Self-organization of dendritic supermolecules, based on isocyanide-gold(I), -copper(I), -palladium(II), and -platinum(II) complexes, into micellar cubic mesophases

Article abstract of DOI:10.1002/chem.200800128

First- and second-generation dendrimers with an isocyanide group as the focal functional point (CN-Gⁿ; n: 1,2) and their corresponding organometallic complexes [MCl(CN-Gⁿ)] (M: Au, Cu), [{CuCl(CN-G ⁿ)₂}₂

Full text of DOI:10.1002/chem.200800128

DOI: 10.1002/chem.200800128
Self-Organization of Dendritic Supermolecules, Based on
Isocyanide–Gold(I), –Copper(I), –Palladium(II), and –Platinum(II)
Complexes, into Micellar Cubic Mesophases
Silverio Coco,*[a] Carlos Cordovilla,[a] Bertrand Donnio,[b] Pablo Espinet,*[a]
María Jesffls García-Casas,[a] and Daniel Guillon[b]
Dedicated to the memory of Naomi Hoshino, a pioneer in the study of metallomesogens
3544
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Chem. Eur. J. 2008, 14, 3544 – 3552

FULL PAPER
Abstract: First- and second-generation
dendrimers with an isocyanide group as
the focal functional point (CN-Gn; n:
1,2) and their corresponding organo-
the first-generation complexes do not
show mesogenic behavior, but all of
the second-generation complexes dis-
play a thermotropic micellar cubic mes-
ophase, over
a
large temperature
range, and some of them directly at
room temperature. The structure of the
mesophase consists of the packing of
two, discrete polyhedral micellar aggre-
metallic complexes [MCl
Au, Cu), [{CuCl
(CN-Gn)2}2], and
trans-[MI
2(CN-Gn)2] (M: Pd, Pt) have
N
Keywords: dendrimers
·
isocya-
AHCTREUNG
nides · liquid crystals · metallomes-
ogens · self-assembly
A
N
gates in a three-dimensional cubic
¯
been synthesized. The free ligands and
Im3m lattice.
Introduction
makes isocyanides very promising building blocks to prepare
dendritic systems, but examples of dendrimers based on iso-
cyanides have not been reported.
Here we report two families (first (n=1)- and second (n=
2)-generation) of dendritic isocyanides and their stable gold,
Many dendrimers have been synthesized, and molecular
design and synthesis of dendritic systems with new struc-
tures and unique physical and chemical properties have
emerged as one of the most important topics in supramolec-
ular chemistry.[1] This is particularly true in metallodendri-
copper, palladium, and platinum complexes: [MCl
ACHTREUNG
(M=Au, Cu), [{CuCl [MI2
N
G
ACHTREUNG
mers,[2] which combine the properties of transition metals,
(M=Pd, Pt). Although the free highly branched isocyanides
and the CN-G1–metal complexes are not liquid crystals
themselves, all CN-G2–metal complexes show a cubic meso-
such as catalytic activity,[3] dichroism, paramagnetism, high
birefringence, or color,[4] and those derived from the dendri-
meric architecture, such as site isolation,[5] recyclability,[6]
and possible cooperative effects. Active metallic moieties
can be incorporated into different parts of a dendrimer,[7] in-
cluding the branching points,[8] core,[9] and periphery,[10] to
give metallodendrimers with desired functionality, and they
may be used in many fields including materials science. In
this respect, a great variety of liquid-crystalline dendrimers
have been reported,[11,12] with only a few as metal-containing
systems.[12,13]
¯
phase, with the Im3m lattice group, in a wide range of tem-
perature, some of them at room temperature.
Results and Discussion
Synthesis and structural characterization: Polyarylester mon-
odendrons bearing an isocyanide function at the focal point
CN-Gn (n=1, 2) have not been reported yet. We have pre-
pared them starting from the nitro dendritic compounds in
three steps, involving first their reduction into the corre-
sponding amines H2N-Gn (n=1, 2) by hydrogen with a pal-
ladium-on-carbon catalyst, then by their subsequent trans-
formation into N-formamides by formylation, and finally by
their dehydration with triphosgene (“bis(trichloromethyl)-
carbonate”) and triethylamine (Scheme 1). At room temper-
A simple and well-known synthetic route to prepare met-
allodendrimers is the use of metals as linking groups, by co-
ordination of functionalized dendritic fragments that can act
as ligands. Isocyanides are versatile functionalities in organic
synthesis and interesting ligands in organometallic chemis-
try, owing to their coordination ability to give very stable
complexes with many transition metals.[14] Isocyanide–metal
complexes are catalysts for polymerization[15] and for activa-
[16]
ꢀ
tion of Si Si bonds, or molecules used for one-dimension-
al electric conductors[17] and for liquid crystals.[18,19] This
Scheme 1. Reagents and conditions: i) H2, Pd/C, CH2Cl2; ii) formic acid,
toluene, reflux; iii) triphosgene, NEt3, CH2Cl2, 08C.
[a] Dr. S. Coco, Dr. C. Cordovilla, Prof. P. Espinet,
Dr. M. J. García-Casas
IU CINQUIMA/Química Inorgµnica
Facultad de Ciencias, Universidad de Valladolid
47071 Valladolid, Castilla y León (Spain)
Fax : (+34)983-423013
ature they are white (CN-G1) or yellow waxy (CN-G2) solids
not particularly smelling that can be stored for long periods
in the freezer.
E-mail: scoco@qi.uva.es
espinet@qi.uva.es
[b] Dr. B. Donnio, Dr. D. Guillon
The nitro derivative NO2-G1 was prepared starting from
dimethyl 5-hydroxyisophthalate in five steps (Scheme 2). Di-
methyl 5-hydroxyisophthalate was alkylated with bromo-
Institut de Physique et Chimie des MatØriaux de Strasbourg (IPCMS)
UMR 7504 (CNRS-ULP), 23 rue du Loess, BP 43
67034 Strasbourg Cedex 2 (France)
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author. It contains gener-
al procedures and instrumentation, representative DSC traces, and
small-angle X-ray patterns of the mesophases of the metallodendri-
methylbenzene to give the protected phenol 1. Saponifica-
tion of the ester groups was carried out with potassium hy-
droxide to afford 5-benzyloxyisophthalic acid (2). Treatment
A
of
2
with thionyl chloride yielded 5-benzyloxy-
Chem. Eur. J. 2008, 14, 3544 – 3552
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3545

P. Espinet, S. Coco et al.
Scheme 2. Reagents and conditions: i) acetone, DMSO, K2CO3, reflux; ii) KOH, EtOH/H2O, reflux; iii) SOCl2, DMF, toluene, reflux; iv) C10H21OH,
NEt3, dioxane; v) H2, Pd/C, CH2Cl2; vi) NEt3, dioxane.
A
anol to yield, after deprotection of phenol group, didecano-
yl-5-hydroxyisophthalate (5). Finally esterification of 5-
nitro-isophthaloyldichloride (6) with 5 produced the desired
nitro derivative NO2-G1. The NO2-G2 derivative was ob-
tained analogously as summarized in Scheme 2.
1
The C, H, N analyses, yields, IR and H NMR data for the
isocyanides and their complexes are given in the Experimen-
tal Section. The IR spectra in KBr of the isocyanide mono-
ꢁ
dendrons show a strong n
N
at 1725 cmꢀ1 supporting the existence of ester groups.
1H NMR spectroscopy of CN-Gn (n=1, 2) shows the reso-
nances of two or three AB2 spin systems corresponding to
the aryl hydrogen atoms present in the G1 and G2 molecules,
respectively. In addition, a triplet is observed at approxi-
mately d=4.36 ppm, corresponding to the first methylene
group of the COOC10H21 moieties. The remaining chain hy-
drogen atoms appear in the range d=0.8–1.8 ppm.
Scheme 3. Schematic representation of the various dendritic complexes
prepared.
The isocyanide complexes were prepared according to
reaction of CN-Gn with [MCl2
cis-[MCl
2(CN-Gn)2] complexes (M=Pd, Pt), which were
characterized in solution by IR spectroscopy (n(C N) (in
A
Scheme 3. The reaction of isocyanides CN-Gn (n=1, 2) with
AHCTREUNG
ꢁ
[AuCl
A
A
methane gave the white complexes [MCl
A
CH2Cl2): M=Pd: 2218 (s), 2236 cmꢀ1 (sh); M=Pt: 2205 (s),
2240 cmꢀ1 (sh)). However these cis-dichloro complexes show
a low stability, possibly due to the high steric hindrance of
the monodendrons in a cis disposition, and pure complexes
could not be isolated.
Cu). In contrast, reaction of two equivalents of the isocya-
nide derivatives with CuCl yielded the binuclear copper(I)
complexes [{CuCl
formed by two tetrahedra sharing an edge. Similarly, reac-
tions of CN-Gn with [MCl2
(NCCH3)2] (M: Pd, Pt) and KI in
tetrahydrofuran afforded the corresponding trans-[MI2(CN-
Gn)2] complexes (M=Pd, Pt). It is interesting to note that
A
ꢁ
U
The IR spectra of the metal complexes exhibit n
absorptions for the isocyanide group at higher wavenumbers
A
E
than for the free ligand, by about 90 cmꢀ1 for AuI, 18–
3546
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Metallodendrimers
FULL PAPER
52 cmꢀ1 for CuI, and 60–80 cmꢀ1 for PdII and PtII complexes.
clearing temperature, due to their very high transition tem-
peratures.
A cubic mesophase with a Im3m symmetry was eventually
deduced by SAXS measurements. The small-angle X-ray dif-
fraction patterns for all mesomorphic complexes exhibit six
Linear [MCl
(CN-Gn)] (M=Au, Cu) and trans-diiodopalladi-
G
¯
um and platinum complexes (D2h symmetry) display one
ꢁ
n
G
(CN-Gn)2]2 (D2h,
B2u +B3u symmetry), and the cis-dichloropalladium and plat-
inum complexes (C2v symmetry), have two bands, as report-
ed for similar metal aryl isocyanide compounds.[20–22]
([AuCl
trans-[PtI
small-angle reflections, for which the reciprocal d-spacings
A
N
ACHTREUNG
The H NMR spectra of the metal complexes are all simi-
p
p p p p p
lar to that of the free isocyanide ligand discussed above. It is
worth noting that coordination of the isocyanides produces
only a slight deshielding for aromatic protons in ortho and
para positions to the isocyanide group (0.2–0.1 ppm for gold
and palladium complexes and less than 0.1 ppm for copper
and platinum complexes), suggesting that the isocyanide be-
comes slightly more p acceptor in character due to the coor-
dination.
were in the ratios 1: 2: 3: 4: 5: 6: 7, pointing to a
cubic supramolecular organization [(h2 +k2 +l2)1/2 =a/dhkl)]
(Table 2). The determination of the cubic symmetry is gener-
ally not trivial, but a logical analysis of the data permits us
to considerably reduce the possibilities. All non-centrosym-
metric groups (groups with the 23, 432 and ꢀ43m Laue
classes) can be disregarded as a consequence of the Friedelꢁs
law,[23,24] thus leaving only 17 cubic space groups to consider
out of an initial 36. This sequence of ratios is not compatible
Mesomorphic behavior: The thermal behavior of all the
compounds was studied by polarized optical microscopy
(POM), differential scanning calorimetry (DSC), and small-
angle X-ray scattering (SAXS) experiments. Although the
first- and second-generation free isocyanides (CN-G1, CN-
G2) and the first-generation metal complexes do not show
mesomorphic properties, all second-generation metalloden-
drimers display a cubic mesophase, some of them occurring
at room temperature. Thermal and thermodynamic data are
collected in Table 1. No birefringent texture could be ob-
with a face centerd cubic network (F) due to the presence
of the reflection corresponding to the ratio 7. Although, a
cubic phase with a primitive Bravais lattice (P) cannot be
excluded (the simple cubic space groups with the symmetry
p
¯
¯
¯
¯
¯
¯
Pm3, Pn3, Pm3m, Pm3n, Pn3n or Pn3m are all compatible
with this sequence of ratios), this option is improbable, since
six intermediate, authorized reflections, with h+k+l=2n+
1, are unexpectedly absent. In contrast, this sequence is
perfectly compatible with a body-centered cubic lattice
(I type).[25] Indeed, for a body-centered cubic lattice, the
considered
sequence
in
this
case
is
p
p
p
p
p
p
p
2: 4: 6: 8: 10: 12: 14 and the reflections can be in-
Table 1. Thermal and termodynamic data for dentritic ligands and com-
plexes.
dexed as (110), (200), (211), (220), (310), (222), and
(321); all satisfied the reflection conditions (0kl:k+l=2n,
Transition temperature[a] [8C] (DH [kJmolꢀ1])
¯
¯
hhl:l=2n, h00:h=2n), and only the symmetry Im3 or Im3m
is theoretically compatible with this set of reflections. An
aggregation into the highest symmetry is generally admitted
CN-G1
Cr 46 (1.6) Cr’ 67 (14.9) Cr’’ 82 (52.9) I
Cr 31 (7.9) I
CN-G2
[AuCl(CN-G1)]
[AuCl(CN-G2)]
[CuCl(CN-G1)]
[CuCl(CN-G2)]
[{CuCl(CN-G1)2}2]
[{CuCl(CN-G2)2}2]
trans-[PdI2(CN-G1)2]
trans-[PdI2(CN-G2)2]
trans-[PtI2(CN-G1)2]
trans-[PtI2(CN-G2)2]
Cr 45 (8.7) Cr’ 129 (73.0) I
and accordingly, the Im3m space group (No. 229)[24] is finally
¯
Cr 94 (32.9) Cub-Im3m 260[b] decomp
¯
retained.
Cr 112 (41.2) I
Cr 110 (28.9) Cub-Im3m 290[b] decomp
¯
An additional, very intense, but diffuse, halo was ob-
served in the wide-angle region at about 4.4–4.6 Š over the
whole temperature range, and was assigned to the liquidlike
order of the molten chains, confirming the liquid nature of
the mesophase.
Cr 70 (25.8) I
Cub-Im3m 268 decomp
[b]
¯
Cr 32 (97.7) I
Cub-Im3m 150 decomp
[b]
¯
I
[b]
¯
Cub-Im3m 291.0 decomp
The two dendritic ligands and the first-generation com-
plexes are not mesogenic, whereas all second-generation
complexes display liquid crystal behavior. Thus, mesomor-
phism is induced upon complexation, but the appearance of
mesomorphic properties depends on the generation. The
melting temperatures of related complexes decrease with in-
creasing of the generation, possibly due to entropy effects
derived from the increase of the number of alkoxy chains in
the second-generation complexes. Moreover, the transition
temperatures into the isotropic liquid are not reached in any
of the mesomorphic complexes (Tdec <Tiso), and since de-
composition occurs at very high temperature, the tempera-
ture domains of stability of the cubic phases are much ex-
tended. These observations clearly suggests that the size of
the dendritic blocks (alkoxy chains and phenyl rings) is in
competition with the interactions brought by the presence
¯
[a] Cr, Cr’, Cr’’: crystalline phases; Cub-Im3m: cubic phase; I: isotropic
liquid; decomp: decomposition. Data collected from the first heating
DSC cycle. The transition temperatures are given as peak onsets. [b] Op-
tical microscopy data.
served for any of the complexes in the explored temperature
range, but only the formation of large, black (optically iso-
tropic) and viscous areas on increasing temperature. Howev-
er, upon mechanical shear, weakly birefringent, transient
dendritic patterns with homeotropic contours were observed
in a polarizing microscope; these contours disappear when
the pressure is released. Isotropization was accompanied by
an increase in the fluidity of the complexes; however, most
of them underwent some decomposition upon reaching the
Chem. Eur. J. 2008, 14, 3544 – 3552
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3547

P. Espinet, S. Coco et al.
Parameters[c]
Table 2. Structural data from X-ray diffraction experiments for the mesomorphic metal isocyanide complexes.
T [8C][a]
Indexation[b]
dhkl(exptl) [Š]
hkl
I
L
dhkl(calcd) [Š]
[AuCl(CN-G2)]
105
30.94
21.89
17.83
15.35
13.76
11.71
4.4
32.23
22.79
18.68
16.07
14.37
13.15
12.16
4.5
32.50
23.06
18.79
16.19
14.59
13.20
12.27
4.6
31.57
22.32
18.15
15.57
14.11
11.90
4.5
110
200
211
220
310
321
–
110
200
211
220
310
222
321
–
110
200
211
220
310
222
321
–
110
200
211
220
310
321
–
vs
s
s
vw
w
w
s
vs
s
vw
vw
w
w
w
s
vs
m
s
vw
w
w
w
s
vs
m
s
vw
w
w
s
vs
m
s
vw
w
w
s
sh
sh
sh
sh
sh
sh
br
sh
sh
sh
sh
sh
sh
sh
br
sh
sh
sh
sh
sh
sh
sh
br
sh
sh
sh
sh
sh
sh
br
sh
sh
sh
sh
sh
sh
br
30.87
21.83
17.82
15.43
13.80
11.67
–
32.21
22.78
18.60
16.11
14.40
13.15
12.17
–
32.51
23.00
18.77
16.25
14.54
13.28
12.29
–
31.46
22.24
18.16
15.73
14.07
11.89
–
a
43.66 Š
3
Vmic
Vmol
N
S
ach
41600 Š
3
4100 Š
10.1
6382 Š
39.5 Š
2
2
[CuCl(CN-G2)]
115
a
45.55 Š
3
Vmic
Vmol
N
S
ach
47250 Š
3
4110 Š
11.5
6946 Š
2
2
37.75 Š
[{CuCl(CN-G2)2}2]
75
a
45.98 Š
48600 Š
15910 Š
3
3
3
Vmic
Vmol
N
S
ach
2
7080 Š
2
36.85 Š
trans-[PdI2(CN-G2)2]
70
30
a
44.49 Š
3
Vmic
Vmol
N
S
ach
44030 Š
3
7990 Š
5.5
6630 Š
2
2
37.65 Š
trans-[PtI2(CN-G2)2]
31.96
22.66
18.52
16.05
14.38
12.12
4.5
110
200
211
220
310
321
–
32.07
22.68
18.51
16.03
14.34
12.12
–
a
45.35 Š
3
Vmic
Vmol
N
S
ach
46635 Š
3
7780 Š
6.0
6885 Š
2
2
35.85 Š
[a] Temperature of the experiment. [b] dhkl(exptl) and dhkl(calcd) are the measured and calculated diffraction spacing; hkl corresponds to the indexation of the
reflections, I to the intensity of the reflections (vs: very strong, s: strong ; m: medium; w : weak; vw : very weak), and L to the line-shape (br and sh
stand for broad and sharp). [c] a is the lattice parameter of the cubic phase a=[ꢀhkldhkl(h2 +k2 +l2)ꢀ2]/Nhkl in which Nhkl is the number of hkl reflections,
Vmic is the micellar volume (Vmic=a3/2), Vmol is the molecular volume calculated from Vmol(T)=Vmetallic +Vligand(T0)”[VCH2(T)/VCH2(T0)], in which
VCH2(T)=26.5616+0.02023T (T in8C, and T0 =228C), Vligand(T0)=MWligand/0.6022, and Vmetallic =MWmetallic/dmetallic ”0.6022. Density (gcmꢀ3) and molecular
mass (gmolꢀ1) of the metallic fragments: AuCl (232.42), 1=7.4; CuCl (99.0) and Cu2Cl2 (198) 1=4.14, PdI2 (360.23) 1=6.003; PtI2 (448.89) 1=6.403
(Data taken from Handbook of Chemistry and Physics, 67th edition, CRC Press, Boca Raton, Florida, USA, 1986–1987). N is the aggregation number
p
(N=Vmic/Vmol). S is the surface of the elementary truncated octahedron (S=a2(6 3+2)/4), and ach is the cross-section area of one terminal chain, calcu-
lated on the surface S (ach =S/2NNch, in which Nch is the number of terminal chains per dendrimer).
of the metallic moieties, which, when both are appropriately
dosed, induce specific molecular conformation able to self-
assemble in a liquid-crystal supramolecular structure.
sidered, the mesophases possess close structural parameters,
suggesting a similar arrangement of the complexes within
the cubic phase.
The dendritic complexes of the second-generation all self-
assemble into a body-centered cubic phase, likely with the
micellar morphology. The gold and copper complexes have
a similar thermal behavior, melting into the cubic phase at
about 1008C. In contrast, the other complexes (the dimeric
copper and the two trans square-planar complexes) exhibit
the mesophase at room temperature. In all cases, the meso-
phase is thermally very stable, the complexes decomposing
before clearing. The mesophases freeze at low temperature
and crystallization is only observed for the derivatives [MCl-
Cubic mesophases are ordered three-dimensional supra-
molecular edifices, with a multicontinuous or a discrete mi-
cellar structure, depending on the molecular self-organiza-
tion within the cubic cell.[11e–g,26] Bi- and tricontinuous cubic
structures consist of two or three regular, interwoven, infin-
¯
ite, interconnected rod networks (referred to as Im3m (P)
[27–30]
¯
and Im3m (I) structures, respectively);
the rods are
formed by the rigid part of the molecules, and the networks
are separated by lipophilic films (their associated minimal
surfaces). The difference between the bicontinuous and the
micellar structures lies in the periodic discontinuities along
A
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Chem. Eur. J. 2008, 14, 3544 – 3552

Metallodendrimers
FULL PAPER
the rods in the x,y,z directions (bicontinuous model) that
appear at mid-height of the cubic-cell edges; the junctions
between three connecting rods then become the micelle (mi-
cellar model). It is therefore not trivial to choose one model
preferentially to the other. Although, as far as the bicontinu-
ous structure is concerned, the molecules need to be able to
stack to form the columns, and thus a specific molecular
conformation is required. For the present systems, on the
basis of their molecular conformations and packing consid-
erations, the micellar model appears therefore more appro-
priate and more likely than the multicontinuous one.
Indeed, all these dendritic molecules have a very large
volume fraction of aliphatic chains in common, and thus a
strong interfacial curvature. This forces the dendrimers to
deviate from the planar, fanlike shape (G1) to adopt a coni-
cal conformation with the isocyanide group, and later the
metallic moiety, located at the apex of the structure. The
steric hindrance of adjacent branches in CN-G2 ligands will
further stabilize the conical-shape conformation. The meso-
gens likely self-assemble head-to-head to form spheroidlike
nonpolar supramolecular clusters, since stacking is strongly
disfavored with such a conformation. The mesophase then
consists of the three-dimensional, periodic and regular pack-
ing of such supramolecular ensembles, one located at the
corners and one at the center of the cubic cell. This self-or-
ganization model is similar to that of the classical dendro-
mesogens[11g] and other thermotropic systems showing such
phases.
pffiffiffi
Figure 1. Representation of the truncated octahedron, a=2 2”e; S=
pffiffiffi
pffiffiffi
(12 3+6)”e2; V=8 2”e3. a: cubic lattice parameter ; e: polyhedron
edge. Schematic representation of the body centered (I) cubic lattice of
¯
Im3m symmetry composed of truncated octahedrons.
lecular conformation, with an average projection of the
solid angle of about 30–368 subtended by the conical-like
dendrons (a’=2p/m, in which m is the number of “dendrons”
within the micellar aggregate),[27] compatible with their
bond system, so as to self-assemble into such a supramolec-
ular aggregate. The cohesion in the three directions of the
space between these polyhedral aggregates according to the
space-group symmetry is ensured by the intermicellar-chain
interdigitation through square faces along the x,y,z direc-
tions for micelles within identical cubic subnetworks (binary
and quaternary axes), and through hexagonal faces for the
connection between micelles belonging to the two distinct
subnetworks (ternary axes). This is evidenced by the rather
compact arrangement of the chains at the interface between
two micelles (the value of the chain-cross section area lies
between 36 and 40 Š2, Table 2). A plausible proposal is
shown in Figure 2.
Recall that for micellar thermotropic cubic phases, the mi-
celles are necessarily inverted; that is, the polar nucleus of
the micelles is embedded in an apolar aliphatic shell.[31] The
broad scattering measured by SAXS corresponding to the
molten organic coating indicates the presence of a continu-
um between the isolated supramolecular metallic clusters.
In thermotropic systems, it is convenient to describe this
phase structure by the geometrical space-filling polyhedron
For the [MI
N
N
which contain two and four isocyanide monodendrons, re-
model.[32] As far as the Im3m phase is concerned, the sym-
¯
metry and the complete filling of the space is achieved by
two truncated octahedrons, one in the center of the cubic
lattice (1”1) and one at the corners (8”1/8). In these ideal-
ized geometrical structures, the center of gravity of the poly-
hedron is therefore occupied by the metallic moieties, em-
bedded in the dendritic continuum, the interface between
each supermolecule being represented by the polyhedral
faces (square and hexagonal faces, with an edge e; Figure 1).
The geometrical relationships between the cubic lattice
and polyhedron characteristics provide us with more insight
into the molecular arrangement within these micellar aggre-
gates. The number of complexes required to fill one of this
polyhedral micelle was calculated. Thus, each micelle con-
tains approximately either twelve, six, and three molecules
of [CuClCN-G2], [MI2
A
ACHTREUNG
plex, each aggregate requires about twelve dendritic isocya-
nide moieties, except for the gold complex in which only ten
monodendrons per micelle were found. It is evident that
these dendritic molecules will adopt the most adequate mo-
Figure 2. Schematic representation of possible conformations of the den-
drimers in each type of molecule, their self-assembling into a supramolec-
ular spherical dendrimer, and the subsequent organization of these spher-
¯
ical dendrimers into a Im3m cubic mesophase.
Chem. Eur. J. 2008, 14, 3544 – 3552
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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3549

P. Espinet, S. Coco et al.
Preparation of didecanoyl 5-benzyloxy-isophthalate (4): A solution of 3
(5.68 g, 18.37 mmol), triethylamine (5.65 mL, 40.42 mmol) and decanol
(7.70 g, 40.42 mmol) in dioxane (100 mL) was stirred for 12 h at room
temperature. Then water (100 mL) was added to separate an oil, which
was extracted with dichloromethane. The organic layer was washed with
diluted hydrochloric acid (3”30 mL) and dried over anhydrous magnesi-
um sulfate. The dichloromethane was evaporated to yield an orange oil.
The crude product was purified by column chromatography (silica gel, di-
chloromethane/hexane 2:1) as an orange solid (8.63 g, 85%). 1H NM R
(CDCl3): d=0.88–1.77 (m, 36H; AlkH), 4.33 (t, J=6.7 Hz, 4H;
CH2OCO), 5.14 (s, 2H; CH2O), 7.40–7.45 (m, 5H; ArH), 7.83 (d, J=
1.4 Hz, 2H; ArH), 8.29 ppm (t, J=1.4 Hz, 1H; ArH).
spectively, easily accessible molecular conformations are
those that situated the two or four conical monodendrons in
a compact arrangement as represented in Figure 2b and c.
Ideally, the formation of polyhedral aggregates with similar
micellar volume from these structurally very different metal
complexes would result from the complementary molecular
association of the same number “twleve” of conical mono-
dendrons corresponding respectively to twelve molecules of
[CuClCN-G2] with one isocyanide derivative, six molecules
of [MI
2(CN-G2)2] that contain two isocyanide moieties, or
A
Preparation of didecanoyl-5-hydroxyisophthalate (5): Pd/C (9.00 g, 5%)
was added to a solution of 4 (16.68 g, 30 mmol) in dichloromethane
(100 mL) and the mixture was stirred overnight under a hydrogen atmos-
phere. The reaction mixture was filtered and the solvent evaporated to
obtain the product as a white solid (12.63 g, 90%). 1H NMR (CDCl3):
d=0.88–1.82 (m, 36H; AlkH), 4.34 (t, J=6.7 Hz, 4H; CH2OCO), 6.46 (s,
1H; OH), 7.82 (d, J=1.3 Hz, 2H; ArH), 8.25 ppm (t, J=1.3 Hz, 1H;
ArH).
three molecules of [{CuCl
isocyanides.
A
As for the gold complex, the necessary number of conical
dendrons to fill a micellar aggregate is smaller than for the
other complexes (only ten dendrimers), consistent with the
lattice contraction, suggesting stronger intermolecular inter-
actions of the metal-containing dendrimer, and consequently
a tighter intermicellar packing. The values of the cross-sec-
tion chain area calculated in each case confirmed the gener-
al trend of the packing of these complexes, as all values lie
in the same range.
Preparation of 5-nitro-isophthaloyl dichloride (6): Compound 6 was pre-
pared from 5-nitroisophthalic acid (1.30 g, 6.18 mmol) and thionyl chlo-
ride as described for compound 3. The product was isolated as a yellow
oil.
Preparation of NO2-G1: Compound 5 (6.00 g, 12.97 mmol) and triethyl-
A
In summary, novel examples of metallodendrimers con-
taining monodendrons with an isocyanide group in the focal
point have been prepared. Although the free ligands are not
liquid crystals, all second-generation complexes show meso-
morphic properties, displaying cubic phases indexed with an
6.18 mmol) in dioxane (50 mL). The mixture was stirred for 12 h at room
temperature, and then water (50 mL) was added. The mixture was ex-
tracted with dichloromethane. The organic layer was washed with diluted
hydrochloric acid (3”15 mL) and dried over anhydrous magnesium sul-
fate, and the solvent was removed. The crude product was purified by
chromatography (silica, dichloromethane/hexane 2:1) affording a white
solid (5.29 g, 78%). 1H NMR (CDCl3): d=0.86–1.81 (m, 72H; AlkH),
4.36 (t, J=6.6 Hz, 8H; CH2OCO), 8.12 (d, J=1.5 Hz, 4H; ArH), 8.65 (t,
J=1.5 Hz, 2H; ArH), 9.30 ppm (m, 3H; ArH).
Preparation of G1OCH2C6H5 (7): A solution of 3 (2.43 g, 7.86 mmol),
triethylamine (2.4 mL, 17 mmol) and 5 (8.00 g, 17 mmol) in dioxane
(100 mL) was stirred for 12 h at room temperature. Water (200 mL) was
added and the product extracted with dichloromethane. The organic
layer was washed with diluted hydrochloric acid (3”30 mL) and dried
over anhydrous magnesium sulfate, and the solvent was removed to give
a white solid (7.09 g, 82%), which was purified by chromatography
¯
Im3m lattice, over a wide range of temperatures. Although
the metal complexes prepared are structurally very differ-
ent, the dendrons of the second-generation manage to ar-
range appropriately despite unfavorable coordination struc-
tures.
Experimental Section
Experimental conditions for the analytical, spectroscopic, and XRD stud-
ies were as reported elsewhere.[19,25] Literature methods were used to pre-
(silica, dichloromethane/hexane 2:1). H NMR (CDCl3): d=0.81–1.75 (m,
72H; AlkH), 4.28 (t, J=6.6 Hz, 8H; CH2OCO), 5.16 (s, 2H; CH2O), 7.31
(m, 5H; ArH), 8.08 (d, J=7.4 Hz, 2H; ArH), 8.09 (d, J=1.4 Hz, 4H;
ArH), 8.63 (t, J=1.4 Hz, 2H; ArH), 8.64 ppm (t, J=1.4 Hz, 1H; ArH).
pare [AuCl
U
G
Preparation of dimethyl-5-benzyloxyisophthalate (1): Potassium carbon-
ate (10.52 g, 76.12 mmol) was added to a stirred solution of dimethyl-5-
hydroxyisophthalate (8.00 g, 38.06 mmol) and benzyl bromide (5 mL,
41.87 mmol) in acetone/dimethyl sulfoxide (150 mL, 10:1). The mixture
was heated to reflux for 22 h. The suspension was filtered and the solvent
Preparation of OH-G1 (8): Pd/C (5%; 4.00 g) was added to a solution of
8 (7.02 g, 6.05 mmol) in dichloromethane (50 mL). The mixture was
stirred overnight under a hydrogen atmosphere. The reaction mixture
was filtered and the solvent was evaporated to obtain the product as a
white solid (5.81 g, 90%). 1H NMR (CDCl3): d=0.83–1.82 (m, 72H;
AlkH), 4.35 (t, J=6.8 Hz, 8H; CH2OCO), 6.53 (s, 1H; OH), 7.96 (d, J=
1.5 Hz, 2H; ArH), 8.08 (d, J=1.5 Hz, 4H; ArH), 8.57 (t, J=1.5 Hz, 1H;
ArH), 8.61 ppm (t, J=1.5 Hz, 2H; ArH).
evaporated under vacuum to yield
a white solid (11.43 g, 100%).
1H NMR (CDCl3): d=3.93 (s, 6H; CH3OCO), 5.13 (s, 2H; CH2O), 7.26–
7.43 (m, 5H; ArH), 7.83 (t, J=0.6 Hz, 1H; ArH), 8.28 ppm (d, J=
0.6 Hz, 2H; ArH).
Preparation of NO2-G2: Compound 8 (5.60 g, 5.23 mmol) and triethyl-
Preparation of 5-benzyloxyisophthalic acid (2): A solution of potassium
hydroxide (8.54 g, 152.24 mmol) and 1 (11.43 g, 38.06 mmol) in ethanol/
water (300 mL, 95:5) was heated to reflux for 75 min. Then water
(300 mL) was added and the solution was acidified with HCl until a pH
value of 2 was reached to precipitate a white solid, which was washed
with water and dried in vacuo (9.11 g, 88%). 1H NMR ((CD3)2CO): d=
5.30 (s, 2H; CH2O), 7.39–7.86 (m, 5H; ArH), 7.86 (d, J=1.4 Hz, 2H;
ArH), 8.30 ppm (t, J=1.4 Hz, 1H; ArH).
C
1
(t, J=6.7 Hz, 16H; CH2OCO), 8.11 (d, J=1.4 Hz, 8H; ArH), 8.43 (d, J=
1.5 Hz, 4H; ArH), 8.63 (d, J=1.4 Hz, 4H; ArH), 9.02 (t, J=1.5 Hz, 2H;
ArH), 9.37 ppm (m, 3H; ArH).
Preparation of NH2-Gn: A solution of NO2-Gn (5.45 mmol) in ethanol/di-
Preparation of 5-benzyloxyisophthaloyl dichloride (3): Dimethyl forma-
mide (1.10 mL, 15.07 mmol) and thionyl chloride (25.45 mL,
348.94 mmol) were added to a solution of 2 (5.00 g, 18.36 mmol) in tolu-
ene (100 mL). The solution was heated to reflux for 3 h. Then volatiles
were pumped off and the product was isolated as a yellowish solid.
chloromethane (20 mL, 1:1) was stirred overnight at room temperature
3550
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 3544 – 3552

Metallodendrimers
FULL PAPER
in the presence of Pd/C (5%; 3.20 g) under a positive pressure of hydro-
gen. The mixture was then filtered. The solution obtained was concen-
trated and cooled to ꢀ158C to give the product.
C
G
ACHTREUNG
1
NH2-G1: White solid (4.92 g, 78%); 1H NMR (CDCl3): d=0.82–1.79 (m,
72H; AlkH), 4.18 (s, 2H; NH2), 4.34 (t, J=6.7 Hz, 8H; CH2OCO), 7.73
(d, J=1.3 Hz, 2H; ArH), 8.07 (d, J=1.3 Hz, 4H; ArH), 8.37 (t, J=
1.3 Hz, 1H; ArH), 8.60 ppm (t, J=1.3 Hz, 2H; ArH).
ꢁ
NH2-G2: Yellow oil (3.20 g, 84%); 1H NMR (CDCl3): d=0.84–1.83 (m,
144H; AlkH), 4.18 (s, 2H; NH2), 4.35 (t, J=6.8 Hz, 16H; CH2OCO),
7.80 (d, J=1.5 Hz, 2H; ArH), 8.10 (d, J=1.4 Hz, 8H; ArH), 8.39 (d, J=
1.5 Hz, 4H; ArH), 8.46 (t, J=1.4 Hz, 1H; ArH), 8.63 (t, J=1.4 Hz, 4H;
ArH), 8.97 ppm (t, J=1.5 Hz, 2H; ArH).
Preparation of CN-Gn: A solution of bistrichloromethyl carbonate (tri-
phosgene; 1.68 mmol) in dichloromethane (25 mL) was added dropwise
to a solution of NHC(O)H-Gn (4.55 mmol), prepared by reaction of the
corresponding amine with formic acid and triethylamine (10.8 mmol) in
dichloromethane (60 mL) at 08C. The mixture was stirred for 1 h and the
solvent was removed. The resulting residues were purified by column
chromatography (silica gel, CH2Cl2/hexane 3:1 as eluent), and the solvent
was evaporated to obtain the desired products.
A
1
ꢁ
G
E
CN-G1: White solid (3.74 g, 76%); IR (KBr): n˜ =2133 cmꢀ1 (C N);
G
ꢁ
ꢁ
1H NMR (CDCl3): d=0.86–1.95 (m, 36H), 4.36 (t, J=6.7 Hz, 8H), 8.09
(d, J=1.5 Hz, 4H), 8.48 (d, J=1.6 Hz, 2H), 8.64 (t, J=1.5 Hz, 2H),
9.03 ppm (t, J=1.6 Hz, 1H); elemental analysis calcd (%) for
C65H93NO12: C 72.26, H 8.68, N 1.30; found: C 72.00, H 8.33, N 1.26.
A
N
CN-G2: Yellow waxy solid (7.21 g, 69%); IR (KBr): n˜ =2125 cmꢀ1 (C
ꢁ
2201 cmꢀ1 (C N); 1H NMR (CDCl3): d=0.86–1.90 (m, 64H), 4.36 (t, J=
6.8 Hz, 32H), 8.12 (d, J=1.5 Hz, 16H), 8.43 (d, J=1.6 Hz, 8H), 8.64 (t,
J=1.5 Hz, 8H), 8.73 (d, J=1.5 Hz, 4H), 9.03 (t, J=1.6 Hz, 4H),
9.22 ppm (t, J=1.5 Hz, 2H); elemental analysis calcd (%) for C274H378I2
N2O56Pd: C 66.40, H 7.69, N 0.57; found: C 66.66, H 7.79, N 0.62.
ꢁ
N); 1H NMR (CDCl3): d=0.86–1.96 (m, 72H), 4.35 (t, J=6.8 Hz, 16H),
8.11 (d, J=1.4 Hz, 8H), 8.40 (d, J=1.5 Hz, 4H), 8.55 (d, J=1.6 Hz, 2H),
8.64 (t, J=1.4 Hz, 4H), 9.01 (t, J=1.5 Hz, 1H), 9.10 ppm (t, J=1.6 Hz,
1H); elemental analysis calcd (%) for C137H189NO28: C 71.61, H 8.29, N
0.61; found: C 71.24, H 8.08, N 0.67.
G
U
Synthesis of [AuCl
solved in dichloromethane (20 mL) was added to a solution of [AuCl-
(tht)] (0.20 g, 0.18 mmol) in dichloromethane (20 mL). After 30 min the
G
2188 cmꢀ1 (C N); 1H NMR (CDCl3): d=0.78–1.90 (m, 64H), 4.37 (t, J=
6.8 Hz, 16H), 8.12 (d, J=1.5 Hz, 8H), 8.66 (m, 32H), 9.15 ppm (t, J=
1.5 Hz, 2H); elemental analysis calcd (%) for C130H186I2N2O24Pt: C 59.83,
H 7.18, N 1.07; found: C 60.33, H 7.11, N 1.19.
ꢁ
ACHTREUNG
solution was concentrated, acetonitrile was added, and the mixture was
cooled.
C
G
(CN-G1)]: White solid (0.24 g, 98%); IR (KBr): n˜ =2229 cmꢀ1 (C
ꢁ
A
2195 cmꢀ1 (C N); 1H NMR (CDCl3): d=0.79–1.80 (m, 64H), 4.29 (t, J=
6.8 Hz, 32H), 8.05 (d, J=1.4 Hz, 16H), 8.35 (d, J=1.6 Hz, 8H), 8.57 (t,
J=1.4 Hz, 8H), 8.64 (d, J=1.5 Hz, 4H), 8.96 (t, J=1.6 Hz, 4H), 9.15 (t,
J=1.5 Hz, 2H); elemental analysis calcd (%) for C274H378I2N2O56Pt: C
65.23, H 7.55, N 0.56; found: C 65.40, H 7.62, N 0.73.
ꢁ
N); 1H NMR (CDCl3): d=0.86–1.96 (m, 36H), 4.36 (t, J=6.8 Hz, 8H),
8.10 (d, J=1.0 Hz, 4H), 8.65 (t, J=1.0 Hz, 2H), 8.68 (d, J=1.1 Hz, 2H),
9.19 ppm (t, J=1.1 Hz, 1H); elemental analysis calcd (%) for
C65H93NAuClO12: C 59.47, H 7.14, N 1.07; found: C 59.15, H 6.84, N 0.89.
(CN-G2)]: White solid (0.23 g, 80%); IR (KBr): n˜ =2227 cmꢀ1 (C
ꢁ
[AuCl
The Supporting Information contains general procedures and instrumen-
tation, representative DSC traces, and small angle X-ray patterns of the
mesophases of the metallodendrimers.
N); 1H NMR (CDCl3): d=0.86–1.96 (m, 72H), 4.36 (t, J=6.8 Hz, 16H),
8.11 (d, J=1.4 Hz, 8H), 8.40 (d, J=1.6 Hz, 4H), 8.63 (t, J=1.4 Hz, 4H),
8.73 (d, J=1.6 Hz, 2H), 9.02 (t, J=1.6 Hz, 2H), 9.26 ppm (t, J=1.6 Hz,
1H); elemental analysis calcd (%) for C137H189NAuClO28: C 65.03, H
7.53, N 0.55; found: C 64.69, H 7.49, N 0.53.
Synthesis of [CuCl
(CN-Gn)]: CuCl (0.020 g, 0.21 mmol) was suspended in
N
Acknowledgements
dichloromethane (20 mL) and a stoichometric amount of the appropriate
CN-Gn was added. After 1 h the solution was filtered. The crude product
This work was sponsored by the D.G.I. (Project CTQ2005-08729/BQU)
and the Junta de Castilla y León (Project VA099 A05). C.C. thanks the
MEC for a grant.
was recrystallized in dichloromethane/diethyl ether, [CuCl
dichloromethane/acetone, [CuCl
(CN-G2)].
[CuCl
(CN-G1)]: White solid (0.08 g, 36%); IR (KBr): n˜ =2179 cmꢀ1 (C
A
AHCTREUNG
ꢁ
A
ACHTREUNG
N); 1H NMR (CDCl3): d=0.86–1.90 (m, 36H), 4.35 (t, J=6.8 Hz, 8H),
8.09 (d, J=1.5 Hz, 4H), 8.64 (t, J=1.5 Hz, 2H), 8.56 (d, J=1.5 Hz, 2H),
9.09 ppm (t, J=1.5 Hz, 1H); elemental analysis calcd (%) for
C65H93NClCuO12: C 66.19, H 7.95, N 1.19; found: C 65.83, H 7.78, N 1.33.
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G
(CN-G2)]: White solid (0.12 g, 37%); IR (KBr): n˜ =2184 cmꢀ1 (C
N); 1H NMR (CDCl3): d=0.86–1.96 (m, 72H), 4.36 (t, J=6.8 Hz, 16H),
8.11 (d, J=1.4 Hz, 8H), 8.40 (d, J=1.4 Hz, 4H), 8.63 (t, J=1.4 Hz, 4H),
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G
suspension of CuCl (0.014 g, 0.14 mmol) in dichloromethane (20 mL).
The solvent was removed and the residue washed with pentane, [{CuCl-
Chem. Eur. J. 2008, 14, 3544 – 3552
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Received: January 22, 2008
Published online: March 31, 2008
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