Turn-on fluorescence in a pyridine-decorated tetraphenylethylene: The cooperative effect of coordination-driven rigidification and silver ion induced aggregation

Article abstract of DOI:10.1039/c9dt03985f

A tetrapyridine-decorated tetraphenylethene (TPE) ligand 1 was designed, which, upon interacting with silver ions, displayed "turn-on" fluorescence in a dilute solution. The fluorescence enhancement can be attributed to the cooperative effect of restricti

Full text of DOI:10.1039/c9dt03985f

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DOI: 10.1039/C9DT03985F
ARTICLE
Turn-on fluorescence in a pyridine-decorated
tetraphenylethylene: the cooperative effect of coordination-
driven rigidification and silver ions induced aggregation
Received 00th January 20xx,
Accepted 00th January 20xx
a
a
a
a
DOI: 10.1039/x0xx00000x
Ning Wang, Junying Zhang, Xing-Dong Xu,* and Shengyu Feng
A tetrapyridine-decorated tetraphenylethene (TPE) ligand 1 was designed, which, upon interacting with silver ions,
displays fluorescence “turn-on” in a dilute solution. The fluorescence enhancement can be attributed to the cooperative
effect of restriction of the intramolecular rotation by metal coordination and silver ions induced aggregation. Furthermore,
the fluorescence turn-on performance of AIE molecule in a dilute solution leads to the application for tunable fluorescence
properties including white-light emission by simply mixing AIE and ACQ molecules together, which might bridge the gap
between AIE and ACQ phenomenon for the construction of color-tunable fluorescence systems.
urgent. To address this need, controlling the rotation of AIE
8
Introduction
chromophore bonds has proved to be an effective strategy.
Consequently, utilizing AIE-active ligands to construct
assemblies with enhanced emission in a wide concentration
range has been developed for exploring the influence of
The search for new light-emitting materials continues to be a
topic of great interest due to their applications in fluorescent
1
2
3
sensors, optoelectronic devices, biological probes and so
9
structural factors on the optical properties. For example, Wu
4
on. Many fluorescent chromophores show strong emission in
9
a]
and coworkers reported an example of anion coordination
induced turn-on fluorescence of an oligourea functionalized
TPE in a wide concentration range.
dilute solutions but are only weakly or non-emissive in
concentrated solutions or the solid state owing to aggregation-
caused quenching (ACQ). In 2001, Tang and coworkers
discovered “aggregation-induced emission” (AIE) for some
compounds which exhibit high fluorescence quantum yields in
the solid state or in colloidal aggregates, but show weak or
almost no fluorescence in dilute solutions. Since their
pioneering work, AIE has been widely studied in terms of the
above-mentioned applications. The AIE phenomenon is
mainly induced by restriction of the intramolecular rotation
Among all the interactions, coordination-driven self-assembly
has been proven to be a powerful tool to construct
supramolecular luminescent materials via the spontaneous
formation of metal-ligand bonds which have moderate bond
energies in the range of 15-25 kcal/mol and predictable
5
1
0
coordination geometries during the past few decades.
6
Numerous complicated and delicate supramolecular
metallacycles and metallacages with well-defined shapes, sizes,
and geometries have been successfully constructed by
employing such a strategy, some of which have presented
wide applications in the fields of molecular recognition,
leading to
a suppression of radiationless deactivation
pathways. This implies that the fluorescence might also be
switched on by restrictions other than aggregation. Although
the ACQ and AIE phenomena seem to oppose each other, their
mechanisms are orthogonal. As a consequence of this situation,
it is possible to find new materials that emit tunable
fluorescence, including white-light emission by the proper
implementation of the two orthogonal interactions in a single
1
1
supramolecular catalysis, drug delivery, etc.
Typically,
fluorescent coordination assemblies are based on Pt(II) or Pd(II)
metal nodes and ligands wherein each component has an
encoded directionality and angularity, which aids
investigations on their structure-property relationships for
tuning desirable properties. The development of self-
assembly systems with other metal nodes to explore their
7
process. Apparently, the fluorescent behaviors of molecules
1
2
with ACQ and AIE property largely depend on the
chromophore concentration, so exploring materials with
strong emission in low concentrations of AIE molecules is
1
3
functions and properties is still worthwhile.
Ligand-protected metallic nanoparticles, such as silver, gold,
and their alloys, have become an exciting and active area of
interdisciplinary research in recent years due to their unique
optical, chemical, and physical properties. More importantly,
silver nanoparticles have shown widespread application
potential based upon properties that have defined their shape,
a. National Engineering Research Center for Colloidal Materials, Key Laboratory of
Special Functional Aggregated Materials of Ministry of Education, School of
Chemistry and Chemical Engineering, Shandong University, Jinan 250100,
Shandong, China. E-mail: xuxd@sdu.edu.cn
Electronic Supplementary Information (ESI) available: Details of synthesis and
characterization, additional spectra and images. See DOI: 10.1039/x0xx00000x
1
4
1
5
size, configuration, and crystal orientations. Normally, silver(I)
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Journal Name
complexes are unstable both in aqueous solution and the solid
state because of their sensitivity to light, temperature, and
oxygen. The development of supramolecular structures based
on silver metal nodes, while rare, has proven to be an effective
strategy to improve both the stability and fluorescence over a
wide concentration range, which will effectively broaden the
View Article Online
DOI: 10.1039/C9DT03985F
1
6
applied fields of silver-based luminescent materials.
Based on our previous research results on luminescent
1
7
materials and coordination-driven self-assembly, we herein Scheme 1 The interaction between pyridine-decorated TPE derivative 1
describe the preparation of a novel TPE derivative 1, which and silver ions and silver ions-dependence emission turn-on process.
showed no fluorescence in dilute solution. Pyridine is a well-
known functional group that can coordinated with metal ions,
methoxy group is a good electronic donor group, especially
when ligands coordinated with metal ions.The fluorescence
Results and discussion
can be selectively switched on by coordination with silver ions
even in the presence of other competitive metal ions in a
dilute solution. More importantly, with a further addition of
Synthesis of compound 1
The pyridine-decorated TPE derivative 1 was synthesized via a
1
8
simple Suzuki cross-coupling reaction in reasonable yield
Scheme S1 in ESI). As shown in Scheme S1, compound 1 was
more silver ions into the solution, the emission intensity
showed continuous enhancement accompanied by the
formation of nanoparticles. The fluorescence turn-on
performance from the cooperative effect of rigidification
through coordination and silver ions-induced aggregation
leads to the application for tunable fluorescence properties
including white-light emission with AIE and ACQ molecules in a
dilute solution.
(
prepared from 1,1,2,2-Tetrakis (4-bromophenyl) ethane and 5
equiv. of 6-methoxypyridine-2-boronic acid pinacol ester in the
dried DMF, with the Pd(PPh
3 4 2 3
) as catalyst and the Cs CO as
acid absorber. The structure of the compound 1 was verified
1
13
by H NMR, C NMR and HR-ESI-MS to be in full agreement
with its structure.
Fig. 1 a) Emission spectra of 1 in H
glycol /THF mixtures with glycol fractions (f
M, ex=380 nm). The inset shows the photograph of 1 at 77 and 298 K in THF (under 365 nm illumination); d) Normalized fluorescence spectra of
in pristine and ground states. Insets: emission images of 1 before and after grinding under 365 nm UV illumination.
2
O/THF mixtures with water fractions (f
w
) from 0 to 90% (2.0×10-5 M, ex=380 nm); b) Emission spectra of 1 in
) from 0 to 90% (2.0×10-5 M, ex=380 nm); c) Emission spectra of 1 at 77 and 298 K in THF (2.0×10-5
w
1
2
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+
AIE Properties
were also conducted for 1. Fig. 2c indicated that when Ag was
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DOI: 10.1039/C9DT03985F
added respectively to the solution of 1 in the presence of other
Fluorescence emission of 1 in the solvents with diverse
H O/tetrahydrofuran (THF) gradients vividly suggested a
2
2
+
3+,
2+
2+
2+
2+
+
2+
+
+
ions such as Ca , Al Cu , Zn , Fe , Ba , Li , Mg , K , Ni ,
+
and Na , the emission spectra displayed a similar pattern at
nearly 540 nm to that with Ag only. The results implied that 1
exhibited high selectivity for Ag even in the presence of other
competitive metal ions. When the Ag+ was removed from the
typical AIE phenomenon. The fluorescence of 1 was weak in
THF solution but was significantly enhanced as the water
fraction increased gradually (Fig. 1a). When the water fraction
reaches 90%, the fluorescence intensity of the solution was
enhanced by more than 87.6 times compared with that of the
pure THF solution. At the same time, we investigated the
fluorescence intensity of 1 in THF/ethylene glycol with varying
ethylene glycol of 0-90%. The viscosity of the system gradually
increases with the increase of ethylene glycol content (up to
+
+
4 9 4
dilute solution of 1 by the addition of equal (C H ) NBr, light
yellow precipitate gradually formed, and the fluorescence
intensity decreased gradually until there was almost no
fluorescence.(Fig. S9) This phenomenon further proved that
+
the importance of Ag in the enhancement of the fluorescence.
2
2.9-fold (Fig. 1b)). The reason for those is that the
intramolecular rotation of the phenyl moiety to limit non-
radiative emission , resulting in the increase in fluorescence.
The AIE enhancement nature can be further proved by the
temperature-dependent photoluminescence. As shown in Fig.
1
c, the emission spectrum of 1 in THF in a frozen glass state
under liquid nitrogen shows obvious enhancement, 14-fold
higher than that at ambient temperature, indicating that the
energy dissipation process is prevented at low temperature.
Interestingly, the emission color of 1 can also be tuned by
external mechanically shifted luminescence upon grinding
using a pestle (Fig. 1d inset). When simply pressed by a metal
spatula, the original sample exhibited a luminescence color
variation from blue to green with emission peak shifted from
4
73 to 520 nm. As shown in Fig. S5, the XRD peaks became
weaker or wider after grinding, which means that a new
amorphous state was formed during the mechanical grinding
process. After fuming, the XRD peaks were recovered to the
original crystalline structure. And the luminescence colour of
the powder variation from green to blue. Compared with the
ordered crystalline state, the arrangement of amorphous form
molecule tends to be flattened due to being squeezed by
external force, which changes the degree of conjugation,
which affects the energy level of the molecule, leading to the
difference in fluorescence colour before and after the grinding.
These results suggest the potential applications of compound
1
for optical recording.
Sensitivity and Selectivity of Mental Ion
Considering that the pyridine group has the strong
1
9
coordination tendency towards metal ions, the fluorescence
2
+
response of ligand 1 toward a series of metal ions such as Ca ,
3
+
2+
2+
2+
2+
+
2+
+
2+
+
Al , Cu , Zn , Fe , Ba , Li , Mg , K , Ni , and Na was
investigated. As expected, 1 showed a weak fluorescence in a
dilute solution due to the free rotation of phenyl moieties with
the nonradiative emission process. As shown in Fig. 2a, the
+
addition of Ag to the solution of 1 induced a significant
enhancement of fluorescence (ca. 23-fold) with the emission
maximum at 537 nm. However, the addition of the other metal
ions produced a negligible change in the fluorescence spectra
Fig. 2 a) Fluorescence spectra of 1 (2.0×10-5 M, ex=380 nm) in the
presence of various metal ions (100 eq); b) Fluorescence spectra of 1
2.0×10-5 M, ex=380 nm) with 100 equivalent silver ions in the presence of
(
+
of 1. Therefore, the results disclosed that 1 was a Ag -specific
various competitive metal ions; c) Fluorescence intensity of 1 at 537 nm
turn-on fluorescent probe. Achieving high selectivity toward
Ag over the other competitive species coexisting is a very
in the presence (red bars) or absence (black bars) of 100 equivalent silver
+
ions with various metal ions to free 1 (2.0×10-5 M, ex=380 nm) in THF
important feature to evaluate the performance of the
solution.
fluorescent probe 1. Therefore, the competition experiments
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The detailed response of ligand 1 to Ag was investigated, as
+
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DOI: 10.1039/C9DT03985F
+
shown in Fig. 3a. With the titration of Ag into compound 1 in
-5
THF solution (2.0×10 M), the fluorescence increased by about
2-fold without a change in the wavelength of the maximum.
3
Generally, due to the strong coordination ability of pyridine,
the titration end-point should be reached with the addition of
+
about two equivalent Ag . However, the fluorescence intensity
of 1 continued to increase with the addition of excess silver
ions and achieved equilibrium with 1000 equivalent silver ions
addition. As shown in Fig. 3b, the binding isotherm based on
the fluorescence titration showed a smooth curve, which is
generally regarded as the criterion for the positive allosteric
2
0
cooperativity. This cooperative process was then analyzed
+
according to the Hill equation: log(Y/1-Y) = n log[Ag ] + log K,
where Y is the fractional saturation of the ligand 1 and K and n
are the association constant and the Hill coefficient,
respectively.Herein, we assume that the concentration of free
+
silver ions [Ag ] is equal to the total silver concentration. Based
on the intercept and slope of the Hill plot (r=0.999), we
obtained log K = 0.93±0.007 and n = 2.47±0.025. The Hill
coefficient is commonly considered as a parameter reflecting
the extent of cooperativity. The n value of 2.47 clearly
demonstrates that silver(I) ions bind with ligand 1 via a
strongly cooperative process. More interestingly, besides the
content of silver ions, the emission intensity also depends on
the concentration of ligand 1. As showed in Fig. 3c, when the
-5
concentration of 1 reached to 2.0 ×10 M, the fluorescence
intensity of 1 displayed a significant enhancement after adding
1
00 equivalent silver ions, which maybe means the occurrence
of aggregation.
Fig. 3 a) Fluorescence titration curves of 1 (2.0×10-5 M, ex=380 nm) in
Fig. 4 a) SEM, b) TEM, c) CLSM images and d) DLS data with an inset
showing the Tyndall effect of the solution of 1 in THF (2.0×10-5 M, ex=380
3 3
response to AgCF SO from 0 to 1000 equivalents in THF solution; b)
Binding isotherms based on the fluorescence titrations at 537 nm. (inset)
Hill plot for the binding of silver(I) ions to 1. Y=Δem/Δemmax; c) Fluorescence
intensity of 1 at 537 nm in the presence of different equivalent silver ions
in various concentrations.
3 3
nm) with the addition of 100 equivalents AgCF SO .
The nature of cooperative interactions from compound 1 and
silver ions stimulated us to investigate its aggregation behavior
in THF solution by using electron microscopy. As demonstrated
in Fig. 4, the self-assembled complex exhibits a nanoparticle
The Cooperative Effect Study
4
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DOI: 10.1039/C9DT03985F
2 4
Fig. 5 X-ray crystal structure a), c), e) and the packing diagram b), d), f) of ligand 1, 1•Ag , 1•Ag .
morphology with a diameter range of 30-100 nm by employing orientation at two ethylenic carbons. Two ligands are stacked
scanning electron microscopy (SEM) and transmission electron in a face-to-face fashion, lead to the formation of H-type
microscopy (TEM) measurements. More intuitively, the yellow aggregates (Fig. 5b). When two equivalents silver ions added
luminescence was emitted from the nanoscale structures, into the ligand, the complex is connected by a N–Ag–N bond to
which was directly observed by laser scanning confocal form a rigid structure, which greatly limits the rotation among
3
microscope (LSCM) images as exhibited in Fig. 4c. These results molecules. Moreover, it was found that the CF tail was
clearly showed that the nanoparticles were formed from the situated on the pyridine group, while the negatively charged
-
interaction between ligand 1 and silver ions. In addition, the SO
3
head group was near the silver ion. The distances of the
same solution of compound 1 with 100 equivalent silver ions fluorine atom to the centroid of pyridine ring coordinated with
showed clear evidence of the Tyndall effect (inset in Fig. 4d), the metal Ag+ was found to be 3.12Å (Fig. 5c), suggesting the
demonstrating the formation of nanoscale aggregates.
existence of strong noncovalent interaction. According to the
previous studies on anion-p interactions, such noncovalent
interactions between fluorine atoms and aromatic rings was
2
2
The crystal structures of 1, 1•Ag , 1•Ag4
2
To further understand the interaction mechanism between
ligands and metal ions in the presence of different silver
consistent with the feature of typical anion-p interactions. Due
-
to the steric effect of the CF
3
SO
3
anions, the complex showed
2
1
trifluoromethanesulfonate, single crystals of ligand 1 and
ligand with 2 equivalents and 100 equivalents metal ions were
grown by several days. The X-ray crystal structures of
J-type packing with the formation of head-to-tail aggregates
with a slipped-stacked geometry. More interestingly, when
more AgOTf was added into the system, we surprisingly found
the existence of the closest contacts between Ag and benzene
ring which is associated with the C3 and C8 atoms (Fig. 5e).
The Ag-C contacts are 2.47 and 2.52 Å for C3 and C8,
respectively, both of which fall in the range of Ag-C
interactions and are obviously shorter than the sum of the van
2 4
compound 1, 1•Ag , 1•Ag were shown in Fig. 5. In the X-ray
crystal structure, the molecule of ligand 1 is positioned at the
crystallographic 2-fold axis along with the central ethylenic
bond which is twisted by 10.8°. Furthermore, the apparent
difference in the orientation of peripheral pyridine groups
relative to the central double bond is caused by their different
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der Waals radii of Ag and C (3.42 Å). More importantly, the interactions in 1 may be considered as mediuVimew AartricolemOanltinice
layers are superimposed along the direction of the tetragonal coordination of the benzene ring to the ADgO(II:)10io.1n0,39a/nCd9DaTr0e3v9e85ryF
c-axis with the formation of an eight-membered ring in a chair significant, in the present case, for the packing of 1 in the
-
conformation between Ag and SO3 . These
aggregated state. The Ag-C interactions and - stacking
interactions play important roles in the formation of TPE-
based polymer, which may be a necessary precursor for the
2
3
formation of silver nanoparticles, such as clusters.
Color-Tunable Solution Based on AIE molecules and ACQ
molecules
As presented above, minor modifications of silver ions content
in a dilute solution of AIE molecule result in significant
variations in their fluorescence properties. Therefore, the
system could be envisaged to have photophysical applications
2
4
by combining classical AIE molecules and ACQ molecules.
With this objective, we carried out optical titrations of ligand 1
in the presence of 9-vinylanthracene with different
concentrations of silver ions. The addition of silver ions to the
solution in THF resulted in enhancement of yellow
luminescence. In contrast, the emission corresponding to the
9
-vinylanthracene moiety in the region between 385 and 475
nm remained unaffected, allowing the colour of emission to be
tuned. Thus, as shown in Fig. 6a, the fluorescence from a
mixture of 1 and 9-vinylanthracene in 10:1 ratio with 40
equivalent silver(I)triflate had equivalent intensities in the blue
and yellow regions of the electromagnetic spectrum. This
emission spectrum was broad and covered the entire visible
region, leading to white light emission with strong
fluorescence intensity. When the emission spectral data were
mapped onto chromaticity coordinates on a Commission
Internationale de L’Eclairage (CIE) 1931 colour space
chromaticity diagram, we obtained values of (0.26, 0.33) for
the (x, y) coordinates. At the same time, adjust the
-
6
-
concentration of 9-vinylanthracene from 2.0×10 M to 2.0×10
4
-5
M in a mixture of 1 (2.0×10 M) with 100 equivalents silver(I)
ions and 9-vinylanthracene in THF solution can also achieve
the purpose of color adjustment (Fig.6b and Fig.6d). Thus, by
combining the AIE molecules and ACQ molecules together, we
have developed a new strategy for tuning the colour of light
emission.
Conclusion
In conclusion, we have designed a novel tetrapyridine ligand 1
that incorporates the TPE chromophore. The almost non-
emissive ligand
1
displays
a
significant fluorescence
enhancement in the presence of silver ions in a dilute solution,
which is attributable to the cooperative effect of restriction of
the intramolecular rotation by metal coordination and silver
ions induced aggregation. Furthermore, the fluorescence turn-
on performance of AIE molecule in a dilute solution leads to
the application for tunable fluorescence properties, including
white-light emission by simply mixing AIE and ACQ molecules
together. This study provides a new strategy in the preparation
of smart luminescent materials, which might bridge the gap
between AIE and ACQ phenomenon for the construction of
color-tunable fluorescence systems.
Fig. 6 a) Fluorescence spectrum and c) the CIE coordinates for a mixture
of 1 (2.0×10-5 M) and 9-vinylanthracene (2.0×10-6 M) in THF solution with
the addition of different equivalents silver(I) ions; b) Fluorescence
spectrum and d) the CIE coordinates for a mixture of 1 (2.0×10-5 M) with
1
2
00 equivalents silver(I) ions and 9-vinylanthracene (from 2.0×10-6 M to
.0×10-4 M) in THF solution, ex=365 nm.
6
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6.31, 75.99, 75.68, 52.13 ppm. HR-ESI-MS of 1: m/z calcd for
7
C
Experimental
Materials and measurements
View Article Online
DOI: 10.1039/C9DT03985F
+
50 40 4 4
H N O : [1+H] 761.3050; found:761.2963.
All reagents and solvents were purchased from commercial
sources. DMF was dried by anhydrous Na
2 4
SO . All reactions
Acknowledgements
were performed in standard glassware under an inert N
2
1
13
This work was supported by the National Natural Science
Foundation of China (Grant No. 21602124), Natural Science
Foundation of Shandong Province (Grant No. ZR2016BQ11),
and the Young Scholars Program of Shandong University
atmosphere. H NMR, and C NMR spectra were recorded on
1
13
Bruker 400 MHz Spectrometer at 298 K. The H and C NMR
chemical shifts are reported relative to residual solvent signals.
Coupling constants (J) are denoted in Hz and chemical shifts (d)
in ppm. Multiplicities are denoted as follows: s= singlet, d=
doublet, m= multiplet, br= broad. The UV-visible absorption
spectra were determined with TU-1901 double beam UV-vis
spectrophotometer as powders. The fluorescence spectra of
(2018WLJH40 and 2016TB012).
Conflicts of interest
There are no conflicts to declare.
the samples were measured with
a Hitachi F-7000
fluorescence spectrophotometer using a monochromated Xe
lamp as an excitation source. Samples for absorption and
emission measurements were contained in 1 cm×1 cm cuvette,
all the tests were carried out in the room temperature if not
mentioned. For the sensitivity and selectivity experiment, the
Notes and references
1
a) X. Chen, Y. Zhou, X. Peng and J. Yoon, Chem. Soc. Rev.
2
010, 39, 2120-2135; b) M. Zhang, B. C. Yin, W. Tan and B. C.
2
+
3+
2+
2+
2+
2+
+
Ye, Biosens. Bioelectron. 2011, 26, 3260-3265.
competitive ions such as Ca , Al , Cu , Zn , Fe , Ba , Li ,
2
a) X. L. Dai, Z. X. Zhang, Y. Z. Jin, Y. Niu, H. J. Cao, X. Y. Liang,
L. W. Chen, J. P. Wang and X. G. Peng, Nature 2014, 515, 96-
2
+
+
+
+
Mg , K , Ni , and Na was added to the solution of 1 firstly,
+
then, Ag was added to the solution in the presence of other
9
9; b) Z. An, C. Zheng, Y. Tao, R. Chen, H. Shi, T. Chen, Z.
Wang, H. Li, R. Deng, X. Liu and W. Huang, Nat. Mater. 2015,
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Zhong, H. Li, G. Xie, X. Wang and C. Yang, J. Am. Chem. Soc.
019, 141, 4704-4710.
ions. SEM images were obtained using an S-4800 (Hitachi Ltd.)
with an accelerating voltage of 1.0 kV or 10.0 kV. Samples
were prepared by dropping dilute solution onto a silicon wafer.
The sample for transmission electron microscopy (TEM)
measurement was prepared by dropping the solution onto a
copper grid and the sample was examined by JEM-1011 with
an accelerating voltage of 100V. DLS was performed on a
Zetasizer Nano. The X-ray crystallographic files, in CIF format,
are available from the Cambridge Crystallographic Data Centre
on quoting the deposition numbers CCDC 1954085-1954087
1
2
3
a) T. D. Ashton, K. A. Jolliffe and F. M. Pfeffer, Chem. Soc.
Rev. 2015, 44, 4547-4595; b) Y. Yang, Q. Zhao, W. Feng and F.
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B. Liu, Chem. Soc. Rev. 2015, 44, 2798-2811; d) X.-D. Xu, L.
Zhao, Q. Qu, J.-G. Wang, H. Shi and Y. Zhao, ACS Appl. Mater.
Interfaces 2015, 7, 17371-17380; e) K. K. Lo, A. W. Choi and
W. H. Law, Dalton Trans 2012, 41, 6021-6047.
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2 4
for 1, 1•Ag , and 1•Ag .
Synthesis
Compound 1: 1,1,2,2-Tetrakis (4-bromophenyl) ethane(100 mg,
.154 mmol) and 6-methoxypyridine-2-boronic acid pinacol
ester(181 mg, 0.77 mmol), catalyst Pd(PPh (35.62 mg,
.0308 mmol) and Cs CO (200.7 mg, 0.616 mmol) were added
J. Luo, Z. Xie, J. W. Y. Lam, L. Cheng, B. Z. Tang, H. Chen, C.
Qiu, H. S. Kwok, X. Zhan, Y. Liu and D. Zhu, Chem. Commun.
0
2
001, 1740-1741.
3 4
)
6
7
J. Mei, N. L. C. Leung, R. T. K. Kwok, J. W. Y. Lam and B. Z.
Tang, Chem. Rev. 2015, 115, 11718-11940.
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Stang, Nat. Chem. 2015, 7, 342-348; c) M. Zhang, S. Yin, J.
Zhang, Z. Zhou, M. L. Saha, C. Lu and P. J. Stang, Proc. Natl.
Acad. Sci. USA 2017, 114, 3044.
0
2
3
to the three-necked flask under nitrogen. Then 30 ml of dried
DMF was added to the system to dissolve the mixture by using
a syringe. The reaction system was allowed to stir for 48 hours
at 100℃. After cooling to room temperature, the solid power
was filtered out and the reaction solution was evaporated
under vacuum. The product was extracted with
dichloromethane and water, the organic phase was washed
with water and dried with anhydrous sodium sulfate and
concentrated. Then the crude product was purified by column
chromatography, with DCM: Acetone=10:1, get the yellow
8
9
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powder as final product (70.0 mg, Yield 59.6%). H NMR(400
MHz, CDCl
3
): δ7.87(d, J=8.0 Hz, 8H), 7.58(t, J=8.0 Hz, 4H),
.30(d, J=8.0 Hz, 4H), 7.21(d, J=8.0 Hz, 8H), 6.64(d, J=8.0 Hz,
H), 3.99(s, 12H). 13C NMR(100MHz, CDCl
): δ162.62, 153.02,
43.34, 139.75, 138.05, 136.02, 130.80, 125.02, 111.60, 108.14,
7
4
1
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2, 4766-4773; d) B. Yuan, D. X. Wang, L. N. Zhu, Y. L. Lan, M.
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Dalton Transactions
View Article Online
DOI: 10.1039/C9DT03985F
A novel designed TPE ligand displayed a large fluorescence enhancement in the presence of silver
ions in a dilute solution. The fluorescence turn-on performance from cooperative effect of
rigidification through coordination and silver ions-induced aggregation lead to the application for
tunable fluorescence properties with AIE and ACQ molecules.