A convenient organic-inorganic hybrid approach toward highly stable squaraine dyes with reduced H-aggregation

Article abstract of DOI:10.1002/adfm.201101565

A generic and effective approach for solving the aggregation effect observed with optical materials in solid state or in a solution with a poor solvent was explored by designing two types of squaraine-containing polyhedral oligomeric silsesquoixane (POSS)-based hybrids. It is expected that incorporation of "huge" inorganic POSS nanoparticles into optical materials via covalent bonding can effectively decrease the strong dipole-dipole and π-π stacking interactions, inhibit intermolecular charge transfer between adjacent squaraine molecules, and improve optical, thermal and chemical stability of the resultant materials. Both theoretical calculations and experimental results indicate that the molecular design strategy is rational and efficacious. The resultant organic-inorganic hybrid optical materials effectively eliminate the aggregation of organic optical chromophoric groups by hindering intermolecular charge transfer and decreasing dipole-dipole and π-π stacking interaction between the chromophores, and exhibit good optical stability, i.e., the absorption peaks of H1 and H2 display only a slight blue-shift, even in the solid. Simultaneously, the hybrids also show significantly enhanced thermal, and chemical stabilities in comparison with the precursor organic optical materials. Add POSS to make definite improvement: Incorporation of "huge" inorganic polyhedral oligomeric silsesquoixane (POSS) nanoparticles into organic optical materials via covalent bonding can effectively decrease the strong dipole-dipole and π-π stacking interactions, and inhibit intermolecular charge transfer between the chromophores to enable preparation of stable optical materials with enhanced thermal, chemical, and photostabilities. Copyright

Full text of DOI:10.1002/adfm.201101565

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A Convenient Organic–Inorganic Hybrid Approach Toward
Highly Stable Squaraine Dyes with Reduced H-Aggregation
Zhengquan Yan, Hongyao Xu,* Shanyi Guang, Xian Zhao, Weiliu Fan,
and Xiang Yang Liu*
phthalocyanines, metal complexes, poly-
methines, squaraines, radical dyes, and azo
dyes,[3] squaraine dyes (SQ) are a particu-
larly promising class of dyes widely applied
in chemosensors,[4] bioimaging,[5] light-
emitting diodes,[6] solar cells[7] etc. because
of their intense absorption properties (ε ≥
105 L·mol−1·cm−1) from the red to the near-
IR region. Nevertheless, the unique rigid
zwitterionic structures of squaraines and
the strong dipole–dipole and π–π stacking
interactions between molecules often lead
to the association/aggregation of SQ mol-
ecules in the solid state or in solutions that
contain poor solvents for SQs, which fur-
ther results in a strong optical-quenching
effect associated with a red- or a blue-shift.
These issues have greatly limited their
practical applications in the optical field as
absorbing materials.
A generic and effective approach for solving the aggregation effect observed
with optical materials in solid state or in a solution with a poor solvent was
explored by designing two types of squaraine-containing polyhedral oligo-
meric silsesquoixane (POSS)-based hybrids. It is expected that incorporation
of “huge” inorganic POSS nanoparticles into optical materials via covalent
bonding can effectively decrease the strong dipole–dipole and π–π stacking
interactions, inhibit intermolecular charge transfer between adjacent squar-
aine molecules, and improve optical, thermal and chemical stability of the
resultant materials. Both theoretical calculations and experimental results
indicate that the molecular design strategy is rational and efficacious. The
resultant organic–inorganic hybrid optical materials effectively eliminate the
aggregation of organic optical chromophoric groups by hindering inter-
molecular charge transfer and decreasing dipole–dipole and π–π stacking
interaction between the chromophores, and exhibit good optical stability, i.e.,
the absorption peaks of H1 and H2 display only a slight blue-shift, even in the
solid. Simultaneously, the hybrids also show significantly enhanced thermal,
and chemical stabilities in comparison with the precursor organic optical
materials.
To overcome molecular aggregation, it
is found that increasing the chromophoric
intermolecular distance may be an effec-
tive method; as described by Law, aggre-
gation often occurs strongly when the dis-
1. Introduction
tance between chromophoric molecules is ca. 3.5 Å due to an
intermolecular charge transfer.[3] Thus, supramolecular encap-
sulating[8] and squaraine-derived-rotaxane strategies[5,9] were
developed. Nevertheless, the above squaraine derivatives often
suffer from inherent reversibility to squaraines themselves.[8]
Additionally, the poor thermal and photostabilities of such
derivatives turn out to be unfavorable factors for their applica-
tion in the optical field.[4,5] Therefore, overcoming the effect of
aggregation of chromophores and improving their thermal and
optical stabilities at the same time remains a big challenge.
It is well-known that incorporation of nanosized inorganic
particles, e.g., polyhedral oligomeric silsesquoixane (POSS,
RxR8x’ Si8O12) with a well-defined nanosized cube-octameric
structure,[10] into organic materials turns out to be an effec-
tive method for improving the thermal and photostability
of the resultant materials.[11–15] We were inspired by Smith
and co-workers’ finding that aggregation of organic optical
chromophores can be inhibited effectively when the inter-
planar distance of optical molecules is larger than ca. 7.0 Å.[9]
Herein, we will explore a generic and effective approach to solve
the issue of the aggregation of optical materials in the solid
state or in solutions that contain poor solvents for the materials
concerned, and also to improve their thermal and optical
Optically absorbing materials have attracted extensive atten-
tion owing to their great potential applications in the fields of
nonlinear optics, photodynamic therapy, optical data storage,
laser printing, biological probes, infrared photography, solar
cells, etc.[1,2] Among all the absorbing materials identified, i.e.,
Dr. Z. Yan, Prof. H. Xu, Prof. S. Guang, Prof. X. Y. Liu
College of Material Science and Engineering & State Key Laboratory for
Modification of Chemical Fibers and Polymer Materials
Donghua University
Shanghai 201620, P. R. China
E-mail: hongyaoxu@163.com; phyliuxy@nus.edu.sg
Prof. X. Zhao, Prof. W. Fan
School of Chemistry and Chemical Engineering
Shandong University
Jinan, 250100, China
Prof. X. Y. Liu
Department of Chemistry and Department of Physics
Faculty of Science, National University of Singapore
2 Science Drive 3, 117542 Singapore
DOI: 10.1002/adfm.201101565
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Si
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Scheme 1. Schematic illustration of nanosized spacer particles (POSS) introduced into squaraine (SQ) at molecular levels to suppress chromophoric
aggregation.
stability by designing two kinds of SQ-containing POSS-based
hybrids (H1 and H2) with different molecular architectures
(see Scheme 1). The key strategy is to incorporate nanosized
octavinyl-silsesquioxanes (OV-POSS) units into organic optical
molecules through covalent bonding. It is expected that incor-
poration of “huge” inorganic POSS nanoparticles into SQ can
effectively overcome the aggregation effect of SQ chromophoric
groups by decreasing the strong dipole–dipole and π–π stacking
interaction and inhibiting the intermolecular charge transfer
between adjacent SQ molecules.
the Gaussian 03 software suite with a B3LYP/6-31G level
of theory,[16] which is used to understand the geometrical
characters of the candidates. To simplify the calculation, the
basic structural units of these two hybrids (H1 and H2) were
selected and the bonds at the end of the structural units were
saturated with hydrogen atoms. The calculated results are
shown in Figure 1. It is striking that the average distances
between chromophores in the basic structural units of H1
and H2 are found to be ca. 8.73 and 28.56 Å, respectively,
which both fulfil the spacing requirement (>7.0 Å) for over-
coming aggregation effectively,[9] i.e., incorporation of “huge”
inorganic POSS nanoparticles into SQ via covalent bonding
should be able to effectively suppress the aggregation effect
owing to the increased interplanar distance between optical
chromophoric groups (more than ca. 7.0 Å),[9] which may
greatly decrease the dipole–dipole and π–π stacking interac-
tions between the optical chromophores, and hinder intermo-
lecular charge transfers.[3]
2. Results and Discussion
2.1. Theoretical Calculations
To validate the rationality of structural design of hybrid
molecules, a theoretical calculation was conducted using
Figure 1. The optimized geometries of a) H1 and b) H2. Si, O, N, C, and H atoms are represented as purple, red, blue, gray, and white-gray,
respectively.
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Figure 2. IR spectra of H1, H2, OV-POSS, and SQ.
Figure 3. 1H NMR spectra of SQ, H1, and H2.
2.2. Synthesis and Characterization
moiety at 1616, 1581, 1449, 1317, and 1248 cm−1 increases from
H1 to H2 in proportion to the molar feeding ratio, which indi-
cates that the number of substituent arms on POSS molecules
increases with the molar feed ratio.
To experimentally verify the molecular design, H1 and H2 were
prepared by a route based on the Heck reaction between OV-
POSS and SQ with a molar feed ratio of 1:1 and 1:2, respec-
tively.[17,18] H1 and H2 are soluble in some common organic
solvents such as N,N-dimethylformamide (DMF), dimeth-
ylsulfoxide (DMSO), etc. However, the resultant hybrids are
insoluble in these organic solvents when the molar feed ratio is
greater than 1:2, i.e., 1:3 or 1:4.
To further confirm the structure of our products, we tried
to use gas chromatography–mass spectrometry (GC-MS)
methods to separate and verify the structure of the products,
such as bead-type H1. GC-MS results indicated that a small
amount of the variously substituted POSS forms (ca. 3 ∼
5 wt%) existed in the resulting product besides the main bead-
type H1 (more than 90 wt%). Simultaneously, it was found that
a little cross-linked by-product (less than 3 wt%) in our product
was retained by the chromatogram column and badly contami-
nated the chromatographic system, which also suggests that it
is difficult to separate and evaluate our products by chromato-
graphic methods.
In the 1H NMR spectra of H1 and H2 (Figure 3), we
can see easily that all the characteristic signals at δ ≈
7.5–9.3, 4.2, 1.9, and 0.9 ppm corresponding to the SQ
moiety and at δ ≈ 5.9 ppm to the OV-POSS moiety emerge.
However, the characteristic signals at δ ≈ 7.5–9.3, 4.2,
1.9, and 0.9 ppm attributed to SQ moiety in H1 and H2
show a slight shift to high frequency because of the elec-
tron-donating effect of the POSS groups, which further
confirms that the Heck reaction was successful. On the
other hand, the characteristic singlet at δ ≈ 5.9 ppm cor-
responding to the characteristic olefin proton of OV-POSS
monomers turns into a doublet in the spectra of H1 and
H2, with an integral area ratio of peak of ca. 2:6 for H1
and ca. 4:4 for H2, respectively, which further confirms that
the molecular structures of the hybrids can be controlled
by changing the molar feed ratio.[17,18] Figure 4 shows the
29Si NMR spectra of H1, H2, and OV-POSS. The spectrum
of OV-POSS possesses a sharp characteristic singlet at ca.
79.3 ppm, while H1 displays two broad characteristic sig-
nals at ca. 70.0 and 80.0 ppm with an integral area ratio
of ca. 2:6; this further confirms that the POSS molecules
have reacted with squaraine molecules to yield a resultant
Therefore, herein we evaluate the resultant hybrid using gel
permeationchromatography(GPC)methods.However,toprotect
the GPC system, the sample solutions in DMF (ca. 2 mg mL−1)
were filtered through 0.45-μm poly(tetrafluoroethylene) syringe-
type filters before injection into the GPC system. Thereafter,
the structure of the hybrids was deduced by means of GPC and
spectral methods as follows.
The IR spectrum of SQ (Figure 2) shows characteristic bands
at 1616, 1581, and 1449 cm−1 that are attributed to the aryl-
ring stretching vibration, at 1317 and 1248 cm−1 to the C–O–C
stretching vibration, and at 596 cm−1 to the C–Br stretching
vibration. The IR spectrum of OV-POSS contains an intense
characteristic Si–O stretching vibration at 1075 cm−1. In the
spectra of H1 and H2, the characteristic signals at 1616, 1581,
1449, 1317, and 1248 cm−1 corresponding to the SQ moiety
emerge, and the C–Br stretching vibration at 596 cm−1 com-
pletely disappears after Heck reaction, which hints that Heck
reaction was successful. Moreover, by taking the intensity of the
Si–O stretching vibration peak at 1075 cm−1 as a standard, the
intensity of all the characteristic bands corresponding to the SQ
Figure 4. 29Si NMR spectra of OV-POSS, H1, and H2.
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hybrid with a bead-type structure. Similar to that of H1, the
spectrum of H2 also displays two broad characteristic peaks
at ca. 70.2 and 80.3 ppm with an integral area ratio of ca.
4:4, which supports the hypothesis that low-cross-linked
network-type hybrids were obtained. This result is consistent
with that from FTIR and 1H NMR spectra, and a similar
phenomenon is observed in our previous work.[17,18]
In a 1:1 (v/v) DMSO–water mixed solvent, the absorption
spectrum of SQ is obviously broad and displays a prominent
blue-shift from 739 nm (the λmax of SQ in pure DMSO) to
590 nm. When a 1:9 (v/v) DMSO–water mixed solvent is
used, the absorption peak of SQ shows a further blue-shift to
560 nm with great spectral quenching. This result means that
the optical properties of SQ are not stable in poor solvents,
even in a mixed solvent containing a small fraction of the poor
solvent, i.e., SQ easily forms H-type aggregates resulting from
intermolecular charge transfers, strong dipole–dipole, and π–π
stacking interactions.[3] However, it is surprising that the absorp-
tion peaks of H1 and H2 in a 1:1 (v/v) DMSO–water mixed sol-
vent exhibit almost no notable change (Figure 5b and Figure 5c).
Even in a 1:9 (v/v) DMSO–water mixed solvent, the absorption
peaks of both H1 and H2 only show a minor blue-shift by only
9 and 7 nm, respectively, which hints that the H-aggregation
of the SQ moiety in H1 and H2 is largely eliminated, i.e., both
H1 and H2 are optically stable, and that incorporation of large
inorganic POSS nanoparticles into SQ can effectively hinder
charge transfer and attenuate strong dipole–dipole and π–π
stacking interactions between SQ molecules, and so eliminate
their aggregation. The method of using huge nanoparticles as
a structural unit to construct a molecular architecture for over-
coming the aggregation effect has never been reported before
as far as we know.
2.3. Decoupling Effect of the Hybrids
A red-shift or blue-shift in UV-vis spectra is commonly used
to examine the aggregation effect in mixed DMSO–water sol-
vents,[19] where DMSO is a good solvent and water is a poor
solvent for SQ and the resultant optical hybrids. In this regard,
the absorption spectra of H1, H2, and SQ in DMSO and in
mixed DMSO–water solvents with different volume ratios were
recorded. As shown in Figure 5a, both H1 and H2 have similar
strong and sharp absorbance spectral profiles to that of the pre-
cursor SQ in DMSO solution. This observation means that all
the molecules of H1, H2, and SQ are well-dispersed in their
good solvents, so the intermolecular interaction is weak and
no aggregation happens. The result also suggests that incor-
poration of “huge” inorganic POSS nano particles into organic
optical materials has little influence on the inherent optical
properties except that the maximal absorption peak red-shifts
by 21 nm for H1 and 27 nm for H2, compared to that of SQ
(λmax = 739 nm), respectively. These red-shifts originate from
the σ–π conjugation between the Si atom of POSS and the
chromophore in the hybrids.[20]
It is well known that SQ in the solid state forms H-aggregates
much more easily than that in a dilute solution, which leads to a
blue-shift of the absorbance spectrum; it also forms J-aggregates
more easily, which results in a red-shift of the absorbance
spectrum with a broader half-peak width than that in a dilute
Figure 5. Partial absorption spectra of a) SQ, b) H1, and c) H2 in DMSO, DMSO–water (1:1, v/v), and DMSO–water (1:9, v/v) and d) absorption
spectra of SQ, H1, and H2 in solid-state films from DMSO.
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solution. To further verify the rationality of our molecular
design, the UV-vis spectra of H1, H2, and SQ in their solid films
were recorded and are shown in Figure 5d. From Figure 5d,
it can be seen that, in the spectrum of solid SQ, an obvious
blue-shift of absorption peak from 739 to 578 nm with a wider
half-peak width of ca. 320 nm was observed than in solution,
i.e., this optical property of SQ is extremely unstable and shows
a much weaker and broader absorption band with a larger blue-
shift in the solid film than that in dilute solution. This result
may be attributed to the presence of H-type aggregates owing to
the unique rigid zwitterionic structure which results in strong
dipole–dipole and π–π stacking interactions and intermolecular
charge transfer. Nevertheless, the absorption peaks of H1
and H2 only display a slight blue-shift of ca. 10 nm and the
optical absorption intensity is almost unchanged, which further
confirms that both H1 and H2 in the solid are still optically
stable. This stability may be attributed to the larger distances
between chromophores (ca. 8.73 Å for H1 and ca. 28.56 Å for
H2, Figure 1), which effectively eliminate the dipole–dipole and
π–π stacking interactions between adjacent optical chromo-
phores, and so suppress intermolecular charge transfers. The
results further support Smith and co-workers’ conclusion that
aggregation of organic optical chromophores can be inhibited
effectively when the interplanar distance of optical molecules
is larger than ca. 7.0 Å.[9] At the same time, the insulation of
inorganic POSS is another important factor that may inter-
rupt charge transfer between the conjugated chromophores
significantly.[21]
Figure 7. Change in absorption upon addition of cysteine (5 mM) to
5 μM solutions of a) H1, b) H2, and c) SQ in DMSO at 25 oC.
hybrids. This observation may be attributed to the barrier effect
of inorganic POSS by limiting heat transfer, which protects
the underlying material from heat attack. Simultaneously, the
vibration hindrance of organic segments connected covalently
to nanosized bulk POSS is also an important factor that results
in thermal stabilization,[22,23] in spite of the decomposition of
POSS in the surface of H1 and H2, which will yield highly
thermally stable SiO2 in the surface that will further protect the
underlying materials from heat attack.[24] A similar result was
found in previous publications.[11–15]
2.5. Chemical Stability
2.4. Thermal Stability
The chemical stability of the hybrids was also investigated.
To achieve this goal, separate samples of H1, H2, and SQ in
DMSO were treated with excess cysteine at room temperature.
The subsequent time-dependence of the absorption changes is
shown in Figure 7. After 5 min treatment with excess cysteine,
the absorption intensity of SQ at 739 nm decreased from
1 to 0.49, while those of H1 at 760 nm and H2 at 766 nm only
decreased from 1 to 0.85 and 0.74, respectively, which indicates
that their chemical stability is in the order: H1 > H2 > SQ, and
the chemical stability of the hybrids is significantly enhanced
over that of the precursor, which may be attributed to the steric
protection provided by the huge cagelike POSS[25] as well as the
insulation of inorganic POSS[21] which hinders electron trans-
port between organic chromophore molecules.
The thermal stabilities of the hybrids (H1 and H2) and the
precursors SQ and OV-POSS were estimated by using thermo-
gravimetric analysis (TGA) under nitrogen at a heating rate of
10 °C·min−1. The results are shown in Figure 6. The thermal
decomposition temperatures (Td, 5 wt% loss) of H1, H2, SQ, and
OV-POSS were 352 °C, 315 °C, 194 °C and 240 °C, respectively.
Namely, the Td values of the hybrids H1 and H2 are strikingly
elevated by 158 °C and 121 °C, respectively, in comparison with
that of SQ, and demonstrate that incorporation of large inor-
ganic POSS nanoparticles into organic optical materials effec-
tively enhances the thermal stability of the resulting functional
2.6. Photostability
The photostability of H1, H2, and SQ in DMSO was also exam-
ined. The samples were placed 100 cm away from a 1000 W
iodine–tungsten lamp in a glass holder and with the tempera-
ture maintained at 25 °C by use of a cold trap. During irradia-
tion, the absorption spectra of H1, H2, and SQ in DMSO were
recorded every 4 hours; the results are given in Figure 8. Sim-
ilar to their chemical stability, an enhancement effect in photo-
stability is observed for H1 and H2 over SQ, which increases
with POSS content owing to the barrier of oxidatively stable
POSS[24] as well as the insulation of inorganic POSS[21] nano-
particles, for which photo-oxidation is unfavorable.
Figure 6. TGA thermograms of a) H1, b) H2, c) SQ, and d) OV-POSS at
a ramp rate of 10 °C min−1 in nitrogen flow.
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8.5 Hz, 1 H, H3), 8.35 (s, 1 H, H5), 8.05 (d, J = 5.7 Hz, 1 H, H8), 7.83
(d, J = 8.5 Hz, 1 H, H5), 3.98 (t, J = 7.7 Hz, 2 H, CH2CH2CH3), 2.84 (s, 3
H, CH3), 1.91 (m, J = 7.5 Hz, 2 H, CH2CH2CH3), 1.15 (t, J = 2.9 Hz, 3H,
CH2CH2CH3); Calcd. for C13H14NBrI: C 39.93, H 3.61, N 3.58; Found:
C 40.03, H 3.67, N 3.54.
Synthesis of 6-Bromo-quinaldine Squaraine Dye (SQ): A mixture of
N-propyl-6-bromo-quinaldinium salt (784 mg, 2 mmol), squaric acid
(114 mg, 1 mmol), and quinoline (1 mL) was refluxed in a mixture of
n-butanol and toluene in the ratio of 1:1 (v/v, 15 mL) with azeotropic
removal of water for 24 h. The solvent was removed by distillation under
reduced pressure to obtain a residue which was purified by column
chromatography on silica gel (eluent: methanol/chloroform = 1:9) to
afford 1.48 g (86%) of SQ as a dark green crystal; IR (KBr): ν = 3016,
2953, 2872 (C–H), 1616, 1581, 1449 (Ar), 1317, 1248 (O–C–O), 596 cm−1
(C–Br); 1H NMR (400 MHz, DMSO-d6, δ): 9.56 (d, J = 5.7 Hz, 2 H, H4),
9.30 (d, J = 6.4 Hz, 2 H, H9), 8.63 (d, J = 9.2 Hz, 2 H, H3), 8.50 (d, J =
8.0 Hz, 2 H, H8), 8.30 (s, 2 H, H5), 8.07 (d, J = 7.8 Hz, 2 H, H7), 4.49 (t,
J = 7.5 Hz, 4 H, CH2CH2CH3). 1.95 (m, J = 7.5 Hz, 4 H, CH2CH2CH3),
0.95 (t, J = 2.6 Hz, 6 H, CH2CH2CH3); Calcd. for C30H27N2Br2O2: C 59.33,
H 4.48, N 4.61; Found: C 59.24, H 4.57, N 4.69.
Figure 8. Curves of absorbance at λmax–time under irradiation from a
1000 W iodine–tungsten lamp of a) H1, b) H2, and c) SQ in DMSO
at 25 oC.
3. Conclusions
Synthesis of POSS-Based Hybrids: The POSS-based hybrids were
prepared with different molar feed ratio of SQ (x) to OV-POSS (y), by a
conventional Heck reaction using Pb(Ac)2 as a catalyst, K2CO3 as an acid
binding agent, and N,N-dimethyl glycine (DMG) as a ligand at ca. 130 °C
in dry N-methyl pyrrolidone. For H1, x:y was 1:1 and x:y was 1:2 for H2. The
reactions were carried out under a nitrogen atmosphere, using a vacuum-
line system. Taking the synthesis of bead-type structural hybrid H1 as
an example, a mixture of SQ (121 mg, 0.2 mmol), OV-POSS (127 mg,
0.2 mmol), DMG (123 mg, 1.2 mmol), palladium acetate (16 mg,
0.06 mmol), and K2CO3 (83 mg, 0.6 mmol) was placed in a 50-mL
sealed three-necked bottle; the bottle was evacuated under vacuum and
then flushed with dry nitrogen three times. After 5 mL of freshly distilled
N-methyl pyrrolidone was added, the reaction mixture was refluxed at
130 °C under nitrogen for 10 h and then cooled to room temperature.
The mixture was then diluted with 50 mL of water and filtered. The
precipitate was washed with toluene first, and then redissolved in
minimal DMSO. The DMSO solution was added dropwise into 100 mL of
H2O to precipitate the hybrids. This purification procedure was repeated
three times.
In conclusion, incorporation of “huge” inorganic POSS nano-
particles into organic optical materials via covalent bonding
at the molecular level can effectively overcome the aggrega-
tion effect of organic chromophoric groups, and significantly
enhance their thermal, chemical, and photo stability. We pro-
vide a generic and effective strategy to prepare optical stable
materials with high thermal and photostability. Notice that
only some of the eight vinyl functional groups in octafunc-
tional POSS in the hybrids (H1 and H2) are occupied. The
rest of the vinyl groups also provide opportunities for fur-
ther incorporation of other functional groups, which may
allow building-in of additional functions to the hybrids in the
future.
4. Experimental Section
The hybrid H2 was prepared by a similar method with a feed ratio of
SQ and OV-POSS of 2:1.
As shown in Scheme 2, the hybrids (H1, H2) were designed and
synthesized through a multistep reaction route.
H1: Dark brown powder; Mn = 1720, PDI, 1.20, (GPC, polystyrene);
Yield: 57%; IR (KBr): ν = 3058, 2957, 2876 (C–H), 1600, 1572, 1447
Synthesis of 6-Bromo-quinaldine: To a 100-mL three-necked bottle was
added hydrochloric acid solution (44.8 mL, 6 mol L−1), 4-bromoaniline
(1535 mg, 8.9 mmol), and acetic acid (0.5 mL, 8.9 mmol). The formed
mixture was refluxed at 100 °C for 0.5 h, followed by addition of iodine/
potassium (50 mg/132 mg, 0.4 mmol/0.8 mmol) and toluene (10 mL).
Then a mixture of toluene (2 mL) and crotonaldehyde (1.5 mL,
17.8 mmol) was added dropwise over a period of 1 h and the resulting
mixture refluxed for another 6 h, before cooling to room temperature,
and making alkaline using ammonia solution to induce complete
precipitatation. The precipitate was filtered and purified by column
chromatography on silica gel (eluent: petroleum ether/ethyl acetate =
1:6) to afford 1.76 g (89%) 6-bromo-quinaldine as a light yellow crystal;
1
(Ar), 1111 (Si–O–Si), 760 cm−1 (C–Si); H NMR (400 MHz, DMSO-d6,
δ): 9.17 (br, H, H4), 7.71 (br, H, H, H3,5,9), 7.21 (br, H, H7,8), 5.82 (br,
H, POSS–CH=CH and CH=CH2), 4.20 (br, H, CH2CH2CH3), 1.77 (br, H,
CH2CH2CH3), 0.93 (br, H, CH2CH2CH3); 29Si NMR (79.49 MHz, solid,
δ): –70.15 (s, Si–CH=CHR), –80.11 (s, Si–CH=CH2).
H2: Dark brown powder; Mn = 2010, PDI, 1.24 (GPC, polystyrene);
Yield: 51%; IR (KBr): ν = 3053, 2955, 2885 (C–H), 1600, 1565, 1483 (Ar),
1104 (Si–O–Si), 759 cm−1 (C–Si); 1H NMR (400 MHz, DMSO-d6, δ):
9.36 (br, H, ArH, H4), 7.84 (br, H, H3,5,9), 7.40 (br, H, H7,8), 5.92 (br,
H, POSS–CH=CH and CH=CH2), 4.19 (br, H, CH2CH2CH3), 1.76 (br, H,
CH2CH2CH3), 0.93 (br, H, CH2CH2CH3); 29Si NMR (79.49 MHz, solid,
δ): –70.25 (s, Si–CH=CHR), –80.27 (s, Si–CH=CH2).
1
IR (KBr): ν = 3048 (C–H), 1596, 1488, 1463 (Ar), 637 cm−1 (C–Br); H
NMR (400 MHz, DMSO-d6, δ): 7.97 (d, J = 8.4 Hz, 1 H, H4), 7.90 (s,
1 H, H5), 7.76 (d, J = 7.4 Hz, 1 H, H8), 7.74 (d, J = 7.0 Hz, 1 H, H3), 7.31
(d, J = 8.8 Hz, 1 H, H5), 2.74 (s, 3 H, CH3); Calcd. for C10H8NBr: C 50.08,
H 3.63, N 6.03; Found: C 60.17, H 3.77, N 6.14.
Supporting Information
Synthesis of N-Propyl-6-bromo-quinaldinium Salt:
A mixture of
Supporting Information is available from the Wiley Online Library or
from the author.
6-bromo-quinaldine (666 mg, 3 mmol), propyl iodide (1.7 g, 10 mmol),
and 2 mL acetonitrile was heated in a sealed tube at 100 °C–105 °C
for 12 h. The formed precipitate was filtered, washed thoroughly with
cold diethyl ether, and purified by column chromatography on silica gel
(eluent: petroleum methanol/chloroform = 1:4) to afford 0.72 g (61%)
N-propyl-6-bromo-quinaldinium salt as a light green crystal; IR (KBr): ν =
3019, 2956, 2870 (C–H), 1601, 1509, 1466 (Ar), 598 cm−1 (C–Br); 1H
NMR (400 MHz, DMSO-d6, δ): 8.68 (d, J = 8.2 Hz, 1 H, H4), 8.53 (d, J =
Acknowledgements
The authors gratefully acknowledge financial support from the National
Natural Science Fund of China (Grant Nos. 20974018, 20971021,
51073031, and 21171034), National Oversea Scholar Cooperation
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Br
Br
Br
ICH2CH2CH3
CH3CN, reflux
HCl, toluene, HAc, I2/KI
reflux
+
N
O
CH3
N
CH3
n Pr I-
NH2
1
2
O
Si
Si
O
O
O
Si
Si
HO
O
OH
O
O
O
O
O
Br
Br
O
O
Si
Si
O
O
O
Si
Si
O
+
N
N
n Pr
n Pr
toluene, n-butanol, refiux
SQ
Si
O
Si
Si
O
Si
O
Si
Si
O
O
O
O
O
O
O
O
O
O
O
O
Si
Si
Si
O
Si
Si
O
Si
Si
Si
O
Si
Si
O
Si
H1
Si
O
O
O
O
O
O
O
O
O
O
O
O
O
O
Si
Si
Si
O
O
O
O
O
Si
Si
O
O
O
Si
O
O
O
O
O
Si
O
O
Si
O
Si
O
O
Si
O
O
Si
Si
O
O
O
O
O
O
O
Si
O
Si
O
Si
Si
O
O
H2
O
O
Si
O
Si
Si
O
O
O
Si
O
O
O
O
O
Si
Si
O
Si
O
O
O
O
O
Si
O
Si
O
Si
O
O
Si
O
O
Si
O
SiH
O
Si
O
O
O
O
O
O
Si
O
O
Si
O
Si
O
Si
O
O
Si
Si
O
O
O
Si
O
O
O
O
Si
O
Si
O
O
Si
O
O
Si
O
O
O
O
Si
O
O
Si
Si
O
Si
O
+
N
N
:
O
n
Pr
Pr
n
Scheme 2. The synthetic routes of the hybrids (H1 and H2).
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Adv. Funct. Mater. 2012, 22, 345–352
2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
351

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Research Fund of China (No. 50928301), Ph.D. Program Foundation of
Ministry of Education of China (No.20070255012), Shanghai Leading
Academic Discipline Project (No. B603), and the Program of Introducing
Talents of Discipline to Universities (No.111-2-04).
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2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Funct. Mater. 2012, 22, 345–352