Ternary rare earth inorganic-organic hybrids with a mercapto-functionalized Si-O linkage and a polymer chain: Coordination bonding assembly and luminescence

Article abstract of DOI:10.1002/ejic.201000273

A series of ternary organic/inorganic/polymer hybrid materials have been assembled on the basis of the coordination chemistry principle. Mercapto-functionalized MBA-Si from MBA (4-mercaptobenzoic acid) behaves as the first coordination unit, which forms s

Full text of DOI:10.1002/ejic.201000273

FULL PAPER
DOI: 10.1002/ejic.201000273
Ternary Rare Earth Inorganic–Organic Hybrids with a
Mercapto-Functionalized Si–O Linkage and a Polymer Chain:
Coordination Bonding Assembly and Luminescence
Kai Sheng,[a] Bing Yan,*[a] Hai-Feng Lu,[a] and Lei Guo[a]
Keywords: Organic-inorganic hybrid composites / Rare earths / Polymers / Bridging ligands / Sulfur / Luminescence
A series of ternary organic/inorganic/polymer hybrid materi-
als have been assembled on the basis of the coordination
chemistry principle. Mercapto-functionalized MBA-Si from
MBA (4-mercaptobenzoic acid) behaves as the first coordina-
tion unit, which forms sulfide linkages, resulting in an inor-
ganic Si–O network after hydrolysis and copolycondensation
with TEOS (tetraethoxysilane). The organic polymers PVPD
[poly(4-vinylpyridine)] and PMMA [poly(methyl methacryl-
ate)] play a role of the second coordination unit, whose or-
ganic polymeric C–C chain originates from addition polymer-
ization of the monomers 4-VPD (4-vinylpyridine) and MMA
(methyl methacrylate), respectively. These hybrids are char-
acterized in detail to compare with the binary hybrids with-
out an organic polymer unit, whose results reveal that the
microstructure, the thermal stability, and especially the pho-
toluminescence properties of the hybrid system are improved
with the introduction of the polymer as the coligand.
the high vibration energy of the hydroxy groups surround-
ing rare earth ions. The other synthesis method involving
covalent bonds can avoid these shortcomings. The resulting
hybrid materials show improved chemical stability and
compatibility owing to the covalent linking of the two
parts.[8] Thus, more and more attention has been paid to the
chemically bonding method to construct organic–inorganic
hybrid materials. Carlos et al. have done important work
and have lately written a review on lanthanide-containing
light-emitting organic–inorganic hybrids.[9] More recently,
Binnemans gives a more extensive overview of the different
types of lanthanide-based hybrid materials and compared
their respective advantages and disadvantages.[10]
The critical step to assemble molecular-based hybrid ma-
terials is to design a functional molecular bridge that can
coordinate rare earth ions and covalently bond to silox-
anes.[11] Our group has realized six main modification
paths, amino group, carboxyl group, hydroxy group, sul-
fonic group, and methylene group modification, and further
introduced an organic polymer into the hybrid materials
not only as a matrix but also as a component that can coor-
dinate to the rare earth ions through the oxygen or nitrogen
atom, as they have attractive properties such as low cost,
light weight, easy to fabricate, and convenient to control
various optical parameters.[12] In our organic/inorganic/
polymer hybrid materials, the bridge molecule acts as small
molecular ligand and the polymer acts as a macromolecular
ligand or coligand.[13] Under these circumstances, both the
small bridge molecules and the polymer can absorb exci-
tation energy and transfer it to rare earth ions to obtain
hybrid materials with excellent luminescent properties.
Introduction
The study on luminescent rare earth (especially Eu3+ and
Tb3+) complexes has gained great interest during the past
decades for their fascinating properties including high
quantum efficiency, narrow emission bands, high color pu-
rity, large Stokes shifts, and long lifetime, which can be ex-
pected to have large potential applications in the fields of
luminescent sensors, lasers, fluorescent probes, light-emit-
ting diodes, optical amplifiers, and so on.[1] Nevertheless,
due to their poor thermal stability and low mechanical re-
sistances, rare earth complexes have been excluded from
practical applications.[2] Therefore, many researchers incor-
porate rare earth complexes into an inert host (silica gel or
polymer matrix) to construct organic–inorganic hybrids by
using the sol–gel method[3,4] to combine remarkable mutual
features of both organic and inorganic components.[5]
Typically, according to the interfacial force between the
organic and inorganic phases of the hybrid materials, the
synthetic procedures can be categorized into two main
routes.[6] One is called the conventional doping method: the
organic compound is dispersed or dissolved into an inor-
ganic host through weak physical interactions (such as hy-
drogen bonding, van der Waals forces, or electrostatic
forces)[7] and easily introduces inhomogeneity and leaching
or clustering of the photoactive center, which results from
[a] Department of Chemistry, Tongji University,
Siping Road 1239, Shanghai 200092, P. R. China
Fax: +86-21-65982287
E-mail: byan@tongji.edu.cn
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201000273.
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Luminescent Rare Earth Organic–Inorganic Hybrids
In this paper, a mercapto-group-functionalized aromatic
compound is selected for the preparation of the precursor,
for the mercapto group is very active in many reactions.[14]
Binary organic–inorganic hybrids based on 2-MBA (2-mer-
captobenzoic acid) have been investigated in detail.[15] Here,
we construct the ternary rare earth (Eu, Tb) organic/inor-
ganic/polymeric hybrid materials based on 4-MBA by using
a different polymer and the sol–gel method, and we synthe-
sized the binary organic–inorganic hybrids simultaneously
for comparison.
Results and Discussion
The scheme for the synthesis process and the predicted
compositions of the precursors and the binary and ternary
hybrid materials are presented in Figure 1 and Figures S1
and S2 in the Supporting Information. As we know, it is
very difficult to prove the exact structure of these kinds of
noncrystalline hybrid materials, and it is hardly possible to
solve the coordination behavior of rare earth ions. However,
the main composition and their coordination effects can be
predicted according to the rare earth coordination chemis-
try principle and the organic functional groups present.
Considering the molecular structure of ligands 4-MBA-Si
(P1, P2, P3), the carboxylate group remains after the mer-
capto modification of 4-MBA. So it can be assumed that
the three COO– groups can provide six coordination sites
from the chemical behavior of the aromatic carboxylates.[16]
The S atom in the sulfide linkage is not coordinated to the
rare earth ions because of its large steric hindrance and its
weak coordination ability. For the ternary hybrids intro-
duced by polymers PVPD [poly(4-vinylpyridine)] and
PMMA [poly(methyl methacrylate)], the functional groups
within them can provide one coordinated nitrogen atom
(pyridine of PVPD) or oxygen atom (methacrylate of
PMMA). Furthermore, according to the previous research
of Horrocks,[17] it can be deduced that one or two water
molecules may participate in the coordination of these hy-
brids. The prediction has also been confirmed by infrared
spectra. Here it needs to be referred that the scheme is only
to show the average coordination chemistry behavior
Figure 1. The predicted structure of the ternary hybrid materials.
around rare earth ions, which does not represent the exact at about 3414 cm–1 and the low absorption peak at 921 cm–1
structure of the hybrids. in the three precursors are assigned to the stretching vi-
The Fourier transform infrared spectra of the initial li- bration and the out-of-plain bending vibration of O–H. The
gand MBA and the three precursors (P1 denote MBA- disappearance of the stretch vibration of (N=C=O) at
TEPIC, P2 denote MBA-APS and P3 denote MBA-CPS, 2250–2275 cm–1 for P1, the ν(N–H) at 1209 cm–1 for P2, and
where TEPIC = 3-(triethoxysiyl)propyl isocyanate, APS = the ν(C–Cl) at 800 cm–1 for P3 indicate the coupling reagent
(3-aminopropyl)trimethoxysilane, and CPS = (3-chloro- is grafted onto MBA. Additionally, the existence of a
propyl)trimethoxysilane) are presented in Figure 2a. As is stretching vibration of Si–C at 1196 cm–1 and the stretching
clearly seen, there exists a broad band centered at around vibration of Si–O at 1099 and 1047 cm–1 suggest the forma-
2934 and 2874 cm–1 in the three precursors, which can be tion of the siloxane bonds. Figure 2b shows the FTIR spec-
ascribed to the asymmetric stretching vibration and sym- tra of selected hybrid materials. The two absorption bands
metric stretching vibration for the methylene (-CH2-) group at 1594 and 1424 cm–1 correspond to the symmetric vi-
of the coupling reagents. The vanishing of the ν(S–H) at bration and asymmetric vibration of the carbonyl group
2541 cm–1 for the three precursors compared to MBA and (COO–), respectively. The three absorption bands around
the appearance of the ν(C–S–C) at 696 cm–1 suggest the 2934 cm–1 are due to the –CH2– vibration, and the broad
modification of the coupling reagent. The large broad band band at 3396 cm–1 corresponds to the O–H (vs). The strong
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K. Sheng, B. Yan, H.-F. Lu, L. Guo
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peak at 1383 cm–1 is assigned to the stretching vibration of
–
NO3 , which indicates the nitrate group is not coordinated
to RE3+. Further, there also exists the Eu–O vibration at
545 cm–1 which suggests the carbonyl group COO– is coor-
dinated to the rare earth ions. For PVPD-Eu-M1, the Eu–
N vibration is located at 476 cm–1.
Figure 3. The ultraviolet absorption spectra of the free ligand MBA
(A), precursors P1 (B), precursor P2 (C), and precursor P3 (D).
Figure S3 (Supporting Information) presents the X-ray
diffraction (from 10 to 70°) spectra of the selected hybrid
materials Eu-M1, PVPD-Eu-M1, and PMMA-Eu-M1,
which reveal that all the obtained hybrid materials are
amorphous in the whole range. All the materials exhibit
similar XRD patterns with a broad peak centered at around
23°, which is the characteristic diffraction of amorphous
siliceous backbone material.[18] By comparison to the bi-
nary hybrids, there is no new diffraction peaks for the ter-
nary hybrids with PVPD or PMMA, which show that the
introduction of the macromolecular ligands in the hybrid
system cannot affect the disordered silicon skeleton.
Furthermore, there are many narrow weak peaks in these
samples, corresponding to the incomplete hydrolysis–con-
densation of the excessive TEOS (tetraethoxysilane) mole-
cules. TEOS molecules can carry on the hydrolysis–conden-
sation process themselves or with a silane coupling reagent.
If the hydrolysis–condensation process of the excessive
TEOS molecules takes place among themselves, the ordered
Si–O network can form a better crystal state. Then the nar-
row peaks appear, but the small amount of the ordered Si–
O network brings the weak intensity. In addition, neither
of the samples exhibit measurable amounts of the phase
corresponding to the free ligands or the free salts, which
can support the formation of the covalently bonded hy-
brids.
Figure 2. FTIR spectra of (a) the free ligand MBA and the three
precursors MBA-Si (P1, P2, P3, respectively) and (b) for the selected
hybrids.
Figure 3 shows the ultraviolet absorption spectra
The DSC and TGA data for the ternary polymeric hy-
(5ϫ10–4  DMF solution) of MBA, P1, P2, and P3. It is brid material PVPD-Eu-M1 (Figure 4) shows 9% weight
observed that there exists a broad absorption band for each loss at 170 °C, which is due to the loss of the residual and
compound (at 273, 264, 279, and 280 nm for MBA, P1, P2, coordinated water molecule. Between 170 and 600 °C, a
and P3, respectively), which is ascribed to the major π–π* weight loss of 37% is observed, which is ascribed to the
electronic transitions. Comparing the precursors with the decomposition of the organics in the material. Correspond-
original compound MBA, a blueshift (about 9 nm) of the ing with this weight loss, are two obvious exothermic peaks
absorption peak appears for P1, whereas for P2 (about at 210 and 530 °C observed from the DSC curve, which is
6 nm) and P3 (about 7 nm) it shifted to a longer wavelength. concordant with the pyrolysis of the material releasing en-
This phenomenon indicates that the electron distribution of ergy. There are additional weight losses of 4% between 600
the conjugating system has changed after modification of and 800 °C and a very gradual loss of 1% at 1000 °C with-
MBA. Besides, we also can infer that the coupling reagents out obvious absorbing and releasing energy in the DSC
are grafted to MBA successfully.
curve. The residual weight (49%) is mainly inorganic Si–O
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Luminescent Rare Earth Organic–Inorganic Hybrids
networks (1090 cm–1 in FTIR). The results show that this for example). Moreover, the polymers PVPD or PMMA be-
kind of organic/inorganic/polymeric hybrid material is have as the termini ligand through simple chelation of the
stable under 210 °C. This thermal stability is higher than nitrogen or oxygen atom, The long organic chains supply
the pure complex and also better than the binary organic/ the template effect to induce the cohydrolysis and copoly-
inorganic hybrid material according to the literature.[15]
condensation process, which results in the long dendritic or
stripe-shaped morphology. In summary, we can conclude
that a more ordered and regular microstructure can be
achieved with the introduction of the polymer.
Figure 4. Selected DSC and TGA traces of the ternary hybrid ma-
terial PVPD-Eu-M1.
Figure S4 (Supporting Information) and Figure 5 show
the micrographs of the selected binary and ternary hybrid
materials, respectively. It can be seen from the images of all
hybrids that homogeneous systems are formed. Moreover,
phase separation phenomenon cannot be observed, which
always appears in the conventional doping method. By
comparison with the binary and the ternary hybrid materi-
als, we can observe distinct differences of the micromor-
phology. For the binary hybrids, the microstructure exhibits
the irregular shaped particles on the surface, whereas for
the ternary hybrids, a more regular and uniform micro-
structure with ordered morphology on the surface can be
obviously observed. This result verifies that the organic
polymer (organic polymeric chains) may play an important
role in the formation of the ultimate complicated hybrid
system. For ternary hybrids, Figure 5a exhibits a petal-
shaped, flake-layered, and globular structure. Figure 5b
presents very ordered dendritic structure. Figure 5c,d show
the perthitic structure with many small irregular particles
on the surface. Figure 5e displays a regular and ordered
Figure 5. SEM images of the ternary hybrid materials: (a) PVPD-
Eu-M1, (b) PMMA-Eu-M1, (c) PMMA-Eu-M2, (d) PVPD-Eu-M3,
(e) PVPD-Tb-M1, (f) PMMA-Tb-M3, (g) amplified image of (f).
Figure S5 (Supporting Information) exhibits the UV/Vis
globular structure. Figure 5f also has many ordered stripes diffuse reflection absorption spectra of selected europium
with many small-sized uniform flake layers on the surface, and terbium hybrids. As can be seen, there is a large broad
which is amplified and clearly shown in Figure 5g for analy- absorption band in each hybrid that is attributed to the π–
sis. The luminescent center with the polymer is firstly ac- π* electronic transition of the aromatic ring in the hybrid
complished by chelation not only through a small bridge system. It is worth noting that the large broad band over-
molecule MBA-Si but also through macromolecular ligands laps from 220 to 500 nm, which proves that not only the
PVPD or PMMA. Owing to the coordination effect and the small molecular ligand MBA could absorb abundant energy
steric hindrance of the polymer (as the terminal ligand), the in the UV/Vis region, but the macromolecular ligand PVPD
structure of the luminescent center becomes rigid. Sub- or PMMA can also enhance the absorbance ability. This
sequently, the cohydrolysis and copolycondensation process energy can be transferred to rare earth ions through the
is completed around the luminescent center. Therefore, it is “antenna effect” and sensitize the rare earth ions.
easy to form a flake or globular structure. The flake struc-
Figure 6 show the selected excitation spectra of all the
ture can be stacked to petal shaped or layer shaped under europium hybrid materials in the solid state at room tem-
different experimental conditions (polarity of the solvent, perature, which are preformed under the maximum wave-
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K. Sheng, B. Yan, H.-F. Lu, L. Guo
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length of 613 nm for Eu3+. A broad absorption band in the cupy the low symmetry sphere in ternary hybrids containing
range from 220 to 450 nm is attributed to the mercapto- PMMA. For terbium hybrids, we can see that the narrow
modified Si–O linkage host.[19] Here, the organically modi- emission lines are recorded upon a broad emission band
fied Si–O hybrid hosts not only behaves as the host but also from 350 to 650 nm. The narrow lines are ascribed to the
as the ligands for the coordination bonds between MBA-Si characteristic Tb3+ emission with peaks at 486, 542, 581,
5
(M1, M2, M3) and Eu3+ [20]
.
The absorption of the photo- and 618 nm corresponding to D4Ǟ7FJ (J = 6–3), respec-
active organically modified group and the –Si–O– network tively, whereas the broad band are attributed to the emis-
both play a role in the energy transfer and luminescence of sion of the organically modified Si–O group that is not
Eu3+ within the hybrid systems. It is noteworthy that the transferred to the terbium ion.
wide excitation bands should contain the charge transfer
state of Eu–O between Eu3+ and the MBA-Si unit. Besides,
the weak narrow lines located at 393 nm are probably due
to transitions within the 4f6 configuration of Eu3+ (7F0–5L6
transition) and overlapped with the wide excitation of the
host.[21]
Figure 6. Selected excitation spectra of the europium hybrid materi-
als; the curves from A to I denote Eu/Tb-M1, PVPD-Eu/Tb-M1,
PMMA-Eu/Tb-M1, Eu/Tb-M2, PVPD-Eu/Tb-M2, PMMA-Eu/Tb-
M2, Eu/Tb-M3, PVPD-Eu/Tb-M3, PMMA-Eu/Tb-M3, respectively.
Figure 7 presents the luminescence spectra of ternary eu-
ropium and terbium organic/inorganic/polymeric hybrid
materials in the visible range (from 550 to 700 nm for euro-
pium and from 400 to 600 nm for terbium). For europium
hybrids, all the emission spectra display the characteristic
Eu3+ 5D0Ǟ7FJ (J = 0–4) intra-4f6 transitions at 575, 589,
614, 649, and 700 nm, respectively.[19] Among these emis-
sion peaks, the orange emission at 589 nm and the predomi- Figure 7. The emission spectra of (a) Eu hybrids and (b) Tb hy-
brids; the curves from B to J denote Eu/Tb-M1, PVPD-Eu/Tb-M1,
PMMA-Eu/Tb-M1, Eu/Tb-M2, PVPD-Eu/Tb-M2, PMMA-Eu/Tb-
M2, Eu/Tb-M3, PVPD-Eu/Tb-M3, PMMA-Eu/Tb-M3, respectively.
nant red emission at 614 nm (associated with 5D0Ǟ7F1 and
5D0Ǟ7F2 transitions, respectively) are obviously observed,
whereas the other transitions are relatively weaker. The de-
tailed luminescence data are shown in Table 1. As we know,
For further investigation of the photoluminescence prop-
the 5D0Ǟ7F2 transition is the electric dipole transition with erties, we measure the decay curves of all the europium and
hypersensitivity to the local symmetry of the coordination terbium hybrid materials at room temperature. All the typi-
sphere of the Eu3+ ions, whereas the magnetic dipole transi- cal decay curves can be described as a single exponential
tion D0Ǟ7F1 is practically independent of the host mate- (ln[S(t)/S0] = –k1t = –t/τ; Figure S6 in the Supporting Infor-
5
rial, so the intensity ratio of the red and orange intensities is mation shows the decay curve of the Eu-M1 hybrids). The
considered as the coefficient to the symmetry around Eu3+
.
resulting luminescent lifetimes of the europium hybrids are
When the ratio is higher, the europium ion generally occu- summarized in Table 1. Furthermore, we selectively deter-
5
pies a lower symmetry microenvironment,[22] and the data mined the emission quantum efficiency of the D0 Eu3+ ex-
shown in Table 1 indicate that the europium ion may oc- cited state for europium-containing hybrids on the basis of
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Luminescent Rare Earth Organic–Inorganic Hybrids
Table 1. Luminescence efficiencies and lifetimes for the europium
hybrid materials.
To study the coordination environment surrounding the
lanthanide ions, especially the influence caused by vi-
brations of water molecules according to Horrocks,[15] it is
expected that the probable number of coordinated water
molecules (nw) can be calculated by Equation (2).
[a]
Hybrid Materials I02/I01
τ [ms][b]
Ar
Anr
η [%][c]
nw
Eu-M1
2.67
3.77
3.65
2.21
3.49
3.52
2.25
3.03
3.31
0.432
0.485
1.052
0.478
0.618
0.794
0.43
195
224
241
176
228
229
194
187
220
2120
1839
951
1916
1390
1030
2132
1333
824
8
~
~2
~1
~2
~1.5
~1
~2
~1.5
~1
PVPD-Eu-M1
PMMA-Eu-M1
Eu-M2
11
25
8
14
18
8
nw = 1.05 (Aexp – Arad
)
(2)
PVPD-Eu-M2
PMMA-Eu-M2
Eu-M3
On the basis of the results, the coordination number of
water molecules (Eu containing hybrid materials) can be
estimated to be 1–2. The coordination water molecules pro-
duce severe vibrations of the hydroxy group, resulting in
large nonradiative transitions and a decrease in the lumines-
cent efficiency. The 4-MBA-Si (P1, P2, P3) bridge molecules
provide three coordinated COO– groups to occupy the
equal six coordination number and the functional group of
polymers show the one coordinated N (PCPD) or O
(PMMA) atom. So the total coordination number for the
Eu (Tb) ion in the ternary hybrids is 8–9, which corre-
sponds to rare earth coordination chemistry behavior.
PVPD-Eu-M3
PMMA-Eu-M3
0.658
0.958
12
21
[a] Integrated intensity of the 5D0
Ǟ
7FJ emission curves. [b] For
the 5D0 excited state of Eu3+, whose error is Ϯ50 µs. [c] For 5D0
quantum efficiency.
5
emission spectra and the lifetimes of the D0 emitting level.
Assuming that only nonradiative and radiative processes
are essentially involved in the depopulation of the 5D0 state,
η can be defined by Equation (1).[23]
Conclusions
(1)
In summary, on the basis of coordination chemistry, ter-
nary rare earth/organic/inorganic/polymeric hybrid materi-
als containing both inorganic networks (Si–O–Si, first li-
gand) and organic polymeric C–C chains (second ligand)
have been assembled. The small bridge molecule ligand pre-
cursor MBA-Si is constructed through mercapto function-
alization with different coupling reagents and the polymer
ligand is synthesized by polymerization reaction. The re-
sults reveal that the ternary hybrid materials present more
regular morphology, stronger luminescence intensity, longer
lifetimes, and higher quantum efficiency than the binary hy-
brids, indicating that the introduction of the polymer can
induce the self-assembly process of the microstructure and
sensitize the luminescence of the hybrid materials.
Here, Ar and Anr represent radiative and nonradiative
transition rates, respectively. Ar can be obtained by sum-
ming over the radiative rates A0J for each 5D0Ǟ7FJ (J = 0–
5
4) transition of Eu3+. Because D0Ǟ7F1 belongs to the iso-
lated magnetic dipole transition, it is practically indepen-
dent of the chemical environments around the Eu3+ ion as
an internal reference for the whole spectra; the experimental
coefficients of spontaneous emission, A0J, can be calculated
according to the equation.[24,25] The emission intensity, I,
5
taken as integrated intensity S of the D0Ǟ7F0–4 emission
curves. On the basis of the above discussion, the quantum
efficiencies of the europium hybrid materials can be deter-
mined, as shown in Table 1. Seen from Equation (1), the
value η mainly depends on the values of two factors: one is
lifetime and the other is I02/I01 (red/orange ratio). If the
lifetime and red/orange ratio are large, the quantum effi-
ciency must be high. As can be seen clearly from Table 1,
the quantum efficiencies of the europium hybrid materials
are determined in the order: PMMA-Eu-M Ͼ PVPD-Eu-
M Ͼ PMAA-Eu-M for the same coupling reagent. That is,
the ternary polymer-containing hybrids exhibit higher lumi-
nescence quantum efficiency than the binary hybrids, in
particular, the ternary PMMA polymer-containing hybrids
show the highest luminescence quantum efficiency, which
are in accord with the order of luminescence intensities and
lifetimes. The results reveal that with the introduction of
the polymer as the macromolecule ligand or coligand, the
luminescence properties of the overall hybrid system are im-
proved by the increasing ratio of the radiative transitions.
Here it is noteworthy that the absolute overall quantum
yields had better be measured in order to show the real
luminescent behavior, but here we merely want to compare
the different hybrids relatively. The deep investigation needs
to be underway.
Experimental Section
Materials: 4-Mercaptobenzoic acid (4-MBA), tetraethoxysilane
(TEOS), and the three cross-linking reagents [3-(triethoxysilyl)-
propyl isocyanate (TEPIC), (3-aminopropyl)trimethoxysilane
(APS), (3-chloropropyl)trimethoxysilane (CPS)] were all analytical
reagents. Other starting reagents were used as received.
Europium and terbium nitrates were obtained by dissolving the
corresponding oxides in concentrated nitric acid.
Synthesis of Precursors and Polymers: Three precursors and the
polymer are prepared according to ref.[13] and depicted in Figure S1
(Supporting Information).
Precursor 1 (P1). Modification by TEPIC: 4-MBA (1 mmol) was
first dissolved in refluxing anhydrous THF by stirring, and then
TEPIC (1 mmol) was added to the solution dropwise. The whole
mixture was heated at reflux at 80 °C for 3 h under an atmosphere
of argon in a covered flask. After cooling, the solvent was removed
under reduced pressure, and then the residue was washed with hex-
ane (3ϫ20 mL). P1 was obtained as a yellow oil. Yield: 0.34 g,
85%. C17H27NO6SSi (401.56): calcd. C 50.85, H 6.78, N 3.49;
1
found C 50.53, H 6.87, N 3.56. H NMR (400 MHz, CDC13): δ =
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0.63 (t, 2-H, CH2Si), 1.25 (t, 9-H, CH2CH3), 1.57 (m, 2-H, lithic bulks and ground into powdered material for the photophysi-
CH2CH2CH2), 3.20 (t, 2-H, CH2CH2CH2), 3.73 (q, 6-H, CH2CH3), cal studies.
7.35 (q, 1-H, -C6H4), 7.42 (t, 1-H, NH), 7.68 (d, 1-H, -C6H4), 7.87
Physical Measurements: All measurements were performed at room
(q, 1-H, -C6H4), 8.74 (d, 1-H, -C6H4), 11.30 (s, 1-H, OH) ppm.
temperature. Infrared spectra were recorded with a Nexus 912
Precursor 2 (P2). Modification by APS: 4-MBA (1 mmol) was first
AO439 FTIR spectrophotometer. We mixed the compound with
dissolved in refluxing pyridine by stirring, and then APS (1 mmol)
was added to the solution dropwise. The whole mixture was heated
at reflux at 100 °C for 8 h under an atmosphere of argon in a cov-
ered flask. After cooling, the solvent was removed under reduced
pressure, and then the residue was washed with hexane (3ϫ20 mL).
P2 was obtained as a yellow oil. Yield: 0.31 g, 87%. C16H26O5SSi
the dried potassium bromide (KBr) and then pressed into pellets.
The spectra were collected over the range 4000–400 cm–1 by averag-
ing 32 scans at a maximum resolution of 8 cm–1. 1H NMR spectra
were recorded in CDCl3 with a Bruker Avance-400 spectrometer
with tetramethylsilane (TMS) as an internal reference. The ultravio-
let absorption spectra (5ϫ10–4  DMF solution) were recorded
with an Agilent 8453 spectrophotometer. The UV/Vis diffuse reflec-
tion spectra of the powder samples were recorded with a BWS003
spectrophotometer. X-ray powder diffraction patterns were re-
1
(358.53): calcd. C 53.60, H 7.31; found C 53.23, H 7.23. H NMR
(400 MHz, CDC13): δ = 0.66 (t, 2-H, CH2Si), 1.25 (t, 9-H,
CH2CH3) 1.71 (m, 2-H, CH2CH2CH2), 3.17 (t, 2-H, CH2CH2CH2),
3.54 (q, 6-H, CH2CH3), 7.21 (q, 1-H, -C6H4), 7.45 (d, 1-H, -C6H4),
7.76 (q, 1-H, -C6H4), 7.97 (d, 1-H, -C6H4), 11.02 (s, 1-H, OH) ppm.
corded by using
a Rigaku D/max-rB diffractometer system
equipped with a Cu anode in a 2θ range from 10 to 70°. Thermo-
gravimetric analysis (TGA) and differential scanning calorimetry
(DSC) traces were performed with a Netzsch STA 409 at a heating
rate of 15 °C/min under a nitrogen atmosphere. The fluorescence
spectra were obtained with a RF-5301 spectrophotometer equipped
with a stablespec-xenon lamp (450 W) as the light source. Lumines-
cent lifetimes were recorded with an Edinburgh FLS 920 phos-
phorimeter by using a 450-W xenon lamp as the excitation source
(pulse width, 3 µs). The microstructures were checked by scanning
electronic microscopy (SEM, Philips XL-30).
Precursor 3 (P3). Modification by CPS: 4-MBA (1 mmol) was first
dissolved in DMF by stirring, and then CPS (1 mmol) was added
to the solution dropwise. K2CO3 (0.01 g) was added as catalyst.
The whole mixture was heated at reflux at 120 °C for 6 h under an
atmosphere of argon in a covered flask. After filtration, the solvent
was removed under reduced pressure, and then the residue was
washed with hexane (3ϫ20 mL). P3 was obtained as a yellow oil.
Yield: 0.26 g, 83%. C13H20O5SSi (316.45): calcd. C 49.34, H 6.37;
1
found C 49.57, H 6.53. H NMR (400 MHz, CDC13): δ = 0.75 (t,
2-H, CH2Si), 1.89 (m, 2-H, CH2CH2CH2), 3.13 (t, 2-H,
CH2CH2CH2), 3.61 (s, 9-H, CH3), 7.12 (q, 1-H,
-C6H4), 7.30 (d, 1-H, -C6H4), 7.78 (q, 1-H, -C6H4), 8.08 (d, 1-H,
-C6H4), 11.02 (s, 1-H, OH) ppm.
Supporting Information (see footnote on the first page of this arti-
cle): Figures of the synthesis process of precursors or polymer, the
binary hybrids, selected X-ray diffraction graph of hybrid materials,
SEM of binary hybrids, UV/Vis diffuse reflection absorption spec-
tra, and the decay curves of the hybrid materials.
Synthesis of the Polymer PVPD (PMMA): 4-Vinylpyridine (PVPD)
[or methyl methacrylate (PMMA)] (1 mmol) was weighed and
transferred into a separating funnel. It was then washed with 0.1 
sodium hydroxide solution to remove the inhibitor. After oscillating
for 5 min and standing for 2 h, the water phase and upper oil phase
were separated. The residual water was removed with anhydrous
copper sulfate. After purification and reduced pressure distillation
under a nitrogen atmosphere, the monomer was injected into a cov-
ered three mouth flask with azobisisobutyronitrile (AIBN) (or
benzoyl peroxide, BPO) as an initiator. The mixture was dissolved
in methanol [or blend-solvent (BS) of toluene and ethyl acetate]
and maintained at 65 °C (or 70 °C) for 8 h (or 6 h) under flowing
high-purity nitrogen. After removal of the solvent, a canary yellow
and stringy liquid was obtained. The product was dried in a vac-
uum desiccator after recrystallization by using methanol and anhy-
drous ether (see Figure S1, Supporting Information).
Acknowledgments
This work is supported by the National Natural Science Founda-
tion of China (20971100) and the Program for New Century Excel-
lent Talents in University (NCET-08–0398).
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Received: March 10, 2010
Published Online: June 21, 2010
Eur. J. Inorg. Chem. 2010, 3498–3505
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3505