From Mesomorphic Phosphine Oxide to Clustomesogens Containing Molybdenum and Tungsten Octahedral Cluster Cores

Article abstract of DOI:10.1002/anie.201503205

New clustomesogens (i.e., metal atom clusters containing liquid crystalline (LC) materials) have been obtained by grafting neutral cyanobiphenyl (CB)- or cholesteryl-containing tailor-made dendritic mesomorphic triphenylphosphine oxide ligands on luminesc

Full text of DOI:10.1002/anie.201503205

Angewandte
Chemie
International Edition: DOI: 10.1002/anie.201503205
German Edition: DOI: 10.1002/ange.201503205
Cluster Compounds
From Mesomorphic Phosphine Oxide to Clustomesogens Containing
Molybdenum and Tungsten Octahedral Cluster Cores**
Viorel Cîrcu,* Yann Molard,* Maria Amela-Cortes, Ahmed Bentaleb, Philippe Barois,
Vincent Dorcet, and StØphane Cordier*
Abstract: New clustomesogens (i.e., metal atom clusters
containing liquid crystalline (LC) materials) have been
obtained by grafting neutral cyanobiphenyl (CB)- or choles-
teryl-containing tailor-made dendritic mesomorphic triphenyl-
phosphine oxide ligands on luminescent (M6Cli8)4+ octahedral
cluster cores (M = Mo, W). The LC properties were studied by
a combination of polarizing optical microscopy (POM),
differential scanning calorimetry (DSC), and X-ray powder
diffraction analyses. While the organic ligands showed various
mesophase types ranging from nematic, SmA columnar
(SmACol), SmA, and SmC phases, it turned out that the
corresponding clustomesogens formed layered phases (SmA)
over a wide range of temperatures that depend on the nature
and density of mesogenic groups employed. Intrinsic lumines-
cence properties of the cluster precursors are preserved over the
entire range of LC phase existence.
technologies.[2] Association of organic mesogenic moieties
with octahedral metallic cluster complexes led to a new family
of liquid crystals, namely the clustomesogens, which exhibit
interesting photoluminescence properties in the red-near-
infrared region due to the cluster core.[3] In the light of recent
findings, quantum yields of nanometer-sized octahedral
clusters can reach values above 60%.[4] The affordable costs
and preparation methods as well as thermal stability, the ease
of handling and processing make them very appealing
materials to be used in different applications based on
emission properties (LED, lighting displays, etc.). Combining
such nanoobjects with liquid-crystalline ordering is a challeng-
ing task[5] and so far, several strategies based on covalent
binding or ionic self-assembly (ISA) were successfully
employed to induce liquid crystalline (LC) properties in
systems containing bulky entities, such as fullerene[6] and
polyoxometalates.[7,8] On the other hand, phosphine or
phosphine oxide ligands were scarcely used in the design of
liquid-crystalline materials, mainly due to their inappropriate
geometry concerning the molecular requirements to generate
mesomorphic behavior.[9] Moreover, even if they are widely
used as ligands in coordination chemistry only few examples
of phosphine-oxide-containing metallomesogens (metal-con-
taining liquid crystals) are known.[10] Generally, only less
bulky phosphines, such as trialkylphosphine (alkyl = methyl,
ethyl, propyl), were employed as co-ligands besides the other
mesogenic ligands. Recently, it has been shown that the
triphenylphosphine oxide core can be successfully used as
a scaffold to obtain columnar liquid crystals that can interact
easily with alkali metals to allow a switch between columnar
and cubic phases.[11] In this Communication, we show that
cholesteryl- and cyanobiphenyl-based phosphine oxide
ligands constitute a valuable class of compounds that can be
successfully used to design LC hybrid materials and in
particular clustomesogens. By using long flexible alkyl
chains to link the mesogenic groups to the coordinating
unit, we prove that it is possible to decouple the mesogenic
entities motion from the bulky metallic (M6Cli8)4+ cluster core
L
iquid crystals are self-assembling molecular materials that
have found various applications ranging from the manufac-
turing of liquid crystal display (LCD) to different molecular
sensors and detectors, optical switches, spatial light modu-
lator, etc., based on their unique features to retain a high
degree of mobility besides long or short-range ordering in the
fluid phase that give rise to anisotropy-related optical,
electrical, and magnetic properties.[1] On the other hand,
metal atom clusters are versatile building blocks for the
design of hybrid nanomaterials with potential applications,
for instance, in the fields of lighting, displays, and biolabeling
[*] Dr. V. Cîrcu, Dr. Y. Molard, Dr. M. Amela-Cortes, Dr. V. Dorcet,
Dr. S. Cordier
UniversitØ de Rennes 1, UMR “Sciences Chimiques de Rennes”
UR1-CNRS 6226, Equipe Chimie du Solide et MatØriaux
Campus de Beaulieu, CS 74205, 35042 Rennes Cedex (France)
E-mail: yann.molard@univ-rennes1.fr
stephane.cordier@univ-rennes1.fr
Dr. V. Cîrcu
Department of Inorganic Chemistry, University of Bucharest
Dumbrava Rosie 23, Bucharest 020464, sector 2 (Romania)
E-mail: viorel.circu@chimie.unibuc.ro
within the [(M6Cli8)La ]4+ building blocks, further abbreviated
6
as ML1–4 (M = Mo and W). This strategy is related to the one
used to incorporate a functional moiety in LC-dendrimers[12]
or the preparation of LC hybrid systems made of inorganic
nanoparticles[13] as well as the design of metallomesogens with
high coordination numbers.[14] Hence, resulting clustomeso-
gens display typical layered LC phases with transition
temperatures influenced by the type and number of meso-
genic groups grafted in the apical position of the (M6Cli8)4+
octahedral cluster core while the emissive properties of the
latter are kept almost unchanged. By using different neutral
A. Bentaleb, Dr. P. Barois
UniversitØ de Bordeaux and CNRS, CRPP, UPR8641
33600 Pessac (France)
[**] The research leading to these results has received funding from the
European Union Seventh Framework Programme (FP7/2007-2013)
under grant agreement number PIEF-GA-2010-272165 and from the
ANR Clustomesogen ANR-13-BS07-0003-01.
Supporting information (including all experimental details) for this
article is available on the WWW under http://dx.doi.org/10.1002/
anie.201503205.
Angew. Chem. Int. Ed. 2015, 54, 10921 –10925
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
10921

.
Angewandte
Communications
phosphine oxide ligands, we modified the mesogenic density
surrounding the rigid metallic scaffold, which allows a deeper
understanding of the requirements to control the nano-
structuration and self-assembling abilities of these super-
molecular systems in order to be able to adjust at will their
self-organization according to targeted applications. The
grafting of six neutral ligands onto the octahedral metallic
clusters was initially investigated by using the tris(p-methoxy-
phenyl)phosphine oxide, the intermediate organic ligand
without mesogenic groups, starting from hexa-triflate [M6Cli8-
(CF3SO3)6]2À (M = Mo, W) precursors. Resulting (CF3SO3)4-
i
a
=
[M6Cl 8(O P(PhOMe)3) ] with M = Mo or W for compounds
6
MoL4 and WL4, respectively, were isolated as yellow crystals
that were subjected to single-crystal X-ray diffraction studies
confirming the formation of Mo6 and W6 hexa-functionalized
À
metallic clusters with formation of a M O bond between the
(M6Cli8)4+ cluster core and organic ligand (see the Supporting
Information (SI) for crystallographic details).
The 31P NMR solution spectra of functionalized Mo6 and
W6 clusters showed not only one signal, but a multiplet
around 55 ppm assigned to the coordinated ligands, together
with a very weak and broad signal around 30 ppm assigned to
the free ligand. This is in stark contrast to the previously
reported NMR data for hexa-substituted Mo6 and W6 clusters
with triphenylphosphine ligands for which only one signal in
the 31P NMR spectrum was recorded.[15] This information
could be interpreted by the existence of two competing
factors: the non-equivalence of the six apical ligands due to
structural conformation and a possible exchange between
apical ligands and outer counteranions in solution. These
findings determined us to have a closer look at the X-ray
crystal structure of compounds MoL4 and WL4 revealing that
À
the six M O bonds are not equivalent (Table S2 in SI).
Further, the monitoring by 31P NMR spectroscopy of the
addition of an excess of phosphine oxide L4 to the solution of
MoL4 led to the collapse of the multiplet signal into two
singlets and to the increase of the free ligand signal intensity
thus evidencing the ligand exchange (Figure S13). Moreover,
temperature-dependent 31P NMR spectroscopy experiments
realized with a CD2Cl2 solution of MoL4 showed upon cooling
the disappearance of this last signal together with a clear
narrowing of the multiplet corresponding to the grafted
ligands (Figure S14). The mesogenic phosphine oxides L1–3
were prepared in moderate to good yield in a straightforward
manner by the reaction of tris(4-hydroxyphenyl)phosphine
oxide with corresponding bromide derivatives.[11,16] The
covalent hexa-functionalization of the Mo6 and W6 metallic
clusters has been achieved by a ligand-exchange reaction
between the [M6Cl8(CF3SO3)6]2À cluster unit with a slight
excess of mesogenic phosphine oxide ligand in dichloro-
methane at room temperature (Scheme 1).[15] The purity of all
compounds was assessed by elemental analysis. The IR
spectra of hexa-substituted Mo6 and W6 clusters show several
shoulders in the 1100–1200 cmÀ1 range assigned to the
Scheme 1. Preparation of new hexa-functionalized Mo6 and W6 clus-
ters.
55 ppm and a broad signal centered around 30 ppm, suggest-
ing a similar behavior in solution with six apical ligands
around the cluster unit (Figure S8). The LC phases exhibited
by both organic ligands and their respective clustomesogens
were assigned based on the polarized optical microscopy
(POM) textures as well as by variable-temperature powder X-
ray diffraction and differential scanning calorimetry (DSC)
studies. Their transition temperatures and the liquid crystal-
line properties are collected in Table 1. Whereas mesogenic
organic ligand L1 shows typical textures for a nematic phase,
the mesogenic phosphine oxide L2 shows a pseudo-focal conic
texture that was assigned to a lamellar columnar phase
(SmACol).[14] The POM pictures are shown in Figures S45–S52.
Interestingly, the X-ray diffractogram of L2 shows two strong
reflections in the small-angle region in the 1:2 ratio that
correspond to a periodicity of 45.3 Š due to a multilayered
smectic phase formed by the piling of triphenyloxide- and
cyanobiphenyl-containing sublayers alternating with the ali-
phatic spacer sublayer. The abnormal intensities profile in the
À
CF3SO3 ion together with a medium intensity absorption
band in the 1000–1100 cmÀ1 range due to P O vibration
=
(Figures S19–S22). The 31P NMR spectra contain the same
features as those found for non-mesogenic Mo6 and W6
clusters MoL4 and WL4, for example, a multiplet around
10922 www.angewandte.org
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2015, 54, 10921 –10925

Angewandte
Chemie
Table 1: Transition temperatures, mesophase assignment, and interlayer
reproducible and the transition temperatures did not
distances for compounds MoL1–3 and WL1–3
Cmpd Transition[a]
DH
[8C][b] [kJmolÀ1
.
change. All samples show a glass transition on heating or
cooling and no sign of crystallization. Obviously, the tran-
sition temperatures depend significantly on the number and
type of mesogenic units per cluster unit employed as well as
the cluster type. As expected, the LC phase is stabilized by the
addition of dendrons to the metallic cluster as already
described for hexa-substituted fullerenes[6b] or polyhedral
silsesquioxanes.[13g] Note that higher transition temperatures
have been recorded for W6 clusters when compared to Mo6
clusters as a consequence of the presence of heavier and
higher polarization of tungsten metal; a similar trend was
reported for Mo and W liquid crystalline materials with no
additional intermolecular interactions.[18] The POM observa-
tions (Figure 1) clearly indicate the formation of a layered
T
DH per mesogenic
d [Š]
(T [8C])
]
unit/[kJmolÀ1
]
L1
L2
L3
g–N
N–I
15
32
24
69
54
95
137
33
47
32
50
33
87
39
94
50
–
–
–
–
–
–
3.6
–
–
3.1
–
0.3
–
–
–
2.1
–
2.9
–
2.5
–
3.0
[c]
g–SmACol
SmACol–I
g–SmC
SmC–SmA
SmA–I
45.3
(65)
49.5
(70)
21.7
–
–
[d]
9.3
–
MoL1 g–SmA
35.7
(40)
35.9
(40)
42.5
(80)
42.8
(80)
50.5
(160)
51.0
(170)
SmA–I
g–SmA
SmA–I
5.0
–
–
WL1
[c]
MoL2 g–SmA
–
75.6
–
102.6
–
44.6
–
SmA–I
g–SmA
SmA–I
WL2
MoL3 g–SmA
SmA–I(dec.) 166
g–SmA 54
SmA–I(dec.) 174
WL3
53.7
[a] g=glass, N=nematic, SmACol =lamellar-columnar, SmA=smectic
A, I=isotropic phase. [b] Temperatures are given as the onset values
recorded in the second heating run, except compounds MoL3 and WL3;
glass temperatures were recorded in the second cooling run as the
inflexion point; [c] transition not detected by DSC; temperature was
Figure 1. POM pictures of the SmA phase of MoL2 taken at 808C
b) without and c) with irradiation in the 380–420 nm range.
assigned by POM; [d] DCp=0.1 kJmolÀ1 KÀ1
.
diffractogram of L2 (Figure S24) with an intense d002 reflection
compared to the d001 reflection was already found for typical
bilayered smectic phases due to a pronounced segregation at
the molecular level, between different units, for example,
cyanobiphenyl units, aliphatic spacers, and the triphenylphos-
phine core.[17] Another broad reflection was seen around
13.2 Š and was assigned to some lateral periodicity within the
layer due to the triphenylphosphine oxide units that show
a strong tendency to stack into columns as previously shown
by Kato and Hatano.[11] The cholesteryl-based organic ligand
L3 displays two enantiotropic layered phases with a slight
decrease of interlayer distance on decreasing the temperature
below 958C (Figure S25) assigned to SmA and SmC phases.
The latter phase was also evidenced by the typical Schlieren
texture developed in the homeotropic regions of the previous
SmA phase. The tilt angle was estimated to 188 at 608C from
SAXS data.
SmA phase. Indeed, upon cooling the isotropic liquid, a clear
fan-shape texture developed together with large homeotropic
regions in the case of MoL2 and WL2, all indicative of
a smectic A phase.
Compounds MoL1 and WL1 show a rather sandy texture
formed by shearing with high birefringent areas on cooling
from the isotropic phase whereas compounds MoL3 and WL3
exhibit a fan-shape texture on heating near the decomposition
temperature. These observations were confirmed by variable
temperature 2D powder X-ray diffraction (Figures S34 and
S35) recorded on cooling, with the exception of MoL3 and
WL3, after a previous heating run above the clearing temper-
ature. The XRD pattern of MoL3 and WL3 were recorded
during the first heating run to prevent the decomposition
above the clearing point. The temperature-dependent dif-
fractograms show the same features for all compounds
(Figures S28–S35). In the small-angle region, two or three
sharp reflections in the 1:2:3 d-spacing ratio, were assigned to
a long-range order of a layered phase. Additionally, the
mesomorphic clusters MoL1–3 and WL1–3 exhibit one diffuse
signal with the maxima located around 4.5 Š (hch) corre-
sponding to the lateral short-range order of the molten alkyl
chains. Another broad and intense reflection was found at the
base of the sharp d002 reflection, around 20 Š (hcluster1), for all
six clusters that is associated with the average correlation
distance between octahedral metallic cluster within the layers
as already found in previously described LC Mo6-based
clusters or for LC SMM-based on dodecamanganese poly-
oxometalate.[8] The relative broadness of this reflection is
indicative of a rather short-range order in intralayer corre-
Although clustomesogens MoL1 and WL1, possessing 18
cyanobiphenyl mesogenic groups around the cluster core,
show an enantiotropic SmA phase at relatively low temper-
atures, the clustomesogens MoL3 and WL3 with bulkier
cholesteryl-based mesogenic groups show an extended stabil-
ity range of SmA phase (1668C for MoL3 and 1748C for WL3)
up to the clearing point when decomposition occurs. On the
other hand, the hexa-substituted clusters with 36 cyanobi-
phenyl mesogenic groups, MoL2 and WL2, show both only one
very sharp enantiotropic transition from isotropic liquid to
the mesophase and no sign of thermal decomposition after
reaching the isotropic phase (Figures S41 and S42). On
subsequent heating–cooling cycles, the DSC traces were
Angew. Chem. Int. Ed. 2015, 54, 10921 –10925
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org 10923

.
Angewandte
Communications
of the clusters are dependent on both inner halide ligands X
(X = Cl, Br, or I) in the cluster core and apical ligands. Thus,
hexanuclear molybdenum and tungsten clusters with chlorine
or bromide as inner ligands with various halides,[20] sulfo-
nates,[21] carboxylates,[2a,3,4] or thiolates[22] in terminal posi-
tions were well studied for their red phosphorescence. On the
other hand, to the best of our knowledge the emission
properties of either Mo6 or W6 clusters with phosphine oxide
as terminal ligands have never been reported although several
such clusters have been prepared.[15,23] The emission proper-
ties were investigated in the liquid crystalline state with
samples deposited on glass slides, heated to isotropic state and
then cooled down slowly to room temperature by using
a polarizing microscope equipped with a hotstage, an
irradiation source (irradiation in the 380-420 nm range), and
a CCD spectrophotometer. It was found that title clustomes-
ogens, exhibit broad emission ranged from 550 up to 900 nm,
with approx. 50 nm red-shifted maxima of emission for W6-
based clusters when compared to Mo6-based clusters. The
emission window is unaffected even in the isotropic phase at
about the clearing point (Figure S53) whereas intensity
slightly decreases upon heating. Moreover, the cluster com-
pounds MoL4 and WL4 without mesogenic groups show the
same characteristics of emission meaning that the introduc-
tion of mesogenic cyanobiphenyl or cholesteryl groups in the
molecule does not affect the luminescence properties (Fig-
ure S54). Indeed, we demonstrated that utilizing various
phosphine oxides as coordinating entities to the cluster core
does not influence its emission properties. Furthermore, after
functionalization with mesogenic groups these properties are
preserved in the liquid-crystal state over the entire temper-
ature range up to isotropic state.
In conclusion, we have demonstrated in this work that
phosphine oxide cores functionalized with appropriate meso-
genic groups can be successfully used as coordination entities
to nanosized metallic clusters to generate LC properties, by
varying both, their number density and position. The emissive
properties of the cluster core are preserved in the LC state,
even at higher temperatures and above the isotropization
temperatures. Although we proved that phosphine oxide
derivatives can be successfully coordinated to metallic
clusters, we expect that, by careful design, they can be used
in the preparation of various clustomesogens and more
generally a wide variety of metallomesogens as such ligands
are able to link to various metallic ions. This will open a new
and exciting avenue for this class of compounds. Attempts are
underway to utilize phosphine oxide modified with different
mesogenic groups in order to finely tune the liquid-crystalline
as well as emissive properties of these metal-based hybrid
materials.
Figure 2. X-ray powder diffraction pattern for compound WL2 at 608C
(l=1.54 Š).
lation between electron-rich cluster units. Interestingly,
clustomesogens MoL2 and WL2 show another additional
very broad reflection around 11–12 Š (hcluster2) indicating
some more local ordering within the clusters layer (Figure 2).
However, again the absence of any other reflection and their
broadness make any other assumption about intercluster
organization difficult. The layer periodicity calculated for
each compound at various temperatures is almost invariant
suggesting that there is little influence of the temperature on
the supramolecular packing within the mesophase. Several
interesting correlations could be made for clusters MoL2,3 and
WL2,3. Thus, the layer periodicities of the metallic clusters do
not differ too much from the one of phosphine oxide ligand
itself, indicating a partially interdigitated packing within the
mesophase and a minor contribution of the cluster units on
the overall organization.
This point is also in good accordance with the assumption
that ligand L2 and L3 self-arranges in a double-layer mor-
phology. For instance, by molecular modeling of L2, one arm
of the star-shaped phosphine oxide ligand was found to
measure in all-extended conformation around 37 Š whereas
the rough diameter of the molecule stands for approximately
55 Š. Interestingly, the interlayer distances of metallic
clusters MoL2 and WL2 (42.5–42.8 Š) are in fact slightly
shorter than the one of corresponding ligand L2 (45.3 Š).
Indeed, one can assume that now the cluster units are placed
in the same sublayer with the triphenylphosphine oxide units.
Such a packing could be interpreted as a double-layer
morphology formed by cylindrical-shaped entities within the
LC phase of metallic clusters. The cyanobiphenyl or choles-
teryl mesogenic groups are placed on each side of the median
plane determined by the metallic cluster units as we
previously observed in our earliest clustomesogens and as it
was found in structurally related nanohybrid materials of this
type.[8,12c,19]
Keywords: cluster compounds · liquid crystals · molybdenum ·
phosphine oxide · tungsten
How to cite: Angew. Chem. Int. Ed. 2015, 54, 10921–10925
Angew. Chem. 2015, 127, 11071–11075
The Mo6 and W6 octahedral metallic cluster are well
known for their broad emission in the near-infrared range
(600–900 nm) upon UV-visible excitation, emission lifetimes
in the microsecond range, and luminescence quantum yields
higher than 60%.[4,20] Generally, the photophysical properties
[1] a) C. Tschierske, Angew. Chem. Int. Ed. 2013, 52, 8828 – 8878;
Angew. Chem. 2013, 125, 8992 – 9047; b) S. Laschat, A. Baro, N.
10924 www.angewandte.org
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2015, 54, 10921 –10925

Angewandte
Chemie
Steinke, F. Giesselmann, C. Hagele, G. Scalia, R. Judele, E.
Kapatsina, S. Sauer, A. Schreivogel, M. Tosoni, Angew. Chem.
Int. Ed. 2007, 46, 4832 – 4887; Angew. Chem. 2007, 119, 4916 –
4973.
Martín-Rapffln, A. Omenat, J. L. Serrano, Chem. Soc. Rev. 2007,
36, 1889 – 1901.
[13] a) L. Cseh, G. H. Mehl, J. Am. Chem. Soc. 2006, 128, 13376 –
13377; b) L. Cseh, G. H. Mehl, J. Mater. Chem. 2007, 17, 311 –
315; c) K. Kanie, A. Muramatsu, J. Am. Chem. Soc. 2005, 127,
11578 – 11579; d) K. Kanie, M. Matsubara, X. Zeng, F. Liu, G.
Ungar, H. Nakamura, A. Muramatsu, J. Am. Chem. Soc. 2012,
134, 808 – 811; e) M. Wojcik, W. Lewandowski, J. Matraszek, J.
Mieczkowski, J. Borysiuk, D. Pociecha, E. Gorecka, Angew.
Chem. Int. Ed. 2009, 48, 5167 – 5169; Angew. Chem. 2009, 121,
5269 – 5271; f) A. Zep, M. M. Wojcik, W. Lewandowski, K.
Sitkowska, A. Prominski, J. Mieczkowski, D. Pociecha, E.
Gorecka, Angew. Chem. Int. Ed. 2014, 53, 13725 – 13728;
Angew. Chem. 2014, 126, 13945 – 13948; g) G. H. Mehl, I. M.
Saez, Appl. Organomet. Chem. 1999, 13, 261 – 272.
[14] T. Cardinaels, K. Driesen, T. N. Pa rac-Vogt, B. Heinrich, C.
Bourgogne, D. Guillon, B. Donnio, K. Binnemans, Chem. Mater.
2005, 17, 6589 – 6598.
[15] a) D. H. Johnston, D. C. Gaswick, M. C. Lonergan, C. L. Stern,
D. F. Shriver, Inorg. Chem. 1992, 31, 1869 – 1873; b) C. S.
Weinert, C. L. Stern, D. F. Shriver, Inorg. Chem. 2000, 39, 240 –
246.
[2] a) S. Cordier, F. Grasset, Y. Molard, M. Amela-Cortes, R.
Boukherroub, S. Ravaine, M. Mortier, N. Ohashi, N. Saito, H.
Haneda, J. Inorg. Organomet. Polym. 2015, 25, 189 – 204; b) S.
Cordier, Y. Molard, K. Brylev, Y. Mironov, F. Grasset, B. Fabre,
N. Naumov, J. Cluster Sci. 2015, 26, 53 – 81; c) S. Cordier, F.
Dorson, F. Grasset, Y. Molard, B. Fabre, H. Haneda, T. Sasaki,
M. Mortier, S. Ababou-Girard, C. Perrin, J. Cluster Sci. 2009, 20,
9 – 21.
[3] a) Y. Molard, F. Dorson, V. Cîrcu, T. Roisnel, F. Artzner, S.
Cordier, Angew. Chem. Int. Ed. 2010, 49, 3351 – 3353; Angew.
Chem. 2010, 122, 3423 – 3427; Y. Molard, A. Ledneva, M. Amela-
Cortes, V. Cîrcu, N. G. Naumov, C. Meriadec, F. Artzner, S.
Cordier, Chem. Mater. 2011, 23, 5122 – 5130; b) M. Amela-
Cortes, F. Dorson, M. PrØvôt, A. Ghoufi, B. Fontaine, F. Goujon,
R. Gautier, V. Cîrcu, C. MØriadec, F. Artzner, H. Folliot, S.
Cordier, Y. Molard, Chem. Eur. J. 2014, 20, 8561 – 8565; c) A. S.
Mocanu, M. Amela-Cortes, Y. Molard, V. Cîrcu, S. Cordier,
Chem. Commun. 2011, 47, 2056 – 2058; d) S. K. Nayak, M.
Amela-Cortes, C. Roiland, S. Cordier, Y. Molard, Chem.
Commun. 2015, 51, 3774 – 3777; e) M. Amela-Cortes, S. Cordier,
N. G. Naumov, C. Meriadec, F. Artzner, Y. Molard, J. Mater.
Chem. C 2014, 2, 9813 – 9823.
[16] a) B. P. Friedrichsen, D. R. Powell, H. W. Whitlock, J. Am.
Chem. Soc. 1990, 112, 8931 – 8941; b) T. Fujihara, S. Yoshida, H.
Ohta, Y. Tsuji, Angew. Chem. Int. Ed. 2008, 47, 8310 – 8314;
Angew. Chem. 2008, 120, 8434 – 8438.
[17] a) Z. T. Nagy, B. Heinrich, D. Guillon, T. Tomczyk, J. Stumpe, B.
Donnio, J. Mater. Chem. 2012, 22, 18614 – 18622; b) P. Barois, J.
Prost, T. C. Lubensky, J. Physique 1985, 46, 391 – 399; c) J. Prost,
P. Barois, J. Chim. Phys. 1983, 80, 65 – 81; d) P. Barois, C. Coulon,
J. Prost, J. Phys. Lett. 1981, 42, 107 – 110.
[4] a) K. Kirakci, P. Kubat, M. Dusek, K. Fejfarova, V. Sicha, J.
Mosinger, K. Lang, Eur. J. Inorg. Chem. 2012, 3107 – 3111; b) K.
Kirakci, P. Kubat, J. Langmaier, T. Polivka, M. Fuciman, K.
Fejfarova, K. Lang, Dalton Trans. 2013, 42, 7224 – 7232.
[5] I. M. Saez, J. W. Goodby, J. Mater. Chem. 2005, 15, 26 – 40.
[6] a) “Liquid-Crystalline Fullerodendrimers and Fullero(Coden-
drimers)”: D. Guillon, B. Donnio, R. Deschenaux in Fullerene
Polymers: Synthesis Properties and Applications (Eds.: N.
Martin, F. Giacalone), Wiley-VCH, Weinheim, 2009, pp. 247 –
270; b) T. Chuard, R. Deschenaux, J. Mater. Chem. 2002, 12,
1944 – 1951.
[7] a) T. Zhang, S. Liu, D. G. Kurth, C. F. J. Faul, Adv. Funct. Mater.
2009, 19, 642 – 652; b) Y. Yang, Y. Wang, H. Li, W. Li, L. Wu,
Chem. Eur. J. 2010, 16, 8062 – 8071; c) S. Yin, W. Li, J. Wang, L.
Wu, J. Phys. Chem. B 2008, 112, 3983 – 3988; d) S. Floquet, E.
Terazzi, A. Hijazi, L. Guenee, C. Piguet, E. Cadot, New J. Chem.
2012, 36, 865 – 868.
[18] S. Schmidt, G. Lattermann, R. Kleppinger, J. H. Wendorff, Liq.
Cryst. 1994, 16, 693 – 702.
[19] a) E. Terazzi, T. B. Jensen, B. Donnio, K. Buchwalder, C.
Bourgogne, G. Rogez, B. Heinrich, J.-L. Gallani, C. Piguet,
Dalton Trans. 2011, 40, 12028 – 12032; b) Y. Jia, H.-Q. Tan, Z.-M.
Zhang, E.-B. Wang, J. Mater. Chem. C 2013, 1, 3681 – 3685;
c) I. M. Saez, J. W. Goodby, Struct. Bonding (Berlin) 2008, 128,
1 – 62.
[20] a) T. C. Zietlow, D. G. Nocera, H. B. Gray, Inorg. Chem. 1986,
25, 1351 – 1353; b) R. D. Mussell, D. G. Nocera, Inorg. Chem.
1990, 29, 3711 – 3717; c) A. W. Maverick, H. B. Gray, J. Am.
Chem. Soc. 1981, 103, 1298 – 1300; d) A. W. Maverick, J. S.
Najdzionek, D. MacKenzie, D. G. Nocera, H. B. Gray, J. Am.
Chem. Soc. 1983, 105, 1878 – 1882; e) T. G. Gray, Chem. Eur. J.
2009, 15, 2581 – 2593.
[8] a) E. Terazzi, G. Rogez, J.-L. Gallani, B. Donnio, J. Am. Chem.
Soc. 2013, 135, 2708 – 2722; b) E. Terazzi, C. Bourgogne, R.
Welter, J.-L. Gallani, D. Guillon, G. Rogez, B. Donnio, Angew.
Chem. Int. Ed. 2008, 47, 490 – 495; Angew. Chem. 2008, 120, 500 –
505.
[21] C. S. Weinert, N. Prokopuk, S. M. Arendt, C. L. Stern, D. F.
Shriver, Inorg. Chem. 2001, 40, 5162 – 5168.
[22] L. F. Szczepura, K. A. Ketcham, B. A. Ooro, J. A. Edwards, J. N.
Templeton, D. L. Cedeno, A. J. Jircitano, Inorg. Chem. 2008, 47,
7271 – 7278.
[23] a) J. C. Sheldon, J. Chem. Soc. 1961, 750 – 751; b) L. F. Szczepura,
B. A. Ooro, S. R. Wilson, J. Chem. Soc. Dalton Trans. 2002,
3112 – 3116.
[9] M. Kimura, T. Hatano, T. Yasuda, J. Morita, Y. Akama, K.
Minoura, T. Shimomura, T. Kato, Chem. Lett. 2009, 38, 800 – 801.
[10] “Metallomesogens”: J. Torroba, D. W. Bruce in Comprehensive
Inorganic Chemistry II, Vol. 8 (Eds.: J. Reedjik, K. Poeppelme-
ier), Elsevier, Amsterdam, 2013, pp. 837 – 917.
[11] T. Hatano, T. Kato, Chem. Commun. 2006, 1277 – 1279.
[12] a) F. J. M. Hoeben, P. Jonkheijm, E. W. Meijer, A. P. H. J.
Schenning, Chem. Rev. 2005, 105, 1491 – 1546; b) M. W. P. L.
Baars, S. H. M. Sçntjens, H. M. Fischer, H. W. I. Peerlings, E. W.
Meijer, Chem. Eur. J. 1998, 4, 2456 – 2466; c) M. Marcos, R.
Received: April 8, 2015
Revised: June 19, 2015
Published online: July 21, 2015
Angew. Chem. Int. Ed. 2015, 54, 10921 –10925
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org 10925