A novel triphenylamine-BODIPY dendron: Click synthesis, near-infrared emission and a multi-channel chemodosimeter for Hg2+ and Fe3+

Article abstract of DOI:10.1039/c6tb02469f

A novel triphenylamine-BODIPY based Schiff base fluorescent probe (TPA-BODIPY-OH) with an emission in the near-infrared (NIR) region was designed and prepared by click reaction. TPA-BODIPY-OH showed three emission bands at 510 nm, 598 nm and 670 nm, and can detect Fe³⁺ and Hg²⁺ ions with remarkable fluorescence enhancement in THF/H₂O (v/v, 1:1, buffered with 10 mM HEPES pH = 7.4) based on the hydrolysis reaction of the -CN bond, and naked eye detection was realized with an obvious color change. The stoichiometry between the probe and ions was deduced from a Job's plot, which is 1:3 for TPA-BODIPY-OH/Fe³⁺ and 1:2 for TPA-BODIPY-OH/Hg²⁺, respectively. The dissociation constant value was found to be 1.35 × 10^-16 M for TPA-BODIPY-OH/Fe³⁺ and 2.06 × 10^-11 M for TPA-BODIPY-OH/Hg²⁺. The low detection limit was calculated from the titration results with the values of 5.15 × 10^-7 M for TPA-BODIPY-OH/Fe³⁺ and 6.81 × 10^-7 M for TPA-BODIPY-OH/Hg²⁺, respectively. In order to investigate the biological applications of TPA-BODIPY-OH, a living cell imaging experiment was carried out. The results demonstrate that TPA-BODIPY-OH can be successfully applied as a bioimaging agent in living cells. In addition, amino-group-functionalized silica fluorescent nanoparticles (FNPs) encapsulating the TPA-BODIPY-OH dyes were prepared and characterized by transmission electron microscopy. TPA-BODIPY-OH/SiO₂ nanoparticles exhibit good dispersibility, and the quantum yield of FNPs at 657 nm was 42.3%.

Full text of DOI:10.1039/c6tb02469f

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Page 1 of 12
Journal of Materials Chemistry B
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A Novel Triphenylamine-BODIPY Dendrons: Click Synthesis, Near-infrared Emission
2
+
3+
and Multi-channel Chemodosimeter for Hg and Fe
2
+
3+
A novel near-infrared emission triphenylamine-BODIPY dendrons for Hg , Fe detection,
fluorescent nanoparticles and living cell imaging.

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ARTICLE
A Novel Triphenylamine-BODIPY Dendrons: Click Synthesis, Near-
2
+
infrared Emission and Multi-channel Chemodosimeter for Hg
and Fe
3+
Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
Bao-xing Shen and Ying Qian*
www.rsc.org/
A novel triphenylamine-BODIPY based Schiff base fluorescent probe (TPA-BODIPY-OH), with an emission in near-infrared
region (NIR) was designed and prepared by click reaction. TPA-BODIPY-OH showed three emission bands at 510 nm, 598
3+
2+
2
nm and 670 nm, which can detect the Fe and Hg ions with remarkable fluorescence enhancement in THF/H O (v/v, 1:1,
buffered with 10 mM HEPES pH=7.4) based on the hydrolysis reaction of -C=N bond, and naked eye detection was realized
with the obvious color change. The stoichiometry between probe and ions was deduced from Job’s plot showed 1 : 3 for
3
+
2+
-
TPA-BODIPY-OH/Fe and 1 : 2 for TPA-BODIPY-OH/Hg , respectively. Dissociation constant value was found to be 1.35×10
16
3+
-11
2+
M for TPA-BODIPY-OH/Fe and 2.06×10 M for TPA-BODIPY-OH/Hg . Low detection limit was calculated from titration
-7
3+
-7
2+
results with the value were 5.15×10 M for TPA-BODIPY-OH/Fe and 6.81×10 M for TPA-BODIPY-OH/Hg , respectively.
In order to investigate the biological applications of TPA-BODIPY-OH, living cell imaging experiment was carried out. The
results demonstrate that TPA-BODIPY-OH can be successfully applied as a bioimaging agent in living cells. In addition,
amino-group-functionalized silica nanoparticles (Si-NPs) encapsulating the dyes TPA-BODIPY-OH (fluorescent nanoparticles
FNPs) was prepared and characterized by transmission electron microscopy. TPA-BODIPY-OH/SiO
good dispersibility, the quantum yield of FNPs at band 657nm was 42.3%.
2
nanoparticles exhibit
have advantageous optical characteristics, such as high
extinction coefficients, high fluorescence quantum yields,
narrow emission bandwidths and relatively high
1
. Introduction
In recent years, there has been a tremendous surge in the
development of reaction-based molecular probes rather than
1
5-17
photostabilities
. Therefore, BODIPY dyes are considered
8-22
1
1
,
2
useful in a variety of research fields
. On account of the
traditional lock-and-key molecular recognition strategy
.
original BODIPY (4, 4-difluoro-4-bora-3a, 4a-diaza-s-indacene)
emits at a relatively short wavelength (around 500 nm),
various approaches have been presented to obtain NIR-
These probes undergo target analytes-assisted irreversible
chemical reactions, coupled with amplified signal transduction.
In most cases, reactive probes display larger spectroscopic
changes than traditional chemical probes, owing to the
significant structural changes to the molecular probe during
the analyte-triggered chemical transformation. In addition,
compared with the fluorescence in the visible light range,
fluorescent dyes emitting in the near-infrared (NIR) spectral
2
3
emitting BODIPY derivatives . An efficient way to red-shift the
maximum absorption and emission is to extend the conjugated
π-system of the BODIPY dyes. So far, the modification reported
included the introduction of π-conjugation substituents such
2
4, 25
26-28
29-31
as ethyneyl
, vinyl
and aromatic groups
onto the 1,
3
-8
7- and 3, 5-positions of BODIPY core. On the other hand,
multichannel sensors that can show responses towards target
analytes have also attracted considerable interest in recent
years because of their particularly favorable features such as
high sensitivity, selectivity, and convenient visible emission
region (650 nm - 900 nm) is gaining momentum . Because of
the NIR-emitting probes tend to reduce photodamage to
biological samples, have deeper tissue penetration, and
minimize background fluorescence as well as the
9
, 10
environmentally-induced light scattering
emitting fluorescent compounds are of considerable interest in
. Therefore, NIR-
3
2
assays due to improved signal-to-noise ratio . It is easy to
understand that the detection of multiple targets with single
sensor is more efficient and less expensive than a one-to-one
analysis method and will attract more and more attention.
However, colorimetric and fluorescent sensors which could be
used for the multichannel monitoring of different metal ions
1
1-14
chemical and biological fields
.
Boron dipyrromethene (BODIPY) fluorescent dyes generally
3
3-35
are rare
As we all known, many metal ions have strong influence on
.
2
biological and environment, especially mercury (Hg ) and iron
+
3
ions (Fe ). Accumulation of mercury in the human body can
+
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cause a wide variety of diseases such as prenatal brain
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DOI: 10.1039/C6TB02469F
Journal Name
HO
3
6
damage, serious cognitive and motion disorders . Although
Schiff base condensation
3
+
Site1
N
Fe is an essential element in the human body, however high
doses of iron ions are dangerous and can be toxic because of
their ability to promote oxidation of lipids, proteins and other
F
B
N
F
B
N
N
N
F
F
Click reaction
N
N
N
N
N
3
7-40
N
O
O
cellular components
. Significant effort has been made by
N
Site1
scientists toward the development of highly sensitive
N
2
dosimeters for Hg and Fe , the majority of them are base on
+
3+
4
1
42
43
HO
perylene bisimide , rhodamine , naphthalimide and so on.
However, most of them exhibit changes only in fluorescence
intensity and the response time is long. What’s more, there is
only a few reports about fluorescence sensors that can realize
the near infrared emission, especially for those probes which
can detect various ions based on a same fluorophore are very
scarce.
N
F
N
F
B
Knoevenagel condensation
Site1: recognition site
2
+
3+
for Hg and Fe
NIR emission
em = 670 nm
Site2: recognition site
λ
HO
Site2
TPAꢀBODIPYꢀOH
Scheme 1 Structure of R/NIR Chemodosimeter TPA-BODIPY-OH for Hg and Fe
OH
3+
for Fe only
2+
3+
In view of these, on the basis of the unique structure
and excellent properties of BODIPY, we fabricate a novel NIR
emission fluorescent probe TPA-BODIPY-OH by Cu(I)-catalyzed
click reactions (as shown in Scheme 1). It’s found that TPA-
2
. Results and discussion
BODIPY-OH has unique three-channel emissions and can 2.1 Click synthesis of TPA-BODIPY-OH dendrons
2
+
3+
detect the Hg , Fe ions in complex aqueous samples via
different detection modes with C=N functionality and 4-
hydroxystyryl groups, which serve as the recognition positions.
The near-infrared (NIR) emission was realized by introducing 4-
hydroxystyryl group and in conjugation to the 3, 5-positions of
triphenylamine-BODIPY core, which is an efficient way to red-
shift the maximum absorption and emission band of the
BODIPY dyes. TPA-BODIPY-OH was a mixture of reaction-based
probe and lock/key-based probe. The BODIPY units of TPA-
BODIPY-OH exhibits weak fluorescence due to the
nonradiative decay from -C=N isomerization and rotation.
The triphenylamine-BODIPY was choosed as the mother
fluorophore for the reason of the excellent optical properties
that it possessed. The emission band of triphenylamine-
BODIPY was about 600 nm, it has been very long even though
without any modification. However, we present
a
triphenylamine-BODIPY based NIR emitting ratiometric
fluorophore probe, which was obtained after 3- and 5-
positions of triphenylamine-BODIPY fluorophore were
substituted with electron-donating 4-hydroxystyryl groups by
Knoevenagel condensation. It leads to the emission band of
BODIPY unit red shift to the near infrared region. Besides, with
the aim of making triphenylamine-BODIPY having broad utility
value, the azide substituted Schiff base BODIPY (BODIPY-OH)
were added to the maternal fluorophore by Cu(I)-catalyzed
click reactions. Interestingly, the BODIPY-OH itself is an
excellent multichannel fluorescent sensor. Simply because the
functional group of the schiff base, which responded
3
+
2+
When Fe or Hg ions were added the hydrolysis of Schiff
2
+
3+
base was promoted by Hg and Fe , which lead to the -C=N
group transform into formyl group and result in considerable
fluorescence enhancement in dosimeter TPA-BODIPY-OH. It
2
+
3+
has high sensitivity for Hg and Fe ions. Another feature of
TPA-BODIPY-OH was the 4-hydroxystyryl groups that conjugate
3
+
2
+
3+
to the 3, 5-positions of BODIPY core, which can bind with Fe
selectively to Hg and Fe ions through an irreversible -C=N
bond hydrolysis reaction. These characteristics were used to
develop multi-channel fluorescent chemodosimeters. On top
of that, it is well known that phenol oxygen can serve as good
ligand donors for metal ions and the phenol group is
deprotonated in the coordination process, which can
and enhance the fluorescence of TPA-BODIPY-OH. By
introducing the Schiff base and 4-hydroxystyryl groups, the
near-infrared emission and multiple recognition based on one
fluorescence probe was realized. We further demonstrated
that TPA-BODIPY-OH could be used to living cell imaging and
exhibited deep red fluorescence in living systems. Moreover,
3
+
selectively serve as ligand donors for Fe ions. Generally
speaking, TPA-BODIPY-OH is an excellent platform for
developing near-infrared and multi-channels identification
probes.
amino-group-functionalized
TPA-BODIPY-OH
fluorescent
nanoparticles were prepared to study the potential application
and photophysical properties of it. This method of probe
design is an excellent platform for developing near-infrared
and multi-channels identification probes.
The syntheses of the dendritic probe TPA-BODIPY-OH,
intermediate compounds Ey-BODIPY-OH and BODIPY-OH were
showed in Scheme 2-4. The intermediate compound Az-
BODIPY was prepared according to the standard synthetic
4
4, 45
procedures of BODIPY
. Vilsmeier formylation using DMF-
POCl gives compound BODIPY-CHO as the sole regioisomer, as
3
this product showed poor stability in air, it was used to the
next reaction without further purification. Then, the BODIPY-
OH was synthesized by Schiff base condensation, using 4-
aminophenol and BODIPY-OH in the presence of ethanol lead
2
| J. Name., 2012, 00, 1-3
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to compound BODIPY-OH in 30% yield. The -C=N is an at 494 nm, 587 nm and 650 nm. The absorption peak at band
important group to build multi-channel reaction based probe 494 nm belongs to the Schiff base BODIPY (BODIPY-OH), which
3
+
2+
for Fe and Hg ions. To obtain the NIR emission fluorophore was added to the triphenylamine-BODIPY by Cu(I)-catalyzed
Ey-BODIPY-OH, p-hydroxy benzaldehyde was conjugated to the click reactions. The absorption peaks at bands 587 nm and 650
3- and 5-positions of Ey-BODIPY by Knoevenagel condensation. nm belong to mother fluorophore triphenylamine-BODIPY and
The conjugated π-system of the Ey-BODIPY-OH was extended TPA-BODIPY-OH chromophore respectively. The molar
and the maximum emission band was red-shift to near infrared extinction coefficient of absorption peaks at 494 nm, 587 nm
4
-1
-1
4
-1
-1
region. At last, Ey-BODIPY-OH combined with BODIPY-OH by and 650 nm was 11.65 × 10 / cm * M , 4.64 × 10 / cm * M ,
4
Cu(I)-catalyzed click reaction to produce the TPA-BODIPY-OH 9.23 × 10 / cm * M respectively. The fluorescence spectrum
-1
-1
dendron.
of TPA-BODIPY-OH was obtained after excitation within the
spectral region of maximal absorption (λex = 460 nm, Fig. 1a),
which showed three emission bands at 510 nm, 598 nm and
670 nm. Reasonably, TPA-BODIPY-OH was exhibits a very weak
emission band at 510 nm, since the molecular structure of the
BODIPY derivates bears a C=N functionality that diminishes the
emission of the BODIPY core caused by a non-radiative
deactivation process involving the rapid isomerization of the
C=N group. The fluorescence quantum yield of TPA-BODIPY-OH
was measured. In pure THF, the fluorescence quantum yield of
N3
N
i CuSO4 5H2O
ii Ascorbic acid, Et3N
iii CHCl3,CH3CH2OH,H2O
O
B
TPAꢀBODIPYꢀOH
Click reaction
N
F
N
F
B
N
OH
N
F
N
F
HO
OH
46
TPA-BODIPY-OH at 510 nm was 22.6% relative to fluorescein
= 0.95 in 0.1 M NaOH). The quantum yield of TPA-BODIPY-
OH at 598 nm and 650 nm were 19.8% and 76.3% respectively,
Scheme 2 Synthesis of NIR emission fluorescent dendrons TPA-BODIPY-OH
(Ф
f
I
I
Si
Si
K CO
which relative to rhodamine B (Ф
f
= 0.31 in H
2
O).
N
Si
i Pd(PPh
N
N
2
3
5
6
6
6
6
5
1
.25x10
2.5x10
2.0x10
1.5x10
1.0x10
3
)
2
Cl
2
CH OH, rt, 2 h
3
(a)
λab=494 nm
λem=670 nm
ii PPh , CuI, N
2
DMF, reflux, 12 h
3
O
O
5
4
4
4
O
1.00x10
λab=650 nm
TPAꢀCHO
absorption
emission
7
5
2
.50x10
.00x10
.50x10
N
λab=587 nm
N
B
N
NH
pꢀhydroxy benzaldehyde
i TFA, DDQ
ii Et N, BF OEt
3 3 2
i piperidine, pꢀTsOH
ii benzene, reflux
N
F
N
F
5.0x10
B
λem=510 nm
λem=598 nm
O
N
F
N
F
0
.00
0.0
800
4
50
500
550
600
650
700
750
EyꢀBODIPY
HO
OH
EyꢀBODIPYꢀOH
Wavelength /nm
Scheme 3 Synthesis of alkynyl substituted triphenylamine-BODIPY derivatives Ey-
BODIPY-OH
(b)
2+
Hg
3+
Fe
blank
N
3
N3
N
3
Ag
+
+
2
3
Al
4.
0x
3
.
5
x1
1
0
6
+
Ca
Cd
Co
Cu
.
O
B
O
B
O
B
2+
u
6
.
iCH
ii 4ꢀAminophenol
3
CH
2
OH
0
06
a
2
+
+
3.0
/
DMF, POCl
0℃ , 2 h
3
x1
y
2
t
i
2
.
6
80℃ ,reflux, 12 h
O
2+
5
s
n
x1
6
N
OH
Fe
Fe
Hg
0
106
06
06
3
+
2.
1.
e
0x
t
N
F
N
F
N
F
N
F
N
F
N
F
2+
n
I
5x1
+
e
K
c
1
AzꢀBODIPY
BODIPYꢀCHO
BODIPYꢀOH
2+
.0
x
n
Mn
1
e
2
+
5
0
.0
.0
c
Ni
x1
Scheme 4 Synthesis of azide substituted Schiff base BODIPY ( BODIPY-OH )
2+
05
s
Zn
7
5
re
7
5
0
7
5
o
2
0
W
7
0
5
7
l
u
a
7
v
6
0
5
F
e
6
5
2
2
.2 The sensing behaviour of NIR emission fluorescence probe
TPA-BODIPY-OH dendrons
le
n
6
0
0
gth
6
5
7
0
5
/nm
5
5
5
2
5
0
0
5
5
7
4
The absorption spectrum and fluorescence spectrum of TPA-
BODIPY-OH in H O/THF=1:1 was studied by UV/Vis and Fig. 1. (a) absorption and fluorescence spectra of TPA-BODIPY-OH in
2
H O/THF (1/1, v/v); (b) fluorescence spectra of TPA-BODIPY-OH in the
2
fluorescence spectroscopy. As shown in Fig. 1a, the UV/Vis
-5
presence of various metal ions in H
2
O/THF (1/1, v/v); CTPA-BODIPY-OH= 10 M;
spectrum of free TPA-BODIPY-OH (H O/THF, 1:1, v/v, buffered
2
-5
C
ion=5×10 M.
with HEPES pH=7.4) displays three maximum absorption band
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Our investigation began with the evaluation of the optical fold and 1.4-fold increase at the plateau, respectively. The
behaviour of TPA-BODIPY-OH in response to the addition of fluorescence intensity ratio (F510nm/F670nm) increased over
+
2+
3+
2+
2+
2+
2+
2+
different ions, such as K , Fe , Al , Ca , Mn , Co , Ni , Zn , 2.8-fold in presence. Here, there are two important factors
+
2+
2+
3+
2+
Ag , Cd , Hg , Fe and Cu . The dosimeter showed an that lead to the change of fluorescence spectrum. The one was
intensity emission bands at 510 nm and 670 nm in the buffer the structure change of the reaction based probe TPA-BODIPY-
2
solution. No obvious change was obtained, except for Hg and OH. Before reaction with the Fe and Hg ions, the weak
+
3+
2+
3
Fe . The detection of Hg and Fe by TPA-BODIPY-OH was fluorescence exhibited at 510 nm due to the nonradiative
+
2+
3+
2
+
3+
studied by optical spectroscopy. The addition of Hg and Fe
5 equiv) to TPA-BODIPY-OH prompted the significant increase Hg ions, the hydrolysis reaction between -C=N and Hg ions
of fluorescence intensity at band 510 nm and 670 nm that was occured so that -C=N transfer into formyl group, which lead to
decay from -C=N isomerization and rotation. After addition of
2
+
2+
(
3
+
assigned to the formation of a new BODIPY derivative (Fig. 1b). the enhancement of fluorescence intensity at 510 nm. As for Fe
3+
The appearance of this spectrum change was accompanied ions, the hydrolysis reaction was induced by H : Fe + H
+
2
O =
+
with a distinct change in the solution's emission colour; the Fe(OH)
3
+ 3H . The protons generated by the process reaction of -
purple-emitting probe solution became distinctly green, as was C=N and the -C=N transfer into formyl group. Therefore, the
clearly visible to the naked eye (Fig. 2). The emission color radiative decay disappeared and fluorescence intensity enhanced.
2+
3
photographs of TPA-BODIPY-OH in the presence of Fe or Hg
+
Due to the special structure of TPA-BODIPY-OH, which has two arms
under excitation at 365 nm was also experience a significant extending outward of the fluorophore core just like a antenna. That
2
change (Fig. 2). The red fluorescence was enhanced after the means after addition of Hg or Fe ions the fluorescence at 510 nm
+
3+
3
+
2+
addition of Fe or Hg ions. Table 1 exhibit the photophysical enhanced and the energy transfer to the whole dendrons and thus
properties of TPA-BODIPY-OH.
lead to the fluorescence enhancement at 670 nm. Meanwhile, the
-hydroxystyryl group extension at the α-position can also binding
4
3
+
with the Fe ions, which lead to the increase of fluorescence
intensity in the emission spectrum. The fluorescence intensity at
5
98 nm suffered an increasment with the fluorescence intensity
3
+
enhanced 2.6-fold at the highest point (15 μM Fe ).
We made a similar experiment to investigate the TPA-
2
+
BODIPY-OH in response to different Hg concentration. The
result was shown in Fig. 3(b). The fluorescence spectrum
exhibited the same variation tendency as titration curve of
3
+
Fe . The emission intensities at 510 nm and 670 nm exhibited
a drastic change with a 2.8-fold and 1.5-fold increase at the
2+
Fig. 2. The corresponding photographs of TPA-BODIPY-OH after the addition metal ions
plateau (20 μM Hg ), respectively, the fluorescence intensity
(
5.0 equivalent) in H
2
O/THF (1/1, v/v, buffered with 10 mM HEPES) using UV lamp at
ratio (F510nm/F670nm) increased over 2.4-fold. However, the
reason that lead to the enhancement of fluorescence intensity
room temperature.
2
on upon of Hg is only the reaction of Hg ion and C=N group.
+
2+
Table1 The molar extinction coefficient, emission band and fluorescence quantum yield
of TPA-BODIPY-OH and TPA-BODIPY-OH fluorescent nanoparticles FNPs.
3
+
2+
The systematic titration of TPA-BODIPY-OH with Fe and Hg
revealed that emission band intensity increases linearly with
3
the increase in concentration of Fe or Hg in the range of 2.5
+
2+
-
40 μM (Fig. 3).
6
4
4
3
.5x10
.0x10
.5x10
(
a)
TPAꢀBODIPYꢀOH/Fe
3+
6
6
6
6
6
6
6
5
[Fe ] / ꢀΜ
3
+
2.5 ꢀΜ
5
ꢀΜ
7
.5 ꢀΜ
3
+
10 ꢀΜ
2
.3 The fluorescence response to different concentration of Fe
3.0x10
2
+
12.5ꢀΜ
5 ꢀΜ
and Hg ions
1
2
.5x10
.0x10
1
7.5ꢀΜ
To further investigate the probe behaviors of TPA-BODIPY-OH
20 ꢀΜ
3
40 ꢀΜ
2
3
towards Fe and Hg ions, the fluorescence titration
+
2+
0 ꢀΜ
3
+
2+
1.5x10
1.0x10
experiments of TPA-BODIPY-OH with Fe and Hg ions were
performed in THF/H (1:1, v/v). Fig. 3 showed the
fluorescence spectrum changes of TPA-BODIPY-OH as a
2
O
5.0x10
3
+
2+
function of the Fe and Hg concentration. The titration curve
3
0.0
+
5
00
550
600
650
700
750
800
850
of Fe was shown in Fig. 3(a). Notably, the fluorescence
intensity at band 510 nm and 670 nm showed a steady
Wavelength /nm
3
increase until a plateau was reached (20 μM Fe ) with a 3.4-
+
4
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ARTICLE
6
4
4
3
3
2
2
1
1
5
.5x10
.0x10
.5x10
.0x10
.5x10
.0x10
.5x10
.0x10
.0x10
6.0
(
b)
2+
5.5
5.0
(b)
ions
I668nm/I510nm
6
6
6
6
6
6
6
5
[Hg ] / ꢀΜ
2+
2+
ions+Hg
I668nm/I510nm
2
.5 ꢀΜ
ꢀΜ
.5 ꢀΜ
TPAꢀBODIPYꢀOH/Hg
5
4
.5
4.0
.5
7
10 ꢀΜ
2.5 ꢀΜ
15 ꢀΜ
7.5 ꢀΜ
20 ꢀΜ
1
3
1
3.0
2.5
2.0
3
0
ꢀΜ
40 ꢀΜ
1
.5
.0
1
0.5
.0
0
0
.0
+
3+
2+
2+
2+
2+
2+
3+
2+
+
2+
2+
2+
Ag Al Ca Cd Co Cu Fe Fe Hg
K Mn Ni Zn
450
500
550
600
650
700
750
Wavelength /nm
Fig. 4. Fluorescence responses of TPA-BODIPY-OH to various cations in THF/H
2
O (1:1,
3
+
2+
v/v) system buffered with HEPES. (CTPA-BODIPY-OH=10 μM; Cion= 50 μM). The high bars
Fig. 3. Fluorescence spectra of TPA-BODIPY-OH with Fe (a) and Hg (b) in THF/H
2
O
+
3+
2+
2+
2+
2+
2+
3+
2+
+
2+
2+
represent the addition of Ag , Al , Ca , Cd , Co , Cu , Fe , Fe , Hg , K , Mn , Ni
,
-
5
(
1:1, v/v) buffered with 10 mM HEPES, CTPA-BODIPY-OH =10 M.
2+
and Zn ions to the solution of TPA-BODIPY-OH, respectively. The short bars represent
3+
2+
the subsequent addition of Fe or Hg to the solution. (λex = 450 nm).
3
+
2+
2
.4 Detection of Fe and Hg ions by TPA-BODIPY-OH
2
.5 Dissociation constant and the detection limit of probe TPA-
High selectivity toward specific analyst over other competitive
species is desired for any sensors, so selectivity and
BODIPY-OH
competition experiments were then carried out. Upon addition For determination of stoichiometry between TPA-BODIPY-OH
+
3+
3+
2+
of 5 equiv of various metal ions aqueous solution (Ag , Al , with Fe or Hg , Job’s plot analyses were used. The method is
2
+
2+
2+
2+
2+
3+
2+
+
2+
2+
2+
3+
Ca , Cd , Co , Cu Fe , Fe , Hg , K , Mn , Ni , and Zn ) to that keeping total concentration of TPA-BODIPY-OH and Fe
2
+
-4
TPA-BODIPY-OH in THF/H
BODIPY-OH displayed significantly enhanced fluorescence
2
O (1:1, v/v) system, probe TPA- (or Hg ) at 10 M, and changing the molar ratio of ions (Xion
;
X
ion = [ion] / ([probe] + [ion])) from 0.1 to 0.9. The result was
3+
effects in the presence of Fe , Hg and almost no obvious shown in Fig. 5(a-b), when molar fraction of Fe was 0.73, the
fluorescence changes from Ag , Al , Ca , Cd , Co , Cu Fe , fitting curve of job’s plot for Fe reach the highest point,
K , Mn , Ni , and Zn . As show in Fig.4a-b, the fluorescence indicating the stoichiometry between TPA-BODIPY-OH and Fe
response to the addition of Fe and Hg was hardly affected was 1:3. The similar experiment was measured for Hg and
by the presence of these commonly coexistent ions, indicating the corresponding result was shown in Fig. 5(b). The highest
the exclusive sensitivity of TPA-BODIPY-OH toward Fe and point was found in the fitting curve with the molar ratio of
Hg . The probe behaviour of the probe towards the Fe and Hg ions at 0.65, which means the stoichiometry between
Hg can be attributed to the reaction of the C=N group. TPA-BODIPY-OH and Hg was 1:2.
3
+
2+
+
3+
2+
2+
2+
2+
2+
3+
+
2+
2+
2+
3+
3
+
2+
2+
3
+
2
+
3+
2+
2
+
2+
Meanwhile, the 4-hydroxystyryl group extension at the α-
6
3
position can also binding with the Fe ions, which is different
+
3.50x10
(
a)
Job's plot TPAꢀBODIPYꢀOH/Fe
2
from Hg .
+
6
6
6
6
6
6
6
3+
3
.25x10
.00x10
6
5
5
4
4
3
3
2
2
1
1
0
0
.0
.5
.0
.5
.0
.5
.0
.5
.0
.5
.0
.5
.0
3
ions
I668nm/I510nm
I668nm/I510nm
(a)
3
+
ions+Fe
2.75x10
2
2
2
.50x10
.25x10
.00x10
1.75x10
0
.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
3
+
3+
[
Fe ]/[Fe +probe]
+
3+
2+
2+
2+
2+
2+
3+
2+
+
2+
2+
2+
Ag Al Ca Cd Co Cu Fe Fe Hg
K Mn Ni Zn
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Journal Name
4
7, 48
6
6
6
6
6
6
6
6
6
reported method
. The fluorescence intensity data (Fig. 3)
n
3
3
3
3
3
2
2
2
2
.40x10
.30x10
.20x10
.10x10
.00x10
.90x10
.80x10
.70x10
.60x10
(b)
2
+
n
Job's plot TPAꢀBODIPYꢀOH/Hg
d min
was fitted to equation: F=(FminKd +Fmax[X] )/(K + [X] ); F and
F
max are the fluorescence intensities with no addition of ion
and excess amount of ion at 670 nm, respectively; n is the
3
binding stoichiometry between TPA-BODIPY-OH and Fe or
+
2
+
Hg ; [X] is the concentration of ions added. The stoichiometry
3+
2+
between probe and Fe or Hg were kept fixed at 3 or 2 in the
final curve fittings, accordingly, the related dissociation
-16
constant value was found to be 1.35×10 M for TPA-BODIPY-
2+
M for TPA-BODIPY-OH/Hg . The
3
OH/Fe and 2.06×10
+
-11
-7
detection limit was measured to be 5.15×10 M for TPA-
3+
BODIPY-OH/Fe (3s/slope, s is the standard deviation of the
4
blank measurement) and 6.81×10 M for TPA-BODIPY-
9
-7
0
.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
2
+
2
+
2+
[
Hg ]/[Hg +probe]
OH/Hg , respectively. Compared with the similar probes that
Fig. 5. (a) Job’s plot of TPA-BODIPY-OH with Fe ; (b) Job’s plot of TPA- have been reported, the results of dissociation constant and
3
+
2
+
BODIPY-OH with Hg ; THF/H
2
O = 1:1 buffered with HEPES (pH=7.4); the detection limit for TPA-BODIPY-OH are better than it.
total concentration of [probe] + [ion] was kept constant at 100 μM (λex= 450
nm).
2. 6 Sensing modes based on Schiff base hydrolysis reaction and
3
+
Fe ion binding
The apparent dissociation constant (K ) was obtained by
d
3
direct fluorometric titration as a function of Fe and Hg
+
2+
using the fluorescence emission spectra according to the
H+
HO
HO
N
N
F
B
N
F
B
N
F
N
F
B
N
N
N
N
B
F
F
F
F
N
N
N
N
N
N
N
N
N
O
N
N
O
O
N
N
O
N
N
H+
N
B
N
B
HO
Fe3+
HO
N
F
N
F
N
F
N
F
Fe3+ H O
3H+
Fe(OH)
2
3
HO
OH
HO
OH
TPA-BODIPY-OH
H
N
2
N
OH
O
O
F
B
N
F
B
N
F
B
N
F
B
N
N
N
N
F
F
F
F
N
N
N
N
N
N
N
N
N
O
N
N
O
O
N
O
O
O
N
B
N
Fe3+
N
F
N
F
N
F
N
F
B
HO
OH
HO
OH
Fe3+
TPA-BODIPY-CHO
3
+
Fig. 6. The possible mechanism of TPA-BODIPY-OH toward Fe ions in THF/H
2
O (1:1, v/v) system buffered with HEPES.
6
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Hg2+
HO
O
N
F
B
N
F
N
N
F
N
F
N
B
F
F
B
B
N
F
F
N
N
N
N
N
N
N
N
N
N
N
O
N
O
N
O
N
O
O
N
Hg2+
N
B
N
B
HO
N
F
N
F
N
F
N
F
Hg N
OH
HO
OH
HO
OH
TPA-BODIPY-CHO
TPA-BODIPY-OH
2
+
2
Fig. 7. The possible mechanism of TPA-BODIPY-OH toward Hg ions in THF/H O (1:1, v/v) system buffered with HEPES
As we discussed above, the dosimeter TPA-BODIPY-OH BODIPY. This result in the enhancement of the fluorescence
displayed an unchanged fluorescence emission in THF/H O intensity at band 670 nm.
2
+
3+
2+
2+
2+
solution on addition of Ag , Al , Ca , Cd , Co , Cu , Fe , K ,
2+
2+
+
To confirm the hydrolysis reaction of -C=N with ions, the
mass spectrum was carried out. The formation of BODIPY-OH
2
+
2+
2+
2+
3+
Mn , Ni , and Zn , but when Hg and Fe ions was added, it
showed obvious enhancement of fluorescence intensity at
band 510 nm and 670 nm. There are two reasons, the first one
is that the change of molecular structure. The -C=N
functionality diminishes the emission of the BODIPY core at
band 510 nm caused by a non-radiative deactivation process
involving the isomerization of the -C=N group. However, after
3+
3+
and Fe mixture upon addition of 5 equiv of Fe to a solution
of BODIPY-OH. As shown in Fig. 8, the peaks of key
+
intermediate compound [BODIPY-OH] ( m/z = 543.2491) was
3+
obtained. After reaction with Fe , the -C=N group turn into -
C=O and the BODIPY-OH changed into BODIPY-CHO. The peaks
+
of ionic fragments [BODIPY-CHO] (m/z = 452.2069) and
2
+
3+
Hg and Fe ions were added, an irreversible C=N bond
hydrolysis reaction occurred (as shown in Fig. 6 and Fig. 7), at
the same time the -C=N transfer into formyl group. Therefore,
the radiative decay disappeared and fluorescence intensity
enhanced at band 510 nm. However, the hydrolysis reaction of
+
BODIPY-CHO]+Na (m/z = 474.1889) was founded in the mass
[
spectrum. The results proved that the reactions between -C=N
3+
and Fe have took place.
3
+
+
-
C=N with Fe ions in aqueous solution was induced by H :
3
+
+
Fe + H O = Fe(OH) + 3H . By reason of the special structure
2
3
of TPA-BODIPY-OH, which has two arms extending outward of
the fluorophore core just like a slight antenna. So after
2
+
3+
addition of Hg or Fe ions the fluorescence at 510 nm
enhanced and the energy transfer to the whole dendrons and
thus lead to the fluorescence enhancement at 670 nm. On the
3
+
other hand, the Fe ions can also coordination with the
phenolic hydroxyl like 4-hydroxystyryl group, which was in
conjugation to the 3- and 5-positions of triphenylamine-
3
+
BODIPY core. The Fe formed complexes with TPA-BODIPY-
CHO (as shown in Fig. 6) via coordination with the 4-
hydroxystyryl moiety. It should be noted that the TPA-BODIPY-
3
+
CHO/Fe complex partially retained the monoanion character.
3
+
The existing negative charge in TPA-BODIPYCHO/Fe resisted
the deprotonation of the second phenolic proton (Ph-OH →
3
+
Fig. 8. Mass spectrum of Schiff base BODIPY ( BODIPY-OH ) with Fe .
.7 Preparation of functionalized fluorescent core-shell
nanoparticles
-
PhO ), as this required the formation of a dianion with the
2
higher energy, the result was reference to the reported
5
0
3+
literature . The binding of Fe with the lone pair on the
oxygen atom in TPA-BODIPY-CHO lead to an increase of
delocalization extent of mother fluorophore triphenylamine-
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Journal Name
4
6
6
5
4
3
2
1
x10
x10
x10
x10
x10
x10
1.250x10
(
a)
emission
6
1
1
.125x10
.000x10
4
4
4
4
6
5
5
5
5
absorption
8.750x10
7
.500x10
6.250x10
5
.000x10
4
4
75
500
525
550
575
600
625
650
675
700
Wavelength /nm
6
6
6
5
5
5
6
6
6
5
5
5
1
1
1
7
5
2
.50x10
.25x10
.00x10
.50x10
.00x10
.50x10
1.50x10
(
b)
SiO NPs/H O
H O/THF (V O:VTHF
)
2
2
2
H
2
6
7
0%
0%
1.25x10
80%
0%
9
1
7
.00x10
.50x10
5.00x10
2.50x10
0
.00
4
75
500
525
550
575
600
625
650
675
700
Wavelength /nm
Fig. 10. (a) Absorption and fluorescence spectrums of TPA-BODIPY-OH fluorescent
Fig. 9. (a) The preparation process and model structure of TPA-BODIPY-OH fluorescent
nanoparticles; (b) Fluorescence spectrum of TPA-BODIPY-OH fluorescent nanoparticles
nanoparticles FNPs; (b) The TEM image of TPA-BODIPY-OH fluorescent nanoparticles.
-5
and TPA-BODIPY-OH in THF/H
60 nm).
2
O system with different water fraction. (C=10 M, λex
=
4
The amino-modified TPA-BODIPY-OH fluorescent nanoparticles
FNPs were synthesized using the oil /water (O/W) micelle
microemulsion method and the preparation process are shown
in Fig. 9(a). The model structure of the FNPs is presented in
Fig. 9. It consists of two parts: (1) the core made of aggregated
chromophore molecules; (2) the silica shell whose internal
surface was modified by vinyl, which would create a non-polar
environment for organic chromophores, while the outside
surface was decorated with amino groups, which would
provide bonding sites for biomolecules. These nanoparticles
were characterized by transmission electron microscopy. The
results showed that the particle sizes of TPA-BODIPY-OH
fluorescent nanoparticles FNPs were about 50 ± 5 nm (Fig.
To further investigate the fluorescence properties of the
TPA-BODIPY-OH fluorescent nanoparticles, the emission
spectrum of TPA-BODIPY-OH fluorescent nanoparticle was
compared with TPA-BODIPY-OH in mixed solvent of water and
THF system with different water fraction, as shown in Fig.
1
0(b). It was obvious that the emission peaks of dyes
encapsulated inside the silica shell were similar to those in
mixed solvent of water and THF system with low water
fraction, and different from those in mix-solvents with high
water fractions such as 70%, 80% and 90%. Moreover, the
fluorescence intensity of TPA-BODIPY-OH fluorescent
nanoparticle was higher than the TPA-BODIPY-OH in mixed
solvent of water and THF system with water fraction over 60%.
What’s moer, the quantum yield of TPA-BODIPY-OH
fluorescent nanoparticles at band 660 nm was up to 42.3%.
Thus, it could be concluded that the excellent photophysical
properties of the TPA-BODIPY-OH was maintained in the Si-NPs.
However, the potential bioapplications based on the Si-NPs
9(b)), and the particles were spheric and dispersed in water.
This property was conducive to the easy uptake of FNPs by
living cells. In addition, the fluorescence spectrum of TPA-
BODIPY-OH fluorescent nanoparticle was characterized by a
fluorometer. The FNPs can be well dispersed in water while
the good inherent photophysical properties of the pure dyes
were maintained, as presented in Fig. 10(a). The absorption
peaks of dye-doped FNPs were at 500, 588, and 658 nm,
whereas the emission peaks were at 520, 605, and 660 nm.
The fluorescence spectrum of the nanoparticles indicating that
the spectral characterization of the TPA-BODIPY-OH dye did
not change to a great extent when it was doped inside the
nanoparticles.
51-54
still need to be further researched
.8 Live cell imaging
.
2
To demonstrate the potential application of them in the
biological systems, the utility of probe TPA-BODIPY-OH in living
cells was studied. A549 cells were cultured on confocal dishs at
4
.6×10 /dish at 37 ℃ under 5 % CO
1
2
for 24 h. Then the cells
-6
were cultured in 10 μL 10 mol TPA-BODIPY-OH at 37
℃
8
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ARTICLE
containing 100 μL cell PBS for 30 min. Afterward, cells were green fluorescence in green field. What’s more if the emissions
washed with PBS for three times to remove the nonspecifically windows were set at yellow-green field or red field, the cells
absorbed dyes. Cell imaging was performed using a laser- can also display yellow-green or red fluorescence, respectively.
scanning confocal fluorescent microscope (leica, TCS-SP8) with These preliminary results indicate the good photostability of
an excitation wavelength of 405 nm. The A549 cells stained by the TPA-BODIPY-OH in a biological environment.
TPA-BODIPY-OH displayed a strong fluorescence in different
channels as shown in Fig. 11a-d. The cells displayed bright
Fig. 11. Fluorescence images of A549 cells incubated with TPA-BODIPY-OH (10 μL, 1 μM) for 30 min. (a) fluorescence image of A549 cells in brightfield; (b) fluorescence image of (a)
in the green channel; (c) fluorescence image of (a) in the yellow-green channel; (d) fluorescence image of (a) in the red channel.
million (ppm). Mass spectra were recorded on Agilent
3
. Conclusions
Technologies 6530 Accurate-Mass Q-TOF LC/MS. All reagents
used were purchased from Aldrich, Fluka or Alfa Aesar and
used without further purification. All solvents used in
spectroscopic measurements were of analytical grade. 3-
Aminopropyltriethoxysilane (APTES, Sinopharm Chemical
Reagent Co., Ltd, Shanghai, China), Aerosol OT (AOT, Aladdin
Industrial Co., Shanghai, China), triethoxyvinylsilane (VTES,
Aladdin Industrial Co., Shanghai, China) were also used.
Reactions were monitored by thin layer chromatography using
Merck TLC Silica gel 60 F254. Silica gel column chromatography
was performed over Merck Silica gel 60. UV-visible absorption
In summary, a novel near-infrared region emitting fluorescent
probe TPA-BODIPY-OH was synthesised by click reaction. The
TPA-BODIPY-OH showed excellent sensitivity for fluorescent
2
+
3+
determination of Hg and Fe ions based on Schiff base
3
+
hydrolysis reaction. Especially for Fe ions, which can realize
the multi-channel detection by -C=N bond and 4-hydroxystyryl
group. “Naked eye” detection was realized with the obvious
colour change from purple-emitting to distinctly green. The
stoichiometry between TPA-BODIPY-OH and ions was deduced
3
+
from Job’s plot showed 1:3 for TPA-BODIPY-OH/Fe and 1:2
2
for TPA-BODIPY-OH/Hg , respectively. Dissociation constant
+
spectra were determined on
a
Shimadzu UV-3600
-16
3+ spectrophotometer. Fluorescence spectra were measured on a
HORIBA FL-4 Max spectrometer. The absorption and
fluorescence spectral titrations of dosimeter TPA-BODIPY-OH
value was found to be 1.35×10 M for TPA-BODIPY-OH/Fe
2+
-11
and 2.06×10
detection limit was calculated from titration results with the
M for TPA-BODIPY-OH/Hg . Besides, low
-7
3+
value were 5.15×10 M for TPA-BODIPY-OH/Fe and 6.81×10
2
-7 were prepared in THF-H O, the solutions of guest cations were
-
6
2
+
prepared in H
2
O in the order of 10 M. Absorption and
M for TPA-BODIPY-OH/Hg , respectively. Furthermore, the
TEM image showed that the sizes of TPA-BODIPY-OH/SiO
fluorescence spectra were recorded after mixing dosimeter
2
+
TPA-BODIPY-OH with metal ions like K , Na , Al , Ca , Mn ,
+
3+
2+
2+
nanoparticles were about 50 ± 5 nm, and the nanoparticles
exhibit excellent dispersibility and photophysical properties,
which indicate that TPA-BODIPY-OH has a great application
potential in ions detection and biomedical field. Cell imaging
experiment was successfully carried out and the A549 cells
displayed a bright red fluorescence. This novel molecular
2
+
2+
2+
2+
+
2+
2+
2+
Fe , Co , Ni , Zn , Ag , Cd , Hg , and Cu . Cell imaging was
performed using laser-scanning confocal fluorescent
microscope (leica, TCS-SP8 ) with an excitation wavelength of
88 nm.
.2 Synthesis
a
4
4
structure will have great significance to help develop near- The synthetic routes adopted for preparation of TPA-BODIPY-
infrared emission fluorescence probes with other specific OH were shown in Scheme 2-4. The detailed synthesis
methods of compound TPA-CHO, Az-BODIPY and compound
natures by click reaction.
2,4-dimethyl pyrrole were in the supporting information.
Compound Ey-BODIPY: 2,4-dimethyl pyrrole (2.01g, 21
4
. Experimental
mmol) and compound TPA-CHO (3.36 g, 10.47 mmol) were
dissolved in dry dichloromethane (200 mL). Three drop of
trifluoroacetic acid (TFA) was added to the solution. The
reaction mixture was stirred at room temperature for 24 h.
The reaction was monitored by TCL. After disappearance of the
aldehyde, a solution of p-chloranil (2.57 g, 10.47 mmol) in
4
.1 Materials and methods
1
13
H NMR and C NMR spectra were recorded on a Bruker DMX
300 NMR spectrometer in CDCl with tetramethylsilane (TMS)
3
as internal standard. Chemical shifts are given in parts per
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dichloromethane was added. The reaction mixture was stirred got 0.18 g, yield: 30%. H NMR (CDCl
View Article Online
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1
3
, ppm, 300 MHz) δ: 8.45
at room temperature for 12 h. Absolute triethylamine (15 mL) (s, 1H), 7.23 (d, J=6.0 Hz, 2H), 7.08 (d, J=6.0 Hz, 4H), 6.86 (d,
was then added to the mixture. At last BF .OEt (15 mL) was J=6.0 Hz, 2H), 6.10 (s, 1H), 4.16 (t, J =6.0 Hz, 2H), 3.60 (t, J =6.0
added dropwise at 0 . The mixture was stirred 12 h again and Hz, 2H), 2.91 (s, 3H), 2.63 (s, 3H), 2.14 (q, J =6.0 Hz, 2H), 1.73
then the reaction mixture was washed with water for three (s, 3H), 1.49 (s, 3H). C NMR (CDCl
times (100×3 mL) and extracted with dichloromethane. The 129.06, 127.02, 122.39, 121.84, 116.07, 115.82, 115.50,
organic layer was dried over Na SO . The solvent was 115.37, 115.21, 77.43, 77.01, 76.58, 64.68, 58.26, 48.16, 45.86,
evaporated and the residue was purified by silica gel column 29.62, 28.72, 18.25, 15.03, 14.79, 13.87, 12.37.
chromatography using dichloromethane as eluent to obtain a Compound TPA-BODIPY-OH: A solution of compound
, ppm, 300 BODIPY-OH (0.15 g, 0.27 mmol), Ey-BODIPY-OH (0.1 g, 0.13
MHz) δ: 7.44 (d, J=9.0 Hz 4H), 7.21 (s, 4H), 7.05 (d, J=9.0 Hz, mmol), sodium ascorbate (0.0028 g, 0.014 mmol), and cupric
3
2
℃
1
3
3
, ppm) δ: 159.43, 151.85,
2
4
1
yellow solid 0.5 g, yield: 8.86 %. H NMR (CDCl
3
4
6
1
7
H), 6.03 (s, 2H), 3.22 (d, J=6.0 Hz, 2H), 2.57 (s, 6H), 1.58 (s, sulfate (0.0035 g, 0.014 mmol) in a mixture of chloroform,
1
3
H). C NMR (CDCl
30.07, 129.34, 124.97, 123.68, 121.29, 116.83, 83.31, 77.45, temperature for 48 h. After completion of the reaction, the
7.00, 76.60, 58. 24, 46.76, 18.28, 14.47, 8.60. solvents were removed under reduced pressure and the crude
Compound Ey-BODIPY-OH: In a 50 mL round-bottomed product was purified by column chromatography (CH Cl
flask equipped with a Dean-Stark trap and a reflux condenser methanol=10 : 1). A purple solid was obtained 0.11 g, yield: 50
3
, ppm) δ: 155.48, 147.13, 142.78, 133.40, ethanol and water (v/v/v = 12 : 3 : 2) was stirred at room
2
2
/
1
3
were added 20 mL benzene, Ey-BODIPY (0.10 g, 0.19 mmol, 1.0 %. H NMR (CDCl , ppm, 300 MHz) δ: 9.97 (d, J=9.0 Hz 2H),
eq.), p-hydroxybenzaldehyde (48 mg, 0.40 mmol, 2.1 eq.), one 9.38 (s, 2H), 8.55 (d, J =24.0 Hz, 4H), 7.81 (s, 4H), 7.49 (d, J=6.0
spatula of p-TsOH, and piperidine (0.5 mL). The reaction Hz, 5H), 7.38 (s, 2H), 7.30 (d, J=6.0 Hz, 7H), 7.15 (m, 11H), 7.09
mixture was stirred overnight at reflux under N
After cooling to room temperature, water was added to the J=9.0Hz, 2H), 6.26 (s, 4H), 4.63 (s, 4H), 4.11 (s, 4H), 2.78 (d,
reaction mixture, it was extracted three times with CH Cl . The J=27.0 Hz, 4H), 2.50 (s, 6H), 2.39 (s, 6H), 1.66 (d, J=12.0 Hz,
organic phase was washed with brine and dried over 6H), 1.41 (s, 6H), 1.23 (d, J=18.0 Hz, 6H). C NMR (CDCl
anhydrous Na SO . The solvent was evaporated and the δ: 186.02, 150.21, 144.91, 143.42, 136.61, 129.16, 126.85,
residue was purified by silica gel column chromatography 124.51, 116.01, 115.35, 109.15, 77.43, 77.00, 76.58, 71.97,
DCM: PE: methanol = 10 : 10 : 1). Ey-BODIPY-OH was obtained 67.89, 66.35, 64.39, 58.19, 45.88, 29.61, 29.24, 18.26, 15.02,
2
atmosphere. (d, J=9.0Hz, 4H), 6.90 (t, J1=12.0 Hz J2=9.0 Hz, 5H), 6.76 (d,
2
2
1
3
3
, ppm)
2
4
(
1
as blue-purple solid (71 mg, 50 %). H NMR (CDCl
MHz) δ: 7.61 (s, 1H), 7.56 (d, 1H), 7.51 (d, J=9.0 Hz, 4H), 7.43 4.3 Preparation of dye-encapsulated amine-functionalized silica
d, J=9.0 Hz, 4H), 7.26 (s, 4H), 7.22 (s, 4H), 7.04 (d, J=6.0 Hz, nanoparticles
3
, ppm, 300 11.73, 8.51.
(
4
3
1
1
5
H), 6.86 (d, J=6.0 Hz, 4H), 6.64 (s, 2H), 3.07 (s, 2H), 1.62 (s,
1
To a clear solution of surfactant AOT (0.44 g) dissolved in
deionized water (20 mL), 0.8 mL of co-surfactant 1-butanol
3
3
H), 1.26 (s, 3H). C NMR (CDCl , ppm) δ: 157.24, 152.75,
47.19, 141.38, 136.04, 133.41, 129.94, 129.20, 124.94,
23.65, 117.58, 116.87, 115.83, 83.35, 77.40, 76.97, 76.55,
8.41, 29.64, 18.34, 14.74.
was added with sonication at 0
℃ to form an oil-in-water
microemulsion system. DMF (60 μL) solution containing TPA-
BODIPY-OH (10 mM) was dropped into the mixture. After
sonicating for 3 min, 0.2 mL VTES was added and the reaction
mixture was stirred for 8 h. APTES (20 μL) was added and the
mixture was further stirred at room temperature for 24 h.
After the formation of nanoparticles, the unreacted starting
materials were removed by dialyzing the solution against
deionized water in an 8-14 kDa cutoff cellulose membrane for
Compound BODIPY-CHO: A mixture of DMF (6 mL) and
POCl
removing the ice bath and warming to room temperature, N
BODIPY (0.50 g, 1.18 mmol) in 1, 2-dichloroethane (30 mL) was
added, which was then heated for 2 h at 50 . When the
reaction mixture was cooled to room temperature, it was
slowly poured into a saturated NaHCO aqueous solution (100
3
(6 mL) was stirred in an ice bath for 30 min. After
3
-
℃
3
7
2 h. The dialyzed solution was then stored at 5 ℃ for later
mL) with an ice bath. The mixture was warmed to room
temperature, further stirred for 30 min, and washed with
water twice (50×3 mL). The organic layer was separated and
use.
2 4
dried over anhydrous Na SO . Then the solvent was
Acknowledgements
evaporated in vacuo. Account for the instability of BODIPY-
CHO, the crude product was used in the next reaction without
purification.
This work was financially supported by the Fundamental
Research Funds for the National Natural Science Foundation of
China (No. 61178057).
Compound BODIPY-OH: A mixture of compound BODIPY-
CHO (0.50 g, 1.1 mmol) and 4-aminophenol (0.16 g, 1.46
mmol) in ethanol (30 mL) was heated at 80
℃ for 12 h. After
Notes and references
the reaction was completed, the mixture was poured into
water (50 mL) and extracted with dichloromethane (100
1
C. Cantürk, M. Üçüncü, and M. Emrullahoğlu, RSC Adv., 2015,
, 30522.
5
mL×3), the organic phase was dried over Na
was evaporated and the residue was purified by silica gel
column chromatography (CH Cl /methanol, 9:1). A purple solid
2 4
SO . The solvent
2
3
H.-r. Cheng and Y. Qian, RSC Adv., 2015, 5, 82887.
R. R. Avirah, K. Jyothish, and D. Ramaiah, J Org Chem, 2008,
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0 | J. Name., 2012, 00, 1-3
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DOI: 10.1039/C6TB02469F
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