Rational design of novel near-infrared fluorescent DCM derivatives and their application in bioimaging

Article abstract of DOI:10.1039/c6tb01096b

The development of innovative strategies for high-performance near-infrared (NIR) fluorescent materials is in urgent demand for bioimaging. By replacing the stronger electron-withdrawing groups or extending the π-conjugated system, novel NIR fluorescent materials of DCM analogues have been developed, along with several striking characteristics: bright NIR fluorescence over 700 nm, large Stokes shift and good photo-stability. It is demonstrated that introducing a stronger electron-withdrawing unit to the acceptor moiety of DCM analogues is a favourably efficient strategy to tune and prolong the emission wavelength into the NIR region with a large Stokes shift. In comparison with the commercial NIR dye ICG, S-DCM-N and S-DCM-P display excellent photostability and low photobleaching. The large Stokes Shift and NIR fluorescence channel of S-DCM-N and S-DCM-P are very favourable for fluorescence labelling with a high signal-to-noise ratio in living species.

Full text of DOI:10.1039/c6tb01096b

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Rational design of novel near-infrared fluorescent DCM derivatives
and its application for bioimaging†
Xiaohang Wang,a Zhiqian Guo,*a,c Shiqin Zhu,a Yajing Liu,b Ping Shi,b He Tiana and Wei-Hong Zhu*a
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
The development of innovative strategies for high-performance near-infrared (NIR) fluorescent materials is in
urgent demand for bioimaging. By replacing the stronger electron-withdrawing groups or extending the π-
conjugated system, novel NIR fluorescent materials of DCM analogues have been developed, along with
several striking characteristics: bright NIR fluorescence over 700 nm, large Stokes shift and good photo-
stability. It is demonstrated that introducing stronger electron-withdrawing unit to the acceptor moiety of
DCM analogues is a favourably efficient strategy to tune and prolong emission wavelength into NIR region with
large Stokes shift. In comparison with the commercial NIR dye ICG, S-DCM-N and S-DCM-P display excellent
photostability and low photobleaching. The large Stokes Shift and NIR fluorescence channel of S-DCM-N and
S-DCM-P can be greatly favourable for fluorescence labelling with a high signal-to-noise ratio in living species.
www.rsc.org/
Some typical NIR fluorophores such as cyanines,5
squaraines,6 rhodamine analogues,7 and BODIPYs8 have been
employed for screening important biomolecules. However, so
far, the rational design of high-performance NIR fluorescent
Introduction
Utilizing optical chromophores as imaging contrasts have
become one of the most powerful tools for non-invasive
visualization of biological processes due to its high sensitivity,
low-cost and high spatialtemporal resolution.1 To date, there is
still a continuous interest in exploring novel high-performance
fluorophore units for in vivo monitoring important biological
species.2 In particular, near-infrared (NIR)-active fluorophores
are preferable as in vivo optical imaging contrasts because NIR
emission can greatly favourable for decreasing tissue
absorption and minimum interference background during
molecular bioimaging processes.3 However, it is still a challenge
for utilizing the established NIR fluorophores to capture valid
signals in molecular imaging process given that most of them
suffer from low photo-stability and severe cross-talk between
the excitation and emission spectra. Therefore, the
development of innovative strategies for NIR fluorescent
materials is in urgent demand for bioimaging.4
materials with large Stokes shifts are still scarce, and probably
ascribing to the difficulties in molecular design and structural
modifications.9 Specifically, the energy band gap from
molecular orbitals in fluorophores are usually difficult to
accurately determine,10 which would lead to the poor
prediction of photo-physical performance in building up
fluorescent materials. In general, extending π-conjugated
frameworks or optimizing the combination of an electron donor
(D) and an acceptor (A) would be usually preferred
consideration for the rational molecular design of NIR
fluorescent materials.11
Recently,
a myriad of dicyanomethylene-4H-chromene
(DCM) as well as its derivatives have been exploited as
fluorescent sensors, logic gates, and photovoltaic sensitizers.12
Generally, DCM is composed of an electron-withdrawing group
(EWG), a π-conjugated linker and an electron-donating group
(EDG), contributing as a typical push-pull system. The priority
strategy to extend the emission wavelength of DCM derivatives
is by introducing stronger electron donor group. However,
traditional modification of electron donors will seriously restrict
the versatile molecular strategy for NIR fluorescence DCM
materials. In this work, we focus on the substituted acceptors
of DCM analogues by replacing the stronger EWG or extending
the π-conjugated system via attaching additional aromatic rings
(Scheme 1), thus narrowing the band energy gap and
modulating its emission completely into the NIR region.
Decorated with the strong electron-withdrawing unit of
tricarbonitrile group is afforded to S-DCM-N and S-DCM-P, and
incorporated aromatic rings into pyran unit to extend its
a Key Laboratory for Advanced Materials and Institute of Fine Chemicals, Shanghai
Key Laboratory of Functional Materials Chemistry, Collaborative Innovation
Center for Coal Based Energy (i-CCE), School of Chemistry and Molecular
Engineering, East China University of Science and Technology, Shanghai 200237,
China
b
State Key Laboratory of Bioreactor Engineering, East China University of Science
and Technology, Shanghai 200237, China
State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian
c
116024, China
*E-mail: guozq@ecust.edu.cn; whzhu@ecust.edu.cn
Electronic Supplementary Information (ESI) available: Reagents and instruments,
synthesis procedures, 1H, 13C NMRand HRMS information, and crystallographic
data for S-DCM-N [CCDC 1472796] are available. See DOI: 10.1039/x0xx00000x
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aromatic system is obtained as C-DCM-N. These two developed yellow oil was purified by silica column chromatography (ethyl
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DOI: 10.1039/C6TB01096B
fluorescent materials of S-DCM-N and S-DCM-P bestows several acetate: petroleum ether = 1 : 1, V/V) to obtain a yellow power
1
striking characteristics, such as high brightness NIR fluorescence (710 mg), yield 51%. H NMR (400 MHz, CDCl3, ppm): δ 4.03 (s,
over 700 nm with large Stokes shift, and enhanced photo- 2H, -CH2-), 7.69-7.54 (m, 5H, Ph-H). 13C NMR (100 MHz, CDCl3,
stability than commercially available NIR dyes like ICG. ppm): δ 25.26, 88.25, 111.31, 111.49, 127.84, 129.71, 132.24,
Furthermore, S-DCM-N and S-DCM-P was successfully applied 133.68, 165.31. Mass spectrometry (ESI-MS, m/z): calcd. for
for labelling cancer cells, showing feasible potential in biological [C12H7N3 − H]¯, 192.0562; found, 192.0563.
application. More importantly, it was demonstrated that the
introducing stronger electron-withdrawing unit to the acceptor
Synthesis of 3
moiety of DCM analogues is a favourably efficient strategy to A mixture of 2 (275 mg, 1.42 mmol) and 4 (249 mg, 1.45 mmol)
modulate and prolong emission wavelength into NIR region was dissolved in acetic anhydride (20 mL) and then heated at
o
with large Stokes shift.
120 C for 6 h. During the heating process, the mixture was
gradually turned from yellow into dark orange. The solvent was
removed by rotary evaporation and then the product was
purified by silica column chromatography (dichloromethane:
petroleum ether = 2 : 1, V/V) to afford an orange powder (150
mg), yield 35%. 1H NMR (400 MHz, CDCl3, ppm): δ 2.25 (s, 3H, -
CH3-), 2.36 (s, 3H, -CH3-), 5.96 (s, 1H, alkene-H), 6.79 (s, 1H,
alkene-H), 7.55-7.47 (m, 2H, Ph-H), 7.64-7.54 (m, 3H, Ph-H). 13
C
NMR (100 MHz, CDCl3, ppm): δ 19.04, 19.11, 84.32, 107.22,
108.82, 112.87, 113.68, 116.44, 128.39, 129.14, 131.94, 133.43,
152.36, 161.99, 163.15, 166.70. Mass spectrometry (ESI-MS,
m/z): calcd for [C19H13N3O + H]+, 300.1137; found, 300.1130.
Scheme 1. Rational molecular engineering strategy for extending emission
wavelength with the building block of DCM chromophore.
Synthesis of S-DCM-N and S-DCM-P
3 (108 mg, 0.36 mmol) and 4-(dimethyl amino)benzaldehyde
(150 mg, 0.96 mmol) were dissolved in anhydrous toluene (15
mL), then piperidine (1.0 mL) and acetic acid (0.5 mL) was added
into the aforementioned mixture. The solution was stirred and
Experimental
Materials and instruments
o
heated at 120 C for 8 h, while the solution color was changed
Unless otherwise noted, all reagents were purchased from
commercial suppliers were used without further purification. All
solvents were of analytical grade or purified using standard
methods prior to use. Deionized water was used to prepare all
aqueous solutions. The 1H and 13C NMR spectra were recorded
on a Bruker AV-400 spectrometer, using with tetramethylsilane
(TMS) as internal standard. High Resolution Mass Spectra
(HRMS) were obtained by
spectrometer. Absorption spectra were measured on a Varian
Cary 500 spectrophotometer at 25 °C. Emission spectra were
from orange to dark blue. Then the solution was cooled to room
temperature and filtered to get the crude product, which was
purified by silica column chromatography (eluent solvent,
dichloromethane: methanol = 100 : 1, V/V) to get solid S-DCM-
1
N as a green powder (86 mg), yield 42%. H NMR (400 MHz,
CDCl3, ppm): δ 3.07 (s, 12 H), 6.65-6.45 (broad, 2H), 6.71 (d, J =
8.8 Hz, 4H), 7.78-7.42 (m, 13 H). 13C NMR (100 MHz, CDCl3,
ppm): δ 40.17, 73.42, 85.40, 111.98, 113.19, 114.91, 115.86,
118.56, 122.49, 129.31, 129.85, 130.43, 132.47, 135.47, 138.76,
151.90, 153.18, 167.65. Mass spectrometry (ESI-MS, m/z):
calcd. for [C12H7N3 + H]+, 562.2607; found, 562.2620.
a Waters LCT Premier XE
recorded on
a
Varian Cary Eclipse fluorescence
spectrophotometer (1 cm quartz cell) at 25 °C. Cell imaging was
performed with Nikon confocal microscope (Nikon Eclipse Ti).
TLC analysis was performed on silica gel plates and column
chromatography was conducted over the silica gel (mesh 200–
300), both of which were obtained from the Qingdao Ocean
Chemicals. The stock solution of S-DCM-N and S-DCM-P were
prepared in DMSO and CH2Cl2.
S-DCM-P was synthesized using the similar procedure as the
1
synthesis of S-DCM-N. H NMR (400 MHz, CDCl3, ppm): δ 6.00
(s, 1H), 6.41 (d, J = 14.4 Hz, 1H), 6.65 (d, J = 16.0 Hz, 1H), 6.92 (s,
1H), 7.03 (s, 4H), 7.16-7.10 (m, 12H), 7.40-7.28 (m, 14H), 7.55-
7.51 (m, 2H), 7.62-7.58 (m, 3H). 13C NMR (100 MHz, CDCl3,
ppm): δ 75.52, 86.48, 108.63, 110.13, 114.41, 115.26, 115.81,
118.07, 121.41, 124.36, 125.60, 127.38, 129.14, 129.39, 129.57,
130.35, 132.73, 135.05, 137.70, 146.63, 150.13, 152.26, 158.99,
160.07, 167.46. Mass spectrometry (ESI-MS, m/z): calcd. for
[C57H39N5O + H]+, 810.3233; found, 810.3232.
Synthesis of 2
In a 50 mL three-necked flask, benzoyl acetonitrile 1 (1.04 g,
7.16 mmol), malononitrile (473 mg, 7.16 mmol), and pyridine
(30 mL) as a solvent were added. After the mixture was heated
at 90 oC for 2 h under a N2 atmosphere, the solution was
removed by rotary evaporation. The dark yellow residue was
dissolved in dichloromethane (50 mL), then washed with
deionized water (3 × 100 mL), and dried over Na2SO4. After
removing organic solvents by rotary evaporation, the dark
Cell culture and imaging using S-DCM-N and S-DCM-P
Human cancer cells SMMC-7721 were supplied by the Institute
of Cell Biology (Shanghai, China). The cell lines of SMMC-7721
o
were cultured at 37 C under a humidified 5% CO2 atmosphere in
RPMI-1640 medium (GIBCO/Invitrogen, Camarillo, CA, USA), which
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were supplemented with 10% fetal bovine serum (FBS, Biological Specifically, to increase electron withdrawing capability of DCM
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Industry, Kibbutz Beit Haemek, Israel) and 1% penicillin-streptomycin derivatives, dicyan and tricyan units areDeOqI:u1i0p.p10e3d9/wC6itThB0p1y09ra6Bn
(10,000 U/ml penicillin and 10 mg/ml streptomycin, Solarbio life rings. Alternatively, a benzene unit or a tetrahydronaphthalene
science, Beijing, China). The cells were plated in 35 mm glass- unit to dicyanopyran moiety is attached for extending the π-
bottom culture dishes and allowed to adhere for 24 h. Before conjugation systems (Scheme 2). The key intermediates 2, 4, 5
the experiments, the cells were washed with PBS buffer and
6 were synthesized according to the established
immediately. The cells were further incubated with S-DCM-N procedures.5,12a,13 These intermediates were further treated
o
and S-DCM-P in the culture medium for 60 min at 37 C, and with malononitrile to generate various strong acceptors for
imaged using a Nikon confocal microscope (Nikon Eclipse Ti).
DCM analogues in acetic anhydride. Finally, the target DCM
derivatives were obtained by the Knoevenagel reaction of 4-
dimethylaminobenzaldehyde
and
4-(diphenylamino)
Results and discussion
benzaldehyde as electron-donating groups, respectively, with
these strong acceptors (3, 7, 8, 9) in the presence of acetic acid,
piperidine and toluene with concomitant removal of water.13 All
Design and synthesis
To establish a rational design strategy for extending the
traditional DCM chromophore from red to NIR emission, two
novel alternative strategies were developed to regulate their
optical properties: one has been performed by decorated with
the stronger electron-withdrawing unit rather than traditional
malononitrile; the other is incorporated aromatic rings into
pyran ring to extend its π-conjugated system (Scheme 1).
these chemical structures were characterized by H, 13C NMR,
1
and HRMS. Clearly, in the 1H NMR spectra of these DCM
derivatives, the characteristic coupling constant (J = 16.0 Hz) of
alkene protons were indicative of the predominated trans-
isomer.
Scheme 2 Synthetic routes for DCM analogues
According to one-dimensional nuclear magnetic resonance In this case, two-dimensional nuclear magnetic resonance
(1H NMR) spectra, it was still difficult to confirm and spectra, the 1H-1H COSY and NOESY experiments were
characterize the chemical structures of S-DCM-N and S-DCM-P. conducted in CDCl3 for the further characterization of S-DCM-N
For instance, in the 1H NMR spectrum of S-DCM-N, it was (Figs. S1 and S2 in the Electronic Supplementary Information,
initially anticipated that the proton signals from –CH3 of 3 would ESI†). Obviously, the singlet peak at δ = 3.07 ppm was assigned
1
disappear and then a new group of alkene-H signals could be to the proton H1 (-NCH3). In the both H-1H NOESY and COSY
observed similarly as the typical DCM analogous. However, spectra, a strong correlation between H1 and the doublet peak
there was only a broad signal centred at 6.5 ppm which should at δ = 6.71 ppm was observed, suggestive that the doublet peak
be ascribed to alkene-H and the stacking of proton signals should be assigned to the proton (H2) of the benzene ring.
during the chemical shift of 7.0-7.4 ppm, making it difficult to Similar, according to the proton-proton coupling constant and
clearly assign the protons of S-DCM-N in the 1H NMR spectrum. the correlations in the NOESY and COSY spectra, the doublet
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peak at δ = 7.45 ppm was assigned to the proton (H3) of the
same aromatic ring as that of the proton (H2). It was noteworthy
that in the NOESY spectrum, there was also an obvious
correlation between the peak (H3) at δ = 7.45 ppm and the
broad peak at 6.65-6.45 ppm, which should be assigned to the
alkene-H protons (H4) neighbouring the aromatic ring.
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DOI: 10.1039/C6TB01096B
Fig. 2 Normalized absorption (a) and emission (b) spectra of DCM analogues
in CH2Cl2.
Table 1 Photophyscial properties of DCM analogues in CH2Cl2 (1 × 10-5 M)
λmax (nm)
ε (M-1 cm-1)
λem (nm)
Φf (%)
S-DCM-N
S-DCM-P
DCM-N
580
568
485
474
515
505
482
38350
37300
42800
20200
35200
34500
36500
732
728
627
632
635
660
618
4.62
3.52
54.87
25.21
59.58
32.37
40.36
DCM-P
Fig. 1 X-ray crystal structure of S-DCM-N and its molecular staging diagram.
B-DCM-N
B-DCM-P
C-DCM-N
1
The serious overlap of chemical shift signal in the H NMR
spectra is still a hurdle to well elucidate the chemical structure
of S-DCM-N. Fortunately, the X-ray single crystal of S-DCM-N
was obtained by the method of slow evaporation from pure
CH2Cl2 solution, which gave us a chance to insight into the
molecular configuration of S-DCM-N. As shown in Fig. 1, the
bond length of C18-C19 and C28-C29 (1.338 and 1.339 Å) indicated
the formation of a double-bond connecting the donor and
acceptor moieties. Here the double-bond in S-DCM-N keeps an
trans conformation, the torsion angles (-178.3o, C5-C18-C19-C20; -
177.2o, C1-C28-C29-C30) and the small dihedral angle (2.84o and
3.00o) between aromatic ring and pyran unit. The benzene ring
of tricyanopropene moiety was appreciably distorted from
planarity, as evidenced by dihedral angles (71.69o).
Furthermore, the cyano group has a torsional of 0.4o and 4.5o
from the pyran unit. The molecular conformation was almost
planar in the ground state, which corresponds to the maximum
conjugation between donor and acceptor. More details of the
single crystal could be found in the ESI†.
Photophysical properties
These DCM analogues bestows broad absorption and
fluorescence bands like typical donor–π–acceptor (D–π–A)
structured chromophores (Fig. 2). As expected, S-DCM-N and S-
DCM-P exhibits a large bathochromic shift in the absorption and
emission spectra, respectively, with respect to DCM-N and
DCM-P. As shown in Fig. S3 (ESI†), S-DCM-N and S-DCM-P
exhibited blue and purple colour in CH2Cl2, respectively.
Specifically, with respect to DCM-N, the S-DCM-N displayed
both large bathochromic shift over 100 nm in the absorption
and emission spectra (Fig. 2). Correspondingly, the emission
band of S-DCM-N centred at 732 nm was largely red-shifted,
thus falling into the NIR region. To further understand
photophysical properties, the absorption and emission spectra
of S-DCM-N and S-DCM-P were evaluated in various solvents
and summarized in Table 1 and Fig. S4 (ESI†). The absorption
band of S-DCM-N was shifted from 566 nm to 590 nm with
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increasing solvent polarity, indicative of the presence of an disappeared sharply to 2% of the initial value VwiewithAritnicle8O0nlinse,
DOI: 10.1039/C6TB01096B
intramolecular charge transfer process (Table S3 and Fig. S4 in indicative of the almost complete decomposition of ICG.
ESI†). Similar spectral features have been found from S-DCM-P Moreover, S-DCM-N and S-DCM-P dissolved in CH2Cl2 retained
and DCM-P. Unexpectedly, C-DCM-N exhibited a short-emissive a strong fluorescence emission after a 3-week storage under
spectral properties similar with DCM-N, probably due to the ambient conditions with daylight exposure. Their remarkable
non-planar structure of the introduced part with the pyran photostability makes them more suitable for the further
moiety, which fails to extend the π-conjugation.
biological application.
To gain insight into molecular design and structural
modifications, electrochemical measurements were carried out
for the energy band gap from molecular orbitals to predict the
photophysical performance of fluorescent materials. The cyclic
voltammetry results of DCM analogues were investigated in
CH2Cl2 at room temperature containing TBAPF6 as the supportive
Bioimaging in living cells
Considering the low background and deep tissue penetration of the
NIR fluorescence, S-DCM-N and S-DCM-P are more suitable for
bioimaging than the traditional DCM dyes. We further explored
whether these novel DCM analogues could be used for bioimaging,
especially in taking advantage of the NIR fluorescence. Human
hepatocarcinoma cell line SMMC-7721 were chosen as model
cell lines to evaluate the capability of DCM analogues in NIR
bioimaging. Confocal laser scanning microscopy was employed
to observe SMMC-7721 human hepatoma cells incubated with
S-DCM-N and S-DCM-P. As shown in Fig. 4b and 4e, the clear
fluorescence images were captured in the intracellular location
after 1 h of incubation, suggestive of their good cell-permeable
property. The strong fluorescence signals at 660−737 nm were
collected, clearly indicating that the large Stokes Shift and NIR
fluorescence channel of S-DCM-N and S-DCM-P can be greatly
favorable for fluorescence labelling with a high signal-to-noise
ratio in living species. The excellent bioimaging properties could
promote us to explore the in vivo application.
electrolyte (Fig. S6 in ESI†) and summarized in Table 2. As shown in
Table 2, the HOMO levels were found 0.86, 1.16, 0.87 and 1.16 V (vs.
NHE) for S-DCM-N, S-DCM-P, DCM-N and DCM-P, respectively.
Electrochemical energy band gaps (E0-0) for each dye were 1.90, 1.93,
2.19 and 2.23 V. Accordingly, the LUMO levels were calculated to be
-1.04, -0.77, -1.32 and -1.07 V, respectively. Thus, incorporation of
the more electron withdrawing moiety indeed lead to a decrease of
LUMO levels, along with a narrow energy band gap of the DCM
chromophore, which is in good correlation with a redshift of the
absorption and emission spectra.
Table 2 Electrochemical properties of DCM analogues
Dyes
HOMO (V)
E0-0 (V)
LUMO (V)
S-DCM-N
S-DCM-P
DCM-N
0.86
1.16
0.87
1.16
1.90
1.93
2.19
2.23
-1.04
-0.77
-1.32
-1.07
DCM-P
ICG
S-DCM-N
S-DCM-P
1.0
0.8
0.6
0.4
0.2
0.0
Fig. 4 Confocal fluorescence images of SMMC-7721 cells incubated with S-
DCM-N (10 μM, a, b and c) and S-DCM-P (10 μM, d, e and f) for 1 h (S-DCM-
N and S-DCM-P were stocked in DMSO, then diluted with PBS buffer solution
pH=7.4 and the final aqueous solution was containing 0.1% DMSO). (a) and
(d) bright field; (b) and (e) λex = 560 nm, the channels were obtained from 660-
737 nm; (c) and (f) overlapped image generated from (a) and (b), (d) and (e).
0
100
200
300
Time (s)
400
500
600
Fig. 3 Time-dependent fluorescence intensity of 10 μM ICG (monitored at
812 nm, and excited at 780 nm), S-DCM-N (monitored at 725 nm and excited
at 580 nm), S-DCM-P (monitored at 725 nm and excited at 580 nm) in CH2Cl2
under portable UV illumination.
Conclusions
We have successfully developed a series of high-performance
DCM derivatives by replacing the stronger electron-
withdrawing groups or extending the π-conjugated system via
introducing a benzene unit or a tetrahydronaphthalene unit to
dicyanopyran moiety. These luminescent materials bestows
several preferable characteristics such as high permeability,
brightness NIR fluorogenic character and good photostability.
As demonstrated, introducing a stronger electron-withdrawing
The photo-stability of S-DCM-N and S-DCM-P in CH2Cl2 were
investigated under the irradiation of a 254 nm light in the
presence of air. In comparison with the commercial NIR dye ICG,
S-DCM-N and S-DCM-P displayed excellent photostability under
the irradiation of UV light. As shown in Fig. 3, the results showed
that over 90% of the initial fluorescence intensity of S-DCM-P
was retained after 420 s, while the fluorescence of ICG
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Sci., 2014, 5, 2804–2808; (i) K. Luo, Y. Yang and Z. Z. Shao, Adv. Funct.
tricarbonitrile group unit to the acceptor moiety of DCM
analogues is a priority strategy to tune and prolong emission
wavelength into NIR region with large Stokes shift.
Furthermore, S-DCM-N and S-DCM-P was successfully applied
for labelling cancer cells, showing feasible potential in biological
application. Our aim in future is the development of multi-
functional NIR fluorescent materials with high florescence yield
based on the novel DCM-based fluorophores for bioimaging
application.
View Article Online
Mater., 2016, 26, 872–880.
DOI: 10.1039/C6TB01096B
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5
6
Acknowledgements
This work was supported by NSFC for Creative Research Groups
(21421004), Distinguished Young Scholars (21325625),
NSFC/China, the Oriental Scholarship, Scientific Committee of
Shanghai (14ZR1409700 and 15XD1501400), Shanghai Pujiang
Program (13PJD010), the Fok Ying Tong Education Foundation
(142014), the Fundamental Research Funds for the Central
Universities (222201313010), and Programme of Introducing
Talents of Discipline to Universities (B16017) and the State Key
Laboratory of Fine Chemicals (KF1509).
7
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Journal of Materials Chemistry B
View Article Online
DOI: 10.1039/C6TB01096B
Rational design of novel near-infrared
fluorescent DCM derivatives and its
applicaꢀon for bioimaging†
Xiaohang Wang, Zhiqian Guo,* Shiqin Zhu, Yajing Liu, Ping
Shi, He Tian and Wei-Hong Zhu*
Tailoring wavelength to NIR emssion is realized by
replacing the stronger electron-withdrawing groups or
extending the π-conjugated system based on DCM
chromophore, along with benificial characteristics such as
bright NIR fluorescence, large Stokes shift and low photo-
bleaching.