Polyanionic aryl ether metallodendrimers based on cobaltabisdicarbollide derivatives. Photoluminescent properties

Article abstract of DOI:10.1021/ma9019575

Fluorescent Frechet-type poly(aryl ether) dendrimers that incorporate the 1, 3, 5-triphenylbenzene as core molecule and 3, 6, 9, or 12 terminal allyl ether groups have been prepared in very good yield by following the Frechet convergent approach. Regiospe

Full text of DOI:10.1021/ma9019575

150 Macromolecules 2010, 43, 150–159
DOI: 10.1021/ma9019575
Polyanionic Aryl Ether Metallodendrimers Based on
Cobaltabisdicarbollide Derivatives. Photoluminescent Properties
†
Emilio Jose Juarez-Perez, Clara Vinas, Francesc Teixidor, Rosa Santillan,
†
†
‡
ꢀ
ꢀ
ꢀ
~
Norberto Farfan, Arturo Abreu, Rebeca Yepez, and Rosario Nunez*
§
^
‡
,†
ꢀ
ꢀ
ꢀ~
†
‡
ꢁ
´
Institut de Ciencia de Materials, CSIC, Campus U.A.B., 08193 Bellaterra, Spain, Departamento de Quımica,
ꢀ
ꢀ
ꢀ
Centro de Investigacion y de Estudios Avanzados del IPN, Apdo. Postal 14-740, CP 07000, Mexico D.F.,
§
´
´
ꢀ
Meꢀxico, Facultad de Quımica, Departamento de Quımica Organica, Universidad Nacional Autonoma de
Meꢀxico, Meꢀxico D.F. 04510, Meꢀxico, and ^Universidad Politeꢀcnica de Pachuca, Carretera Pachuca-Cd.
ꢀ
Sahaguꢀn, Km 20, ExHacienda de Santa Barbara, Zempoala, Hidalgo, Mexico
Received September 3, 2009; Revised Manuscript Received October 30, 2009
ꢀ
ABSTRACT: Fluorescent Frechet-type poly(aryl ether) dendrimers that incorporate the 1,3,5-triphenyl-
benzene as core molecule and 3, 6, 9, or 12 terminal allyl ether groups have been prepared in very good yield by
ꢀ
following the Frechet convergent approach. Regiospecific hydrosylilation reactions on the allyl ether
functions with the cobaltabisdicarbollide derivative Cs[1,10-μ-SiMeH-3,30-Co(1,2-C2B9H10)2] lead to differ-
ꢀ
ent generations of Fechet-type polyanionic metallodendrimers decorated with 3, 6, and 9 cobaltabisdicar-
bollide units. Starting dendrimers exhibit photoluminescence properties at room temperature under
ultraviolet irradiation; nevertheless, after functionalization with cobaltabisdicarbollide derivatives, the
fluorescence properties are quenched. Products are fully characterized by FTIR, NMR, and UV-vis
spectroscopies. For metallodendrimers, the UV-vis absorptions have been a good tool for estimating the
experimental number of cobaltabisdicarbollide units peripherally attached to the dendrimeric structure and
consequently to corroborate the unified character of the dendrimers. Because of the anionic character of these
compounds and the boron-rich content, we actually focus our research on biocompatibility studies and
potential applications.
Introduction
different strategies for tumor targeting or can be used as building
blocks for the synthesis of boron-containing biomolecules. For
In the past years, the incorporation of boron clusters in the
interior or on the periphery of hydrocarbon,1 poly(lysine)2 and
aliphatic polyester dendrimers,3 and other macromolecules and
dendrimeric systems4 has become an area of great attention. The
design of water-soluble boron-rich macromolecules is of signifi-
cance for boron neutron capture therapy (BNCT) or for drug
delivery. Recently, we have been interested in the use of different
types of dendrons and dendrimers as platforms for the incorpora-
tion of boron-based clusters in order to obtain high boron
content molecules.5 However, closo-carboranes are extremely
lipophilic, generating water-insoluble structures with limited
bioavailability and preventing their application in BNCT. Thus,
with the aim of preparing boron-rich anionic systems, we have
developed different synthetic strategies for the incorporation of
nido-carboranes into dendrimeric structures.6 Cobaltabisdicar-
bollide, [(3,30-Co-(1,2-C2B9H11)2]-,7 is a boron-rich monoanio-
nic cluster that possesses extraordinary chemical and thermal
stability, hydrophobicity,8 weakly coordinating character,9 and
low nucleophilicity.10 These features make it suitable for a wide
range of applications, such as the extraction of radionuclides,11
doping agent in conducting polymers,12 or in ion selective
PVC membrane electrodes for medical drug analysis,13 among
others.14,15 Cobaltabisdicarbollide derivatives have also been con-
sidered promising agents as boron-rich carriers for cancer treat-
ment and diagnosis in boron neutron capture therapy (BNCT).16
These boron compounds can be delivered into tumor cells using
that reason, this metallacarborane has been bonded to different
organic groups and biomolecules, such as nucleosides17 and
porphyrins.18
19
ꢀ
Frechet-type poly(aryl ether) dendrimers are of current
interest because of their properties and multiple applications.20
ꢁ
More recently, it has been reported that Frechet-type dendrimers
are biocompatibles and have been used for biomedical applica-
tions, such as drug delivery.20d On the other hand, Frechet-type
ꢀ
dendrimers with homoallyl and allyl ether end groups, similar to
those prepared in this work, have been previously reported by
Zimmerman et al. to produce cross-linking dendrimers via ring-
closing metathesis reactions.21 In other examples, dendrimers
containing allyl ether groups were chosen for their selective
removal with Pd catalysts in order to obtain dendrimers with
peripheral hydroxyl groups.22 In this work, the terminal allyl
ether groups will be active groups for hydrosilylation reactions.
In our continuing investigation of structure/properties relation-
ship in cobaltabisdicarbollide-containing dendrimers,23 we now
report the synthesis and characterization of a new family of star-
shaped molecules and dendrimers. These dendrimers consist of a
ꢀ
1,3,5-triphenylbenzene unit as fluorescent core, Frechet-type
poly(aryl ether) fragments as connecting groups, and 3, 6, 9,
and 12 terminal allyl ether groups that will be hydrosilylated by
[1,10-μ-SiMeH-3,30-Co(1,2-C2B9H10)2]-.24 Our fluorescence core
molecule, 1,3,5-triphenylbenzene (TPB), is a class of C3-symme-
try compound important in electrodes and electroluminescent
devices. The 1,3,5-triphenylbenzene core has been used to devel-
op organic light emitting diodes (OLEDS)25 and has also been
used in the synthesis of dendrimers and fullerene fragments.26
*Corresponding author: Tel þ34 93 580 1853; Fax þ34 93 580 5729;
e-mail rosario@icmab.es.
pubs.acs.org/Macromolecules
Published on Web 11/20/2009
r 2009 American Chemical Society

Article
Macromolecules, Vol. 43, No. 1, 2010 151
Scheme 1. Preparation of Compound 2
Scheme 2. Preparation of Dendrimers 5a and 5b
In this work we study the photoluminescent properties of
dendrimers, before and after functionalization with cobaltabis-
dicarbollide derivatives.
prepared using a convergent approach. In a first step the
allyl groups of compound 2 were removed using a procedure
previously described in the literature, with Pd(OAc)2 in the
presence of PPh3,33 to give 1,3,5-(4-hydroxyphenyl)benzene,
334 (see Scheme 1). Benzyl chloride derivatives 4a and 4b were
prepared using procedures described in the literature,21d,22
and the spectral data of 4a were compared with that already
published.33 The reaction of 4a and 4b with 3 at reflux of
acetonitrile in the presence of K2CO3 and catalytic amounts
of 18-crown-6 ether34,35 gave 5a and 5b as amber oils, in 95%
and 92% yield, respectively (see Scheme 2).
Finally, the reaction of (3,5-hydroxy)benzyl alcohol
with 3,5-bis(allyloxy)benzyl chloride gave 3,5-bis(3,5-bis-
(allyloxy)benzyloxy)benzyl alcohol which was reacted with
SOCl2 and Et3N in CH2Cl2 to give 6. Subsequent reaction of
6 with 3 under reflux of acetone in the presence of K2CO3 and
catalytic amounts of Bu4NF35 gave 7 as amber oil in 53%
yield (Scheme 3).
General Procedure for Peripheral Functionalization with
Cobaltabisdicarbollide Units. To decorate the periphery of
the fluorescent star-shaped molecule 2 and dendrimers 5a,b
and 7 with cobaltabisdicarbollide units, hydrosilylation re-
actions of the allyl ether end groups with Cs[1,10-μ-SiMeH-
3,30-Co(1,2-C2B9H10)2], 8 (see Figure 1),24 in the presence of
Karstedt catalyst in THF at 50 ꢀC, were carried out. The
reaction of 3 equiv of 8 with 1 equiv of 2 afforded the cesium
salt of the anionic three-functionalized compound 10, in
54% yield (Scheme 4). When compound 8 reacts with
dendrimers 5a and 7, using the ratios 6:1 and 12:1, respec-
tively, under the same conditions, a complete hydrosilylation
of dendrimers was observed to obtain polyanionic metallo-
dendrimers 11 and 12 (Schemes 4 and 5). These metalloden-
drimers were precipitated as orange solids by addition of
hexane and isolated as cesium salts, 11 and 12, in 63 and 51%
Results and Discussion
Synthesis of Poly(aryl ether) Star-Shaped Molecules and
Dendrimers with Fluorescent Cores. In this work we have
prepared dendrimers with 1,3,5-triarylbenzene as core and
ꢀ
3, 6, 9, and 12 terminal allyl ether groups by using the Frechet
convergent strategy. These dendrimers have been used as
precursors to attach metallacarborane derivatives at the peri-
phery via hydrosilylation reactions.
The synthesis of 1,3,5-triarylbenzene can be carried out
using Suzuki cross-coupling or cyclocondensation reactions
from substituted acetophenones.27 The cyclocondensation
allows the synthesis of many chemical species, such as multi-
metallic pincer,28 star-shaped thiophenes,29 and organic-
inorganic hybrid mesoporous materials,30 which can be
carried out with triflic acid,29 sulfuric acid-sodium piro-
sulfate,30 perfluorinated resins,31 and tetrachlorosilane in
ethanol.28
The sequence of reactions used for the preparation of
1,3,5-tris(4-allyloxyphenyl)benzene, 2), is shown in Scheme 1.
4-Allyloxyacetophenone, 1, was first synthesized in quan-
titative yields from 4-hydroxyacetophenone and allyl
bromide in the presence of potassium carbonate under reflux
of acetone; the spectroscopic data of 1 were compared
with those reported in the literature.32a Triple condensation
of 1 in absolute ethanol using tetrachlorosilane led to 2 in 80%
yield.
Next generation dendrimers;1,3,5-(4-(3,5-bis(allyloxy)-
benzyloxy)phenyl)benzene, 5a; 1,3,5-(4-(3,4,5-tris(allyloxy)-
benzyloxy)phenyl)benzene, 5b; and 1,3,5-(4-(3,5-bis(3,5-bis-
(allyloxy)benzyloxy)benzyloxy)phenyl)benzene, 7, were

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Juarez-Perez et al.
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152 Macromolecules, Vol. 43, No. 1, 2010
Scheme 3. Preparation of Dendrimer 7
yield, respectively. Nevertheless, all attempts for the com-
plete hydrosilylation of compound 5b, which contains nine
terminal allyl ether functions, were unsuccessful even using a
large excess of 8, changing the catalyst, reaction times, and
temperatures (Scheme 5). The Supporting Information con-
tains a Monte Carlo simulation study about the steric
hindrance for these metallodendrimers. In all cases, the
binding of the cobaltacarborane anion 8 to the allyl ether
functions was monitored by IR and 1H NMR spectroscopy,
following the disappearance of the Si-H signal in both
spectra and, above all, the absence of allyl protons in the
1H NMR.
Figure 1. Representation of cobaltabisdicarbollide derivatives 8 and 9.
The increase of the number of cobaltabisdicarbollide
fragments in a dendrimeric structure provides the increase
of boron content in the molecule, which is capital in produ-
cing a useful drug delivery agent. Compound 12, with 12
cobaltabisdicarbollide units, is the molecule with highest
content of these metallacarboranes described in the litera-
ture, which possesses about 30 wt % boron. These boron-
enriched molecules possess a great potential as boron drug
delivery compounds; however, due to the presence of 1,3,
4-phenylene core, these dendrimeric structures could be
potentially useful in materials science to form structures
for liquid crystal materials and develop materials with
photoelectric and luminescent properties.36
∼4.50 ppm attributed to the Cc-H protons of the cobalta-
bisdicarbollide are also observed in metallodendrimers. The
1H NMR spectra also exhibit resonances at low frequencies,
in the range 0.32-0.38 ppm for Cc-SiCH3 protons. The
13C{1H} NMR spectra show different resonances in the
aromatic region, from 160.5 to 100.5 ppm for all compounds.
Depending on the metallodendrimer, different resonances
attributed to the carbon atoms of the ether groups
(-OCH2-) are observed between 65.00 and 78.50 ppm for
10, 11, and 12. After functionalization with cobaltabisdicar-
bollide, dendrimers 10-12 show resonances around 55.25
and 40.50 ppm attributed to the Cc-H and Cc-Si atoms,
respectively. The resonances for the Si-CH3 units bonded
to the Cc appear between -6.03 and -7.09 ppm, whereas
the -CH2- carbons are displayed in the range 22.3-
8.41 ppm.
Characterization of Star-Shaped Molecules and Dendri-
mers before and after Functionalization. The starting com-
1
pounds 1-7 were characterized on the basis of FT-IR, H
NMR, 13C NMR, and UV-vis spectroscopy and mass
spectrometry, whereas compounds 10, 11, and 12 were also
characterized by 11B and 29Si NMR and elemental analyses.
All compounds show resonances between 7.80 and 7.00 ppm
attributed to the aromatic protons at 1, 4, and 5 positions of
the central phenyl ring of the 1,3,5-triphenylbenzene core in
The 11B NMR spectra of 10-12 exhibit an identical
2:2:4:2:2:2:2:2 pattern in the range from þ8.40 to -22.30
ppm, typical of cobaltabisdicarbollide derivatives.37 Because
of the similarity of these spectra with that of Cs[1,10-μ-SiMe2-
3,30-Co(1,2-C2B9H10)2],24 9, in which the μ-Si(Me)2 group is
bridging the dicarbollide ligands (Figure 1), it has been
possible to confirm the formation of these metallodendri-
mers. The boron resonance with a relative intensity of 4 is
due to a coincidental overlap of two resonances with a 2:2
relative intensity. All three cobaltabisdicarbollide-functio-
nalized compounds 10, 11, and 12 show only one peak about
12.0 ppm in the 29Si NMR spectra, corresponding to the -μ-
SiMeCH2-. This resonance is shifted about 8.5 ppm down-
field with respect to the starting compound 8 (δSi = 2.94
ppm)24 but is very close to that shown for 9 at 13.98 ppm,
which always proves the formation of the expected
1
the H NMR spectra. Dendrimers 2, 5a, 5b, and 7 show
resonances in the range δ 6.20 and 5.20 ppm attributed to the
allyl protons, which have been assigned according to the area
and coupling constants. These signals disappear after hydro-
silylation reaction, indicating the anti-Markovnikov addi-
tion of the -μ-Si-H function of 8 to the double bonds and
subsequently the formation of complete functionalized me-
tallodendrimers 10, 11, and 12. In the latter compounds,
the presence of -CH2- proton resonances around 4.00
(-OCH2-), 1.90 (-CH2), and 1.00 ppm (-SiCH2-) corro-
borates their formation (Figure 2). Broad resonances at

Article
Macromolecules, Vol. 43, No. 1, 2010 153
metallodendrimers. The IR spectra of 10-12 present typical
υ(B-H) strong bands for closo clusters around 2550 cm-1
and intense bands near 1257 cm-1 corresponding to the
δ(Si-CH3).
to the π to π* transitions in the aromatic core, similar to the
maximum at 254 nm reported for 1,3,5-triphenyl-substituted
benzene compounds (Figure 4).26b Cobaltabisdicarbollide-
functionalized dendrimers show two maxima absorption
bands, one in the region 271-276 nm attributed to the
dendrimeric core and the second band between 307 and
310 nm, which corresponds to the [1,10-μ-CH2Si(CH3)-1,2-
Co(C2B9H11)2]- fragment (Figure 5), due to the similarity
with the previously reported Cs[1,10-μ-Si(CH3)2-1,2-Co-
(C2B9H11)2], 9.24
As was already reported for metallocene-containing den-
drimers,39 in our case the UV-vis spectroscopy has been a
suitable method to estimate the number of terminal cobalta-
bisdicarbollide units and corroborate the level of functiona-
lization for metallodendrimers 10-12. The silyl-containing
cobaltabisdicarbollides show absorption bands at 310 and
462 nm in the UV-vis spectra that follow the Lambert-Beer
law.23 This method consists of the UV-vis absorption’s
measurement of solutions that contain the functionalized
dendrimer and study the trend of the molar absorptivity (ε).
The molar absorptivities (εmax) of the cobaltabisdicarbol-
lide-containing dendrimers must be proportional to the
number of metallacarboranes attached to the periphery.23
The number of cobaltabisdicarbollide fragments for each
dendrimer can be estimated by comparing the absorptivity
(ε) of the dendrimers with that obtained for monomer 9 (ε0).
The spectra do not show well-defined peaks, which made
calculating the molar absorptivities at λ = 309 nm difficult,
to overcome this problem a line-fitting analysis was per-
formed (Figures S3-S5 in the Supporting Information).
Different mass spectrometry techniques have been used
for the characterization of compounds: high-resolution mass
spectrometry (HMRS), ESI-MS, and MALDI-TOF-MS.
The formula of the star-shaped compound 10 was well
established by using ESI-MS mass spectrometry, and the
molecular ion peak appears at m/z = 1837.1 (M-Cs), in
concordance with the calculated pattern (Figure 3). The
MALDI-TOF mass spectra of dendrimers 11 and 12 were
recorded in the ion mode without matrix, where a big
fragmentation was observed. This fragmentation phenom-
enon was previously observed for cobaltabisdicarbollide-
containing carbosilane and carbosiloxane dendrimers.23
Thus, this technique cannot be used to fully characterize
this type of dendrimer. Hypothetically, the reason could be
due to the relative strong UV absorption of these metallo-
dendrimers at 337 nm, which corresponds precisely to the λ
of the laser used in the MALDI experiment. A similar
behavior was already observed by Caminade et al. in the
case of phosphorus-containing dendrimers.38
Absorption and Emission Measurements. The UV-vis
absorption measurements for compounds 2, 5a, 5b, 7, 10,
11, and 12 were performed in acetonitrile. Tables 1 and 2 list
the spectroscopic and photophysical data obtained for these
compounds. Starting dendrimers 2, 5a,b, and 7 display a
significant solvatochromic shift and exhibit bands of absorp-
tion maxima in the region 269-272 nm, which correspond
Scheme 4. Hydrosilylation Reactions of 2 and 7 with the Cobaltabisdicarbollide Derivative 8 To Obtain Metallodendrimers 10 and 12

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Juarez-Perez et al.
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154 Macromolecules, Vol. 43, No. 1, 2010
Scheme 5. Hydrosilylation Reactions of 5a To Obtain Metallodendrimer 11
Thus, the deconvolution with Gaussians permitted accurate
discernment of the band positions and the retrieval of λ and ε
data with more accuracy. Table 2 shows the molar absorp-
tivity values (ε) for all metallodendrimers and the calculated
number of cobaltabisdicarbollide units using the Lam-
bert-Beer law. The number of metallacarboranes calculated
fits quite well with the theoretical numbers, corroborating
the well functionalization and the unified character of the
different metallocarborane-containing dendrimers.
It is worth noting that compounds 2, 5a, 5b, and 7 exhibit
blue emission with λmax around 364 nm after excitation at
270 nm in acetonitrile. Nevertheless, dendrimers 10, 11, and
12 do not show appreciable fluorescence emission. Table 1
collects the data, and Figure 4 shows the photoluminescent
(PL) normalized spectra for compounds 2, 5a, 5b, and 7.
Fluorescence lifetimes (the time lag between the absorp-
tion and emission of photons) for compounds 2, 5a, 5b, and 7
were measured to give values around 9.4 ns, and their decay
is described by a single exponential. The fluorescence quan-
tum yield, Φ, is defined as the ratio of the total number of
photons emitted within the total number of absorbed
photons. The four samples have a quantum yield around
20%. However, metallodendrimers 10, 11, and 12 do
not show any fluorescence within our detection limit. The
absence of fluorescence can be rationalized as a quenching
after functionalization with the cobaltabisdicarbollide moi-
eties. As a control experiment, PL measurements of a solu-
tion containing 1 equiv of compound 2 and 3 equiv of
Cs[1,10-μ-Si(CH3)2-Co(1,2-C2B9H10)2], 9, were performed,
resulting in a quantum yield of Φ = 14%. This fact
indicates that the quenching by the cobaltabisdicarbollide
moiety is more effective when it is chemically bonded to the
fluorescent core. Furthermore, this fact confirms that the
intermolecular effects are not significant. Two possible
mechanisms, electron exchange and dipole-dipole, can be
invoked to account for the aromatic core dendrimer to
cobaltabisdicarbollide energy transfer. Electron exchange
can be discarded because saturated units connecting the
respective parts behave like insulators toward electronic
communication because the HOMO-LUMO energy se-
paration is large. On this basis, we propose that the occur-
rence of energy transfer is due possibly to the dipole-dipole
mechanism.
The starting dendrimers exhibit photoluminescence at
room temperature under ultraviolet irradiation due to the
core molecule. However, after functionalization with
C-substituted cobaltabisdicarbollide, the fluorescence prop-
erties are quenched. By using steady-state and time-resolved
luminescence measurements, we show that for these metal-
lodendrimers a mechanism different than photon emission

Article
Macromolecules, Vol. 43, No. 1, 2010 155
Table 1. UV-Vis Spectroscopic and Photophysical Data for
Dendrimers 2, 5a,b, and 7
absorption
emission
λ
max (nm) ε (10-3 dm3 mol-1 cm-1
)
λmax (nm) Φ (%) μ (ns)
2
269
270
270
272
127
66
65
78
364
364
364
363
20
21
21
22
9.3
9.5
9.5
9.5
5a
5b
7
Table 2. Number of Cobaltabisdicarbollide Units Calculated
of the Metallocarborane-Terminated Dendrimers Using the
Lambert-Beer Law
theoretical
λmax number of cobalta-
dendrimer (nm) bisdicarbollides
calculateda
number of cobalta-
bisdicarbollides
εa
monomerb 310
1
3
6
12
ε0 = 12 687
35 328
67 163
10
11
12
310
309
307
2.8 ( 0.3
5.3 ( 0.5
12.6 ( 0.7
159 485
a ε/ε0 represents the experimental cobaltabisdicarbollide units
number calculated according to Lambert-Beer law. b Cs[1,10-μ-Si(CH3)2-
Figure 2. 1H NMR spectra of (a) dendrimer 5a and (b) metalloden-
drimer 11.
Co(1,2-C2B9H10)2]24 is used as monomer.
fluorescence cannot be envisaged. It is our opinion, however,
that when these moieties are bonded to the dendrimeric sur-
face, the Jablowsky diagram changes from an emissive system
A to a nonemissive system B (Figure 7).
Conclusions
A new family of star-shaped molecules and dendrimers, which
consist of 1,3,5-triphenylbenzene unit as fluorescent core,
ꢀ
Frechet-type poly(aryl ether) fragments as connecting groups,
and 3, 6, 9, and 12 terminal allyl ether groups have been prepared
by a convergent approach to be used as scaffold for incorporating
cobaltabisdicarbollide derivatives. Thus, the hydrosylilation
reaction of the allyl ether groups with [1,10-μ-SiMeH-3,30-
Co(1,2-C2B9H10)2]- using optimal reaction conditions leads to
ꢀ
Fechet-type polyanionic metallodendrimers (whith 3, 6, and 9
Figure 3. Simulated and experimental ESI spectra for compound 10.
negative charges) decorated with cobaltabisdicarbollide units.
UV-vis spectroscopy was used to estimate the number of
peripheral cobaltabisdicarbollide units by using the Lambert-
Beer law. Concerning the photoluminescent properties, the
starting dendrimers exhibit fluorescence at room temperature
under ultraviolet irradiation; nevertheless, after functionalization
with cobaltabisdicarbollide derivatives, the fluorescence was
quenched. By using steady-state and time-resolved luminescence
measurements, it is shown that for metallodendrimers 10-12 a
mechanism different than photon emission could be available to
go from excited singlet state to the ground electronic state, mainly
due to peripheral functionalization. Because of the anionic
character of these compounds and the boron-rich content, we
are actually focusing our research on biocompatibility studies
and potential applications in medicine as antiviral or BNCT
agents.
could be available to go from excited singlet state to the
ground electronic state due mainly to peripheral functiona-
lization.
Simulation of UV-Vis and Fluorescence Spectra. Excited
states of 2 were calculated using a semiempirical method
PM6 implemented in MOPAC40 to simulate its absorption
spectra with the effect of a solvent model (COSMO) sur-
rounding the molecule.41 The ground state (S0) and the first
singlet excited state (S1) have been optimized, allowing to do
a direct comparison of calculated results with experimental
data for the fluorescence spectrum of 2. The computed
absorption and fluorescence wavelength in acetonitrile for
2 is represented in Figure 6.
The calculated wavelengths and general pattern are in very
good agreement with experimental data, with a theoretical
error on the Stokes shift around 16%. The computed fluore-
scence wavelength (355 nm) is in very good agreement with
the one measured (363 nm). Furthermore, the calculated
relative energy difference between S1 f S0 is 4.29 eV and the
calculated Stokes shift is 1.34 eV, which would represent
about 30% of quantum yield. If the experimental Stokes shift
is used, the percentage of quantum yield reaches 26%, which
is very close to the experimental value of 20%. Unfortunately,
parametrization for the semiempirical optimization of cobal-
tabisdicarbollide-containing compounds is not available,
and therefore, insight into the quenching mechanism of the
Experimental Section
Instrumentation. The melting point of 2 was recorded on an
Electrothermal 9200 apparatus and is uncorrected. Microanalyses
were performed in the analytical laboratory using a Carlo Erba
EA1108 microanalyzer. IR spectra wererecorded withKBr pellets
or NaCl on a Shimadzu FTIR-8300 spectrophotometer. UV-vis
spectroscopy was carried out with a Shimadzu UV-vis 1700
spectrophotometer, at 23 ꢀC temperature, using 1 cm quartz
cuvettes. Fluorescence spectra were measured on Cary Eclipse
fluorescence spectrophotometer. The electrospray-ionization
mass spectra (ESI-MS) were recorded on a Bruker Esquire 3000

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Juarez-Perez et al.
156 Macromolecules, Vol. 43, No. 1, 2010
Figure 4. UV-vis and normalized fluorescence spectra for starting dendrimers 2, 5a, 5b, and 7.
divinyltetramethyldisiloxane complex, 2.1-2.4% platinum in
vinyl terminated polydimethylsiloxane) was obtained from
ABCR and used as received. Compounds 1,32a 3,34 4a,33 6,42
3,4,5-trisallyloxy(benzyloxy)benzene,43 8, and 924 were pre-
pared according to the literature procedures.
Preparation of 1,3,5-Tris(4-allyloxyphenyl)benzene (2). Com-
pound 2 was prepared from 1 (4.80 g, 27.27 mmol) and tetra-
chlorosilane (12.5 mL, 109.08 mmol) in absolute ethanol at
room temperature for 24 h. The precipitate was filtered and
washed with methanol to give 2 as a white powder. Yield: 80%
(3.44 g, 7.26 mmol); mp 83-85 ꢀC. 1H NMR (300 MHz, CDCl3):
δ 7.68 (3H, s, H-1), 7.64 (6H, d, J3(H,H) = 8.7, H-4), 7.04 (6H,
d, J3(H,H) = 8.7, H-5), 6.11 (3H, ddt, Jtrans = 17.2, Jcis = 10.4,
J3allylic = 5.3, H-8), 5.48 (3H, dd, Jtrans = 17.2, J2(H,H) = 1.3,
H-9a), 5.34 (3H, dd, Jcis = 10.4, J2(H,H) = 1.3, H-9b), 4.62 (6H,
d, J3allylic = 5.3, H-7). 1H NMR (300 MHz, acetone-d6): δ 7.75
(9H, m, H-1, H-4), 7.07 (6H, m, H-5), 6.10 (3H, m, H-8), 5.45
(3H, d, J(HH) = 17.3, H-9a), 5.27 (3H, d, J(HH) = 10.6, H-9b),
4.64 (6H, d, J3allylic = 5.1, H-7). 13C NMR (75.47 MHz, CDCl3):
δ 158.5 (C-6), 142.0 (C-2), 134.2 (C-3), 133.4 (C-8), 128.5 (C-4),
124.1 (C-1), 118.0 (C-9), 115.2 (C-5), 69.1 (C-7); MS [m/z], 475
([M þ H]þ, 35), 474 (Mþ, 100), 434 (27), 433 (81), 292 (42), 351
(21). IR (νmax/cm-1): 3130, 1642, 1608, 1511, 1400, 1325, 1234,
1180, 996, 833, 777. HRMS C13H31O3 [M þ H]þ, calculated
475.2268; found 475.2266, with an error of 0.361 ppm.
Figure 5. UV-vis spectra for metallacarborane-containing poly-
(aryl ether) dendrimers 10-12.
spectrometer using a source of ionization and a ions trap analyzer.
MALDI-TOF-MS mass spectra were recorded in the negative ion
mode using a Bruker Biflex MALDI-TOF [N2 laser; λexc 337 nm
(0.5 ns pulses); voltage ion source 20.00 kV (Uis1) and 17.50 kV
(Uis2)]. Mass spectra were recorded on a Hewlett-Packard 5989A
spectrometer using electron ionization; HRMS (high-resolution
mass spectroscopy) spectra were obtained on an Agilent Technol-
ogies G1969A and APCI (atmospheric pressure chemical
ionization) ionization time-of-flight spectrometer, coupled to a
HPLC model 1100. The 1H, 1H{11B} NMR (300.13, 300 and 400
MHz), 11B, 11B{1H} NMR (96.29 MHz), 13C{1H} NMR (75.47
and 100 MHz), and 29Si{1H} NMR (59.62 MHz) spectra were
recorded on a Bruker DPX 300, a Bruker ARX 300 and a Jeol
Eclipse 400 spectrometers equipped with the appropriate decou-
pling accessories at room temperature in deuterated chloroform or
acetone-d6 solutions. Chemical shift values for 11B NMR and
Preparation of 3,4,5-Tris(allyloxy)benzyl Chloride (4b). To a
solution of 3,4,5-trisallyloxy(benzyloxy)benzene (0.91 g, 3.29
mmol) in dry CH2Cl2 were added 5 mL (3.62 mmol) of Et3N
under a nitrogen atmosphere. The solution was cooled to 0 ꢀC,
and SOCl2 (0.262 mmol) was added slowly. The reaction
mixture was stirred for 24 h at RT, and after, water was
added and the organic phase extracted with CH2Cl2, dried and
evaporated under vacuum to give 4b as an amber oil. Yield: 95%
(0.92 g). 1H NMR (300 MHz, CDCl3): δ 6.60 (2H, s, H-3),
6.18-5.98 (3H, m, H-7, H-70), 5.44 (2H, dd, Jtrans = 17.2, Jgem
1.5 Hz, H-8), 5.35 (1H, dd, Jtrans = 17.2, Jgem = 1.5 Hz, H-8’),
5.27 (2H, dd, Jcis = 10.4, Jgem = 1.5 Hz, H-8), 5.19 (1H, d, Jcis
=
=
11B{1H} spectra were referenced to external BF3 OEt2, and those
10.4, J = 1.5, H-80), 4.55 (6H, d, J = 5.4, H-6), 4.47 (2H, s, H-1).
13C NMR (75.47 MHz, CDCl3): δ 152.8 (C-4), 138.1 (C-5), 134.6
(C-70), 133.3 (C-7), 132.7 (C-2), 117.4 (80), 117.2 (8), 107.6 (C-3),
73.9 (C-60), 69.6 (C-6), 46.6 (C-1). IR (NaCl, νmax/cm-1): 3080,
1825, 2868, 1590, 1502, 1440, 1422, 1332, 1234, 1128, 1111, 989,
926, 708. MS [m/z], 296 (Mþ þ 2, 8), 294 (Mþ, 22), 255 (16), 253
(46), 81 (29), 41 (100). HRMS C16H20O3Cl 295.1095, with an
error of 0.1055 ppm.
3
for 1H, 1H{11B}, 13C{1H}NMR, and 29Si{1H} NMR spectra were
referenced to SiMe4. Chemical shifts are reported in units of parts
per million downfield from reference, and all coupling constants
are reported in hertz.
Materials. All manipulations were carried out under a dini-
trogen atmosphere using standard Schlenck techniques. Sol-
vents were reagent grade and were purified by distillation from
appropriate drying agents before use. 3,5-Hydroxybenzyl alco-
hol, 4-hydroxyacetophenone, SiCl4, allyl bromide, potassium
carbonate, 18-crown-6 ether, palladium(II) acetate, tetrabuty-
lammoniun, tetramethylammonium, and fluoride hydrate
were purchased from Aldrich. Karstedt’s catalyst (platinum
Preparation of 1,3,5-Tris[4-(3,5-bis(allyloxy)benzyloxy)-
phenyl]benzene (5a). Compound 5a was synthesized from 1,3,5
tris(4-hydroxyphenyl)benzene (3) (0.625 g, 1.76 mmol) and 3,5-
bis(allyloxy)benzyl chloride (4a) (1.50 g, 5.30 mmol) under
reflux of acetonitrile for 48 h, in the presence of K2CO3 and

Article
Macromolecules, Vol. 43, No. 1, 2010 157
Figure 6. Computed absorption and fluorescence wavelength in acetonitrile for 2.
under reflux of acetone for 56 h, in the presence of K2CO3 and
catalytic amounts of Bu4NF hydrate. The solid residue was
removed by filtration; the organic phase was washed with H2O,
dried with Na2SO4, and evaporated under vacuum to give a
residue. The crude product was percolated over silica get eluting
with hexane/EtOAc (7:3) and washed with pentane to give 7 as
an amber oil. Yield: 53% (0.350 g, 1.67 mmol). 1H NMR (400
MHz; CDCl3): δ 7.68 (3H, s, H-1), 7.63 (6H, d, Jo = 8.9, H-4),
7.07 (6H, d, Jo = 8.9, H-5), 6.72 (6H, d, Jm = 1.8, H-9), 6.62
(12H, d, Jm = 1.5, H-14), 6.58 (3H, t, Jm = 1.8 Hz, H-11), 6.48
(6H, t, Jm = 1.5, H-16), 6.10-6.00 (12H, m, H-18), 5.42 (12H,
dd, Jtrans = 17.4, Jgem = 1.5, H-19a), 5.27 (12H, dd, Jcis = 11.9,
Figure 7. Jabloswky diagram for emissive (system A) and nonemissive
(system B) systems.
J
gem = 1.5, H-19b), 5.06 (6H, s, H-7), 4.99 (12H, s, H-12), 4.53
(24H, d, J = 5.4 Hz, H-17). 13C NMR (100 MHz, CDCl3): δ
160.2 (C-10), 160.0 (C-15), 158.5 (C-6), 141.8 (C-2), 139.5 (C-8),
139.3 (C-13), 134.2 (C-3), 133.2 (C-18), 128.4 (C-4), 123.9 (C-1),
117.8 (C-19), 115.3 (C-5), 106.5 (C-9), 106.3 (C-14), 101.8 (C-
catalytic amounts of 18-crown-6 ether. The solid residue was
removed by filtration, and the solvent was evaporated under
vacuum to give an oily residue. The crude oil product was
percolated on silica get eluting with hexane/EtOAc (8:2) to give
1
11), 101.5 (C-16), 70.1 (C-12, 7), 69.0 (C-17). IR (NaCl, νmax/
5a as an amber oil. Yield: 95% (1.61 g, 1.67 mmol). H NMR
cm-1): 3135, 1642, 1597, 1400, 1324, 1167, 1052, 830.
(300 MHz, CDCl3): δ 7.67 (3H, s, H-1), 7.61 (6H, d, Jo = 8.8, H-
4), 7.08 (6H, d, Jo = 8.8, H-5), 6.68 (6H, d, Jm = 2.2, H-9), 6.48
(3H, t, Jm = 2.2, H-11), 6.14-6.00 (6H, m, H-13), 5.46 (6H, dd,
Preparation of Metallodendrimer 10. In a Schlenk flask, 2
(63.1 mg, 0.133 mmol), 10 μL of Karstedt catalyst, and 2 mL of
THF were stirred for 10 min at room temperature. To this
solution, Cs[1,10-μ-Si(CH3)H-3,30-Co(1,2-C2B9H10)2], 8 (200.0
mg, 0.401 mmol), was added, and the mixture was stirred
overnight at 50 ꢀC. After, 10 mL of Et2O was added to produce
two phases. The Et2O phase was discarded by decantation. To
the other oily dark orange phase, 10 mL of hexane was added
to precipitate 10 as an orange solid. Yield: 54% (142.1 mg).
1H NMR (300 MHz, acetone-d6): δ 7.77 (m, 9H, C-Haryl), 7.06
(d, 6H, 3J(HH) = 8.5, C-Haryl), 4.56 (brs, 6H, Cc-H), 4.07 (t,
6H, 3J(HH) = 6.4, -O-CH2-), 1.92 (m, 6H, -CH2-CH2-),
1.07 (300 MHz, acetone, 6H, -CH2-Si), 0.38 (s, 9H, Si-CH3).
1H{11B} NMR (96.29 MHz, acetone-d6): δ 7.77 (m, 9H,
C-Haryl), 7.06 (d, 6H, 3J(HH) = 8.5, C-Haryl), 4.56 (br s,
6H, Cc-H), 4.07 (t, 6H, 3J(HH) = 6.4, -O-CH2-), 3.43 (brs,
2H, B-H), 3.30 (br s, 2H, B-H), 3.10 (br s, 2H, B-H), 2.38 (br s,
2H, B-H), 2.22 (br s, 2H, B-H), 1.94 (br s, 2H, B-H), 1.92 (m,
6H, -CH2-CH2-), 1.69 (br s, 6H, B-H), 1.07 (m, 6H,
-CH2-Si), 0.38 (s, 9H, Si-CH3). 11B NMR (96.29 MHz,
acetone-d6): δ 8.26 (d, 2B, 1J(BH) = 118), 2.84 (d, 2B,
1J(BH) = 136), -1.68 (d, 4B, 1J(BH) = 140), -3.47 (2B),
-4.68 (d, 2B, 1J(BH) = 130), -14.34 (d, 2B, 1J(BH) =
180), -16.62 (d, 2B, 1J(BH) = 148), -22.10 (d, 2B, 1J(BH) =
147). 13C NMR (75.47 MHz, acetone-d6): δ 157.2-114.6 (Caryl),
69.50 (O-CH2), 55.31 (Cc-H), 41.29 (Cc-Si), 22.3 (-CH2-),
12.01 (Si-CH2), -6.03 (Si-CH3). 29Si NMR (59.62 MHz,
acetone-d6): δ 11.96. IR (KBr, νmax/cm-1): 3059 (pI, υ(Cc-H),
3030 (pI, υ(C-H)aryl), 2874 (pI, υ(C-H)alkyl), 2546
(mI, υ(B-H)), 1257 (I, δ(Si-CH3)), 1234 (I, υas(Caryl-O-
C)), 1041 (I, υs(Caryl-O-C)), 829 (I, γ(Si-CH3)). Anal.
Calcd for C48H102B54 Co3Cs3O3Si3: C, 29.26; H, 5.22. Found:
C, 29.32; H 5.34. ESI-MS: (m/z) calcd 1837.8; found 1837.1
(M-Cs).
Jtrans = 17.3, J = 1.5, H-14a), 5.31 (6H, dd, Jcis = 10.5, J = 1.5
Hz, H-14b), 5.08 (6H, s, H-7), 4.56 (12H, dt, J(HH) = 5.3,
J(HH) = 1.4, H-12). 1H NMR (300 MHz, acetone-d6): 7.74 (t,
J = 4.4, H-1, H-5), 7.12 (6H, d, J = 8.7, H-5), 6.70 (6H, s, H-9),
6.50 (3H, s, H-11), 6.10 (6H, m, H-13), 5.41 (6H, d, J(HH) =
17.3, H-14a), 5.24 (6H, d, J(HH) = 10.5, H-14b), 5.12 (6H, s, H-
7), 4.57 (12H, d, J(HH) = 3.7, H-12). 13C NMR (75.47 MHz,
CDCl3): δ 160.2 (C-10), 158.6 (C-6), 142.0 (C-2), 139.5 (C-8),
134.3 (C-3), 133.3 (C-13), 128.6 (C-4), 124.1 (C-1), 118.0 (C-14),
115.4 (C-5), 106.3 (C-9), 101.5 (C-11), 70.2 (C-7), 69.1 (C-12). IR
(NaCl, νmax/cm-1): 3128, 2924, 1643, 1601, 1510, 1400, 1324,
1168, 1016, 828. HRMS C63H61O9 [M þ H]þ, calculated
961.4310; found 961.4331, with an error of 2.173 ppm.
Preparation of 1,3,5-Tris[4-(3,4,5-tris(allyloxy)benzyloxy)-
phenyl]benzene (5b). The procedure was the same as for 5a using
3 (0.70 g, 1.97 mmol) and 4b (1.90 g, 5.58 mmol), to obtain
compound 5b as an amber oil. Yield: 90% (2.05 g, 1.81 mmol).
1H NMR (400 MHz; CDCl3): δ 7.67 (3H, s, H-1), 7.63 (6H, d,
JO = 8.6, H-4), 7.07 (6H, d, JO = 8.6, H-5), 6.69 (6H, s, H-9),
6.12-6.04 (9H, m, H-13, H-130), 5.43 (6H, dd, Jtrans = 17.2, J =
3.3, H-14a), 5.33 (3H, dd, Jtrans = 17.2, J = 3.3 H-14a0), 5.28
(6H, d, Jcis = 12.0, H-14b), 5.21 (3H, d, Jcis = 12, H-14b0),
4.64-4.59 (18H, m, H-12, H-120), 4.99 (6H, s, H-7). 13C NMR
(100 MHz, CDCl3): δ 158.9 (C-6), 153.2 (C-10), 142.2 (C-2),
137.9 (C-11), 135.1 (C-3), 134.5 (C-130), 133.8 (C-13), 132.7 (C-
8), 128.8 (C-4), 124.3 (C-1), 118.0 (C-140), 117.9 (C-14), 115.7 (C-
5), 107.2 (C-9), 74.6 (C-120), 70.7 (C-7), 70.4 (C-12). IR (NaCl,
ν
1232, 1112, 992, 926, 828.
max/cm-1): 3126, 2926, 2838, 1643, 1594, 1509, 1439, 1329,
Preparation of 1,3,5-Tris[4-(3,5-bis(3,5-bis(allyloxy)-
benzyloxy)benzyloxy)phenyl]benzene (7). Compound 7 was
synthesized from 3 (0.78 g, 0.28 mmol) and 3,5-bis[3,5-bis-
(allyloxy)benzyloxy]benzyl chloride (6) (0.50 g, 0.88 mmol)

ꢀ
Juarez-Perez et al.
ꢀ
158 Macromolecules, Vol. 43, No. 1, 2010
Preparation of Metallodendrimer 11. In a Schlenk flask, 5a
(68.0 mg, 0.071 mmol), 10 μL of Karstedt catalyst, and 2 mL of
THF were stirred for 10 min at room temperature. To the
solution Cs[1,10-μ-Si(CH3)H-3,30-Co(1,2-C2B9H10)2], 8 (211.7
mg, 0.424 mmol), was added, and the mixture was stirred
overnight at 50 ꢀC. After, 10 mL of Et2O was added to produce
two phases. The Et2O was discarded by decantation. To the
other oily dark orange phase, 10 mL of hexane was added to
precipitate 11 as an orange solid. Yield: 63% (176.2 mg). In
other attempts, the addition of an aqueous solution of [NMe4]Cl
to the residue gives the corresponding tetramethylammonium
salt of the metallodendrimer as an orange solid. Yield: 55%. 1H
NMR (300 MHz, acetone-d6): δ 7.77 (m, 9H, Haryl), 7.15 (d, 6H,
3J(HH) = 12.0, C-Haryl), 6.69 (s, 6H, C-Haryl), 6.50 (s, 3H,
C-Haryl), 5.12 (s, 6H, -OCHH2-), 4.56 (brs, 12H, Cc-H), 4.00
stock solutions, three different concentrations ranging bet-
ween 1.92 ꢀ 10-5 and 1.95 ꢀ 10-7 M for each compound are
prepared. Fluorescent measurements are developed in two
situations, with degassed solutions with N2 and with
ambient oxygen atempered, and no significance difference in
wavenumber has been noted. Lifetime fluorescence measure-
ments were performed on a EasyLife V. The excitation was
performed with a 278 pulsed LED, and the emission was
measured at 364 nm.
Computational Methods. All calculations have been carried
out with PM6 implemented in MOPAC.40 The bulk solvent
effects on the geometries are evaluated by means of the con-
ductor-like screening model (COSMO) continuum approach
using as EPS 37.5 for acetonitrile.41
(t, 12H, 3J(HH)
= 6.4, -OCHH2-), 1.87 (m, 12H,
Acknowledgment. This work has been supported by the
CICYT (MAT2006-05339), the Generalitat de Catalunya
-CH2-CH2-), 1.04 (m, 12H, -CH2-Si), 0.37 (s, 18H,
Si-CH3). 1H{11B} NMR (300 MHz, acetone-d6): δ 7.77 (m,
9H,C-Haryl), 7.15 (d, 6H, 3J(HH) = 12.0, C-Haryl), 6.69 (s, 6H,
C-Haryl), 6.50 (s, 3H, C-Haryl), 5.12 (s, 6H, -OCHH2-), 4.56
ꢀ
(2005/SGR/00709), and CONACYT-Mexico. E.J.J.-P. thanks
the Ministerio de Educacion y Ciencia for a FPU grant.
ꢀ
3
(brs, 12H, Cc-H), 4.00 (t, 12H, J(HH) = 6.4, -OCHH2-),
Supporting Information Available: This material is available
free of charge via the Internet at http://pubs.acs.org.
3.40 (br s, 12H, B-H), 3.29 (br s, 12H, B-H), 3.09 (br s, 12H,
B-H), 2.38 (br s, 12H, B-H), 2.20 (br s, 12H, B-H), 1.88 (br s,
12H, B-H), 1.87 (m, 12H, -CH2-CH2-), 1.66 (br s, 72H,
B-H), 1.04 (m, 12H, -CH2-Si), 0.37 (s, 18H, Si-CH3). 11B
NMR (96.29 MHz, acetone-d6): δ 8.35 (d, 2B, 1J(BH) = 120),
2.86 (d, 2B, 1J(BH) = 135), -1.72 (d, 4B, 1J(BH) = 146), -3.50
References and Notes
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Escamilla, G. H. Angew. Chem., Int. Ed. Engl. 1994, 33, 666.
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Jungblut, P. W.; Moroder, L. Angew. Chem. 1996, 108, 970. Angew.
Chem., Int. Ed. Engl. 1996, 35, 909.
(3) (a) Parrott, M. C.; Marchington, E. B.; Valliant, J. F.; Adronov,
A. J. J. Am. Chem. Soc. 2005, 127, 12081. (b) Ma, L.; Hamdi, J.;
Wong, F.; Hawthorne, M. F. Inorg. Chem. 2006, 45, 278. (c) Parrott,
M. C.; Valliant, J. F.; Adronov, A. Langmuir 2006, 22, 5251. (d)
Benhabbour, S. R.; Parrott, M. C.; Gratton, S. E. A.; Adronov, A.
Macromolecules 2007, 40, 5678.
(4) (a) Barth, R. F.; Adams, D. M.; Soloway, A. H.; Alam, F.;
Darby, M. V. Bioconjugate Chem. 1994, 5, 58. (b) Armspach, D.;
Cattalini, M.; Constable, E. C.; Housecroft, C. E.; Phillips, D. Chem.
Commun. 1996, 1823. (c) Housecroft, C. E. Angew. Chem., Int. Ed.
1999, 38, 2717. (d) Thomas, J.; Hawthorne, M. F. Chem. Commun.
2001, 1884. (e) Yao, H.; Grimes, R. N.; Corsini, M.; Zanello, P.
Organometallics 2003, 22, 4381. (f) Mollard, A.; Zharov, I. Inorg.
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1
1
(2B), -4.76 (d, 2B, J(BH) = 130), -14.59 (d, 2B, J(BH) =
189), -16.79 (d, 2B, 1J(BH) = 140), -22.30 (d, 2B, 1J(BH) =
166). 13C{1H} NMR (75.47 MHz, acetone-d6): δ 160.4-100.3
(Caryl), 69.70 (O-CH2), 55.21 (Cc-H), 40.7 (Cc-Si), 22.3
(-CH2-), 8.03 (Si-CH2), -7.09 (Si-CH3). 29Si NMR (59.62
MHz, acetone-d6): δ 12.04. IR (KBr, υmax/cm-1): 3061 (pI,
υ(Cc-H), 2976 (pI, υ(C-H)aryl), 2874 (pI, υ(C-H)alkyl), 2554
(mI, υ(B-H)), 1257 (I, δ(Si-CH3)), 1233 (I, υas(Caryl-O-C)),
1053 (I, υs(Caryl-O-C)), 828 (I, γ(Si-CH3)). Anal. Calcd for
C117H276B108Co6N6O9Si6: C, 39.02; H, 7.73; N, 2.33. Found: C,
38.08; H, 7.77; N, 2.09. MALDI-TOF-MS: (m/z) 530.5 ((M þ
H2O)/6, 37%), 1051.6 (M/2, 3%).
Preparation of Metallodendrimer 12. The procedure was the
same as for 10 using 7a (41.2 mg, 0.021 mmol), 10 μL of Karstedt
catalyst, and 2 mL of THF to give 12 as an orange solid. Yield:
51% (86.0 mg). 1H NMR (300 MHz, acetone-d6): δ 7.77 (m, 6H,
C-Haryl), 7.12 (m, 6H, Haryl), 6.78 (s, 6H, C6H5), 6.69 (s, 12H,
C6H5), 6.54 (s, 6H, C6H5), 6.45 (s, 6H, C-Haryl), 6.37 (s, 3H,
C-Haryl), 5.11 (s, 6H, -OCHH2-), 5.06 (s, 12H, -OCHH2-),
4.50 (brs, 24H, Cc-H), 3.99 (s, 24H, -OCHH2-), 1.85 (m, 24H,
-CH2-CH2-), 1.01 (m, 24H, -CH2-Si), 0.32 (s, 36H,
Si-CH3). 11B NMR (96.29 MHz, acetone-d6): δ 8.40 (d, 2B,
1J(BH) = 121), 3.03 (d, 2B, 1J(BH) = 130), -1.59 (d, 4B,
1J(BH) = 140), -3.38 (2B), -4.54 (d, 2B, 1J(BH) = 120), -14.22
(d, 2B, 1J(BH) = 170), -16.46 (d, 2B, 1J(BH) = 141), -21.90 (d,
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~
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~
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Kivekas, R. Org. Lett. 2005, 7, 231. (b) Nꢀunez, R.; Gonzalez-Campo,
€€
(5) (a) Nunez, R.; Gonzalez, A.; Vinas, C.; Teixidor, F.; Sillanpaa, R.;
~
ꢀ
€
A.; Vinas, C.; Teixidor, F.; Sillanpaa, R.; Kivekas, R. Organometallics
~
ꢀ
2005, 24, 6351. (c) Nꢀunez, R.; Gonzalez-Campo, A.; Laromaine, A.;
€€
€
~
Teixidor, F.; Sillanpaa, R.; Kivekas, R.; Vinas, C. Org. Lett. 2006, 8,
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(6) (a) Gonzalez-Campo, A.; Vinas, C.; Teixidor, F.; Nunez, R.;
ꢀ
~
~
€
€€
Kivekas, R.; Sillanpaa, R. Macromolecules 2007, 40, 5644. (b) Lerouge,
1
2B, J(BH) = 160). 13C{1H}NMR (75.47 MHz, acetone-d6): δ
~
~
F.; Vinas, C.; Teixidor, F.; Nꢀunez, R.; Abreu, A.; Xochitiotzi, E.; Santillan,
ꢀ
ꢀ
R.; Farfan, N. Dalton Trans. 2007, 1898. (c) Gonzalez-Campo, A.;
160.6-106.3 (Caryl), 78.36 (O-CH2), 69.60 (O-CH2), 65.11
(O-CH2), 55.24 (Cc-H), 40.6 (Cc-Si), 22.3 (-CH2-), 14.9,
8.41 (Si-CH2), 3.70, -1.01, -7.04 (Si-CH3). 29Si NMR (59.62
MHz, acetone-d6): δ 12.40. IR (KBr, υmax/cm-1): 3056 (pI,
υ(Cc-H)aryl), 2963 (pI, υ(C-H)aryl), 2872 (pI, υ(C-H)alkyl),
2535 (mI, υ(B-H)), 1258 (I, δ(Si-CH3)), 1226 (I, υas-
(Caryl-O-C)), 1040 (I, υs(Caryl-O-C)), 834 (I, γ(Si-CH3)).
Anal. Calcd for C183H408B216Co12Cs12O21Si12: C, 27.75; H, 5.19.
Found: C, 27.26; H, 5.47. MALDI-TOF-MS: (m/z) 530.4 ((M/12
þ H2O, 19%).
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