Colorimetric and ratiometric red fluorescent chemosensor for fluoride ion based on diketopyrrolopyrrole

Article abstract of DOI:10.1021/ol101081m

(Equation Presented). Three new diketopyrrolopyrrole (DPP) compounds are shown to be colorimetric and ratiometric red fluorescent sensors for fluoride anions with high sensitivity and selectivity. The recognition mechanism is attributed to the intermolecular proton transfer between a hydrogen atom on the lactam N positions of the DPP moiety and the fluoride anion.

Full text of DOI:10.1021/ol101081m

ORGANIC
LETTERS
2010
Vol. 12, No. 15
3320-3323
Colorimetric and Ratiometric Red
Fluorescent Chemosensor for Fluoride
Ion Based on Diketopyrrolopyrrole
Yi Qu, Jianli Hua,* and He Tian*
Key Laboratory for AdVanced Materials and Institute of Fine Chemicals, East China
UniVersity of Science & Technology, Shanghai 200237, P.R. China
jlhua@ecust.edu.cn; tianhe@ecust.edu.cn
Received May 11, 2010
ABSTRACT
Three new diketopyrrolopyrrole (DPP) compounds are shown to be colorimetric and ratiometric red fluorescent sensors for fluoride anions
with high sensitivity and selectivity. The recognition mechanism is attributed to the intermolecular proton transfer between a hydrogen atom
on the lactam N positions of the DPP moiety and the fluoride anion.
The recognition and detection of the fluoride ion are of
growing interest because it is associated with nerve gases,
the analysis of drinking water, and the refinement of uranium
used in nuclear weapons manufacture. As a consequence,
fluoride-indicating methodologies, which are developed to
provide critical information for fluoride hazard assessment
and fluoride pollution management, are in high demand.
Among these techniques, fluorescent molecular sensing,
which translates molecular recognition into tangible fluo-
rescence signals, has received much attention.1 To increase
the selectivity and sensitivity, ratiometric measurements are
utilized, which involve the observation of changes in the ratio
of the intensities of the absorption or the emission at two
wavelengths.
Ratiometric fluorescent probes have an important feature:
they permit signal ratio and thus increase the dynamic range
and provide built-in correction for environmental effects. The
perceived color change would be useful not only for the
ratiometric method of detection but also for rapid visual
sensing. Up to now, many investigations have been con-
ducted to create ratiometric fluorescent probes for cations.2
In contrast, only a few ratiometric fluorescent sensors for
(2) (a) Zhu, B. C.; Zhang, X. L.; Jia, H. Y.; Li, Y. M.; Liu, H. P.; Tan,
W. H. Org. Biomol. Chem. 2010, 8, 1650. (b) Xu, Z. C.; Yoon, J. Y.; Spring,
D. R. Chem. Commun. 2010, 46, 2563. (c) Ma, B. L.; Wu, S. Z.; Zeng, F.
Sensors Actuators, B 2010, 145, 451. (d) Xu, Z. C.; Baek, K. H.; Kim,
H. N.; Cui, J. N.; Qian, X. H.; Spring, D. R.; Shin, I. J.; Yoon, J. Y. J. Am.
Chem. Soc. 2010, 132, 601. (e) Du, J. J.; Fan, J. L.; Peng, X. J.; Li, H. L.;
Sun, S. G. Sensors Actuators, B 2010, 144, 337. (f) Goswami, S.; Sen, D.;
Das, N. K. Org. Lett. 2010, 12, 856. (g) Wang, H. H.; Xue, L.; Qian, Y. Y.;
Jiang, H. Org. Lett. 2010, 12, 292. (h) Zhou, Y.; Wang, F.; Kim, Y.; Kim,
S.-J.; Yoon, J. Y. Org. Lett. 2009, 11, 4442. (i) Tian, M. Q.; Ihmels, H.
Chem. Commun. 2009, 45, 3175. (j) Li, H. B.; Yan, H. J. J. Phys. Chem.
C 2009, 113, 7526.
(1) (a) Amendola, V.; Esteban-Go´mez, D.; Fabbrizzi, L.; Licchelli, M.
Acc. Chem. Res. 2006, 39, 343. (b) Esteban-Go´mez, D.; Fabbrizzi, L.;
Licchelli, M. J. Org. Chem. 2005, 70, 5717. (c) Boiocchi, M.; Boci, L. D.;
Esteban-Go´mez, D.; Fabbrizzi, L.; Licchelli, M.; Monzani, E. J. Am. Chem.
Soc. 2004, 126, 16507. (d) Liu, Z. Q.; Shi, M.; Li, F. Y.; Fang, Q.; Chen,
Z. H.; Yi, T.; Huang, C. H. Org. Lett. 2005, 7, 5481. (e) Kim, T. H.; Swager,
T. M. Angew. Chem., Int. Ed. 2003, 19, 4803. (f) Uchiyama, S.; Iwai, K.;
de Silva, A. P. Angew. Chem., Int. Ed. 2008, 47, 4667. (g) Nolan, E. M.;
Lippard, S. J. Chem. ReV. 2008, 108, 3443. (h) Hetrick, E. M.; Schoenfisch,
M. H. Annu. ReV. Anal. Chem. 2009, 2, 409. (i) ZhaoQ.; LiF. Y.; HuangC. H.
Chem. Soc. ReV. 2010, DOI: 10.1039/B915340c.
10.1021/ol101081m  2010 American Chemical Society
Published on Web 06/30/2010

F- have been reported in the literature.3 Thus, realization of
ratiometric measurements for F- is still a challenge.
1,4-Diketo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DPP) and its
derivatives represent a class of brilliant red and strongly
fluorescent high performance pigments that have exceptional
light, weather, and heat stability.4 Recently, significant
progress has been made to use DPP-containing materials in
polymer solar cells (PSCs),5 field effect transistors (FET),6
OLEDs,7 two-photon absorption,8 and dye sensitizing solar
cell applications. Also, the hydrogen atom on the lactam N
positions of the DPP moiety may be a useful receptor for
fluorescence sensors, and the strong H-F interaction will
result in deprotonation of a DPP amide moiety in the
presence of a fluoride ion, causing a dramatic change in color
and fluorescence of the compounds. In addition, a number
of fluorene-based DPP compounds show good optical and
electrical properties due to their high photoluminescence
efficiency and good chemical and thermal stability.9 There-
fore, it could be expected that some core-monosubstituted
DPP derivatives with good solubility should be “naked-eye”
colorimetric and ratiometric fluorescent sensors for fluoride
ions. However, to the best of our knowledge, there are no
reports on the fluorescent sensors based on DPP derivatives.
Here, we designed and synthesized three new DPP deriva-
tives (1-3 shown in Figure 1), in which a long alkyl chain
was contacted on the lactam N atom of the DPP moiety to
improve the solubility, and some substitutes were connected
to the 3,6-positions of electron-withdrawing pyrrolo[3,4-
c]pyrrole-1,4-dione via 1,4-phenylene conjugation bridges,
respectively. Indeed, it has been shown that even simple
chromophores can operate as efficient colorimetric and
ratiometric fluorescent sensors for naked-eye detection of
anions.
Figure 1. Molecular structures of DPP compounds 1-3.
Synthetic routes to the DPP-based compounds (1-3) are
shown in the Supporting Information (Scheme S1). DPP was
converted to soluble DPP-R by N-alkylation of the lactam
units, in which the alkyl DPP can produce the byproduct
with two sides substituted; fortunately, 1 can be easily
separated by column chromatography. 2 and 3 (shown in
Supporting Information) were easily synthesized by the
Suzuki coupling reaction 1 with phenylboronic acid and 9,9-
dimethyl-9H-fluoren-2-yl boronic acid, respectively. The
structures were characterized by standard spectroscopic
methods (Supporting Information).
Table 1. Photophysical Properties of 1-3 in DCMa
λabs/nmb
ε/104
λem/nmc
1
1F
2
2F
3
3F
477
571
485
585
497
594
3.1
1.8
4.4
2.4
3.0
1.6
531
613
545
630
563
635
(3) (a) Liu, B.; Tian, H. J. Mater. Chem. 2005, 15, 2681. (b) Qu, Y.;
Hua, J. L.; Jiang, Y. H.; Tian, H. J. Polym. Sci., Part A: Polym. Chem.
2009, 47, 1544. (c) Li, Y.; Cao, L. F.; Tian, H. J. Org. Chem. 2006, 71,
8279. (d) Mashraqui, S. H.; Betkar, R.; Chandiramani, M.; Quinonero, D.;
Frontera, A. Tetrahedron Lett. 2010, 51, 596. (e) Yang, X. F.; Qi, H. P.;
Wang, L. P.; Su, Z.; Wang, G. Talanta 2009, 80, 92.
a The photophysical properties were measured with 5.0 × 10-6
M
(4) (a) Toyo Ink Mfg. K.K. Japan Patent. 2055-362-A, 1990. (b) Fuji
Photo Film K.K. Japan Patent. 2039-159-A 1990. (c) Dainippon Ink Chem.
K. K. Japan Patent. 3011-357-A, 1990. (d) Ciba-Geigy Ltd. European Patent.
0.353184-A, 1990. (e) Mizuguchi, J.; Rochat, A. C. J. Imag. Technol. 1991,
17, 123. (f) Mizuguchi, J.; Giller, G.; Baeriswyl, E. J. Appl. Phys. 1994,
75, 514. (g) LanghalsH. German Patent 3901 988, 1990. (h) Hao, Z.; Iqbal,
A. Chem. Soc. ReV. 1997, 26, 203.
solutions. b Only the longest absorption peaks are shown. c Emission
maximum wavelength excited at the absorbance maximum.
In the experiments, n-Bu4NF (TBAF) as a fluoride source
was gradually added to a dichloromethane (DCM) solution
of the DPP compound. The deprotonated abilities of 1-3
with the fluoride ion were investigated by the UV-vis
absorption and fluorescence spectra. Here, 1F, 2F, and 3F
represent the corresponding DPP-based compounds of 1, 2,
and 3 with addition of the fluoride ion, respectively. Their
photophysical properties are summarized in Table 1. When
TBAF was added to the DCM solution of 3, an apparent
color change from orange to purple in ambient light, as
shown in the inset of Figure 2a, can be observed by the naked
eye. Upon progressive addition of TBAF, the intensity at
497 nm was gradually decreased, and a large bathochromic
shift (∼80 nm) of the maximum could be observed (Figure
2a). Meanwhile, a completely new band at 594 nm is
developed with clear isosbestic points at 543 nm indicating
(5) (a) Thompson, B. C.; Fre´chet, J.M. J. Angew. Chem., Int. Ed. 2008,
47, 58. (b) Wienk, M. M.; Turbiez, M.; Gilot, J.; Janssen, R. A. J. AdV.
Mater. 2008, 20, 2556. (c) Tamayo, A. B.; Walker, B.; Nguyen, T.-Q. J.
Phys. Chem. C 2008, 112, 11545. (d) Tamayo, A. B.; Dang, X.-D.; Walker,
B.; Seo, J.; Kent, T.; Nguyen, T.-Q. Appl. Phys. Lett. 2009, 94, 103301.
(e) Zhang, G. Q.; Liu, K.; Fan, H. J.; Li, Y.; Zhan, X. W.; Li, Y. F; Yang,
M. J. Synth. Met. 2009, 159, 1991.
(6) Yanagisawa, H.; Mizuguchi, J.; Aramakil, S.; Sakai, Y. Jpn. J. Appl.
Phys. 2008, 47/6, 4728.
(7) Zhu, Y.; Rabindranath, A. R.; Beyerlein, T.; Tieke, B. Macromol-
ecules. 2007, 40, 6981.
(8) (a) Jiang, Y. H.; Wang, Y. C.; Hua, J. L.; Qian, S. Q.; Tian, H. J.
Polym. Sci., Part A 2009, 47, 4400. (b) Guo, E. Q.; Ren, P. H.; Zhang,
Y. L.; Zhang, H. C.; Yang, W. J. Chem. Commun. 2009, 45, 5859.
(9) (a) Morales, A. R.; Yanez, C. O.; Schafer-Hales, K. J.; Marcus, A. I.;
Belfield, K. D. Bioconjugate Chem. 2009, 20, 1992. (b) Hung, Y- C.; Jiang,
J- C.; Chao, C- Y.; Su, W- F.; Lin, S- T. J. Phys. Chem. B 2009, 113,
8268. (c) Zhou, E. J.; Cong, J. Z.; Yamakawa, S.; Wei, Q. S.; Nakamura,
M.; Tajima, K.; Yang, C. H.; Hashimoto, K. Macromolecules 2010, 43,
2873. (d) Baheti, A.; Tyagi, P.; Thomas, K. R. J.; Hsu, Y- C.; Lin, J. T. J.
Phys. Chem. C 2009, 113, 8541.
Org. Lett., Vol. 12, No. 15, 2010
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the formation of a second species with stronger push-pull
electron effect. As shown in the inset of Figure 2b, the
emission spectra of 3 also displayed obvious changes when
the fluoride ion was added. With the fluoride ion addition, a
decrease of the emission at 563 nm and the emergence of a
red-shifted emission band at 635 nm were observed.
Scheme 1
.
Intermolecular Proton Transfer between 3 and the
Fluoride Ion
1
Figure 3
.
Partial H NMR spectra of sensor 3 in CDCl3 in the
presence of (a) 0 equiv, (b) 1 equiv, and (c) 2 equiv of TBAF.
To confirm this assumption, proton NMR titrations were carried
out (Figure 3). It was found that the amide NH proton signal
(∼10.56 ppm) decreased and finally disappeared with addition of
F-, which is well recognized to be due to hydrogen bonding
formation; therefore, the result is consistent with the breaking of
hydrogen bonding when the fluoride ion was added.
A near-linear correlation of sensor 3 between intensity ratios
of absorbance at 594 nm to those at 497 nm (A594/A497) vs
fluoride ion concentration in DCM was obtained (Figure 4a).
Figure 2
.
(a) UV-vis absorption spectra of 3 (5.0 × 10-6 M) in
DCM upon addition of 0-2.0 µM of TBAF. Inset: color changes
upon addition of F-. (b) Emission spectra of 3 (5.0 × 10-6 M) in
DCM upon the addition of 0-2.0 µM of TBAF. Inset: red emission
during titration experiment with F-.
On the basis of the above facts, a possible explanation
for the ratiometric absorption changes is the intermolecular
proton transfer (IPT) process between the amide moiety and
fluoride ion and its change from electronically neutral (Ar-
DPP-NH-Ar) without a fluoride ion to negatively charged
(Ar-DPP-N--Ar) with a fluoride ion (Scheme 1). The
modulation in the electron-donating capabilities of the amide
group in the presence and absence of fluoride directly
influences the internal charge transfer (ICT) from the amide
moiety to the conjugated system of the sensors. In the
presence of fluoride, the ICT effect from the amide anion to
the electron-withdrawing moiety is enhanced, which was
facilitated by the deprotonation of the amide moiety. This
enhancement in ICT effect also affords the reduced intensity
and bathochromic shift of fluorescence as a function of
fluoride concentration.
Figure 4. (a) Plot of the absorbance ratio of 3 between 594 and
497 nm (A594 nm/A497 nm) vs concentration of F-in DCM. (b) Plot of
the emission intensity ratio of 3 between 635 and 563 nm (I635 nm
/
I563 nm) vs concentration of F- in DCM.
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Org. Lett., Vol. 12, No. 15, 2010

This demonstrates the potential utility of sensor 3 for
calibrating and determining fluoride ion concentration in
DCM. Furthermore, F- could be detected at the parts per
million level when sensor 3 was employed at 5.0 × 10-6
M, and A594/A497 also increased linearly in this concentration
range. A corresponding correlation between emission ratio-
metric response of 3 at 635 and 563 nm (I635/I563) and fluoride
ion concentration in DCM was obtained in Figure 4b which
demonstrated that 3 can serve as a ratiometric fluorescent
sensor for F-. Similar effects were observed for 1 and 2 (see
Supporting Information).
Figure 6. (Top) Color (a, left) and fluorescence (b, right) change
of 1 (from left to right: 1 only; 1 + F-; 1 + Cl-; 1 + Br-; 1 + I-).
(Bottom) Color (c, left) and fluorescence (d, right) change of 2
(from left to right: 2 only; 2 + F-; 2 + Cl-; 2 + Br-; 2 + I-)
In summary, we have developed a novel prototype of
highly efficient colorimetric and fluorescent fluoride sensors
1-3 incorporating DPP. For receptors 1-3 in DCM, the
addition of fluoride results in ViVid orange-to-red absorption
color change and yellow-to-red emission color change due
to deprotonation, in which 3 exhibits the best sensitive
property and detects fluoride concentrations in a range of
0-10 µM at visible region wavelengths. The core mono-
substituted DPP design is an effective approach to develop
novel colorimetric and red fluorescent fluoride sensors.
Figure 5. (a) Absorbance ratiometric response of 3 between 594
and 497 nm to the halide ions (150 µM).(b) Emission ratiometric
response of sensor 3 to the halide ions (150 µM). The emissions
were at 635 and 563 nm and excited at 435 nm.
The experimental results suggest that compound 3 shows
high selectivity in colorimetric and fluorescent sensors for
the fluoride anion. As depicted in Figure 5a, the absorbance
at 594 nm was approximated 3-fold than that at 497 nm with
addition of 30 equiv of TBAF. Furthermore, no changes
were found with addition of other halide ions (also see
Figure S6 in the Supporting Information). Figure 5b shows
that emission intensity at 635 nm of 3 was approximated
8-fold than that at 563 nm with addition of 30 equiv of
F-, while Cl-, Br-, and I- caused no changes in the
emission spectra. Moreover, the selective properties of 1
and 2 show a similar response to the titration of TBAF
(Figure 6). Appearance of the red color and red emission
of 1 and 2 can also be expected because of deprotonation
of the NH proton caused by TBAF addition. However,
other halide ions produced insignificant changes in both
absorption and emission spectra.
Acknowledgment. This work was supported by NSFC/
China (20772031), National Basic Research 973 Program
(2006CB806200), the Fundamental Research Funds for the
Central Universities (WJ0913001), and the Scientific Com-
mittee of Shanghai.
Supporting Information Available: Synthetic procedures
of sensors 1-3, the absorption and fluorescent titration study
of sensors 1 and 2, full characterization for the DPP sensors
(1-3) described in this paper, and the pictures of the sensors
with addition of different halide ions. This material is
available free of charge via the Internet at http://pubs.acs.org.
OL101081M
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