AIPE-active platinum(ii) complexes with tunable photophysical properties and their application in constructing thermosensitive probes used for intracellular temperature imaging

Article abstract of DOI:10.1039/c9tc01905g

Aggregation-induced phosphorescent emission (AIPE) luminogens based on phosphorescent transition metal complexes have many application advantages in bioimaging compared with fluorescent organic dyes because of their long excitation lifetime and reduced ph

Full text of DOI:10.1039/c9tc01905g

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ISSN 2050-7526
PAPER
~
Nguyên T. K. Thanh, Xiaodi Su et al.
Fine-tuning of gold nanorod dimensions and plasmonic properties using
the Hofmeister effects
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ARTICLE
AIPE-active platinum(II) complexes with tunable photophysical
properties and the application in constructing thermosensitive
probes used for intracellular temperature imaging
Received 00th January 20xx,
Accepted 00th January 20xx
Shengheng Lin,‡a Honghao Pan,‡a Lin Li,a Rui Liao,a Shengzhen Yu,a Qiang Zhao,c Huibin Sun,*a Wei
Huang,*a,b,c
DOI: 10.1039/x0xx00000x
Aggregation-induced phosphorescent emission (AIPE) luminogens based on phosphorescent transition metal complexes
have many application advantages in bioimaging compared with fluorescent organic dyes because of their long excitation
lifetime and reduced photobleaching. Up to now, however, there are few reports about phosphorescent complexes with
AIPE properties, and the reported mechanism of AIPE also needs to be studied in detail. Herein, two series of Pt(II) complexes
with different Schiff base ligand structures were designed and synthesized, and all these platinum complexes exhibited
obvious AIPE properties. By introducing various electron-rich and electron-deficient functional groups into the Schiff base
ligand, the relationship between the AIPE activity and ligand chemical structure was studied in detail. Based on these, a
complex with 50% solid-state quantum efficiency has been obtained. Furthermore, one strategy to construct thermoprobes
by combining this kind of AIPE-active complexes with thermosensitive N-isopropylacrylamide hydrogel was proposed. The
photophysical properties of the resulted thermoprobe were studied in detail in different physiological environment including
pH, ionic and amino acid, which show great stability and low cytotoxicity. Finally, the application of this kind of thermoprobe
in intracellular temperature distribution imaging was demonstrated.
induced emission enhancement (AIEE) effects discovered by
Tang and co-workers from a silole dye in 2001, and shortly later
1 Introduction
by
Park and
co-workers from
cyano-substituted
Organic luminescent materials have attracted numerous
research interests due to their unique optical properties and
great application potentials in organic light emitting diodes,
data recording and storage, and sensors.1-4 However, most of
the traditional organic luminescent materials suffer from
aggregation-caused quenching (ACQ) in the condensed phase
due to the strong dipole-dipole interactions between the
organic molecules,5,6 which has greatly restricted the
applications of organic luminogens in many fields, especially in
fluorescent chemosensors and bioimaging in vitro and in vivo.7,8
To alleviate or even avoid this phenomenon, many efforts have
been made to develop novel organic luminescent materials with
solid-state light emission. The more representative works are
the aggregation induced emission (AIE) and aggregation
oligophenylenevinylenes.9,10 Since their initial discovery,
libraries of AIEgens have been rationally designed, synthesized,
and widely used in various fields.11-13 To date, most of the
establish AIEgens are limited to pure organic fluorescent
luminogens. As an important kind of organic luminogens,
however, phosphorescent AIEgens reported are few with
limited examples based on Pt(II), Ir(III), Ag(II) and RE(I)
complexes.14-21 In fact, it is proverbial that compared with
fluorescent luminogens the phosphorescent ones have many
application advantages especially in bioimaging since their long
excitation lifetime and reduced photobleaching.22,23 Therefore,
the development of phosphorescent AIEgens and investigation
of the underlying AIE mechanics are important and significant
for further enriching the AIE material libraries and practical
application.
Phosphorescent transition-metal complexes, especially
Pt(II) complexes, have been widely studied in materials science
in the past few decades due to their rich spectroscopic and
luminescence properties such as much longer emission
lifetimes compared with other transition metal complexes,
large Stokes shifts, easy color tunability and high photo-
stability.24-26 However, for conventional Pt(II) complexes,
a.
China Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced
Materials (IAM), Jiangsu National Synergistic Innovation Center for Advanced
Materials (SICAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road,
Nanjing 211816, P.R. China. *E-mail: iamhbsun@njtech.edu.cn;
iamwhuang@njtech.edu.cn
b.Shaanxi Institute of Flexible Electronics (SIFE), Northwestern Polytechnical
University (NPU), 127 West Youyi Road, Xi'an 710072, China
c. Key Laboratory for Organic Electronics and Information Displays & Institute of
Advanced Materials (IAM), SICAM, Nanjing University of Posts &
Telecommunications, 9 Wenyuan Road, Nanjing 210023, P.R. China.
† Electronic Supplementary Information (ESI) available: Experimental details. 1H because of the square planar coordination field and conjugated
NMR and Mass spectra. extra absorption and emission spectra. CCDC 1905320. For
ligand structure, there always exists Pt-Pt and/or π-π
interactions upon excitation in aggregated state, which
generate a new metal-metal-to-ligand charge transfer (MMLCT)
ESI and crystallographic data in CIF or other electronic format see
DOI: 10.1039/x0xx00000x
‡ They contributed to this work equally.
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Journal Name
excited state that results in broad and red-shifted emissions in rigidity of the microenvironment of the Pt(II) complexes. The
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DOI: 10.1039/C9TC01905G
comparison to those of solution state. On the one hand, using photophysical properties of the resulted thermoprobe are
the sensitivity of such interactions to external stimuli such as studied in detail in different physiological environment
solvents, pH, temperature, biomolecules and so on, Yam and co- including pH, ionic and amino acid, which show great stability
workers demonstrated that Pt(II) complexes with terpyridine, and low cytotoxicity. Finally, the application of this kind of
2,6-bis(benzimidazole-2’-yl)pyridine, and 2,6-bis(1-alkylpyrazol- thermoprobe in intracellular temperature distribution imaging
3-yl)pyridine ligands are successful classes of phosphorescent is demonstrated.
luminogens for the design of functional materials.27-29 But on
the other hand, these Pt-Pt and/or π-π interactions also often
lead to the luminescence performance degradation. Therefore,
2. Experimental section
exploration of novel Pt(II) complexes with aggregation induced
phosphorescent emission (AIPE) properties is highly desirable
for further expanding their application in luminescent sensors
and bioimaging. Up to now, however, only a few Pt(II) platinum
complexes with AIE effects have been reported.30-32
2.1 General experimental information
All reagents and chemicals were procured from commercial
sources and used without further purification. All solvents were
of analytical grade and purified according to standard
1
procedures. H NMR spectra were recorded on a Bruker Ultra
Our group has been extensively working on the design and
synthesis of new Ir(III) and Pt(II)-based complexes.33-35 In our
previous studies, a class of platinum complexes with AIPE
activity based on Schiff base ligands was discovered by
chance.30 In continuing our previous work, herein, we have
designed and synthesized a new series of Pt(ppy)(LX) type
complexes based on Schiff base ligand (LX) structures, aiming at
further systematic exploiting the relationship between the
Schiff base structures and the AIPE properties including the
emission colours, quantum efficiencies, luminescence lifetime
and so on (Scheme 1a). Moreover, a new method of
constructing phosphorescent thermoprobes by incorporating
this kind of AIPE-active Pt(II) complexes into water-soluble
acrylamide-based thermosensitive polymers was proposed
(Scheme 1b). The phosphorescent polymer P1 showed weak
green emission, which was significantly enhanced upon
increasing the temperature from 28 to 40oC because of the
conformational changes of polymer chains from an extended
structure to an aggregated state, leading to an increase in
Shield Plus 400 MHz spectrometer and chemical shifts were
expressed in ppm using Me4Si as an internal standard. Mass
spectra were obtained on a Bruker autoflex matrix-assisted
laser desorption ionization time-of-flight (MALDI-TOF) mass
spectrometer. The UV-vis absorption spectra were recorded
using Shimadzu UV-3600 UV-vis-NIR spectrophotometer.
Photoluminescence spectra were measured on an Edinburgh FL
920 spectrophotometer equipped with
controller. Excited-state lifetime studies were performed with
an Edinburgh FL920 photocounting system with
a temperature
a
semiconductor laser as the excitation source. The absolute
quantum yields of the complexes were determined through an
absolute method by employing an integrating sphere. The
number-average molecular weight (Mn) and weight-average
molecular weight (Mw) of the polymers were characterized in
THF by GPC at 308 K using polystyrene as standard. The average
particle size was measured via DLS on Nano ZS90 with a
temperature controller.
Scheme 1 (a) The chemical structures of AIPE-active Pt(II) complexes, (b) Schematic illustration of constructing and temperature distribution imaging cellular cytoplasm
thermo-sensitive probe using AIPE-active Pt(II) complexes and thermosensitive hydrogel.
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2.2 Synthesis
here have been deposited with the Cambridge Crystallographic
Data Center (Deposition No. 1905320)
The Schiff base ligands were synthesized according to a
procedure modified from that reported in the literature.36
Generally, an EtOH solution dissolved by salicylaldehyde was
2.4 Intracellular temperature distribution imaging
The solutions with different pH, amino acids and anions
added to a stirred EtOH solution of aniline. After adding were prepared from the corresponding nitrate salts or
catalytic amount of AcOH, the reaction mixture was stirred at hydrochloride salts in deionized water. The in vitro cytotoxicity
room temperature for 2 hr. Concentration and subsequent silica toward HepG2 cells was measured using the methyl thiazolyl
gel column purification gave the corresponding ligand. The tetrazolium (MTT, Beyotime) assay. HepG2 cell used for imaging
synthesis of all the Pt(II) complexes was performed according to were first incubated in culture dishes, washed with PBS three
the same procedure.37 Briefly, Pt(II) µ-dichloro-bridged dimers times and then incubated with P1 0.01mg mL-1 PBS. Cell imaging
were synthesized from the starting materials of K2PtCl4 and C^N experiments were then performed with an Olympus IX81 laser
ligand according to the previous report.37 A solution of Pt(II) µ- scanning confocal microscope after washing and covered with
dichloro-bridged dimers, 3 equiv of the Schiff base ligand and PBS. After each temperature change, we waited for about 10
10 equiv of Na2CO3 in 2-ethoxyethanol was heated to reflux for min before starting a new measurement.
16 h. Then the reaction mixture was concentrated under
reduced pressure. Excess of water was added gradually to give
orange or red precipitate of crude product that was
3 Results and discussion
subsequently filtered and washed with water. The obtained
crude product was purified by silica gel column
chromatography, giving the desired complexes in moderate
yields. Thermo-sensitive probe P1 is obtained by general free
radical random copolymerization method.38 The detailed
synthesis and characterization of all the compounds are
provided in the ESI.
3.1 Absorption and photoluminescence properties
The UV-vis absorption spectra of all the ten Pt(II) complexes
were measured at room temperature in CH2Cl2 solution (Fig. 1),
and the detailed electronic absorption data are given in Table 1.
The shape of absorption spectra of all the complexes in CH2Cl2
solution are similar with a relatively wide absorption band and
display intense absorption bands below 300 nm with molar
extinction coefficients of ~10-4, which are assigned to the spin-
allowed ligand-centered 1LC (ligand centered) transitions.
According to the theoretical calculation results (Table S1, S2 and
2.3 X-ray crystallography
The single-crystal of complex 1e was obtained from CH2Cl2
solution mixed with hexane. And the X-ray diffraction data of
complex 1e were collected on a Bruker Smart Apex CCD
diffractometer with graphite monochromated Mo-Kα radiation
(λ = 0.71073 Å). All calculations and molecular graphics were
S3, ESI†), the weak absorption bands at about 350–450 nm can
1
1
be attributed to the spin-allowed MLCT transitions and LLCT
transitions and the weak absorption peak over 450 nm can be
attributed to spin forbidden 3MLCT and 3LC transitions. These
carried out on
a computer using Mercury software.
Crystallographic data (cif files for 1e) for the structure reported
Table 1. Optical data of platinum complexes series 1 and 2.
b
c
Complex
λabs(logε)/nma
λem/nmb
λem/nmc
φem
φem
τb/ns
1a
260 nm (4.79), 311 nm (4.37), 364 nm (4.13),
402 nm (3.93)
259 nm (5.13), 309 nm (4.58), 364 nm (4.53),
400 nm (4.31)
254 nm (4.80), 306 nm (4.30), 364 nm (4.30),
391 nm (4.01), 461 nm (3.48)
255 nm (4.85), 306 nm (4.30), 364 nm (4.16),
397 nm (3.92), 469 nm (3.60)
255 nm (5.15), 307 nm (4.57), 364 nm (4.61),
403 nm (4.22), 462 nm (4.01)
264 nm (4.79), 331 nm (4.24), 364 nm (4.19),
395 nm (4.07), 435 nm (3.95)
263 nm (4.76), 331 nm (4.18), 364 nm (4.15),
399 nm (4.03), 433 nm (3.90)
260 nm (4.84), 312 nm (4.32), 331 nm (4.23),
363 nm (4.21), 395 nm (4.07), 434 nm (3.92)
263 nm (4.90), 312 nm (4.37), 331 nm (4.34),
364 nm (4.35), 397 nm (4.14), 431 nm (4.07)
262 nm (4.98), 311 nm (4.42), 334 nm (4.38),
365 nm (4.51), 405 nm (4.11), 435nm (3.96)
571
567
14%
27%
31%
50%
25%
15%
8%
7%
1484
1b
1c
1d
1e
2a
2b
2c
2d
2e
578
566
580
617
552
578
536
546
567
574
559
571
617
546
572
533
541
567
8%
2114
2149
2944
1270
2021
884
11%
13%
12%
5%
3%
23%
8%
6%
2070
2%
189（26.24%）
674（73.76%）
1219
13%
7%
a In CH2Cl2 (air-saturated). b Pristine crystal. c Ground powder.
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Fig.1 (a) Absorption spectra in CH2Cl2 solution with the concentration of 1 × 10-5 M, photoluminescence spectra in the solid state, and photographs in solution and solid state of
series 1 complexes at the room temperature from left to right respectively. (b) Absorption spectra in CH2Cl2 solution with the concentration of 1 × 10-5 M, photoluminescence spectra
in the solid state, and photographs in solution and solid state of series 2 complexes at the room temperature from left to right respectively.
charge transfer properties of the UV-vis absorption spectra can Among them, 1d exhibits the strongest crystal-state emission
be further confirmed by the phenomena of Uv-vis absorption with the absolute quantum efficiency of 50% at room
spectra changing in different solvents (Fig S1 and S2, ESI†). The temperature (Table 1). Specifically, for series 1, except
variation in substituents on aniline group of Schiff base ligand compound 1e, both the introduction of electron-withdrawing
caused a negligible effect on the absorption spectra of the and electron-donating groups on the structure of aniline cause
complexes. But, interestingly, the change of substituents on ο- a weak red-shift of the solid-state emission spectra, whereas for
hydroxybenzaldehyde group of Schiff base ligand causing series
obvious blue-shift of the absorption spectra band-edge of series introduction
complexes compared with that of series (Fig. 1). hydroxybenzaldehyde group leads to obvious blue-shift of the
2
this effect is more obvious. On the contrary, the
of electron-donating groups on ο-
2
1
Unconventionally, all the complexes showed no obvious solid-state emission, which is similar to those of absorption
luminescence in dilute solution except for 1e and 2e. Although spectra. In addition, compared with the corresponding
the quantum efficiency of 1e and 2e are so low that no obvious compounds in series 1, the complexes of series 2 also exhibit
emission spectra can be tested, the faint emission can still be lower quantum efficiency and shorter lifetime. Particularly, 2b
seen from their CH2Cl2 solution under UV lamp (Fig. 1). This and 2d exhibit the lowest quantum efficiency and shortest
exception may be due to the formation of intramolecular lifetime, which may be due to the Schiff Base and metal centre
hydrogen bond between the fluorine atom on the aniline group dominated excited state properties according to the theoretical
of Schiff base ligand and hydrogen atom on the adjacent ppy calculation results (Table S4, ESI
ligand, which leads to the molecule more rigid and then partly In order to better show this AIPE phenomenon of all the
inhibits the non-radiation transition process caused by the complexes, herein, a commonly used method to compare the
†).
distortion of the molecular structure.
emission intensities of AIE-active fluorophores in THF-H2O
mixture with different H2O fractions was adopted. The addition
of non-solvent water into the dilute THF solutions can turn on
3.2 AIPE properties of the complexes
the PL emission of all the complexes (Fig S4, S5, ESI†). Taking
The room-temperature photoluminescence spectra of all
complexes and their images under UV light (λex = 365 nm) both
in solution and pristine crystal state were recorded and shown
in Fig. 1. As expected, all complexes exhibit the intense emission
at room temperature in solid state. The emission profiles of all
complexes in solid state cover a wide range from green to red,
reflecting that the modification of Schiff base is effective in
tuning the emission color of this kind of AIPE-active complexes.
complex 2c as an example, as shown in Fig. 2, the PL spectrum
in pure THF is undetectable. As the water content increasing
from 0% to 40%, the PL spectra of 2c keep at a low level and
show slowly increase. When the water fraction is above 40%,
the PL spectra of 2c in THF-H2O mixtures are boosted
significantly to yield approximately ten-fold enhancement. All
the other complexes also show the similar phenomenon (Fig. S4,
S5, ESI†)
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high emission quantum efficiency of 25%. To better understand
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this phenomenon, the single crystal of 1e has been obtained
from their CH2Cl2 solution mixed with hexane and characterized
by X-ray crystallography (Table S5, ESI†). The molecular packing
in crystal-state is depicted in Fig. 3, which shows no evident Pt-
Pt and π-π interactions. And this excluded the possibility of the
3
formation of MMLCT states responsible for the crystal-state
emission. By the way, there exists obvious multiple hydrogen
bonding among the fluorine atoms of aniline and the hydrogen
atoms of aromatic ring of the surrounding molecules, showing
strong intermolecular interaction, which is possibly the reason
why 1e displays a longer maximum emission wavelength and
higher quantum efficiency than other compounds.
3.3 Thermo-sensitive polymer P1
Fig. 2 PL spectra of 2c in THF/water mixtures with different fractions (fw). Inset: Variation
in relative PL intensity of 2c with different fractions of water and photographs of 2c in
THF/water with 70% water fractions taken under 365 nm UV light.
Next, the excellent photophysical properties of this kind of
complexes prompted us to study their potential applications in
constructing biosensors based on the AIPE characteristics.
Herein, we introduced complex 1d into poly N-
isopropylacrylamide backbone a thermosensitive polymer,
which can undergo
a reversible lower critical solution
temperature phase transition between a swollen hydrated state
and a shrunken dehydrated state in the temperature range of
about 20 to 40oC,39-41 to construct
a
thermosensitive
phosphorescent probe P1 (Fig. 4, Fig. S8, ESI†) via the synergistic
effects between the temperature-dependent conformational
transition properties of polymer chains and the AIPE properties
of the complexes. The detailed synthetic routes of P1 were
shown in ESI, which was mainly composed of three units,
including the thermosensitive unit, the hydrophilic unit and the
AIPE unit. The photoluminescence response of P1 in PBS buffer
to temperature has been investigated by emission spectral
change (Fig. 4a). With increasing temperature from 28 to 38oC,
P1 displayed emission enhancement owing to the increase in
rigidity of the microenvironment of the AIPE units caused by the
aggregation of polymer chains due to the increase of
hydrophobicity. And the dynamic light scattering (DLS) analysis
also revealed that the hydrodynamic diameter of P1 was
reduced to 100 nm at 14oC but increased to 700 nm at 38oC (Fig.
Fig. 3 Intermolecular interactions in 1e crystal.
The AIPE mechanism of such kind of complexes has been
proposed to be the “restricted distortion of excited-state
structure (RDES)”, which blocks the non-radiative pathways and
generating AIPE activity in the solid state.29 As we all know, the
solid-state photoluminescence properties of organic
luminescent materials are influenced by two factors, one is the
chemical structure of the molecule itself, and the other is the
intermolecular interaction determined by the chemical
structure of both the luminogens and surrounding media. In
order to study the effect of intermolecular interactions on the
properties of AIPE in the crystalline state of this kind of
complexes, we investigated the changes of photoluminescence
spectra of the sample before and after grinding. As shown in
Table 1, the maximum emission wavelengths of all complexes,
except 1e and 2e, show several nanometre blue-shift after
grinding, which may be due to the destruction of the weak π-π
interactions. And after fully grinding, the quantum efficiency of
all complexes showed a significant decrease (Table 1 and Fig. S6
S9, ESI†).
ESI†). To further confirm that the AIPE properties comes from
RDES other than special intermolecular interactions, solid
poly(methyl methacrylate) films doped with different amounts
of 2c were fabricated, which was emissive even at a low content
of 0.5% (Fig. S7, ESI†).
As previously described, 1e exhibits special AIPE properties
with the longest maximum emission wavelength of 617 nm and
Fig. 4 Emission spectra of P1 (0.01 w/v%) in PBS (pH = 7.4) at various temperatures.
Inset: chemical structure of P1
.
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Fig. 6 Confocal laser scanning microscopy images of HepG2 cells labeled with P1
and Mito Tracker Deep Red at 25°C, 30°C, and 35°C. The green channels were
acquired by collecting the luminescence from 450 to 600 nm, while the red
channels were from 650 to 750 nm (excition wavelength was 405nm).
Colocalization analysis of Merged (R= 0.53). Scale bar = 15 µm.
with P1 and mitochondrial tracker was collected from two
separate channels: 450 to 600 nm of the green channels were
acquired by collecting the luminescence from P1, while 650 to
750 nm of the red channels were collected from that of
mitochondrial tracker. The results showed that P1 can
efficiently internalized by the endocytosis of HepG2 cells and
was mainly located in the cytoplasm. The average emission
intensity obtained from HepG2 cells after increasing the
environmental temperature from 25oC to 35oC is summarized in
Fig.6. The luminescence intensity in the green channel
increased with temperature rising, whereas in the red channel
changed slightly. Specifically, when HepG2 cells were incubated
with P1 (0.5 mg/ml prepared in fresh media) for 2 hr at 25oC,
there was weak phosphorescence emission, and an obvious
emission enhancement was observed with increasing
temperature from 25 to 35oC. Interestingly, we found that the
phosphorescence intensity in different regions of the HepG2
cell is various, indicating that the temperature in the different
regions of the cell may be different. By comparing the
luminescence position of P1 and mitochondrial, we further
found that these hotspots were mainly distributed around
mitochondria, which may be due to the fact that the
mitochondrion is the energy provider of the whole cell. The
results indicated that P1 can be used in intracellular
temperature distribution imaging.
Fig. 5 (a) Reversibility of the luminescence response of P1 (0.01 w/v%) to
temperature variation in PBS. (b) Cytotoxicity of P1 on HepG2 cells determined by
MTT assay.
3.4 The application in intracellular temperature distribution
imaging
The potential application of P1 for intracellular temperature
distribution imaging has been evaluated. As shown in Fig. 5a,
the luminescence response of P1 exhibited good reversibility
when the temperature was changed between 28 and 38oC
repeatedly. Considering that cytotoxicity is a key issue that
limits the application of luminescence probes in living organism,
the cytotoxicity of P1 toward HepG2 cells at various
concentrations was evaluated by the 3-(4,5-dimethyl-2-
thiazolyl)-2,5-diphenyltetrazolium bromide (MTT) assay.42 Even
if the concentration of P1 is 0.5 mg/mL and incubated for 2 hr,
the cell viability is still close to 100% (Fig. 5b), which
demonstrated its good biocompatibility. Besides that,
considering the complexity of intracellular environment, further
investigation to verify the stability of photoluminescence of P1
in different intracellular species has been conducted. The
experiments demonstrated that P1 has good stability under
different pH, amino acid and ion conditions condition, which
also lay the foundation for its application in the field of living
4. Conclusions
In summary, two series of cyclometalated Pt(II) complexes
Pt(ppy)(LX) were successfully synthesized under mild
conditions, all of them have significant AIPE properties with long
emission lifetime and high solid state quantum efficiency. The
emission color could be easily tuned from yellow to red by
simply changing the electron withdrawing ability of the
substituent group in the N^O ligands. By studying the emission
cell detection (Fig. S11, ESI†).
The use of P1 for intracellular temperature distribution
imaging was demonstrated via confocal laser scanning
microscopy upon excitation at 405 nm. The ambient
temperature was controlled using a heating stage and digital
thermocouple. The colorful imaging of the HepG2 cells labelled
properties in their solid state, we found all series
2 shown
different degree hypochromatic shift and lower quantum
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20 X.-G. Hou, Y. Wu, H.-T. Cao, H.-Z. Sun, H.-B. Li, G.-G. Shan and
Z.-M. Su, Chemical Communications, 2014, 50, 6031-6034.
21 Y. Wu, H.-Z. Sun, H.-T. Cao, H.-B. Li, G.-G. Shan, Y.-A. Duan, Y.
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efficiency compared with series
methoxyl group at the 4th position of the Schiff base ligand.
Particularly, we have developed novel water-soluble
1 because of the existence of
a
thermosensitive probe P1 by incorporating this kind of AIPE
luminogen in N-isopropylacrylamide hydrogel, which showed
good biocompatibility and stability and could be applied to
intracellular temperature distribution imaging. To the best of
our knowledge, this is the first example of using AIPE luminogen
to construct thermosensitive luminescent probe. In the future
work, efforts will be made to optimize the polymer
configuration and polymerization methods to prepare more
efficient and stable high-resolution temperature-sensitive
probe.
22 Q. Zhao, C. Huang and F. Li, Chem. Soc. Rev., 2011, 40, 2508-
2524.
23 K. Y. Zhang, Q. Yu, H. J. Wei, S. J. Liu, Q. Zhao and W. Huang,
Chem. Rev., 2018, 118, 1770-1839.
Conflicts of interest
There are no conflicts to declare.
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1991, 111, 145-152.
25 V. W. W. Yam, K. M. C. Wong and N. Y. Zhu, J. Am. Chem. Soc.,
2002, 124, 6506-6507.
Acknowledgements
This work was supported by the National Natural Science
Foundation of China (21504040). Natural Science Foundation of
Jiangsu Higher Education Institutions (15KJB150012). The
National Science Foundation of China (81672508). China-
Sweden Joint Mobility Project (51811530018). The National Key
Basic Research Program of China (973 Program,
2015CB932200). We are grateful to the High Performance
Computing Center of Nanjing Tech University for supporting the
computational resources.
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Journal of Materials Chemistry C
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DOI: 10.1039/C9TC01905G
Table of Contents
Two series of AIPE-active platinum(II) complexes with tunable photophysical properties were
synthesized and their application in constructing thermosensitive probes was demonstrated.