showed a substantially different
temperature profile from the fresh sample. The Mçssbauer
spectrum of desolvated 2 at 298 K is composed of one quad-
rupole doublet with d=À0.03 and DEQ =0.96 mmsÀ1, char-
acteristic of LS-FeIII species. When the temperature was low-
The ETCST behavior was strongly dependent upon the
release of the solvent molecules in 2. The desolvation in-
volves changes in hydrogen-bond networks between solvent
molecules and terminal cyanide nitrogen atoms. Subtle
changes in hydrogen bonds can lead to structure deforma-
tion and in some cases shifted redox potentials of metal cen-
ters, which may activate phase-transition-like ETCST. Such
solvent effects have been also observed in {[Co-
ered,
a
new quadrupole doublet (d=0.12 and DEQ =
ACHTGNUERTN(NUNG tmphen)2]3[Fe(CN)6]2}·24H2O (tmphen=3,4,7,8-tetrameth-
0.56 mmsÀ1) appeared at 250 K and its fraction increased as
the temperature was lowered. The Mçssbauer spectrum at
20 K showed two doublets with parameters of d=0.06 and
DEQ =1.24 mmsÀ1, and d=0.18 and DEQ =0.58 mmsÀ1, char-
acteristic of LS-FeIII and LS-FeII species, respectively. Con-
sidering the peak area ratio of the two doublets (FeIII:FeII =
yl-1,10-phenanthroline)[4b] and [Fe(tp)(CN)3]2Co
ACTHNGUTERU(NNG bpe)·5H2O
(bpe=1,2-bis(4-pyridyl)ethane).[10]
Photomagnetic experiments: Light irradiation experiments
using laser lights (405, 532, and 808 nm) were conducted on
the desolvated 2 at 5 K in the SQUID magnetometer
(Figure 4). Rapid increases of
the cmT values were observed
upon light irradiation (405 and
808 nm), and plots of cm versus
irradiation time are shown in
Figure S7 in the Supporting In-
formation. The cmT values satu-
rated at 13.6 and 11.2 emu
molÀ1 K after irradiation (808
and 405 nm) for 4 and 8 h, re-
spectively. No effect was ob-
served following the irradiation
532 nm. Note that the cm values
also increased when the lasers
were turned off, and this is due
to the decreased temperature
upon turning off the laser lights.
After turning off the laser
source, the photoinduced spe-
cies showed gradual increase of
the cmT values as the tempera-
tures were raised, reaching a
plateau value of 17.8 emu
molÀ1 K at 30 K, followed by a
gradual decrease to 10.8 emu
molÀ1 K at 150 K. The experi-
Figure 6. Temperature dependence of Mçssbauer spectra of the desolvated 2. The solid lines were calculated
Lorentzian curves by using the parameters in the text.
ment suggests that the photoin-
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Chem. Eur. J. 2011, 17, 9612 – 9618

Cluster Compounds
FULL PAPER
duced transition of the LT phase, [(LS-FeII) (LS-FeIII)
3ACTHNUGTRENNUG 5HCATUNGTRNE(NUGN HS-
out in the temperature of 90–293 K, using a DSC (Perkin–Elmer Pyris 1).
The mass of sample and temperature scan rate were 1.1465 mg and
2 KminÀ1, respectively.
CHTUNGTRENNUNG
CoII) (LS-CoIII)3] to the metastable HT phase of [(LS-FeIII)8-
Materials: All solvents and chemicals were reagent-grade, purchased
commercially, and used without further purification unless otherwise
noted. Toluene was distilled from CaH2. 4’-(Diphenylamino)acetophe-
none was prepared by the literature method.[13]
LT phase upon temperature increase. The light conversion
ratio was 0.76, supposing gFe =2.7 and gCo =2.3, respective-
ly.[2d,3b] Note that the photoinduced HT phase did not show
out-of-phase signals in the ac susceptibility measurements,
and that the reverse electron transfer in the metastable HT
phase was not observed upon green light (532 nm) irradia-
tion.
Synthesis of 3-[4-(diphyenylamino)phenyl]-1-(2-pyridyl)propan-1,3-dione
(HL’): A solution of sodium ethoxide (641 mg, 9.47 mmol), 4’-(diphenyl-
AHCTUNGERTGaNNUN mino)acetophenone (1.50 g, 5.22 mmol) and ethyl 2-pyridinecarboxylate
(1.72 g, 11.3 mmol) in toluene (150 mL) was refluxed under nitrogen for
1.5 h. The solvent was removed under reduce pressure, and the residue
was acidified with aqueous acetic acid. The red precipitate was extracted
with diethyl ether and dried with sodium sulfate. The solvent was evapo-
rated and the crude product recrystallized from methanol to afford 1.84 g
(4.73 mmol) of HL’ as a red crystalline solid. Yield 91%; elemental anal-
ysis calcd (%) for C26H20N2O2: C 79.57, H 5.14, N 7.14; found: C 79.30, H
5.40, N 7.01; 1H NMR (270 MHz, CDCl3): d=7.03 (m, 2H), 7.28 (m,
6H), 7.32 (m, 4H), 7.43 (m, 1H), 7.46 (s, 1H), 7.85 (s, 1H), 7.93 (m, 2H),
8.11 (m, 1H), 8.68 ppm (m, 1H).
Conclusion
In summary, two novel tetradecanuclear complexes 1 and 2
were prepared. The capping ligand (HL) has an acidic
proton and a bulky group, which stabilize a crown like core
structure by intramolecular hydrogen bonds and by prohibit-
ing polymerization reactions, respectively. Complex 1 is an
single-molecule magnet, and 2, after an 18 day storage
period, showed thermal- and light-induced electron-transfer-
coupled spin transition behavior.
Synthesis
of
3-(2-pyridyl)-5-[4-(diphenylamino)phenyl]-1H-pyrazole
(HL): Hydrazine monohydrate (130 mL, 2.83 mmol) in methanol (10 mL)
was added to a solution of HL’ (1.00 g, 2.55 mmol) in CHCl3 (20 mL) and
the mixture was refluxed for 2 h. The solvent was evaporated and crude
product was washed with acetonitrile. A yellow solid was yielded and re-
crystallized from CHCl3 to afford 0.901 g (2.32 mmol) of ligand HL as a
pale yellow crystalline solid. Yield 90%; elemental analysis calcd (%) for
C26H20N4·0.2H2O: C 79.64, H 5.24, N 14.29; found: C 79.64, H 5.43, N
14.48. 1H NMR (270 MHz, CDCl3): d=7.03 (s, 2H), 7.25 (m, 6H), 7.66
(m, 6H), 7.82 (m, 2H), 8.63 ppm (m, 1H).
Experimental Section
Synthesis of [Fe8Ni6(CN)24(tp)8(HL)
10CAHTUNTGRENNUG(CH3CN)2]CAHTUNGTERNN[GUN PF6]4·11CH3CN·7H2O
(1): Ni[BF4]2·6H2O (5.4 mg 0.016 mmol) and ligand HL (12.5 mg,
G
,
X-ray crystallography: A crystal was mounted on a glass capillary, and
data were collected at À1808C (Bruker SMART APEXII diffractometer
coupled with a CCD area detector with graphite monochromated MoKa
(l=0.71073 ꢁ) radiation). The structure was solved using direct methods
and expanded using Fourier techniques within the SHELXTL pro-
gram.[11] Empirical absorption corrections by SADABS (G.M. Sheldrick,
1994)[12] were carried out. In the structure analyses, non-hydrogen atoms
were refined with anisotropic thermal parameters. Hydrogen atoms were
included in calculated positions and refined with isotropic thermal pa-
rameters riding on those of the parent atoms. PXRD data were collected
with CuKa radiation on a MAC Science M18XHF-SRA, and an assess-
ment of the crystal symmetry and of the lattice parameters was per-
formed by the Le Bail Method.[9]
0.032 mmol) were combined in acetonitrile (2 mL). The solution was
stirred for 5 min. The resulting orange solution was combined with a so-
lution of nBu4NPF6 (31 mg, 0.08 mmol) and nBu4N[Fe(CN)3(tp)] (9.4 mg,
0.016 mmol) in acetonitrile (2 mL). Slow evaporation gave red crystals of
1. Yield: 6.8 mg (41%); elemental analysis calcd (%) for
C360H286N114B8F24Fe8Ni6P4·7H2O: C 55.43, H 3.88, N 20.47; found: C
55.24, H 3.93, N 20.41. Crystal data for 1: C382H333N125B8F24Fe8Ni6O7P4,
Mr =8252.16, monoclinic, space group P21/n, a=21.937(1), b=26.108(1),
c=35.764(2) ꢁ, b=93.227(3)8, V=20449.9(16) ꢁ3, Z=2, T=93 K,
1calcd =1.340 MgmÀ3, 63644 reflections collected of which 34345 were
unique (Rint =0.0869), R1 [I>2s(I)]=0.1003, wR2=0.2516.
Synthesis of [Fe8Co6(CN)24(tp)8(HL)
(2): Complex 2 was obtained by the same synthetic approach as 1, but by
using Co[BF4]2·6H2O instead of Ni[BF4]2·6H2O. Yield: 7.3 mg (44%); el-
10CAHTUNTGRENNUG(CH3CN)2]CAHTUNGTERNN[GUN PF6]4·14CH3CN·5H2O
Physical measurements: Magnetic susceptibility data were collected using
a Quantum Design MPMS-5S SQUID magnetometer. Magnetization
data for the fresh 1 and the desolvated 2 are shown in Figure S8 in the
Supporting Information. The temperature scan rate was fixed to
1 KminÀ1, and each measurement was performed 60 s after the tempera-
ture had stabilized. Magnetic data was corrected for the diamagnetic con-
tribution associated with the sample holder, and the diamagnetism of the
sample was corrected using Pascalꢂs constants. Photomagnetic experi-
ments were carried out using light from DPSS laser (405 nm; Edmund
optics ZM18, 532 nm; Opto Tech KE.01, and 808 nm; Intelite I808–
120G-CAP, 10 mW) and the light was guided by means of a flexible opti-
cal fiber (Newport F-MBD; 3 m length, 1.0 mm core size, 1.4 mm diame-
ter) into the SQUID magnetometer. Irradiation was performed on the
ground sample inside the SQUID sample chamber at 5 K. One end of
the optical fiber was located 40 mm above the sample and the other was
attached to the laser coupler (Body; Newport M-F-916T and lens; M-
10X). The temperature dependence of magnetic susceptibility after light
irradiation was measured using an applied magnetic field of 2 T and a
scan rate of 1 KminÀ1 in scanning mode. Variable-temperature Mçssba-
uer experiments were carried out using a 57Co/Rh source in a constant-
acceleration transmission spectrometer (Topologic Systems) equipped
with an Iwatani HE05/CW404 Cryostat. The spectra were recorded in the
temperature range of 20–298 K. The spectrometer was calibrated by
using a standard a-Fe foil. Thermal analysis of desolvated 2 was carried
A
ACHTUNGTRENNUNG
emental analysis calcd (%) for C360H286N114B8Co6F24Fe8P4·5H2O: C 55.68,
H 3.84, N 20.56; found (dried at ambient condition for 18 days): C 55.40,
H 4.01, N 20.52. Crystal data for 2: C388H338N128B8Co8F24Ni6O5P4, Mr =
8340.60, monoclinic, space group P21/n, a=21.986(4), b=26.275(4), c=
35.993(6) ꢁ, b=93.302(3)8, V=20724(6) ꢁ3, Z=2, T=93 K, 1calcd
=
1.337MgmÀ3, 98297 reflections collected of which 36413 were unique
(Rint =0.0804), R1 [I>2s(I)]=0.0790, wR2=0.2155.
CCDC-802155 (1) and 802156 (2) contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgements
This work was supported by a Grant in Aid for Scientific Research for
Priority Area “Coordination Programming” (area 2107) from MEXT
(Japan) and by the JSPS.
Chem. Eur. J. 2011, 17, 9612 – 9618
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
9617

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Received: May 9, 2011
Published online: August 9, 2011
9618
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Chem. Eur. J. 2011, 17, 9612 – 9618