Synthesis and characterization of photoluminescent vinylbiphenyl decorated polyhedral oligomeric silsesquioxanes

Article abstract of DOI:10.1039/b814496f

Grubbs cross-metathesis has been used to functionalize octavinylsilsesquioxane with fluorescent vinylbiphenyl-modified chromophores to design new hybrid organic-inorganic nanomaterials. Those macromolecules have been characterized by NMR, microanalyses, M

Full text of DOI:10.1039/b814496f

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PAPER
www.rsc.org/obc | Organic & Biomolecular Chemistry
Synthesis and characterization of photoluminescent vinylbiphenyl decorated
polyhedral oligomeric silsesquioxanes†‡
Nicolas R. Vautravers,a Pascal Andre´,*b A. M. Z. Slawina and David J. Cole-Hamilton*a
Received 20th August 2008, Accepted 4th November 2008
First published as an Advance Article on the web 11th December 2008
DOI: 10.1039/b814496f
Grubbs cross-metathesis has been used to functionalize octavinylsilsesquioxane with fluorescent
vinylbiphenyl-modified chromophores to design new hybrid organic-inorganic nanomaterials. Those
macromolecules have been characterized by NMR, microanalyses, MALDI-TOF mass spectrometry
and photoluminescence. This last method was shown to be an interesting tool in the analysis of the
purity of the cube derivatives.
regard to its effect on fluorescence quantum yield as well
Introduction
as for the design of multifunctional colloidal molecules.20,21
A
Dendrimers are tree-like, highly branched, monodisperse macro-
molecules composed of a central core, branches comprising
repeated branching units radiating from it, and surface groups
located on the exterior of the dendrimer providing further
functionality. They offer numerous interesting properties resulting
from the globular shape they often adopt at high generation, so the
range of their applications spans through drug delivery systems,1
molecular recognition,2–5 catalysis supports,6–9 magnetic resonance
imaging contrast agents,10 DNA intercalation compounds11 and
light-emitting materials.12,13
key issue for these potential applications of silsesquioxanes is
their relative ease of synthesis in multigram quantities, avoiding
22
acidic or basic conditions23,24 which might disrupt the POSS
core. Recent advances have seen many new POSS species pre-
pared by cross-metathesis,17,25,26 hydrosilylation27,28 or hydrolysis
of RSiY3.29 We previously reported on the successful elaboration
of a variety of new functionalisable dendrimer cores based on
octavinylsilsesquioxane20,30 and wish further to extend our studies
in this paper. We expand the library of organic-inorganic hybrid-
decorated polyhedral oligomeric silsesquioxanes by presenting the
synthesis of a new family of photoluminescent vinylbiphenyl-
terminated POSS-cored dendrimers together with their optical
characterization. While trying to gain deeper insight into the
effect of these chromophore-grafted rigid POSSs on fluorescence
quantum yield, we show that the photoluminescent properties
of these organic-inorganic hybrid macromolecules demonstrate
some limitations of traditional characterisation techniques for the
identification of minor side products.
Among these dendrimers, cubic polyhedral oligomeric
silsesquioxanes (POSSs) of chemical formula R8Si8O12, with R
groups at the vertices of a cube and bridged by oxygen atoms, are
of special interest because of their nanometre-size allowing the use
of silicon atoms for the design of multifunctional molecules. They
have been mainly employed in materials chemistry ranging from
14
15
models of silica surface
and zeolites
to organic-inorganic
hybrid polymers.16 POSS-chromophore hybrid molecules have
also attracted interest, among other reasons, because of their
better casting and layer-forming properties than those of pure
chromophores, especially in the context of applications including
organic semiconductors and solution processable light-emitting
diodes.17–19 Additionally, the attachment of luminescent chro-
mophores to the rigid POSS core is of scientific interest with
Results and discussion
Three macromolecules (S) have been prepared via Grubbs
metathesis between the readily available octavinylsilsesquioxane
and a vinylbiphenyl-decorated monomer (M) (Scheme 1). During
the Grubbs coupling, the homometathesis side product (H) from
M was always produced together with the macromolecule and
ethene. The reaction system is even more complex, as the olefin
metathesis is reversible (equilibrium); in the given case, the removal
of ethene assures complete conversion from octavinylsilsesquiox-
ane + M to S + H. The cross-metathesis between two POSS species
has never been observed, probably for steric reasons.
The vinyl biphenyl group was selected because of its versatile
chemistry and strong photoluminescence properties. The chemical
functionalising groups R were chosen for their abilities to further
elaborate on xxthe resulting compound structure and properties
by simple chemistry. In this context, three M monomers were
synthesised via Suzuki coupling between styreneboronic acid and
the desired haloaromatic compound. This yielded chromophores
with a vinylbiphenyl backbone decorated with one methylenedioxy
group M1, two methoxy groups M2 or two methyl dicarboxylate
aEaStCHEM, School of Chemistry, University of St. Andrews, St. Andrews,
Fife, KY16 9ST, UK. E-mail: djc@st-and.ac.uk; Fax: +44-1334-463808;
Tel: +44-1334-463805
bOrganic Semiconductor Centre, SUPA, School of Physics and Astronomy,
University of St Andrews, St Andrews, Fife, Scotland, KY16 9SS, UK.
E-mail: pa11@st-and.ac.uk
† Electronic supplementary information (ESI) available: Crystal structure
of H3. CCDC reference number ??. For ESI and crystallographic data in
CIF or other electronic format see DOI: 10.1039/b814496f
‡ C34H28O8, M = 564.56, monoclinic, space group P21/c, a = 4.7172(6)
◦
3
˚
˚
˚
b = 14.805(2), c = 19.787(3) A, b = 93.810(4) U = 1378.8(3) A , Z =
-3
-1
2, Dc = 1.360 Mg m , m = 0.097 mm (Mo-Ka, l = 0.71073 A). The
data were collected at T = 93(2) K, 8788 reflections were measured
on a Rigaku MM007RA/Confocal Optics/Mercury CCD diffractometer
equipped with an Xstream low-temperature device yielding 2459 unique
data (Rmerg = 0.0307). Conventional R = 0.0432 for 2121 reflections with
I ≥ 2s, GOF = 1.051. Final wR2 = 0.1201 for all data. The largest peak
-3
˚
in the residual map is 0.203 e A .
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Scheme 1 Synthetic pathway of macromolecule (S) and homo-Grubbs side product (H) from vinylbiphenyl monomer (M) and octavinylsilsequioxane.
groups M3 (Scheme 2). The two first monomers M1 and M2
can lead, after deprotection, to diol-decorated biphenyls which
allow subsequent functionalization through a variety of reactions
such as transesterification or nucleophilic substitution,31 whilst
dimethyl ester groups present on M3 are interesting candidates for
polymerisation.
The photophysical properties and mass characterisation of these
three compounds were then investigated through a combination
of absorbance (Abs), photoluminescence (PL), photolumines-
cence excitation (PLE) measurements and High Resolution Mass
Spectrometry (HRMS) as reported in Fig. 1 and Table 1; see
experimental for details.
The photophysical properties of the three monomers are fairly
consistent with those of vinylbiphenyl which is characterised in
THF by absorption and photoluminescence peaks at 278 nm
and 317 nm, respectively,20,32 while the observed shifts result
from the slight perturbation of the electronic properties induced
by the functional groups; see Table 1. The PLQY variation
observed between each monomer can be rationalised by the
degree of freedom, i.e. rotational and vibrational, associated
Scheme 2 Formation of monomer (M) via Suzuki coupling between
styreneboronic acid and the desired haloaromatic compound.
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Table 1 Absorbance peak, position of the first photoluminescence peak, photoluminescence quantum yield (PLQY) measured at the indicated wavelength
and high resolution mass spectroscopy (HRMS)
Structure
M1
M2
M3
Abs. peak (nm)
1st PL peak (nm)
PLQY (%)
301
374
300
374
280
355
40 @ 300 nm
225.0921, requires 225.0911
60 @ 300 nm
263.1046, requires 263.1048
14 @ 280 nm
297.1129, requires 297.1127
HRMS (g/mol)
For each monomer, the close match between the PLE spectrum
and the absorbance testifies to the high purity of the prepared
compounds, further confirmed by mass spectrometry (Table 1).
Monomers (M) were then coupled to octavinylsilsesquioxane
via a Grubbs-type reaction, affording the corresponding macro-
molecules (S) (Fig. 2). After precipitation in a mixture of ethyl
acetate (120 mL) and petroleum ether (40–60) (500 mL), the three
macromolecules were subjected to column chromatography, and
their purity was attested on the one hand by both microanalysis
and MALDI mass spectroscopy (Table 2) and on the other hand
by the cross-peaks that appear on their 29Si1H HMQC 2D NMR
spectrum, illustrated in Fig. 3 for the macromolecule S2. The cross-
peaks correspond to the clean coupling between a corner silicon
atom and the alkenyl protons at 6.49 ppm and 7.51 ppm. The sharp
cross-peaks indicate that the cube is intact and unique and that
each corner is equivalent. Similar observations have been made
for the other three macromolecules, highlighting the uniqueness
of each cube.
The optical characterisation and mass characterisation of the
macromolecules is reported in Fig. 4 and Table 2. Due to a more
extensive electron delocalisation into the POSS core, grafting M
monomers onto the POSS cube leads to the expected slight red
shift in the absorbance and PL spectra compared to the free
dendrons.20,32 Broader PL spectra are also observed for the three
S macromolecules as more conformations become accessible to
the chromophores.35 The side products give rise to absorption
features at ca. 345 nm, confirmed by extra peaks in this region in
the PLE spectrum. These photophysical methods seem to provide
the only analytical technique that reveals the presence of this side
product. In the case of S1 and S2, the side-products precipitated
as powders during the course of the Grubbs coupling and were
isolated by filtration, whilst silica gel column chromatography was
performed for S3, as both product and side product were soluble
in the reaction mixture.
Fig. 1 Normalized absorbance (Abs., ꢀ), photoluminescence (PL, ꢀ,
exc: 290 nm) and photoluminescence excitation (PLE, ᭺, ldetec: 340 nm)
spectra associated with the monomers M1 (A), M2 (B) and M3 (C).
l
with the external functional groups as would be expected in
rigidochromic systems.33,34 For instance, the methoxy groups of
M2 induce an increase of the PLQY when compared to the pure
vinylbiphenyl chromophore, 60% and 45% respectively, whereas
the PLQY decreases dramatically passing from the rigid diol-
protected monomers M1 and M2 to the more flexible ester M3.
The H side products were identified by HRMS as arising from
self-metathesis of the M monomers (Table 3 and Fig. 5). In
the mixtures S1 + H1 and S2 + H2, the grafted M segments
possess low solubility in apolar solvents, not much enhanced by
the substituents R; see Scheme 1. In the POSS compounds S,
the grafted M segments have worse possibilities for higher regular
Table 2 Absorbance peak, position of the first photoluminescence peak, photoluminescence quantum yield (PLQY) measured at the indicated wavelength
and matrix-assisted laser desorption/ionization (MALDI) mass spectroscopy
Structure
S1
S2
S3
Abs. peak (nm)
1st PL peak (nm)
PLQY (%)
311
382
310
380
285
375
<50 @ 300 nm
2202.44, requires 2201.84
<55 @ 300 nm
2330.30, requires 2329.92
<11 @ 290 nm
2802.41, requires 2801.08
MALDI (g/mol)
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Fig. 3 29Si1H HMQC 2D NMR of S2.
Fig. 4 Normalized Abs. (ꢀ), PL (ꢀ, lexc: 290 nm) and PLE (᭺, ldetec
:
420 nm) spectra associated with the macromolecules S1 (A), S2 (B) and
S3 (C).
H3 with substituent MeO2C- groups was characterised
crystallographically‡. The X-ray structure of H3 reveals that the
molecule is planar, has an E double bond and is disposed about
a centre of symmetry at the middle of the double bond. The
˚
central bond length is 1.330(3) A. The terminal aryl rings are
Fig. 2 Representation of macromolecules S1, S2 and S3.
inclined by 26◦ with respect to the central aryl rings whilst the
ester substituents are essentially coplanar with the terminal aryl
rings.
crystallization than in the H products, which are hence less soluble
and precipitate more easily. In the case of S3, this effect is cancelled
by the high solubility of the M segments given by the ester groups
on them; see Scheme 2. The chromatographic behavior of both
S3 and H3 is thus dominated by mutual affinity and similar high
solubility making their separation more complex.
The photophysical properties of these homo-metathesis prod-
ucts are shown in Fig. 6 and Table 3. As a result of the increase
in the conjugation length associated with the dimerisation, the
expected red shift of both the absorption and PL features for
the three homo-metathesis products compared with the free
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Table 3 Absorbance peak, position of the first photoluminescence peak, photoluminescence quantum yield (PLQY) measured at the absorbance
maximum and high resolution mass spectroscopy (HRMS)
Structure
H1
H2
H3
Abs. peak (nm)
1st PL peak (nm)
PLQY (%)
350
402
350
400
345
390
66 @ 350 nm
421.1436, requires 421.1440
80 @ 350 nm
453.2061, requires 453.2066
70 @ 350 nm
565.1864, requires 565.1860
HRMS (g/mol)
Fig. 5 Representation of homo-metathesis products H1, H2 and H3‡.
momomers is observed; see Table 2 and Table 3. The PL spectra
of the homo-metathesis products display similar substructures,
although they are shifted slightly because of the different effects
of the aromatic substituents. For all three H chromophores, the
PLQY is much higher than for M and S molecules, being up to
80% for H2, consistent with the rigidochromy already mentioned
for the monomers. In addition, absorption and PLE spectra
match one another and the maxima correspond exactly to the
side products identified during the photophysical studies of the S
macromolecules.
In this context, the high PLQYs of these dimers explain
why the relatively small amount of homo-metathesis product
remaining after purification of the macromolecules would lead
to an overestimation of the PLQY of the macromolecules. The
higher intensity of the photoluminescence from the side product
observed in the PLE for S3 (see Fig. 6C) can now be explained:
H3 has been isolated chromatographically, but its similar polarity
or intercalation within the macromolecule makes complete sepa-
ration from the macromolecule difficult, even after several cycles.
Conversely, the precipitation of H1 and H2 in the course of the
Grubbs reaction, followed by their filtration, allows for better
purification.
Fig. 6 Normalized Abs. (ꢀ), PL, (ꢀ, lexc: 290 nm) and PLE (᭺, ldetec
:
420 nm) spectra associated with the homo-metathesis products H1 (A),
H2 (B) and H3 (C).
do (at least in the cases of M1 and S1) exhibit the lowest PLQY.
Rather unexpectedly, the PLQYs for M2, S2 and H2 are higher
than those for M1, S1 and H1. The origin of this effect is not
clear.
While targeting specific applications in the biomedical and mate-
rial fields, it is crucial to select the appropriate synthetic pathways
to control the exact composition of the final product without
inducing side effects or altering the thermal/mechanical/electrical
material properties. In this context it is then worth noting
that the presence of the homo-metathesis product within the
final product has only been identified through its photophysi-
cal properties. None of NMR, MALDI-TOF or microanalysis
were able to distinguish between the small molecule and the
macromolecule.
The PLQY of all the compounds synthesized and characterised
in the present work are compared in Table 1, Table 2 and Table 3.
On the basis of simple considerations of translational, vibrational
and rotational degrees of freedom, M3, S3 and H3 should, and
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ˆ2 Ê
ˆ
Conclusions
Ê
ˆ Ê
ˆ
Ar
l
l
I l
Ê
(
(
)
)
(
)
)
n
n
Dx
r
r
x ˜ Á
r ¯ Ë
˜
Φ = Φ
x
r
Á
˜ Á
˜
Á
A
I l
D
Ë
¯
We have shown the synthesis and characterization of three new
light-emitting macromolecules based on vinylbiphenyl decorated
polyhedral oligomeric silsesquioxanes. They have been charac-
terized by NMR, microanalysis and MALDI-TOF spectroscopy.
Optical measurements were shown to be an interesting and crucial
tool in analyzing the purity of these compounds.
(
Ë
¯ Ë
¯
x
x
x
r
where U stands for PLQY, the subscripts x and r refer to the
compound to be characterized and to the reference solutions,
respectively. l is the excitation wavelength, A(l) is the absorbance,
I(l) is the relative intensity of the exciting light, n is the solvent
refractive index, and D is the integrated area under the corrected
emission spectrum.
Experimental
All manipulations were carried out under dry, deoxygenated
(CrII on silica) nitrogen using standard Schlenk techniques.
Before use, solvents were degassed and dried by distillation
from sodium diphenyl ketyl (THF) or calcium hydride (CH2Cl2).
Water was distilled and stored under nitrogen. 4-bromo-
1,2-(methylenedioxy)benzene, 4-bromo-1,2-dimethoxybenzene,
4-Styryl-1,2-(methylenedioxy)benzene (M1)
A mixture of 4-bromo-1,2-(methylenedioxy)benzene (1.3 mL,
10.8 mmol), 4-styrene boronic acid (2 g, 13.5 mmol), [Pd(PPh3)4]
(374 mg, 0.32 mmol), K2CO3 (2M, 37.8 mmol) and THF (70 mL)
was heated at 75 ◦C for 48 hours. After cooling to room
temperature, CH2Cl2 (50 mL) and water (20 mL) were added and
the layers were separated. The aqueous layer was extracted with
CH2Cl2. The combined organic layers were washed with water and
dried over MgSO4. After evaporation of the solvents, flash column
chromatography with CH2Cl2 afforded M1 as a white luminescent
powder (2.38 g, 98%) (Found: C, 80.0; H, 5.2. C15H12O2 requires
C, 80.4; H 5.4%); dH(300.13 MHz; CDCl3; Me4Si) 5.27 (1 H, d,
=
4-styrene boronic acid, [Pd(PPh3)4], [Ru( CHPh)Cl2(PCy3)2]
(Grubbs’ catalyst, 1st gen.) and lithium 2,4-pentanedioate were
purchased from Aldrich and used without further purification.
Microanalyses were carried out on a Carlo Erba 1110 CHNS
analyser. A Micromass GCT provided Chemical Ionisation (CI)
at low and high resolution and a Micromass LCT provided a
low and high resolution Electrospray Ionisation Service (ESI).
NMR spectra were recorded on a Bruker Avance 300 or a Bruker
3
3
= =
JHH 11.6, CH2 CH), 5.79 (1 H, d, JHH 18.3, CH2 CH), 6.01 (2
1
Avance II 400 NMR spectrometer. The H, 13C and 29Si NMR
H, s, OCH2O), 6.76 (1 H, dd, 3JHH 11.6 Hz, 3JHH 18.3, CH2 CH),
6.90 (1 H, m), 7.09 (2 H, m) and 7.49 (4 H, m); dC(75.5 MHz;
=
spectra were recorded with reference to tetramethylsilane. 31P
NMR spectra were referenced externally to 85% H3PO4. Matrix-
assisted laser desorption/ionization (MALDI) mass spectra were
obtained using a Micromass TOF Spec 2E mass spectrometer
system equipped with a 337 nm N2 laser operating in the positive
ion detection mode. Samples were generated by adding NaI to the
matrix (a-cyano-4-hydroxycinnamic acid or 2,5-dihydroxybenzoic
acid, as an ionization promoter) and dissolved in a suitable solvent
(THF or CH2Cl2) before being transferred to the sample holder
and dried. The spectra were calibrated using a tryptic digest of the
b-galactosidase protein.
=
CDCl3; Me4Si) 101.6 (OCH2O), 107.9, 109.0, 114.2 (CH2 CH),
120.9, 127.3, 127.4, 135.5, 136.7, 136.8, 140.7, 147.5 and 148.8;
m/z (CI) 225.25 (M+1. C15H13O2 requires 225.26).
1,3,5,7,9,11,13,15-Octakis[2-ethenyl]pentacyclo-
[9.5.1.13,9.15,15.17,13]octasiloxane (S1)
An oven-dried flask equipped with a condenser and a mag-
netic stirring bar was charged under nitrogen with
octavinylsilsesquioxane37 (100 mg, 0.16 mmol) and 4-styryl-
1,2-(methylenedioxy)benzene M1 (624 mg, 2.78 mmol) in CH2Cl2
(10 mL). The solution of Grubbs¢ catalyst (5 mg, 0.006 mmol)
Data for H3 were corrected for Lorentz, polarization and
absorption effects. The structures were solved by direct methods
and refined by full-matrix least squares on xxF2 for all data using
SHELXTL software. The non-hydrogen atoms were refined with
anisotropic thermal parameters and C–H hydrogen atoms were
assigned riding isotropic thermal parameters and constrained to
idealised geometries.
Absorption spectra were recorded using a Cary 300 spectropho-
tometer, 10 mm optical path fluorescence cuvettes (Hellma) and
the concentration was adjusted to reach an optical density of about
0.1. Photoluminescence (PL) spectra were recorded with a Jobin
Yvon Horiba Fluoromax 2 fluorimeter. Spectra were corrected
for grating and detector sensitivity variation with wavelength.
Except when stated otherwise, all the photophysical properties
were characterised at room temperature and in non degassed
THF solution. The photoluminescence quantum yields (PLQY)
were measured against quinine sulfate (Fluka) in 0.5 M sulfuric
acid (Sigma-Aldrich) solution used as a standard because of its
known quantum yield of 54.6% as well as its very small sensitivity
to oxygen quenching. PLQY falls down to 45% in non degassed
THF. The following equation was used to perform the appropriate
corrections:36
◦
in CH2Cl2 (3 mL) was injected in the mixture heated at 55 C to
maintain a gentle reflux. The reaction was stopped and cooled to
room temperature after disappearance of the vinyl signals in the
1H NMR spectrum (90 hours). The mixture was filtered (isolation
of H1), concentrated and precipitated by adding the crude
product in CH2Cl2 to a solution of ethyl acetate (120 mL) and
petroleum ether (40–60) (500 mL). The residue was loaded onto a
silica gel column and eluted with CH2Cl2 affording S1 as a white
powder (231 mg, 67%) (Found: C, 65.2; H, 4.0. C120H88O28Si8
requires C, 65.5; H, 4.0%); dH(300.13 MHz; CDCl3; Me4Si) 6.01
3
=
(16 H, s, OCH2O), 6.37 (8 H, d, JHH 18.6, SiCH CH), 6.90 (8
3
=
H, m), 7.09 (16 H, m), 7.44 (8 H, d, JHH 18.6, SiCH CH) and
7.54 (32 H, m); dC(75.5 MHz; CDCl3; Me4Si) 101.6 (OCH2O),
=
108.0, 109.0, 117.0 (SiCH CH), 120.9, 127.3, 127.4, 135.5, 136.7,
=
140.7, 147.6, 148.5 (SiCH CH) and 149.0; dSi(79.5 MHz; CDCl3;
Me4Si) -77.6 (O3Si); m/z (MALDI) 2202.44 (M. C120H88O28Si8
requires 2201.84).
(H1) (282 mg, 69% based on unreacted M1); m/z (CI) 421.1436
(M+1. C28O4H21 requires 421.1440).
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3,4-Dimethoxy-4¢-vinylbiphenyl (M2)
mixture of 4-bromo-1,2-dimethoxybenzene (2.3 mL,
washed with water and dried over MgSO4. The residue was
loaded onto a silica gel column and eluted with CH2Cl2 to afford
M3 as a white powder (531 mg, 76%) (Found: C, 73.0; H, 4.6.
C18H16O4 requires C, 73.0, H 5.4%); dH(300.13 MHz; CDCl3;
A
16.0 mmol), 4-styrene boronic acid (3 g, 20.3 mmol), [Pd(PPh3)4]
(562 mg, 0.48 mmol), K2CO3 (2M, 56.8 mmol) and THF
(70 mL) was heated at 75 ◦C for 48 hours. After cooling to room
temperature, CH2Cl2 (50 mL) and water (20 mL) were added
and the layers were separated. The aqueous layer was extracted
with CH2Cl2. The combined organic layers were washed with
water and dried over MgSO4. After evaporation of the solvents,
flash column chromatography with CH2Cl2 afforded M2 as a
white luminescent powder (2.05 g, 53%) (Found: C, 79.6; H, 6.9.
C16H16O2 requires C, 80.0; H, 6.7%); dH(300.13 MHz; (CD3)2SO;
Me4Si) 3.79 (3 H, s, OCH3), 3.85 (3 H, s, OCH3), 5.28 (1 H, d,
Me4Si) 3.99 (6 H,s, OCOCH3), 5.33 (1 H, d, 3JHH 11.1, CH2 CH),
=
3
3
=
5.83 (1 H, d, JHH 17.8, CH2 CH), 6.78 (1 H, dd, JHH 11.1,
3
3
=
JHH 17.8, CH2 CH), 7.53 (2 H, d, JHH 8.3), 7.65 (2 H, d,
3JHH 8.3), 8.48 (2 H, d, JHH 1.6) and 8.65 (1 H, t, JHH 1.6);
4
4
=
dC(75.5 MHz; CDCl3; Me4Si) 52.6 (OCOCH3), 114.8 (CH2 CH),
127.0, 127.5, 129.5, 131.3, 132.3, 136.3, 138.0, 138.4, 141.7 and
166.2 (OCOCH3); m/z (CI) 297.1129 (M+1. C18H17O4 requires
297.1127).
1,3,5,7,9,11,13,15-Octakis[2-{4 Dimethyl 4¢-vinyl biphenyl-3,5-
dicarboxylate}ethenyl]pentacyclo-[9.5.1.13,9.15,15.17,13]octasiloxane
(S3)
3
3
=
=
JHH 11.1, CH2 CH), 5.87 (1 H, d, JHH 17.8, CH2 CH), 6.77
3
3
3
=
(1 H, dd, JHH 11.1, JHH 17.8, CH2 CH), 7.03 (1 H, d, JHH
8.3), 7.22 (1 H, d, 3JHH 8.3), 7.23 (1 H, s), 7.53 (2 H, d, 3JHH 8.2)
3
and 7.65 (2 H, d, JHH 8.2); dC (75.5 MHz; (CD3)2SO; Me4Si)
55.5 (OCH3), 110.2, 112.1, 114.0 (CH2 CH), 118.7, 126.4, 126.6,
An oven-dried flask equipped with
a condenser and a
=
magnetic stirring bar was charged under nitrogen with
octavinylsilsesquioxane37 (20 mg, 0.032 mmol) and dimethyl
4¢-vinylbiphenyl-3,5-dicarboxylate M3 (164 mg, 0.55 mmol) in
CH2Cl2 (10 mL). The solution of Grubbs¢ catalyst (1 mg,
0.001 mmol) in CH2Cl2 (3 mL) was injected in the mixture heated
at 55 ◦C to maintain a gentle reflux. The reaction was stopped
and cooled down to room temperature after disappearance of the
132.3, 135.6, 136.2, 139.5, 148.6 and 149.0; m/z (ESI) 263.1046
(M+Na. C16H16O2Na requires 263.1048).
1,3,5,7,9,11,13,15-Octakis[2-ethenyl]pentacyclo
[9.5.1.13,9.15,15.17,13]octasiloxane (S2)
An oven-dried flask equipped with a condenser and a magnetic
stirring bar was charged under nitrogen with octavinylsilsesquiox-
ane37 (100 mg, 0.16 mmol) and 3,4-dimethoxy-4¢-vinybiphenyl M2
(662 mg, 2.76 mmol) in CH2Cl2 (10 mL). The solution of Grubbs¢
catalyst (5 mg, 0.006 mmol) in CH2Cl2 (3 mL) was injected in
the mixture heated at 55 ◦C to maintain a gentle reflux. The
reaction was stopped and cooled down to room temperature
after disappearance of the vinyl signals in the 1H NMR spectrum
(90 hours). The mixture was filtered (isolation of H2), concentrated
and precipitated by adding the crude product in CH2Cl2 to a
solution of ethyl acetate (120 mL) and petroleum ether (40–
60) (500 mL). The residue was loaded onto a silica gel column
and eluted with a gradient of CH2Cl2 and (CH3)2CO (CH2Cl2
→ (CH3)2CO) affording S2 as a white powder (252 mg, 69%)
(Found: C, 65.3; H, 4.8. C128H120Si8O28 requires C, 65.9; H, 5.2%);
1
vinyl signals in the H NMR spectrum (90 hours). The mixture
was filtered, concentrated and then precipitated by adding the
crude product in CH2Cl2 to a solution of ethyl acetate (120 mL)
and petroleum ether (40–60) (500 mL). The residue was loaded
onto a silica gel column and 3 bands were eluted with a gradient
of CH2Cl2 and EtOAc (CH2Cl2 (M3)→ CH2Cl2/EtOAc (20/1)
(H3)→ EtOAc (S3)) affording (S3) as a white powder (54 mg,
62%) (Found: C, 61.8; H, 3.6. C120H88O44Si8 requires C, 62.3; H
4.3%); dH(300.13 MHz; CDCl3; Me4Si) 3.99 (48 H, s, OCOCH3),
3
3
=
=
6.47 (8 H, d, JHH 19.2, SiCH CH), 7.50 (8 H, d, JHH 19.2,
4
=
SiCH CH), 7.68 (32 H, m), 8.49 (16 H, d, JHH 1.6) and 8.66 (8
H, t, JHH 1.6); dC(75.5 MHz; CDCl3; Me4Si) 52.7 (OCOCH3),
118.3 (SiCH CH), 127.1, 127.4, 127.9, 131.3, 131.5, 137.8, 138.5,
4
=
=
141.3, 147.8 (SiCH CH) and 166.4 (OCOCH3); dSi(79.5 MHz;
CDCl3; Me4Si) -78.5 (O3Si); m/z (MALDI) 2802.41 (M+Na.
C120H88O44Si8Na requires 2801.08).
dH(300.13 MHz; CDCl3; Me4Si) 3.93 (24 H, s, OCH3), 3.96 (24 H,
3
=
=
s, OCH3), 6.39 (8 H, d, JHH 19.2, SiCH CH), 6.95 (8 H, d,
(H3) (72 mg, 64% based on unreacted M3); dH(400.13 MHz;
3JHH 8.68), 7.16 (16 H, m), 7.46 (8 H, d, 3JHH 19.2, SiCH CH) and
=
=
CDCl3; Me4Si) 4.00 (12 H, s, OCOCH3), 7.24 (2 H, s, CH CH),
7.58 (32 H, m); dC(75.5 MHz; CDCl3; Me4Si) 56.0 (OCH3), 110.3,
7.67 (4 H, d, 3JHH 8.5), 7.71 (4 H, d, 3JHH 8.5), 8.50 (4 H, d, 4JHH
1.7), 8.50 (4 H, d, 4JHH 1.7), 8.67 (2 H, d, 4JHH 1.7); dC(75.5 MHz;
=
111.5, 117.2 (SiCH CH), 119.4, 127.0, 127.4, 133.5, 136.0, 141.6,
=
148.8 (SiCH CH), 148.9 and 149.2; dSi(79.5 MHz; CDCl3; Me4Si)
=
CDCl3; Me4Si) 52.6 (OCOCH3), 127.3, 127.5, 128.6 (CH CH),
-78.3 (O3Si); m/z (MALDI) 2330.30 (M. C128H120Si8O28 requires
2329.92).
(H2) (271 mg, 63% based on unreacted M2); m/z (CI) 453.2064
(M+1. C30O4H29 requires 453.2066).
129.4, 131.3, 132.0, 137.2, 138.2, 141.4, and 166.3 (OCOCH3);
m/z (CI) 565.1864 (M+1. C34O8H29 requires 565.1860).
Acknowledgements
Dimethyl 4¢-vinylbiphenyl-3,5-dicarboxylate (M3)
The authors gratefully acknowledge the Scottish Higher Edu-
cation Funding Council (SHEFC, P.A.) and the EC (IDECAT
Network of Excellence Grant No NMP3-CT-2005–011730,
N. R. V.) for financial support. P.A. would like to thank the
Scottish University Physics Alliance (SUPA) for funding his
Advanced Research Fellowship and both the School of Physics
and Astronomy at St Andrews and Prof. I.D.W. Samuel for their
support.
A mixture of dimethyl 5-iodobenzene-1,3-dicarboxylate38 (755 mg,
2.36 mmol), 4-styrene boronic acid (436 mg, 2.95 mmol),
[Pd(PPh3)4] (82 mg, 0.071 mmol), K2CO3 (2M, 4.2 mL, 8.40 mmol)
and THF (70 mL) was heated at 75 ◦C for 48 hours. After
cooling to room temperature, CH2Cl2 (50 mL) and water (20 mL)
were added and the layers were separated. The aqueous layer
was extracted with CH2Cl2. The combined organic layers were
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20 P. Andre´, G. Cheng, A. Ruseckas, T. van Mourik, H. Fru¨chtl, J. A.
Crayston, R. E. Morris, D. Cole-Hamilton and I. D. W. Samuel, J.
Phys,. Chem. B, 2008, Accepted.
21 V. Balzani, P. Ceroni, S. Gestermann, C. Kauffmann, M. Gorka and F.
Vogtle, Chem. Commun., 2000, 853.
References
1 F. Aulenta, W. Hayes and S. Rannard, Eur. Polym. J., 2003, 39, 1741.
2 C. Valerio, J.-L. Fillaut, J. Ruiz, J. Guittard, J.-C. Blais and D. Astruc,
J. Am. Chem. Soc., 1997, 119, 2588.
3 F. Zeng and S. C. Zimmerman, Chem. Rev., 1997, 97, 1681.
4 R. P. Brinas, T. Troxler, R. M. Hochstrasser and S. A. Vinogradov, J.
Am. Chem. Soc., 2005, 127, 11851.
5 J. Leclaire, R. Dagiral, S. Fery-Forgues, Y. Coppel, B. Donnadieu,
A.-M. Caminade and J.-P. Majoral, J. Am. Chem. Soc., 2005, 127,
15762.
6 A. M. Caminade, V. Maraval, R. Laurent and J. P. Majoral, Curr. Org.
Chem., 2002, 6, 739.
7 L. J. Twyman, A. S. H. King and I. K. Martin, Chem. Soc. Rev., 2002,
31, 69.
8 D. Astruc, K. Heuze, S. Gatard, D. Mery, S. Nlate and L. Plault, Adv.
Synth. Catal., 2005, 347, 329.
22 F. J. Feher, D. Soulivong and A. G. Eklund, Chem. Commun., 1998,
399.
23 F. J. Feher, R. Terroba and J. W. Ziller, Chem. Commun., 1999, 2153.
24 E. Rikowski and H. C. Marsmann, Polyhedron, 1997, 16, 3357.
25 F. J. Feher, D. Soulivong, A. G. Eklund and K. D. Wyndham, Chem.
Commun., 1997, 1185.
26 Y. Itami, B. Marciniec and M. Kubicki, Chem. Eur. J., 2004, 10, 1239.
27 J. D. Froehlich, R. Young, T. Nakamura, Y. Ohmori, S. Li and A.
Mochizuki, Chem. Mater., 2007, 19, 4991.
28 K. Wada, N. Watanabe, K. Yamada, T. Kondo and T.-A. Mitsudo,
Chem. Commun., 2005, 95.
29 A. R. Bassindale, Z. Liu, I. A. MacKinnon, P. G. Taylor, Y. Yang, M.
E. Light, P. N. Horton and M. B. Hursthouse, J. Chem,. Soc., Dalton
Trans., 2003, 2945.
9 L. H. Gade, Dendrimer Catalysis, Springer GmbH edn., Berlin,
Germany, 2006.
10 H. Kobayashi and M. W. Brechbiel, Curr. Pharm. Biotechno., 2004, 5,
30 G. Cheng, N. R. Vautravers and D. J. Cole-Hamilton, Org. Biomol.
Chem, DOI: 10.1039/B812140K.
539.
11 B. Felber and F. Diederich, Helv. Chim. Acta, 2005, 88, 120.
12 P. L. Burn, S.-C. Lo and I. D. W. Samuel, Adv. Mater., 2007, 19, 1675.
13 F. C. D. Schryver, T. Vosch, M. Cotlet, M. v. d. Auweraer, K. Mullen
and J. Hofkens, Acc. Chem. Res., 2005, 38, 514.
14 J. Dobler, M. Pritzsche and J. Sauer, J. Am. Chem. Soc., 2005, 127,
10861.
31 D. Satas, and A. A. Tracton, Coatings technology handbook, 2nd edn.,
Marcel Dekker, New York, 2001.
32 I. B. Berlman, Handbook of fluorescence spectra of aromatic molecules,
2d edn., Academic Press, New York, 1971.
33 J. McKiernan, J. C. Pouxviel, B. Dunn and J. I. Zink, J. Phys. Chem.,
1989, 93, 2129.
15 A. R. Bassindale, D. J. Parker, M. Pourny, P. G. Taylor, P. N. Horton
and M. B. Hursthouse, Organometallics, 2004, 23, 4400.
16 J. Choi, J. Harcup, A. F. Yee, Q. Zhu and R. M. Laine, J. Am. Chem.
Soc., 2001, 123, 11420.
34 M. von der Auweraer, M. van den Zegel, N. Boens, F. C. Deschryver
and F. Willig, J. Phys. Chem., 1986, 90, 1169.
35 M. Pope, and C. E. Swenberg, Electronic processes in organic crystals
and polymers, 2nd edn., Oxford University Press, New York, Oxford,
1999.
17 M. Y. Lo, C. Zhen, M. Lauters, G. E. Jabbour and A. Sellinger, J. Am.
Chem. Soc., 2007, 129, 5808.
36 J. N. Demas and G. A. Crosby, J. Phys. Chem., 1971, 75, 991–1024.
37 M. Voronkov, T. N. Martynova, R. G. Mirskov and V. I. Bely, J. Gen.
Chem. USSR (Engl. Transl.), 1979, 49, 1328.
18 M. Y. Lo, K. Ueno, H. Tanabe and A. Sellinger, Chem. Rec., 2006, 6,
157.
19 S.-C. Lo and P. L. Burn, Chem. Rev., 2007, 107, 1097.
38 M. Mazik and A. Konig, J. Org. Chem., 2006, 71, 7854.
724 | Org. Biomol. Chem., 2009, 7, 717–724
This journal is
The Royal Society of Chemistry 2009
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