Tetrahedral silicon-centered imidazolyl derivatives: Promising candidates for OLEDs and fluorescence response of Ag (I) ion

Article abstract of DOI:10.1016/j.jorganchem.2010.06.026

A series of novel tetrahedral silicon-centered imidazolyl derivatives, Bis(4-(imidazol-1-yl)phenyl)dimethylsilane (1), Tri(4-(imidazol-1-yl)phenyl) methyl silane (2), Bis(4-(imidazol-1-yl)phenyl)diphenylsilane (3), Tri(4-(imidazol-1-yl)phenyl)phenylsilane (4), [Bis(4-(imidazol-1-yl)phenyl)](4- bromophenyl)phenylsilane (5) and [Tri(4-(imidazol-1-yl)phenyl)](4-bromophenyl) silane (6) have been synthesized and characterized by FTIR, ¹H NMR, ¹³C NMR and mass spectroscopy. They all display high thermal stability, are fluorescent with emission in the region of violet to blue, and possess large HOMO-LUMO energy gaps ranging from 4.9585 to 5.1879 eV, which could be potentially used as blue emitters or hole blocking materials in OLEDs. Moreover, the metal ion titrations based on Ag (I) and compounds 1-4 reveal that these ligands show distinguishable fluorescence response with increasing of Ag (I) ions.

Full text of DOI:10.1016/j.jorganchem.2010.06.026

Journal of Organometallic Chemistry 695 (2010) 2329e2337
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Tetrahedral silicon-centered imidazolyl derivatives: Promising candidates for
OLEDs and fluorescence response of Ag (I) ion
*
Dengxu Wang, Yuzhong Niu, Yike Wang, Jianjun Han, Shengyu Feng
Key Laboratory of Special Functional Aggregated Materials of Ministry of Education; School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of novel tetrahedral silicon-centered imidazolyl derivatives, Bis(4-(imidazol-1-yl)phenyl)dime-
thylsilane (1), Tri(4-(imidazol-1-yl)phenyl)methyl silane (2), Bis(4-(imidazol-1-yl)phenyl)diphenylsilane
(3), Tri(4-(imidazol-1-yl)phenyl)phenylsilane (4), [Bis(4-(imidazol-1-yl)phenyl)](4-bromophenyl)phe-
nylsilane (5) and [Tri(4-(imidazol-1-yl)phenyl)](4-bromophenyl)silane (6) have been synthesized and
characterized by FTIR, 1H NMR, 13C NMR and mass spectroscopy. They all display high thermal stability,
are fluorescent with emission in the region of violet to blue, and possess large HOMO-LUMO energy gaps
ranging from 4.9585 to 5.1879 eV, which could be potentially used as blue emitters or hole blocking
materials in OLEDs. Moreover, the metal ion titrations based on Ag (I) and compounds 1e4 reveal that
these ligands show distinguishable fluorescence response with increasing of Ag (I) ions.
Ó 2010 Elsevier B.V. All rights reserved.
Received 14 April 2010
Received in revised form
30 May 2010
Accepted 24 June 2010
Available online 3 July 2010
Keywords:
Organosilicon compounds
Imidazolyl derivatives
Luminescence
OLEDs
Fluorescence response
1. Introduction
in OLEDs or as sensors for metal ions by themselves or by binding to
the main or side chains in polymers [31e33]. Furthermore, it has
Luminescent materials based on tetrahedral silicon-centered
organic small molecules have attracted extensive interests due to
their potential applications in sensor technologies as well as
organic light emitting devices (OLEDs) [1e11]. These silicon-based
molecules have many advantages such as well-defined structures
and high color purity as evidenced by narrow emissions with high
photoluminescence quantum yields in solid films [12,13]. They have
been demonstrated to have good film-forming properties with high
glass-transition temperature (Tg) and high thermal stability, and
can be used to develop non-aggregating amorphous electrolumi-
nescent devices [14e17]. A large number of silicon-cored molecules
have been designed, synthesized and used as highly efficient blue
electroluminescent devices [18e21]. Furthermore, these tetrahe-
dral shaped molecules based on silane core have been proved to be
fascinating building blocks for constructing 3D porous metal-
organic frameworks (MOFs) [22e25].
been demonstrated that these molecules can be used as efficient
ligands to assemble coordination polymers with intriguing
molecular topologies and can be potentially used in the fields of
photoelectronic devices, molecular recognition, ion changes and
luminescent sensors [34e36].
Motivated by the demand for OLEDs and functional MOFs, we
combined imidazolyl moiety and silicon core together derived from
the precursors, RnSi(p-C6H4Br)4ꢀn. In our previous work, we have
designed and synthesized a silicon-centered imidazole compound,
Me2Si(p-C6H4-imdazol-1-yl)2 (1). Based on this silicon-linked
ligand, a novel three-dimensional (3D) MOF with a unique 3D-
braided framework has been achieved. The research on the porous
properties of the MOF showed that it possessed selective anion
exchange property [37]. As an extension of our previous investi-
gation, a series of novel tetrahedral silicon-centered imidazolyl
compounds, MeSi(p-C6H4-imdazol-1-yl)3 (2), Ph2Si(p-C6H4-imda-
zol-1-yl)2 (3), PhSi(p-C6H4-imdazol-1-yl)3 (4), Ph(p-C6H4Br)Si(p-
C6H4-imdazol-1-yl)2 (5) and (p-C6H4Br)Si(p-C6H4-imdazol-1-yl)3
(6) were synthesized via mono-lithiation, SieC coupling reaction
and Ullmann condensation reaction. Luminescent properties
investigation revealed that all of them exhibited a strong and
narrow emission in the region of violet to blue and could be
potentially used as blue emitters in OLEDs. The interactions
between these compounds and Ag (I) ion were also discussed.
Imidazole-containing compounds have been widely investi-
gated for their potential applications in OLEDs and coordination
chemistry [26e30]. In the past decades, imidazole and its deriva-
tives have been successfully applied as electron transport materials
* Corresponding author. Tel.: þ86 531 8836 4866; fax: þ86 531 8856 4464.
E-mail address: fsy@sdu.edu.cn (S. Feng).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.06.026

2330
D. Wang et al. / Journal of Organometallic Chemistry 695 (2010) 2329e2337
2. Results and discussion
1,4-dibormobenzene, which reacted with the appropriate chloro-
substituted silanes to give a series of bromophenyl-containing
silanes, 8e12 [38e40]. Then, the tetrahedral silicon-centered imi-
dazolyl derivatives, 1e6 were achieved using modified Ullmann
condensation method under copper-catalyzed system by the
reactions of 8e12 and imidazole. In our previous work, compound 1
has been synthesized using CuI as a catalyst and N, N-dimethyl-
glycine as a promoter at 110 ꢁC for 48 h in DMSO (Method B) in
2.1. Synthesis and crystal structure
The tetrahedral silicon-centered imidazolyl derivatives, 1e6
were synthesized in a similar procedure according to the synthetic
routes described in Scheme 1. Firstly, a reaction between 1,4-
dibormobenzene and 1 equivalent n-BuLi afforded mono-lithiated
Scheme 1. Synthesis routes of bromophenyl-containing silanes 8e13 and imidazolyl derivatives 1e7. (i) CuSO4, K2CO3, 180 ꢁC, 24 h; (ii) CuI/N, N-dimethylglycine, K2CO3, DMSO,
110 ꢁC, 48 h.

D. Wang et al. / Journal of Organometallic Chemistry 695 (2010) 2329e2337
2331
a good yield [37]. However, Method B did not work when it was
used to synthesize the imidazolyl derivatives 2e6 despite the raw
materials 8e12 owning similar structures. The main by-product
obtained was testified to be 1-phenylimidazole, as evidenced by 1H
NMR and mass spectrometry (Fig. S1). It is proposed that in this
reaction N, N-dimethylglycine acts as a Lewis acid, which could
induce SiePh rupture. This can be proved by the comparable yield
of the by-product with the starting materials, although N, N-
dimethylglycine was able to promote the formation of Ullmann-
type CeN bond [41]. In order to achieve the target compounds, the
reaction temperature was raised to 180 ꢁC using CuSO4 instead of
CuI/N, N-dimethylglycine as the catalyst for 24 h without solvent in
the Teflon autoclave (Method A). The first synthesis of compound 1
by using Method A indicated that Ullmann condensation reaction
could also proceed well in this case. Compared to the synthesis of 1
in Method B, the yield was slightly lower in Method A. Furthermore,
the imidazole-containing silanes, 2e6 were also synthesized
successfully by using Method A. Compounds 2 and 3 were sepa-
rated in a moderate yield of w25%. Compounds 4 and 5 were
isolated as two main products from the same starting material, tri
(4-bromophenyl)phenylsilane (11) in the yields of 14.9% and 11.0%,
respectively. The synthesis of compound 6 was more challenging
because of the possibility of the formation of mono-, di-, tri-, or
tetra-substituted product as well as the existence of unreacted
starting materials and other by-products in the reaction mixture,
which made the separation and purification difficult. In addition,
the similar polarity of the substituted products further complicated
the product separation. Initially the tetra-substituted product, tetra
(4-(imidazol-1-yl)phenyl)silane was our target product. However,
the tri-substituted product, 6 was isolated in 10% yield as the main
product. We attempted to raise the reaction temperature to 200 ꢁC
or prolonged the reaction time to 48 h. It was found that there was
no obvious enhancement for the formation of 6 or the tetra-
substituted product but more by-products, mainly 1-phenyl-
imidazole were observed. This may be attributed to the great steric
hindrance of tetra(4-bromophenyl)silane (12). On the other hand,
the formation of Ullmann-type CeN bond may accompany with the
cleavage of SiePh bond under this high reaction temperature. In
addition, we have also synthesized the mono-substituted product,
(4-(imidazol-1-yl)phenyl)trimethylsilane (7) and the synthesis
procedure was similar to that of compound 1 (Scheme 1). It was
demonstrated that compound 7 can be achieved successfully
according to Method B in a high yield. Compounds 1e7 were fully
characterized by FTIR, 1H NMR, 13C NMR and mass spectroscopy.
In our previous report [37], single crystal X-ray diffraction
analyses show that the molecule of 1 has a tetrahedral structure
around silicon atom with the average dihedral angel of 41.024ꢁ
between imidazole ring and benzene ring, which indicates that the
degree of conjugation throughout the molecule is relatively small.
It is noteworthy that the adjacent molecules stack along ab plane
Fig. 1. Packing diagram showing the
1. Water molecules are omitted for clarify.
p
e
p
interactions between adjacent molecules of
scanning calorimetry (DSC) show that neither obvious melting
points (Tm) nor glass-transition temperatures (Tg) were detected for
compounds 4, 5 and 6 while Tm of compounds 1 and 2 were
observed at 174 ꢁC and 221 ꢁC, respectively, and the crystalline
temperature (Tc) and Tm of compound 3 were observed at 58 ꢁC and
169 ꢁC, respectively (Fig. S2).
2.3. Photophysical properties and molecular orbital calculations
To investigate the possibilities of 1e6 applying in OLEDs, UVevis
and luminescent spectra were measured. Fig. 2 shows the UVevis
absorption spectra of 1e6 in CH2Cl2 solution. As expected, 1e6 all
with intermolecular pep interactions between imidazole rings and
benzene rings with the shortest atomic contact distance being
ꢀ
w2.9 A (Fig. 1).
2.2. Thermal properties
The thermal properties of compounds 1e6 were firstly deter-
mined by the thermogravimetric analysis (TGA) with a heating rate
of 10 ꢁC/min under nitrogen. The results show that 2e6 are stable
up to over 300 ꢁC while 1 decomposes at about 250 ꢁC, which may
be owing to the lower thermal stability of two SieCH3 groups in 1
compared to other compounds with more SiePh groups (Fig. S3).
Compounds 1 and 2 show a small percentage of weight loss below
200 ꢁC, which can be attributed to the loss of solvent molecules
embedded in the compounds. The examinations by differential
Fig. 2. UVevis spectra of 1e6 in CH2Cl2 solution (1 ꢂ 10ꢀ5 M).

2332
D. Wang et al. / Journal of Organometallic Chemistry 695 (2010) 2329e2337
Fig. 3. Emission spectra of 1e6 (a) in CH2Cl2 solution (1 ꢂ 10ꢀ5 M, lex ¼ 250 nm); (b) in the solid state (lex ¼ 290 nm).
exhibit one similar intense absorption band with lmax at w255 nm,
which can be attributed to the * transitions involving the
UVevis and luminescent spectra of the mono-substituted imid-
azole derivative, compound 7 were also measured. The results
revealed that compound 7 displayed a similar UVevis absorption
and emission spectra to that of compound 1e6, which were
distinctly due to imidazole and phenyl groups in the compound
7 (Fig. S6 and S7). Therefore, silicon core had weak effect on the
pep
phenyl and imidazole groups. Furthermore, 1e6 are all luminescent
and emit a violeteblue color in solution and in the solid state when
irradiated by UV light. Similar to UVevis spectra, 1e6 display
analogic fluorescence spectra with the maximum emission wave-
length at w310 nm in CH2Cl2 solution (Fig. 3a). In the solid state,
1e6 display a broad emission from violet to blue region with the
emission wavelength maximum ranging from 356 nm (3) to
399 nm (6) (Fig. 3b and Table 1). Moreover, the emission spectra in
the solid state for 1e6 are considerably red-shifted compared with
that in solution, which is obviously caused by extensive intermo-
p
-conjugated system, which led to the low conjugation degree of
the whole compound.
Compared with previous reports on luminescent organic
small molecules or polymers used as OLEDs [42e44], the UVevis
spectra and emission spectra of 1e6 are all blue-shifted. The
reasons for this might be that, imidazole as a functional group in
lecular interactions, such as
p
e
p
stacking interactions as displayed
these molecules obviously owns lower p-conjugated system
by compound 1 (Fig. 1). In addition, compounds 4 and 5 exhibit
stronger emission than other compounds, indicating that in 4 and 5
stronger intermolecular interactions may exist. Despite these imi-
dazolyl derivatives showing strong and narrow emissions in the
region of violet to blue, the emission quantum efficiencies are low
and vary between 0.051 (6) and 0.12 (5).
with lower electron density, and hence makes limited contri-
butions to luminescent properties compared with other func-
tional groups, such as 2,20-dipyridylamine, carbazole, condensed
nucleus and so on [5e7]. Moreover, as mentioned above, the
dpepp conjugation action of silicon atom is generally limited
and silicon atom is more inclined to interrupt the
system and disturb the coplanarity of the
p
-conjugated
-conjugated
The low luminescence quantum efficiencies may be attrib-
p
uted to two reasons: (i) low
p
-conjugated degree of aromatic
compounds. However, the incorporation of silicon atom to these
compounds can improve their color purity due to the narrow
emission, which makes them promising candidates for blue
emitters in OLEDs displays.
In order to gain a deeper insight into their electronic and lumi-
nescent properties, molecular orbital calculations have been per-
formed at the level of B3LYP/6-31G(d) using the Gaussian 03 suite of
programs [45]. The contour plots of the HOMO and LUMO frontier
molecular orbitals and HOMO, LUMO energies and energy gaps of
1e6 are shown in Fig. 4 (2, 4 and 6) and Fig. S8 (1, 3 and 5). As can be
rings in these compounds. For example, in the crystal structure
of compound 1, the average dihedral angel between imidazole
ring and benzene ring is 41.024ꢁ, which is a convincing evidence
of the small conjugation degree throughout the molecule. (ii)
The limited d
atom has empty 3d orbitals which can conjugate with adjacent
atom or -conjugated system to form ep conjugation.
pepp conjugation effect of the silicon core. Silicon
p
d
p
p
However, this conjugation action is generally limited. To inves-
tigate how silicon cores affect the luminescent properties,
Table 1
UVevis and Luminescent data for compounds 1e6.
Compound
UVevis absorption (nm)
3
(Mꢀ1 cmꢀ1
)
Excitation (nm)
Emission (nm)
Quantum yield
0.094
Conditions (298 K)
1
252
4.54 ꢂ 104
7.29 ꢂ 104
4.51 ꢂ 104
6.60 ꢂ 104
3.50 ꢂ 104
9.78ꢂ 104
256
235, 330
250
244, 328
255
309
395
315
398
308
356
312
388
307
398
313
399
CH2Cl2
Solid slate
CH2Cl2
Solid slate
CH2Cl2
Solid slate
CH2Cl2
Solid slate
CH2Cl2
Solid slate
CH2Cl2
2
3
4
5
6
254
254
255
252
256
0.062
0.093
0.073
0.12
244, 320
255
315
251
245, 330
255
243, 334
0.051
Solid slate

D. Wang et al. / Journal of Organometallic Chemistry 695 (2010) 2329e2337
2333
Fig. 4. HOMO and LUMO energies, energy gaps and orbital diagrams of 2, 4 and 6.
seen from Fig. 4 and Fig. S8, the HOMOs of these compounds are
similar, with dominating contributions from the orbitals of the
imidazolyl groups, while LOMOs involves contributions from the
entire molecules. The bromo-substituted groups in 5 and 6 didn’t
have contribution to the HOMO or LUMO orbitals. The results also
indicated that the tetrahedral silicon core does not have significant
effect on the electronic properties of 1e6, which is consistent with
previous reports [6,7]. It is noteworthy that these compounds all
have a deep energy gap with the range from 4.9585 eV (6) to
5.1879 eV (1). The deep HOMO level for this series of molecules is
a strong indication that they may be potentially useful candidates as
efficient hole blocking materials in OLEDs [7,46].
intensity gradually decreasing (Fig. S9). The fluorescent titration
results reveal that all the compounds show fluorescent
a
quenching response and a slight blue-shift with the addition of
AgClO4 (Fig. 5). Similar to other N-donor ligands, the fluorescent
changes for all the compounds are completed when adding about
1 equivalent AgClO4, although compounds 2 and 4 have a larger
number of potential sites than 1 and 3. This suggests that the full
fluorescent quenching effect of Ag (I) ion can be viewed without
saturation of all of the coordination sites on the ligand or that Ag
(I) displays multiple coordination modes and a single Ag(I) ion
may bind to several ligands in solution. For compound 1, when the
[Ag]/[Lig] ratio reached 1:1, the fluorescence intensity dropped
50% (Fig. 6). Unlike in solution, the silver complex in the solid state
with the [Ag]/[Lig] ratio of 1:1 displayed a dramatic decrease with
the overall reduction of 93% [37]. It is proposed that Ag(I) ion has
a much larger heavy-atom effect on the fluorescence of 1 in the
solid state than in solution. Similar to compound 1, the fluorescent
intensity of compounds 2, 3 and 4 also decreased but showed
greater fluorescent reduction. As the end of the fluorescent
quenching, the overall reduction is 75% for 2, 97% for 3 and 95% for
4 (Fig. 6). The evaluation over various imidazolyl derivatives, 1e4,
reveals that the fluorophore is responsive to Ag (I) with better
response of compounds 3 and 4. In addition, as a typical
compound, binding analysis using the method of continuous
variations (Job’s plot) established a 1:1 stoichiometry for the 4-
Agþ complex. Following the Benesi- Hildebrand-type analysis, the
binding constant Ka value was determined to be 1.37 ꢂ 105
(Supporting information), which proved that strong binding force
existed between 4 and Ag(I) ion in CH2Cl2 solution. Theses results
speculate that the potential show distinct luminescence responses
2.4. Interactions with Ag (I) ion
In recent years much attention has been paid on the negative
impact of silver ions on the environment and organisms due to the
extensive applications and broad prospects of silver in the elec-
tronic industry and optical fields. It has been demonstrated that
fluorescence spectroscopy is an effective method to detect trace
amounts of silver ions in environmental and biological system
because of its high sensitivity and facile operation [47e49]. So here
we examined the impact of Ag(I) ion binding on the fluorescence of
compounds 1e4 using AgClO4 as the titrant.
The UVevis spectroscopic properties of compounds 1e4
interacting with Ag (I) ion in CH2Cl2 solution were firstly evalu-
ated. With the increasing of silver ions (0e2 equiv for 1 and 3,
0e3 equiv for 2 and 4), the maximum absorptions of compounds 1,
2 and 4 show a slight blue-shift with no intensity decreasing,
while that of compound 3 also displays a small blue-shift but

2334
D. Wang et al. / Journal of Organometallic Chemistry 695 (2010) 2329e2337
Fig. 5. Fluorescent titration results of compounds 1e4 in CH2Cl2 solution with AgClO4 at 1 ꢂ 10ꢀ5 M (lex ¼ 250 nm for all the compounds).
Fig. 6. The reduction of fluorescence intensities of 1e4 in CH2Cl2 solution upon addition of Ag (I) (lex ¼ 250 nm for all the compounds).
on binding to Ag (I) center when these imidazolyl derivatives act
as ligands in coordination chemistry.
properties and molecular orbital calculation indicated that these
organic small molecules could be potentially applied not only as
blue emitter but also hole blocking materials in OLEDs. According
to the investigation of metal ion titration, compounds 1e4 showed
distinct fluorescence response for Ag(I) ion. Further research will
focus on the construction of functional MOFs based on these
imidazole-containing building blocks and examining their
numerous potential properties such as molecular recognition, ion
exchange etc.
3. Conclusions
In summary, a series of novel imidazolyl functionalized tetra-
hedral silicon-centered molecules have been synthesized and
characterized. TGA measurements revealed that all the
compounds have high thermal stability. The luminescent

D. Wang et al. / Journal of Organometallic Chemistry 695 (2010) 2329e2337
2335
4. Experimental
1063, 1008, 810, 728, 698. 1H NMR (300 MHz, CDCl3)
d
7.35e7.54
(m, 17H).
4.1. General
4.6. Synthesis of tetra(4-bromophenyl)silane (12)
Unless otherwise noted, all reagents were obtained from
commercial suppliers and used without further purification.
Dimethyl sulfoxide (DMSO) was first dried over CaH2 at 80 ꢁC for 1
day and distilled under vacuum pressure. Then DMSO was stored
The preparation procedure of 12 was similar to that of 10. Yield:
52.6%. IR (KBr pellet cmꢀ1): 3075, 3010, 1617, 1458, 1376, 1058, 995,
803. 1H NMR (300 MHz, CDCl3)
d
7.35 (d, 8H, J ¼ 8.1 Hz), 7.52 (d, 8H,
ꢀ
with 4 A molecule sieves prior to use. Ether was dried by distillation
J ¼ 8.4 Hz).
from the sodium ketyl of benzophenone. FTIR were recorded on
a Bruker Tensor27 spectrophotometer, the spectrometers were
acquired in the frequency range 4000e400 cmꢀ1 at a resolution of
4 cmꢀ1 with a total of 32 scans. 1H NMR and 13C NMR spectra were
measured on a Bruker AVANCE-300 or 400 NMR Spectrometer.
High-resolution mass spectra were obtained using positive mode
on Aglient Technologies 6510 Q-TOF LC-MS. Elemental analyses (C,
H, N) were obtained on a PerkineElmer 240 elemental analyzer.
TGA was performed with a MettlerToledo SDTA-854 TGA system in
nitrogen at a heating rate of 10 ꢁC/min. DSC measurements were
carried out in MettlerToledo DSC822 series ramping from 10 to
300 ꢁC at the rate of 10 ꢁC/min in a steady flow of nitrogen (20 ml/
min). The fluorescence spectra were determined with ISS K2-
Digital spectrophotometer: excitation slit width ¼ 10 nm, emission
slit width ¼ 3 nm. Luminescence quantum yields were measured
4.7. Synthesis of (4-bromophenyl)trimethylsilane (13)
The preparation procedure of 13 was similar to that of 8 except
that the product was distillated under vacuum pressure with b. p.
110e114 ꢁC/6 mmHg. IR (KBr pellet cmꢀ1): 3070, 3034, 3014, 2955,
2896, 1573, 1479, 1375, 1248, 1106, 1066, 1011, 830, 812, 752, 660. 1H
NMR (300 MHz, CDCl3)
2H, J ¼ 8.1 Hz).
d
0.25 (s, 9H), 7.36 (d, 2H, J ¼ 8.1 Hz), 7.47 (d,
4.8. Synthesis of bis(4-(imidazol-1-yl)phenyl)dimethylsilane (1)
4.8.1. Method A
Bis(4-bromophenyl) dimethylsilane (1.85 g, 5 mmol), imidazole
(0.85 g, 12.5 mmol), K2CO3 (2.76 g, 20 mmol) and CuSO4 (0.016 g,
0.1 mmol) were heated at 180 ꢁC for 24 h in a Teflon autoclave
under argon. After cooling to ambient temperature, the mixture
was dissolved in 50 mL CHCl3 and washed with water. The water
layer was separated and extracted with CHCl3 (3 ꢂ 30 mL). The
combined organic layers were washed with water (3 ꢂ 30 mL),
dried over anhydrous MgSO4 and filtered. The solvents were
evaporated under reduced pressure and a white solid was obtained
by column chromatography (CH2Cl2/MeOH as eluent). Yield: 40.1%.
using quinine sulfate in 0.1 N H2SO4
(F
¼ 54.6%) as reference. The
quantum yields were calculated according to the procedures
described elsewhere [50,51].
4.2. Synthesis of bis(4-bromophenyl)dimethylsilane (8)
1,4-dibromobenzene (2.36 g, 10 mmol) was dissolved in dry
Et2O (100 mL) and cooled to ꢀ78 ꢁC under argon. n-BuLi (2.5 M in
hexanes, 4 mL,10 mmol) was added into this solution dropwise and
stirred for another 1 h at ꢀ78 ꢁC. Dichlorodimethylsilane (0.64 g,
5 mmol) was then added dropwise at this temperature. After the
end of the addition, the reaction mixture was slowly raised to room
temperature and stirred overnight. Then the reaction was
quenched by 30 mL H2O and the organic layer was separated. The
water layer was washed by 30 mL Et2O twice. The organic layers
were combined, washed by brine, dried over anhydrous MgSO4 and
then filtered. Removal of the solvents under vacuum gave the crude
product, which was recrystallized from hexane to obtain 8. Yield:
78.3%. IR (KBr pellet cmꢀ1): 3031, 3012, 2961,1566, 1477,1375,1254,
1105, 1066, 1007, 832, 812, 723, 660. 1H NMR (300 MHz, CDCl3)
4.8.2. Method B
A four-bottled flask was charged with bis(4-bromophenyl)
dimethylsilane (1.85 g, 5 mmol), imidazole (0.85 g, 12.5 mmol),
K2CO3 (2.76 g, 20 mmol), CuI (0.19 g, 1 mmol) and N, N-dimethly-
glycine (0.20 g, 2 mmol) and backfilled with argon, followed by
addition of 25 ml DMSO. Then the mixture was heated at 110 ꢁC for
48 h before it was partitioned between water and ethyl acetate. The
organic layer was separated, and the aqueous layers were washed
with ethyl acetate. The combined organic layers were washed with
brine, dried with MgSO4 and concentrated in vacuum. A white
powder was obtained by column chromatography (CH2Cl2/MeOH
as eluent). Yield: 46.5%. IR (KBr pellet cmꢀ1): 3112, 3031, 2959,
1596, 1511, 1399, 1373, 1303, 1251, 1097, 1056, 959, 903, 817, 739,
d
0.53 (s, 6H), 7.34 (d, 4H, J ¼ 8.1 Hz), 7.49 (d, 4H, J ¼ 8.1 Hz).
4.3. Synthesis of Tri(4-bromophenyl)methylsilane (9)
659, 538. 1H NMR (400 MHz, DMSO)
d
8.26 (s, 2H), 7.75 (s, 2H), 7.65
138.2,
(s, 8H), 7.11 (s, 2H), 0.60 (s, 6H). 13C NMR (400 MHz, DMSO):
d
The preparation procedure of 9 was analogous to that described
for 8. Yield: 83.5%. IR (KBr pellet cmꢀ1): 3074, 3006, 2962, 1568,
1549, 1476, 1376, 1252, 1110, 1066, 1009, 809, 781, 721. 1H NMR
136.6, 136.0, 135.9, 130.4, 120.3, 118.4, ꢀ2.3. HRMS (FAB) calcd for
C20H20N4Si (MHþ): 345.1530, found 345.1527. Anal. Calcd for
C20H20N4Si/CH2Cl2: C, 64.02; H, 5.63; N, 14.22. Found: C, 64.64; H,
5.61; N, 14.76.
(300 MHz, CDCl3)
d
0.79 (s, 3H), 7.30 (d, 6H, J ¼ 8.4 Hz), 7.50 (d, 6H,
J ¼ 8.1 Hz).
4.9. Synthesis of tri(4-(imidazol-1-yl)phenyl)methylsilane (2)
4.4. Synthesis of bis(4-bromophenyl)diphenylsilane (10)
A Teflon autoclave was charged with tris(4-bromophenyl)
methylsilane (1.28 g, 2.5 mmol), imidazole (1.02 g, 15 mmol), K2CO3
(1.38 g, 10 mmol) and CuSO4 (0.016 g, 0.1 mmol) and backfilled with
argon. The mixture was heated at 180 ꢁC for 24 h. The treatment
procedure for product was analogous to that described for 1 in
Method A and a white solid was obtained. Yield: 25.3%. IR (KBr
pellet cmꢀ1): 3107, 3031, 2955, 2894, 1595, 1512, 1402, 1304, 1253,
1191, 1098, 1054, 958, 903, 823, 791, 739, 656, 537. 1H NMR
The preparation procedure of 10 was similar to that of 8 except
that the product was recrystallized from CHCl3eEtOH. Yield: 65.9%.
IR (KBr pellet cmꢀ1): 3065, 3024, 1645, 1568, 1477, 1377, 1111, 1063,
1008, 810, 728, 698. 1H NMR (300 MHz, CDCl3)
d 7.36e7.59 (m,18H).
4.5. Synthesis of tri(4-bromophenyl)phenylsilane (11)
The preparation procedure of 11 was similar to that of 10. Yield:
(300 MHz, DMSO)
d
8.32 (s, 3H), 7.83 (s, 3H), 7.73 (d, 6H, J ¼ 8.4 Hz),
55.6%. IR (KBr pellet cmꢀ1): 3065, 3024, 1645, 1568, 1477, 1377, 1111,
7.63 (d, 6H, J ¼ 8.4 Hz), 7.13 (s, 3H), 0.94 (s, 3H). 13C NMR (300 MHz,

2336
D. Wang et al. / Journal of Organometallic Chemistry 695 (2010) 2329e2337
DMSO)
d
140.27, 138.66, 137.77, 135.79, 132.25, 122.17, 120.10, ꢀ1.71.
613.1166, found 613.1152. Anal. Calcd for C33H25N6SiBr: C, 64.60; H,
4.11; N, 13.70. Found: C, 64.58; H, 4.15; N, 13.60.
HRMS (FAB) calcd for C28H24N6Si (MHþ): 473.1904, found 473.1903.
Anal. Calcd for C28H24N6Si: C, 71.16; H, 5.12; N, 17.78. Found: C,
71.02; H, 5.12; N, 17.13.
4.13. Synthesis of (4-(imidazol-1-yl)phenyl)trimethylsilane (7)
4.10. Synthesis of bis(4-(imidazol-1-yl)phenyl)diphenylsilane (3)
The synthesis and treatment procedures for 7 were similar to
that described for 1 in Method B and a yellow solid was afforded.
Yield: 56.8%. IR (KBr pellet cmꢀ1): 3114, 3026, 2956, 2895, 1600,
1513, 1486, 1402, 1365, 1302, 1251, 1122, 1093, 1056, 960, 903, 840,
A Teflon autoclave was charged with bis(4-bromophenyl)phe-
nylsilane (1.23 g, 2.5 mmol), imidazole (0.68 g, 10 mmol), K2CO3
(1.03 g, 7.5 mmol) and CuSO4 (0.008 g, 0.05 mmol) and backfilled
with argon. The mixture was heated at 180 ꢁC for 24 h. The treat-
ment procedure for product was analogous to that described for 1
in Method A and a colorless crystal was obtained. Yield: 25.6%. IR
(KBr pellet cmꢀ1): 3109, 3062, 3045, 3024, 1595, 1511, 1426, 1402,
1302, 1249, 1190, 1111, 1098, 1052, 958, 901, 818, 792, 740, 656, 537.
817, 752, 657, 533. 1H NMR (400 MHz, DMSO)
d
8.28 (s, 1H), 7.76 (s,
1H), 7.64 (s, 4H), 7.12 (s, 1H), 0.27 (s, 9H). 13C NMR (400 MHz,
DMSO):
d
138.9, 137.9, 136.0, 135.2, 130.4, 120.1, 118.4, ꢀ0.7. HRMS
(FAB) calcd for C12H16N2Si (MHþ): 217.1156, found 217.1145. Anal.
Calcd for C12H16N2Si: C, 66.62; H, 7.45; N, 12.95. Found: C, 66.03; H,
7.38; N, 12.65.
1H NMR (300 MHz, DMSO)
J ¼ 8.4 Hz), 7.62 (d, 4H, J ¼ 8.4 Hz), 7.46e7.53 (m, 10H), 7.15 (s, 2H).
d 8.33 (s, 2H), 7.80 (s, 3H), 7.76 (d, 4H,
4.14. Metal titration experiments
13C NMR (300 MHz, DMSO)
d 140.42, 139.57, 138.00, 135.08, 133.90,
132.36, 130.55, 122.27. HRMS (FAB) calcd for C30H24N4Si (MHþ):
469.1843, found 469.1823. Anal. Calcd for C30H24N4Si: C, 76.89; H,
5.16; N, 11.96. Found: C, 75.60; H, 5.10; N, 11.73.
Compounds 1e4 in dichloromethane solution (1 ꢂ 10ꢀ3 M) and
silver perchlorate in methanol solution (1 ꢂ 10ꢀ3 M) were firstly
prepared. Then a series of Ag (I) and ligands in dichloromethane
were prepared with the [Ag]/[Lig] ratio from 0 to 2.0 for compounds
1 and 3 and 0 to 3.0 for compounds 2 and 4, while maintaining the
ligands concentration of 1 ꢂ 10ꢀ5 M. Then the emission spectrum
was measured after 24 h and the excitation wavelength was
employed at 250 nm for all the compounds.
4.11. Synthesis of tri(4-(imidazol-1-yl)phenyl)phenylsilane (4) and
[bis(4-(imidazol-1-yl)phenyl)] (4-bromophenyl)phenylsilane (5)
A Teflon autoclave was charged with tris(4-bromophenyl)phe-
nylsilane (1.43 g, 2.5 mmol), imidazole (1.02 g, 15 mmol), K2CO3
(1.38 g, 10 mmol) and CuSO4 (0.016 g, 0.1 mmol) and backfilled with
argon. The mixture was heated at 180 ꢁC for 24 h. The treatment
procedure for product was analogous to that described for 1 in
Method A and two products were obtained. 4 as a white solid was
afforded by column chromatography with CH2Cl2/MeOH (25:1) as
eluent (Rf ¼ 0.2). Yield: 14.9%. IR (KBr pellet cmꢀ1): 3109, 3062,
3027, 1595, 1511, 1428, 1403, 1303, 1249, 1192, 1098, 1053, 959, 902,
Acknowledgements
This research was supported by the National Natural Science
Foundation of China (Grant Nos. 20574043, 20874057) and the Key
Natural Science Foundation of Shandong Province of China (No.
Z2007B02).
819, 736, 670, 656, 552. 1H NMR (300 MHz, DMSO)
d
8.33 (s, 3H),
140.51,
7.46e7.53 (m,18H), 7.14 (s, 3H). 13C NMR (300 MHz, DMSO)
d
Appendix. Supplementary materials
139.59, 138.27, 138.01, 137.80, 134.79, 133.56, 132.33, 130.63, 122.32,
120.07. HRMS (FAB) calcd for C33H26N6Si (MHþ): 535.2061, found
535.2049. Anal. Calcd for C33H26N6Si: C, 74.13; H, 4.90; N, 15.72.
Found: C, 73.95; H, 4.58; N,15.20. Meanwhile, 5 as a white solid was
afforded by column chromatography with CH2Cl2/MeOH (15:1) as
eluent (Rf ¼ 0.3). Yield: 11.0%. IR (KBr pellet cmꢀ1): 3110, 3062,
3028, 1596, 1511, 1481, 1426, 1404, 1303, 1258, 1190, 1100, 1053, 959,
Characterization for the by-product obtained, 1H NMR spectrum
of compounds 1e7, TGA and DSC curves of compounds 1e6, exci-
tation spectra of compounds 1e7 and emission spectra of
compound 7 in solution and in the solid state, UV spectra of
compound 7, molecular orbital calculation for compounds 1, 3 and
5, UV change results of compounds 1e4 in CH2Cl2 solution with
AgClO4 and binding analysis for Agþ with compound 4. Supple-
mentary data associated with this article can be found, in the online
version, at doi:10.1016/j.joranchem.2010.06.026.
901, 813, 736, 699, 655, 547. 1H NMR (400 MHz, DMSO)
2H), 7.45e7.49 (m, 3H), 7.50e7.55 (m, 5H), 7.60e7.63 (m, 4H),
7.73e7.76 (m, 5H), 7.13 (s, 2H). 13C NMR (300 MHz, DMSO)
138.17,
d 8.30 (s,
d
137.61, 137.43, 137.21, 135.62, 135.42, 131.19, 131.03, 130.15, 129.98,
128.27, 128.18, 119.97, 117.69. HRMS (FAB) calcd for C30H23N4SiBr
(MHþ): 547.0948, found 547.0927. Anal. Calcd for C30H23N4SiBr: C,
65.81; H, 4.23; N, 10.23. Found: C, 65.62; H, 4.30; N, 10.18.
References
[1] Y.N. Luponosov, S.A. Ponomarenko, N.M. Surin, O.V. Borshchev, E.A. Shumilkina,
A.M. Muzafarov, Chem. Mater. 21 (2009) 447.
[2] H. Kai, J. Ohshita, S. Ohara, N. Nakayama, A. Kunai, I.-S. Lee, Y.-W. Kwak,
J. Organomet. Chem. 693 (2008) 3490.
[3] Y.N. Luponosov, S.A. Ponomarenko, N.M. Surin, A.M. Muzafarov, Org. Lett. 10
(2008) 2753.
4.12. Synthesis of [tri(4-(imidazol-1-yl)phenyl)](4-bromophenyl)
silane (6)
[4] T. Lee, I. Jung, K.H. Song, H. Lee, J. Choi, K. Lee, B.J. Lee, J.Y. Pak, C. Lee, S.O. Kang,
J. Ko, Organometallics 23 (2004) 5280.
A Teflon autoclave was charged with tetra(4-bromophenyl)
silane (1.63 g, 2.5 mmol), imidazole (1.36 g, 20 mmol), K2CO3
(2.07 g, 15 mmol) and CuSO4 (0.016 g, 0.1 mmol) and backfilled with
argon. The mixture was heated at 180 ꢁC for 24 h. The treatment
procedure for product was analogous to that described for 1 in
Method A and a yellow solid was afforded. Yield: 10.5%. IR (KBr
pellet cmꢀ1): 3107, 3027, 1596, 1511, 1480, 1403, 1372, 1249, 1192,
1097, 1053, 958, 902, 816, 737, 655, 552. 1H NMR (300 MHz, DMSO)
[5] J. Roncali, P. Leriche, A. Cravino, Adv. Mater. 19 (2007) 2045.
[6] D.-R. Bai, X.Y. Liu, S.N. Wang, Chem. Eur. J. 13 (2007) 5713.
[7] D.-R. Bai, S.N. Wang, Organometallics 23 (2004) 5958.
[8] M.-L. Hung, C.-W. Ko, T.-H. Liu, U. S. Patent 0 115 674 2006.
[9] K. Nii, U. S. Patent 0 135 167 2004.
[10] J. Qgasawara, S. Watanabe, U. S. Patent 0 214 572 2005.
[11] T. Igarashi, T. Taguchi, U. S. Patent 6 310 231 2001.
[12] Q. Shen, S.Y. Ye, G. Yu, P. Lu, Y.Q. Liu, Synth. Met 158 (2008) 1054.
[13] X.M. Liu, J. Xu, X. Lu, C. He, Org. Lett. 7 (2005) 2829.
[14] X.M. Liu, T. Lin, J. Huang, X.T. Hao, K.S. Ong, C. He, Macromolecules 38 (2005)
4157.
d
8.33 (s, 3H), 7.47e7.83 (m, 19H), 7.14 (s, 3H). 13C NMR (DMSO)
d
140.52, 139.80, 138.92, 138.00, 137.79, 133.60, 132.33, 130.62,
[15] S. Wang, W.J. Oldham Jr., R.A. Hudack, G.C. Bazan, J. Am. Chem. Soc. 122 (2000)
5695.
123.69, 122.33, 120.07. HRMS (FAB) calcd for C33H25N6SiBr (MHþ):

D. Wang et al. / Journal of Organometallic Chemistry 695 (2010) 2329e2337
2337
[16] L.-H. Chan, R.-H. Lee, C.-F. Hsieh, H.-C. Yeh, C.-T. Chen, J. Am. Chem. Soc. 124
(2001) 6469.
[36] J. Fan, G.T. Yee, G.B. Wang, B.E. Hanson, Inorg. Chem. 45 (2006) 599.
[37] D.X. Wang, H.Y. He, X.H. Chen, S.Y. Feng, Y.Z. Niu, D.F. Sun, CrystEngComm 12
(2010) 1041.
[38] R.P. Davies, R.J. Less, P.D. Lickiss, K. Robertson, A.J.P. White, Inorg. Chem. 47
(2008) 9958.
[39] G. Kwak, T. Masuda, Macromolecules 35 (2002) 4138.
[40] J. Ohshita, T. Watanabe, D. Kanaya, H. Ohsaki, M. Ishikawa, Organometallics 13
(1994) 5002.
[41] H. Zhang, Q. Cai, D.W. Ma, J. Org. Chem. 70 (2005) 5164.
[42] P.M. Beaujuge, J.R. Reynolds, Chem. Rev. 110 (2010) 268.
[43] Z.Q. Jiang, H.Q. Yao, Z.Y. Liu, C.L. Yang, C. Zhong, J.G. Qin, G. Yu, Y.Q. Liu, Org.
Lett. 11 (2009) 4132.
[17] W.J. Oldham Jr., R.J. Lachicotte, G.C. Bazan, J. Am. Chem. Soc. 120 (1998) 2987.
[18] W.-S. Han, H.-J. Son, K.-R. Wee, K.-T. Min, S. Kwon, I.-H. Suh, S.-H. Choi,
D.H. Jung, S.O. Kang, J. Phys. Chem. C 113 (2009) 19686.
[19] Y.-Y. Lyu, J. Kwak, W.S. Jeon, Y. Byun, H.S. Lee, D. Kim, C. Lee, K. Char, Adv.
Funct. Mater. 19 (2009) 420.
[20] Y.-Y. Lyu, J. Kwak, O. Kwon, S.-H. Lee, D. Kim, C. Lee, K. Char, Adv. Mater. 20
(2008) 2720.
[21] Y.-H. Kim, H.-C. Jeong, S.-H. Kim, K. Yang, S.-K. Kwon, Adv. Funct. Mater. 15
(2005) 1799.
[22] G. Huang, C. Yang, Z.T. Xu, H.H. Wu, J. Li, M. Zeller, A.D. Hunter, S.S.-Y. Chui,
C.-M. Che, Chem. Mater. 21 (2009) 541.
[23] H.J. Kang, T.H. Noh, J.S. Jin, O.S. Jung, Inorg. Chem. 47 (2008) 5528.
[24] C. Rim, H. Zhang, D.Y. Son, Inorg. Chem. 47 (2008) 11993.
[25] M.M. Maye, J. Luo, I.I.S. Lim, L. Han, N.N. Kariuki, D. Rabinovich, T.B. Liu,
C.J.T. Zhong, J. Am. Chem. Soc. 127 (2005) 1519.
[44] Y.-L. Liu, X.-Q. Ran, J.-K. Feng, A.-M. Ren, L.-Y. Zou, Aust. J. Chem. 63 (2010)
125.
[45] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman,
J.A. Montgomery Jr., T. Vreven, K.N. Kudin, J.C. Burant, J.M. Millam, S.S. Iyengar,
J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A. Petersson,
H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida,
T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J.E. Knox,
H.P. Hratchian, J.B. Cross, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann,
O. Yazyev, A.J. Austin, R. Cammi, C. Pomelli, J.W. Ochterski, P.Y. Ayala,
K. Morokuma, G.A. Voth, P. Salvador, J.J. Dannenberg, V.G. Zakrzewski,
S. Dapprich, A.D. Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck,
K. Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S. Clifford,
J. Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi,
R.L. Martin, D.J. Fox, T. Keith, M.A. Al-Laham, C.Y. Peng, A. Nanayakkara,
M. Challacombe, P.M.W. Gill, B. Johnson, W. Chen, M.W. Wong, C. Gonzalez,
J.A. Pople, Gaussian 03, Revision B.04. Gaussian, Inc., Pittsburgh, PA), 2003.
[46] A.P. Kulkarni, C.J. Tonzola, A. Babel, S.A. Jenekhe, Chem. Mater. 16 (2004) 4556.
[47] H.-H. Wang, L. Xue, Y.-Y. Qian, H. Jiang, Org. Lett. 12 (2010) 292.
[48] A. Chatterjee, M. Santra, N. Won, S. Kim, K.J. Kim, B.S. Kim, H.K. Ahn, J. Am.
Chem. Soc. 131 (2009) 2040.
[26] W. White, Z.M. Hudson, X.D. Feng, S. Han, Z.-H. Lub, S.N. Wang, Dalton Trans.
39 (2010) 892.
[27] C.-H. Chen, W.-S. Huang, M.-Y. Lai, W.-C. Tsao, J.T. Lin, Y.-H. Wu, T.-H. Ke,
L.-Y. Chen, C.-C. Wu, Adv. Funct. Mater. 19 (2009) 2661.
[28] L. Zhao, S.B. Li, G.A. Wen, B. Peng, W. Hua, Mater. Chem. Phys. 100 (2006) 460.
[29] M.-H. Hu, G.-L. Shen, J.-X. Zhang, Y.-G. Yin, D. Li, Cryst. Growth Des. 9 (2009)
4533.
[30] G.-C. Xu, Y.-J. Ding, T. Okamura, Y.-Q. Huang, Z.-S. Bai, Q. Hua, G.-X. Liu,
W.-Y. Sun, N. Ueyama, Cryst. Growth Des. 9 (2009) 395.
[31] K. Takagi, K. Sugihara, T. Isomura, J. Polym. Sci. Part A: Polym. Chem. 47 (2009)
4822.
[32] Z.J. Fang, S.M. Wang, L. Zhao, Z.X. Xu, J. Ren, X.B. Wang, Q.F. Yang, Mater.
Chem. Phys. 107 (2008) 305.
[33] W. Pisula, F. Dierschke, K. Müllen, J. Mater. Chem. 16 (2006) 4058.
[34] S. Noro, S. Kitagawa, T. Akutagawa, T. Nakamura, Prog. Poly. Sci. 34 (2009)
240.
[49] L. Liu, D. Zhang, G. Zhang, J. Xiang, D. Zhu, Org. Lett. 10 (2008) 2271.
[50] S.R. Meech, D.C. Philips, J. Photochem. 65 (1983) 229.
[51] J.P. Cross, M. Lauz, P.D. Badger, S. Petoud, J. Am. Chem. Soc. 126 (2004) 16278.
[35] H.Y. He, D. Collins, F.N. Dai, X.L. Zhao, G.Q. Zhang, H.Q. Ma, D.F. Sun, Cryst.
Growth Des 10 (2009) 895.