Rational enhancement of the coordination capability of Ru(III)(salen)-nitronyl nitroxide building block: A step towards 2p-3d-4d magnetic edifices

Article abstract of DOI:10.1016/j.ica.2008.02.047

The reaction of [Ru(salen)(PPh₃)Cl] and the 5-imidazol-substituted nitronyl nitroxide radical (NIT-(5)ImH) yields the [Ru(salen)(PPh₃)(NIT-(5)ImH)](ClO₄) (1) complex which has been characterized by single crystal X-ray diffraction. This analysis reveals that the Ru(III) ion is coordinated to a tetradentate salen^2- ligand in equatorial positions while one PPh₃ ligand and one NIT-(5)ImH radical are coordinated in axial positions. This led to Ru^III ions in tetragonally elongated octahedral geometry. From the magnetic point of view ferromagnetic intramolecular interaction (J₁ = +2.47 cm^-1) have been found between the Ru(III) ion and the coordinated NIT-(5)ImH while no significant intermolecular antiferromagnetic interactions are observed at low temperature leading to a ground spin state S = 1. The absence of intermolecular magnetic interaction is explained by considering the crystal packing of (1) where the [Ru(salen)(PPh₃)(NIT-(5)ImH)]⁺ moieties are relatively well isolated. This has to be compared with the situation observed in the previously reported [Ru(salen)(PPh₃)-(NIT)]⁺ compound (2) where ferromagnetic Ru^III-NIT interaction were identified and the crystal packing generate intermolecular antiferromagnetic interactions that complicated the study. The analysis of this compound confirms the rather isotropic g values that were found of (2) and of [Ru(salen)(PPh₃)(N₃)], (3) a radical-free analogue. Moreover it is also a step towards extended structures based on Ru^III-NIT moieties since this compound possesses a free bischelating site likely to coordinate additional metallic ions.

Full text of DOI:10.1016/j.ica.2008.02.047

Inorganica Chimica Acta 361 (2008) 3427–3431
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Rational enhancement of the coordination capability of Ru(III)(salen)-nitronyl
nitroxide building block: A step towards 2p–3d–4d magnetic edifices
Fabrice Pointillart a, , Kevin Bernot a,b,1, Jeremy Colas a, Lorenzo Sorace a, Roberta Sessoli a
*
a L.A.M.M, Department of Chemistry and INSTM Reasearch Unit, Università di Firenze, Via Della Lastruccia 3, 50019 Sesto Fiorentino (FI), Italy
b Sciences Chimiques de Rennes, UMR 6226 CNRS-INSA Rennes, Equipe ‘‘Matériaux Inorganiques: Chimie Douce et Réactivité”, INSA Rennes, 20 Avenue des Buttes de Coësmes,
CS 14315, 35043 Rennes Cedex, France
a r t i c l e i n f o
a b s t r a c t
Article history:
The reaction of [Ru(salen)(PPh3)Cl] and the 5-imidazol-substituted nitronyl nitroxide radical (NIT-
(5)ImH) yields the [Ru(salen)(PPh3)(NIT-(5)ImH)](ClO4) (1) complex which has been characterized by
single crystal X-ray diffraction. This analysis reveals that the Ru(III) ion is coordinated to a tetradentate
salen2ꢀ ligand in equatorial positions while one PPh3 ligand and one NIT-(5)ImH radical are coordinated
in axial positions. This led to RuIII ions in tetragonally elongated octahedral geometry. From the magnetic
point of view ferromagnetic intramolecular interaction (J1 = +2.47 cmꢀ1) have been found between the
Ru(III) ion and the coordinated NIT-(5)ImH while no significant intermolecular antiferromagnetic inter-
actions are observed at low temperature leading to a ground spin state S = 1. The absence of intermolec-
ular magnetic interaction is explained by considering the crystal packing of (1) where the
[Ru(salen)(PPh3)(NIT-(5)ImH)]+ moieties are relatively well isolated. This has to be compared with the
situation observed in the previously reported [Ru(salen)(PPh3)-(NIT)]+ compound (2) where ferromag-
netic RuIII–NIT interaction were identified and the crystal packing generate intermolecular antiferromag-
netic interactions that complicated the study. The analysis of this compound confirms the rather isotropic
g values that were found of (2) and of [Ru(salen)(PPh3)(N3)], (3) a radical-free analogue. Moreover it is
also a step towards extended structures based on RuIII–NIT moieties since this compound possesses a free
bischelating site likely to coordinate additional metallic ions.
Received 23 January 2008
Accepted 26 February 2008
Available online 4 March 2008
Even if Italy won the world cup, Pr.
Gatteschi’s french students are glad to
dedicate him this article
Keywords:
Ruthenium
Schiff base
Radical
Crystal structure
Ferromagnetism
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
when working with heavier metal ions, whose chemistry is usually
rather tricky, and diamagnetic bridged complexes based on Ru(III)
Discrete or infinite polynuclear complexes with bridging li-
gands are widely used in the rational synthesis of molecule based
magnets. Some of these polynuclear complexes can indeed present
interesting physical properties as slow relaxation of the magneti-
zation, long range magnetic ordering, conductivity, chirality, lumi-
nescence,. . . [1,2]. To design them different approaches have been
explored during the last 20 years: one pot reactions or step by step
reactions implying the use of a low-nuclearity metallic precursor.
The nature of the bridging ligand is of fundamental importance
in determining the obtainment of such compounds. The ligand
can be a diamagnetic one, like acetato [3], cyanuro [4], oxalato
[5], oxamato [6], oximato [7], and oxo [8] bridges or a paramag-
netic one like TCNE (tetracyanoethenide) [9], TCNQ (7,7,8,8-tetra-
cyano-p-quinodimethane) [10], nitronyl nitroxide [11], verdazyl
[12] bridging radicals. This approach proved to be fruitful even
[13], Re(II) [14] and Re(IV) [15] have been reported. With the aim
of increasing the magnetic exchange interaction in this complexes
one should use ligand that possesses its own spin. Accordingly we
have recently designed the first complex in which a mononuclear
complex based on a heavy metal ion (RuIII, (S = 1/2) was linked to
a paramagnetic bridging ligand (a nitronyl nitroxide radical). More
precisely the NITpPy radical (NITpPy = 2-(4-pyridyl)-4,4,5,5-
tetramethylimidazoline-1-oxyl-3-oxide) was associated to the 4d
precursor
[Ru(salen)(PPh3)Cl]
(H2salen = N,N0-ethan-1,2-diyl-
bis(salicylidenamine), PPh3 = triphenylphosphine) leading to the
[Ru(salen)(PPh3)(NITpPy)](ClO4) complex [16]. Its crystallographic
structure revealed a dimerization of the compound, where two
[Ru(salen)(PPh3)(NITpPy)]+ moieties were stacked through p–p
interactions between the aromatic rings of the NITpPy radical. This
led to the presence of short contacts between the N–O groups of
the two radicals and mediates intermolecular antiferromagnetic
interaction (J = ꢀ5.0 cmꢀ1). However an intramolecular ferromag-
netic interaction was found between the Ru(III) ion and the radical
through the coordinated pyridine group (J = 9.0 cmꢀ1). One has to
note that this compound was the first radical-based complex that
* Corresponding author. Tel.: +39 0554573268; fax: +39 0554573372.
E-mail addresses: fabrice.pointillart@univ-rennes1.fr (F. Pointillart), kevin.ber-
not@unifi.it (K. Bernot), roberta.sessoli@unifi.it (R. Sessoli).
1
Fax: +33 2 23 23 84 38.
0020-1693/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2008.02.047

3428
F. Pointillart et al. / Inorganica Chimica Acta 361 (2008) 3427–3431
displays 2p-Ru(III) (S = 1/2) ferromagnetic exchange interaction.
Attempts to coordinate further this complex with 3d metal ions
to built extended structures were unsuccessful given the poor
reactivity of the free N–O groups.
of 1 is dissolved in a minimum of CH3OH and slow evaporation
gives suitable single crystals for X-ray diffraction measurements.
Caution: Perchlorate salts are potentially explosive and should
be handled with care and in small amounts [20].
Hence we describe in this paper the synthesis and magneto-
structural characterization of a compound of formula [Ru(salen)-
3. Results and discussion
(PPh3)(NIT-(5)ImH)](ClO4)
1 (NIT-(5)ImH = 2-(5)-imidazole-4,4,
5,5-tetramethylimidazoline-1-oxil-3-oxyde) where the former
NitpPy radical was replaced by an imidazole substituted nitronyl
nitroxide radical (noted NIT-(5)ImH). Consequently well beyond
adding a new compound to the RuIII-NIT family, this new com-
pound, providing a free bischelating site is a promising building
block for the synthesis of 2p–4d-based molecular magnets.
3.1. Methods and synthesis
The synthetic approach used for building [Ru(salen)(PPh3)(NIT-
(5)ImH)](ClO4)
1 is similar to the one employed for the
[Ru(salen)(PPh3)(NITpPy)](ClO4) complex (2) [16]. In fact we have
previously shown that the [Ru(salen)(PPh3)Cl] precursor is efficient
to coordinate the pyridine substituted radical NITpPy [16]. As the
basicity of pyridine and imidazole derivatives is very similar, we
have now coordinated this same precursor to an imidazole substi-
tuted radical, hereafter NIT-(5)ImH. This change of the aromatic
group is not expected to alter the nature of the magnetic interac-
tions between the Ru(III) ion and the radical and consequently
we should dispose here of a similar ferromagnetically coupled
building block. Thus, 1 can be considered as a rational enhance-
ment of the coordination capability of the previously reported
[Ru(salen)(PPh3)(NITpPy)](ClO4) complex [16].
2. Experimental
[Ru(salen)(PPh3)Cl] complex [16] and the new (2-(5)-imidazole-
4,4,5,5-tetramethylimidazoline-1-oxil-3-oxyde) ligand (noted NIT-
(5)ImH) are synthesized following already reported method [17].
The radical ligand was purified by chromatography on neutral alu-
mina (Type III, ethyl acetate eluent) to give pure NIT-(5)ImH [18].
All other reagents were purchased from Aldrich and used as
received.
3.2. Description of the crystal structure
2.1. Materials and methods
ꢀ
The compound 1 crystallizes in the triclinic system (P1, No. 2,
space group) (Table 1). An ORTEP view [21] of the corresponding
asymmetric unit is shown in Fig. 1.
The temperature dependence of the molar magnetic suscepti-
bility vM of [Ru(salen)(PPh3)(NIT-(5)ImH)](ClO4) 1 was investi-
gated in the range 5–300 K in an applied magnetic field of 1 T
and its magnetization at 2.7 K in the range 0–6.5 T on a Cryogenic
S600 SQUID magnetometer. Data were corrected for the intrinsic
diamagnetism of the sample and for a temperature independent
paramagnetism (TIP) contribution of 1.0 ꢁ 10ꢀ4 cm3 molꢀ1. X-band
EPR spectra were measured on a Bruker Elexsys E500 spectrometer
equipped with a continuous flow 4He cryostat to work at low tem-
perature. All measurements were performed on pellets in order to
avoid in field orientation on this compound.
The Ru(III) ion is coordinated to a salen2ꢀ ligand, with the two
axial positions of the Ru(III) ion occupied by one PPh3 and one
NIT-(5)ImH ligands. The Ru(III) ion is localised in the plane of the
salen2ꢀ ligand. The electro-neutrality of the molecule is ensured
by each perchlorate anion for one [Ru(salen)(PPh3)(NIT-(5)ImH)]+
mono-cationic moiety.
The four equatorial bonds Ru–X (two Ru–Osalen and two Ru–
salen) have very similar lengths (mean lengths of 1.994 Å) while
N
the two axial ones are longer (mean length of 2.249 Å) (see Table
2). This difference is due to the nature, the electronic density and
flexibility of the donor atoms in axial and equatorial positions.
The coordination polyhedron of Ru(III) ion can be thus described
as an elongated octahedral geometry of tetragonal symmetry.
2.2. X-ray crystallographic analysis
X-ray data were collected at 150 K with an Oxford Diffraction
Xcalibur3 diffractometer using MoKa radiation (k = 0.71073 Å).
Data reduction was accomplished using CRYSALIS.RED p171.29.2
[19a]. Absorption correction was performed using both ABSGRAB
and ABSPACK softwares included in the CRYSALIS package. The
ABSGRAB correction allows for a determination of l parameter
(l = 0.527 mmꢀ1). The structure was solved by direct methods,
developed by successive difference Fourier syntheses, and refined
by full-matrix least-squares on all F2 data using SHELXL 97 [19b].
Hydrogen atoms were included in calculated positions and allowed
to ride on their parent atoms.
Table 1
Crystallographic data for [Ru(salen)(PPh3)(NITImH)](ClO4)
Compound
Formula
[Ru(salen)(PPh3)(NITImH)](ClO4)
44H44N6O8Cl1P1Ru1
953.35
C
M (g molꢀ1
)
Crystal system
Space group
Cell parameters
a (Å)
b (Å)
c (Å)
triclinic
P1 (No. 2)
ꢀ
10.110(5)
14.367(5)
16.696(5)
111.799(5)
91.875(5)
106.041(5)
2139.0(14)
2
2.3. Preparation of [Ru(salen)(PPh3)(NIT-(5)ImH)](ClO4) 1
a (°)
b (°)
332.5 mg of Ru(salen)(PPh3)Cl (M = 664.5 g molꢀ1, n = 0.5 mmol)
c (°)
V (Å3)
are dissolved in 15 mL of CH3OH. To this solution is added a CH3OH
solution (10 mL) containing 97.4 mg of AgBF4 (M = 194.7 g molꢀ1
,
Cell formula units, Z
T (K)
293(2)
n = 0.5 mmol). The resulting mixture is heated under reflux during
1 h. The formed AgCl solid is removed by filtration and a CH3OH
solution (10 mL) containing 111.5 mg of NIT-(5)ImH (M =
223 g molꢀ1, n = 0.5 mmol) is added to the filtrate. The blue mix-
ture was heated under a gently reflux for 1 h. After this delay,
306.3 mg of solid NaClO4 (M = 122.5 g molꢀ1, n = 2.5 mmol) are
added to the mother solution. After 5 min, a dark green crystalline
powder of 1 appears. Yield: 405 mg (85%). The crystalline powder
Diffraction reflection
7.72° 6 2h 6 41.62°
1.480
0.527
qcalc (mg/m3)
l (mmꢀ1
)
Number of reflections
Independent reflections
Fo > 4r(Fo)
14547
4435
2053
Number of variables
R1, wR2
554
0.0943, 0.2152

F. Pointillart et al. / Inorganica Chimica Acta 361 (2008) 3427–3431
3429
Fig. 2. Packing view of [Ru(salen)(PPh3)(NITImH)](ClO4) showing the shortest int-
ermolecular distances between the nitronyl nitroxide radicals.
complex. The Ru–X distances, the conformation of the salen2ꢀ and
the interactions between the salen2ꢀ and PPh3 ligands are very
close in both structures. The fundamental difference between the
two structures is the packing of the molecules in the crystal. In-
deed, the substitution of the pyridine group by an imidazole group
leads to a drastic change of interactions between the radical li-
gands. In the packing of 1, no significant interactions between
the nitronyl nitroxide are found while for [Ru(salen)(PPh3)(NIT-
pPy)](ClO4) a dimerization of the molecules has been reported. This
dimeric structure led to short contacts between the nitronyl nitr-
oxide ligands that considerably affect the magnetic properties of
the complex.
Fig. 1. ORTEP view of the asymmetric unit of [Ru(salen)(PPh3)(NITImH)](ClO4) with
thermal ellipsoids at 50% probability. Hydrogen atoms are omitted for clarity.
Table 2
Selected bond lengths (Å) for [Ru(salen)(PPh3)(NITImH)](ClO4)
[Ru(salen)(PPh3)(NITImH)](ClO4)
3.3. EPR study
Ru1–O3salen
Ru1–O4salen
Ru1–N5salen
Ru1–N6salen
Ru1–N4NITHIm
Ru1–P1
N1–O1
N2–O2
Ru1–Ru1
1.977(9)
1.997(10)
2.004(14)
1.999(13)
2.140(10)
2.358(4)
1.295(14)
1.278(15)
8.332(34)
The X-band EPR spectrum of 1 at 5 K is reported in Fig. 3. It con-
sists of an intense and partially asymmetric band (DHpp = 120 Oe)
centered around g = 2.01. The observed g value is compatible with
that observed in [Ru(salen)(PPh3)(NITpPy)] derivative (2), whereas
the linewidth is much smaller. The first feature is a consequence of
both the quasi-isotropic ligand field around Ru(III), as suggested by
the EPR spectrum of the related Ru(salen)(PPh3)(N3)] [16] complex
(3), and of the contribution of the radical spin to the active
EPR state. On the other hand, the increased sharpness of the
band should be attributed to the absence of the strong intramolec-
ular interaction between two Ru–NIT moieties with mutually
The coordinated salen2ꢀ and triphenylphosphine ligands inter-
act together through p stacking interaction [22] between the phe-
nyl rings of the triphenylphosphine and the salen2ꢀ. The plane–
plane distance is equal to 3.45 Å. The salen2ꢀ ligand coordinated
to the Ruthenium cation is not planar and the two aromatic rings
form an angle of about 166°. This distortion is due to the proximity
of a non-planar phenyl group of the triphenylphosphine (at a dis-
tance of 3.53 Å). It also permits to increase the distance between
the aromatic system of the tetradentate ligand and the phenyl
group and so to decrease the repulsion/steric hindrance between
these two groups. The coordinated NIT-(5)ImH ligand is quasi pla-
nar with a torsion angle close to 0° (4.5°) between both imidazole
and the imidazoline cycles. Hydrogen bonds are found between the
hydrogen atom localised on the N3 nitrogen atom and the O2 oxy-
gen (2.149 Å). A second one involves the same hydrogen atom but
with the O6 oxygen of the perchlorate anion (2.097 Å). An analysis
of the crystal packing (Fig. 2) shows that the interactions between
the radical ligands NIT-(5)ImH are very small and the shortest N–N
and N–O distances are of 4.715 and 4.824 Å, respectively.
In summary, the crystallographic structure of 1 is very similar
to the one of the already reported [Ru(salen)(PPh3)(NITpPy)](ClO4)
Fig. 3. X-band (9.364 GHz) EPR spectrum of a powder sample of [Ru(salen)(PPh3)
(NITImH)](ClO4) measured at 5 K.

3430
F. Pointillart et al. / Inorganica Chimica Acta 361 (2008) 3427–3431
perpendicular elongation axis observed in [Ru(salen)(PPh3)(NIT-
pPy)](ClO4). Finally, it is interesting to note that the spectrum does
not show evidence for a fine structure. This suggests that, if pres-
ent, any zero field splitting of the resulting triplet state should be
small.
3.4. Magnetic properties
The thermal variations of the molar magnetic susceptibility vM
and the vMT product of 1 are shown in the Fig. 4. vM versus T curve
shows a continuous increase from 300 to 5 K while the vMT product
takes a constant value of 0.79 cm3 K molꢀ1 from 300 to about 75 K.
Below 75 K, this latter increases to take the value of
0.89 cm3 K molꢀ1 at 5 K (inset of Fig. 4). The observed value at
room temperature is in agreement with what expected for one
NIT-(5)ImH radical (S = 1/2, g = 2.00) and one Ru(III) ion with g
slightly larger than 2.00, as observed in other compounds contain-
ing low spin state Ru(III) ions [16,23]. The shape of the vMT versus T
curve is characteristic of a dominant ferromagnetic interaction be-
low 75 K.
Fig. 5 shows the experimental magnetization of 1 and the calcu-
lated Brillouin function [1] at 2.7 K assuming one uncorrelated
S = 1/2 with g = 2.00 (nitronyl nitroxide radical) and one uncorre-
lated S = 1/2 with g = 2.05 (Ru(III) ion). For any field, the experi-
mental magnetization of 1 is higher than that of the uncorrelated
system. This comparison confirms the presence of a ferromagnetic
exchange interaction that can be assigned to the intramolecular
Ru(III)-NIT-(5)ImH exchange pathways has for the previously re-
ported compound. This statement can be rationalized considering
that the ground state of Ru(III), as evidenced by the EPR spectrum
of [Ru(salen)(PPh3)(N3)] (3) [16], is characterised by a relevant con-
tribution of the 4dxy magnetic orbital of Ru(III) ion. Consequently
the Ru(III)-radical ferromagnetic interaction can be attributed to
the orthogonality of this orbitals with the 2pz magnetic orbitals
of the NIT-(5)ImH radical.
Fig. 5. The experimental (grey circles) and calculated magnetization (full black line)
for [Ru(salen)(PPh3)(NITImH)](ClO4) at 2.7 K in field range 0–6 T.
justifies this approach [24]. The best fit (R = 0.999, Fig. 4) high-
lights a ferromagnetic interaction between the Ru(III) ion and
the coordinated NIT-(5)ImH ligand (J = +2.47 0.07 cmꢀ1
,
H = ꢀJSRuSNITꢀ(5)ImH) considering the mean g value g = 2.05. The
difference with the g value obtained by EPR, of 2%, probably re-
flects a sample weighing error, and is then physically unrelevant.
The ferromagnetic interaction found in 1 is smaller than that in
[Ru(salen)(PPh3)(NITpPy)](ClO4) (J = + 9.00 cmꢀ1) probably due to
an electronic delocalisation on the coordinated nitrogen atom of
the imidazole ring that is weaker than the one of the pyridine
derivative. However in 1 no antiferromagnetic interaction is
observed at low temperature contrary to what seen on
[Ru(salen)(PPh3)(NITpPy)](ClO4) [16]. As already suggested this is
due to the crystal packing of 1, where the insulation of the mole-
cule is drastically enhanced since no N–Oꢂ ꢂ ꢂO–N contacts are pres-
ent here. Consequently the spin state at low temperature of 1 is
S = 1 when it was S = 0 for [[Ru(salen)(PPh3)(NITpPy)](ClO4)]2.
A quantitative determination of the molar magnetic susceptibil-
ity is performed by fitting the data through a Bleaney–Bowers
expression [1], the interaction of NIT-(5)ImH and Ru(III) with the
magnetic field being considered to be isotropic (cf. EPR measure-
ments). The experimental vM curve has been fitted in the 5–
300 K range with a mean value of g for the complex 1. We note
here that, while in principle the use of isotropic exchange hamilto-
nian is not perfectly justified for systems containing orbitally
degenerate centres, the largely isotropic nature of Ru(III) centers
evidenced by the EPR spectrum of [Ru(salen)(PPh3)(N3)] (3) [16]
4. Conclusion
In summary, we have synthesized and characterized by X-ray
diffraction a new Ru(III)–Nitroxide complex where ferromagnetic
exchange interactions have been found between the Ru(III) ion
and the radical ligand. The appropriate choice of a new nitronyl
nitroxide radical coordinated on the Ru(III) ion has permitted to
suppress the intermolecular antiferromagnetic interaction ob-
served in our previously reported complex [Ru(salen)(PPh3)(NIT-
pPy)](ClO4) (2). Compound 1 is thus a S = 1, 2p–4d, building
block, where the free bis-chelating coordination site is likely to
coordinate additional metallic ions to form extended structures.
Synthesis of heterometallic 2p–3d–4d complexes based on the pre-
cursor 1 are in progress.
Acknowledgments
We acknowledge the financial support from Italian MURST
(FIRB and PRIN grants), from the EC through the Human Potential
Program RTN-QUELMOLNA (MRTN-CT-2003-504880), from the
NE-MAG-MANET (NMP3-CT-2005-515767) and of Ente Cassa di
Risparmio di Firenze. F.P. thanks German DFG (SPP1137) for his
post-doctoral fellowship. D. Rovai is acknowledged for her assis-
tance in the synthesis.
Appendix A. Supplementary material
Fig. 4. Plot of vM vs T for [Ru(salen)(PPh3)(NITImH)](ClO4) (grey circles) measured
at 1 T and its best fit in full black line. In the inset is shown the experimental
CCDC 674627 contains the supplementary crystallographic data
product vM
T vs T (grey squares) and its best fit in full black line for [Ru-
for 1. These data can be obtained free of charge from The Cam-
(salen)(PPh3)(NITImH)](ClO4) measured at 1 T.

F. Pointillart et al. / Inorganica Chimica Acta 361 (2008) 3427–3431
3431
(b) V.M. Mereacre, A.M. Ako, R. Clérac, W. Wernsdorfer, G. Filoti, J. Bartolomé,
C.E. Anson, A.K. Powell, J. Am. Chem. Soc. 129 (2007) 9248.
[9] (a) E.J. Brandon, C. Kollmar, J.S. Miller, J. Am. Chem. Soc. 120 (1998) 1822;
(b) D.K. Rittenberg, K. Sugiura, Y. Sakata, I.A. Guzei, A.L. Rheingold, J.S. Miller,
Chem. Eur. J. 5 (1999) 1874;
bridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/da-
ta_request/cif. Supplementary data associated with this article
can be found, in the online version, at doi:10.1016/
j.ica.2008.02.047.
(c) D.K. Rittenberg, L. Baars-Hibbe, A. Böhm, J.S. Miller, J. Mater. Chem. 10
(2000) 241;
References
(d) J.S. Miller, Inorg. Chem. 39 (2000) 4393.
[10] (a) K. Sugiura, S. Mikami, M.T. Johnson, J.S. Miller, K. Iwasaki, K. Umishita, S.
Hino, Y. Sakata, J. Mater. Chem. 10 (2000) 959;
(b) M.T. Johnson, A.M. Arif, J.S. Miller, Eur. J. Inorg. Chem. 6 (2000) 1781;
(c) H. Miyasaka, T. Madanbashi, K. Sugimoto, Y. Nakazawa, W. Wernsdorfer,
K. -I Sugiura, M. Yamashita, C. Coulon, R. Clérac, Chem. Eur. J. 12 (2006) 7028.
[11] (a) A. Caneschi, D. Gatteschi, N. Lalioti, C. Sangregorio, R. Sessoli, G. Venturi, A.
Vindigni, A. Rettori, M.G. Pini, M.A. Novak, Angew. Chem. 113 (2001) 1810;
(b) L. Bogani, C. Sangregorio, R. Sessoli, D. Gatteschi, Angew. Chem., Int. Ed. 44
(2005) 5817;
[1] (a) O. Kahn, Molecular Magnetism, VCH, New York, 1993;
(b) D. Gatteschi, J. Villain, R. Sessoli, Molecular Nanomagnets, Oxford
University Press, Oxford, UK, 2006.
[2] (a) G. Christou, D. Gatteschi, D.N. Hendrickson, R. Sessoli, MRS Bull. 25 (2000)
66;
(b) D. Gatteschi, R. Sessoli, Angew. Chem., Int. Ed. Engl. 42 (2003) 268;
(c) L. Thomas, F. Lionti, R. Ballou, D. Gatteschi, R. Sessoli, B. Barbara, Nature 383
(1996) 145;
(d) J.R. Friedman, M.P. Sarachik, J. Tejada, R. Ziolo, Phys. Rev. Lett. 76 (1996)
3830;
(e) W. Wernsdorfer, R. Sessoli, Science 284 (1999) 133;
(f) S. Hill, R.S. Edwards, N. Aliaga-Alcalde, G. Christou, Science 302 (2003) 1015;
(g) R. Sessoli, D. Gatteschi, A. Caneschi, M.A. Novak, Nature 365 (1993) 141;
(h) L. Bogani, L. Cavigli, K. Bernot, R. Sessoli, M. Gurioli, D. Gatteschi, J. Mater.
Chem. 16 (2006) 2587.
(c) K. Bernot, L. Bogani, A. Caneschi, D. Gatteschi, R. Sessoli, J. Am. Chem. Soc.
128 (2006) 7947;
(d) K. Fegy, N. Sanz, D. Luneau, E. Belorizky, P. Rey, Inorg. Chem. 37 (1998)
4518;
(e) K. Fegy, D. Luneau, E. Belorizky, M. Novac, J.-L. Tholence, C. Paulsen, T. Ohm,
P. Rey, Inorg. Chem. 37 (1998) 4524.
[12] (a) F. Pointillart, C. Train, P. Herson, J. Marrot, M. Verdaguer, New J. Chem. 31
(2007) 1001;
(b) T.M. Barclay, R.G. Hicks, M.T. Lemaire, L.K. Thompson, Inorg. Chem. 40
(2001) 5583.
[13] (a) W.-F. Yeung, P.-H. Lau, T.-C. Lau, H.-Y. Wei, H.-L. Sun, S. Gao, Z.-D. Chen,
W-T. Wong, Inorg. Chem. 44 (2005) 6579;
[3] (a) T. Lis, Acta Crystallogr., Sect. B 36 (1980) 2042;
(b) R. Sessoli, H.L. Tsai, A.R. Schake, S. Wang, J.B. Vincent, K. Folting, D.
Gatteschi, G. Christou, D.N. Hendrickson, J. Am. Chem. Soc. 115 (1993) 1804.
[4] (a) R. Lescouëzec, L.M. Toma, J. Vaissermann, M. Verdaguer, F.S. Delgado, C.
Ruiz-Perez, F. Lloret, M. Julve, Coord. Chem. Rev. 249 (2005) 2691;
(b) V. Marvaud, C. Decroix, A. Scuiller, C. Guyard-Duhayon, J. Vaissermann, F.
Gonnet, M. Verdaguer, Eur. J. Chem. 9 (2003) 1677;
(c) V. Marvaud, C. Decroix, A. Scuiller, F. Tuyeras, C. Guyard-Duhayon, J.
Vaissermann, J. Marrot, F. Gonnet, M. Verdaguer, Eur. J. Chem. 9 (2003) 1692.
[5] (a) H. Tamaki, Z.J. Zhong, N. Matsumoto, S. Kida, M. Koikawa, N. Achiwa, Y.
Hashimoto, H. Okawa, J. Am. Chem. Soc. 114 (1992) 6974;
(b) S. Decurtins, H.W. Schmalle, P. Schneuwly, H.R. Oswald, Inorg. Chem. 32
(1993) 1888;
(b) W.-F. Yeung, W.-L. Man, W-T. Wang, T.-C. Lau, S. Gao, Angew. Chem., Int.
Ed. Engl. 40 (2001) 3031;
(c) E.J. Beck, K.D. Drysdale, L.K. Thompson, L. Li, C.A. Murphy, M.A.S. Aquino,
Inorg. Chim. Acta 279 (1998) 121;
(d) F.A. Cotton, J. Lu, A. Yokochi, Inorg. Chim. Acta 275–276 (1998) 447;
(e) F.A. Cotton, Y. Kim, T. Ren, Inorg. Chem. 31 (1992) 2723;
(f) F.A. Cotton, Y. Kim, T. Ren, Polyhedron 12 (1993) 607;
(g) F.A. Cotton, M. Matusz, B. Zhong, Inorg. Chem. 27 (1988) 4368;
(h) M. Handa, Y. Sayama, M. Mikuriya, R. Nukada, I. Hiromitsu, K. Kasuga,
Chem. Lett. (1996) 201;
(i) Y. Sayama, M. Handa, M. Mikuriya, I. Hiromitsu, K. Kasuga, Chem. Lett.
(1998) 777;
(j) Y. Sayama, M. Handa, M. Mikuriya, I. Hiromitsu, K. Kasuga, Bull. Chem. Soc.
Jpn. 64 (1995) 1647;
(k) M. Mikuriya, K. Tamaka, M. Handa, I. Hiromitsu, D. Yoshioka, D. Luneau,
Polyhedron 25 (2005) 2658;
(l) Y. Liao, W.W. Shum, J.S. Miller, J. Am. Chem. Soc. 124 (2002) 9336;
(m) T.E. Vos, Y. Liao, W.W. Shum, J.-H. Her, P.W. Stephens, W.M. Reiff, J.S.
Miller, J. Am. Chem. Soc. 126 (2004) 11630.
(c) S. Decurtins, H.W. Schmalle, P. Schneuwly, J. Ensling, P. Guetlich, J. Am.
Chem. Soc. 116 (1994) 9521;
(d) S. Decurtins, H.W. Schmalle, R. Pellaux, P. Schneuwly, A. Hauser, Inorg.
Chem. 35 (1996) 1451;
(e) M. Hernandez-Molina, F. Lloret, C. Ruiz-Perez, M. Julve, Inorg. Chem. 37
(1998) 4131;
(f) R. Sieber, S. Decurtins, H. Stoeckli-Evans, C. Wilson, D. Yufit, J.A.K. Howard,
S.C. Capelli, A. Hauser, Chem. Eur. J. 6 (2000) 361;
(g) E. Coronado, J.R. Galan-Mascaros, C.J. Gomez-Garcia, J.M. Martinez-Agudo,
Inorg. Chem. 40 (2001) 113;
(h) R. Andres, M. Brissard, M. Gruselle, C. Train, J. Vaissermann, B. Malezieux,
J.-P. Jamet, M. Verdaguer, Inorg. Chem. 40 (2001) 4633;
(i) F. Pointillart, C. Train, M. Gruselle, F. Villain, H.W. Schmalle, D. Talbot, P.
Gredin, S. Decurtins, M. Verdaguer, Chem. Mater. 16 (2004) 832;
(j) F. Pointillart, C. Train, K. Boubekeur, M. Gruselle, M. Verdaguer,
Tetrahedron: Asymmetry 17 (2006) 1937;
(k) F. Pointillart, C. Train, F. Villain, C. Cartier dit Moulin, P. Gredin, L.-M.
Chamoreau, M. Gruselle, G. Aullon, S. Alvarez, M. Verdaguer, J. Am. Chem. Soc.
129 (2007) 1327.
[14] (a) E.J. Schelter, J.K. Bera, J. Basca, J.R. Galan-Mascaros, K.R. Dunbar, Inorg.
Chem. 42 (2003) 4456;
(b) E.J. Schelter, A.V. Prosvirin, K.R. Dunbar, J. Am. Chem. Soc. 124 (2004) 7656.
[15] (a) R. Chiozzone, R. Gonzalez, C. Kremer, G. De Munno, J. Cano, F. Lloret, M.
Julve, J. Faus, Inorg. Chem. 38 (1999) 4745;
(b) J.M. Lillo, D. Armentano, G. De Munno, W. Wernsdorfer, M. Julve, F. Lloret, J.
Faus, J. Am. Chem. Soc. 128 (2006) 14218.
[16] F. Pointillart, K. Bernot, L. Sorace, R. Sessoli, D. Gatteschi, Dalton Trans. (2007)
2689.
[17] (a) J.H. Osiecki, E.F. Ullman, J. Am. Chem. Soc. 90 (1968) 1078;
(b) E.F. Ullmann, L. Call, J.H. Osiecki, J. Org. Chem. 35 (1970) 3623;
(c) E.F. Ullman, J.H. Osiecki, D.G.B. Boocock, R. Darcy, J. Am. Chem. Soc. 94
(1972) 7049.
[18] K. Fegy, D. Luneau, T. Ohm, C. Paulsen, P. Rey, Angew. Chem., Int. Ed. Engl. 37
(1998) 1270.
[19] (a) Oxford Diffraction, CRYSALIS CCD and CRYSTALIS RED, Oxford Diffraction,
Oxfordshire, England, 2000.;
(b) G.M. Sheldrick, SHELXL-97, Program for Refinement of Crystal Structures,
University of Göttingen, Germany, 1997.
[20] C.N.R. Rao, A. Ranganathan, V.R. Pedireddi, A.R. Raju, Chem. Commun. (2000)
39.
[21] C.K. Johnson, ORTEP, Report ORNL-5138, OakRidge National Laboratory,
OakRidge, TN, 1976.
[22] C. Janiak, J. Chem. Soc., Dalton Trans. (2000) 3885.
[23] J. Larionova, B. Mombelli, J. Sanchiz, O. Kahn, Inorg. Chem. 37 (1998) 679.
[24] A.V. Palii, B.S. Tsukerblat, E. Coronado, J.M. Clemente-Juan, J.J. Borràs-Almenar,
J. Chem. Phys. 118 (2003) 5566.
[6] (a) E. Pardo, R. Ruiz-Garcia, F. Lloret, J. Faus, M. Julve, Y. Journaux, M.A. Novak,
F.S. Delgado, C. Ruiz-Perez, Chem. Eur. J. 13 (2007) 2054;
(b) G. Blay, I. Fernández, J.R. Pedro, R. Ruiz-García, M.C. Muñoz, J. Cano, R.
Carrrasco, Eur. J. Org. Chem. 9 (2003) 1627;
(c) E. Pardo, K. Bernot, M. Julve, F. Lloret, J. Cano, R. Ruiz-García, F.S. Delgado, C.
Ruiz-Pérez, X. Ottenwaelder, Y. Journaux, Inorg. Chem. 43 (2004) 2768;
(d) E. Pardo, K. Bernot, M. Julve, F. Lloret, J. Cano, R. Ruiz-García, J. Pasán, C.
Ruiz-Pérez, X. Ottenwaelder, Y. Journaux, Chem. Commun. (2004) 920;
(e) E. Pardo, R. Ruiz-García, F. Lloret, M. Julve, J. Cano, J. Pasán, C. Ruiz-Pérez, Y.
Filali, L.M. Chamoreau, Y. Journaux, Inorg. Chem. 46 (2007) 4504;
(f) E. Pardo, K. Bernot, F. Lloret, M. Julve, R. Ruiz-García, J. Pasán, C. Ruiz-Pérez,
D. Cangussu, V. Costa, R. Lescouëzec, Y. Journaux, Eur. J. Inorg. Chem. (2007)
4569.
[7] (a) C.J. Milios, T.C. Stamatatos, S.P. Perlepes, Polyhedron 25 (2006) 134;
(b) S. Ueki, Y. Kobayashi, T. Ishida, T. Nogami, Chem. Commun. (2005) 5223;
(c) S. Ueki, A. Okazawa, T. Ishida, T. Nogami, H. Nojiri, Polyhedron 26 (2007)
1970.
[8] (a) T.C. Stamatatos, K.A. Abboud, W. Wernsdorfer, G. Christou, Angew. Chem.,
Int. Ed. 46 (2007) 884;