A fluorescent color/intensity changed chemosensor for Fe3+ by photo-induced electron transfer (PET) inhibition of fluoranthene derivative

Article abstract of DOI:10.1016/j.dyepig.2011.11.007

A fluorescent color/intensity changed fluoranthene derivative chemosensor for Fe³⁺ has been prepared and confirmed by ¹H-NMR, ¹³C-NMR, HRMS, and crystal data, which displays a high selectivity and antidisturbance for Fe

Full text of DOI:10.1016/j.dyepig.2011.11.007

Dyes and Pigments 94 (2012) 60e65
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Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
A fluorescent color/intensity changed chemosensor for Fe3þ by photo-induced
electron transfer (PET) inhibition of fluoranthene derivative
,
a
a
a
c
b
a
Zhanxian Li a , Lifeng Zhang , Xiaoya Li , Yongkai Guo , Zhonghai Ni , Jianhong Chen , Liuhe Wei ,
*
Mingming Yu a
,b,
*
a Department of Chemistry, Zhengzhou University, Zhengzhou 450001, China
b Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technical Institute of Physics and Chemistry, CAS, Beijing 100190, China
c School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou 221006, China
a r t i c l e i n f o
a b s t r a c t
A fluorescent color/intensity changed fluoranthene derivative chemosensor for Fe3þ has been prepared
and confirmed by 1H-NMR, 13C-NMR, HRMS, and crystal data, which displays a high selectivity and
antidisturbance for Fe3þ among environmentally and biologically relevant metal ions. Fluorescence
studies show that fluorescent emission peak blue shifts about 100 nm with fluorescent intensity
enhancing 75-fold, indicating a Fe3þ-selective dual-emission behavior. Further study demonstrates the
detection limit on fluorescence response of the sensor to Fe3þ is down to 10ꢀ7 M range. The fluorescence
signals of chemosensor can be restored with o-phenanthroline, showing the binding of chemosensor and
Fe3þ is really chemically reversible.
Article history:
Received 25 September 2011
Received in revised form
14 November 2011
Accepted 20 November 2011
Available online 29 November 2011
Keywords:
Fluoranthene
Ó 2011 Elsevier Ltd. All rights reserved.
Fluorescent chemosensor
Fe3þ sensor
Photo-induced electron transfer
Fluorescence signal restore
Selectivity
1. Introduction
fluorescence enhancement are much more efficient when inter-
acting with analytes. Therefore, there is an urgent need to develop
The design of fluorescent chemosensors for various metal ions is
an important area because of their fundamental role in medical,
environmental and biological applications [1e4]. Up to now,
a number of fluorescent sensors for transition metal ions, such as,
Cu2þ [5e12], Zn2þ [13e22], Pb2þ [23e25], and Hg2þ [26e30] have
been reported. Surprisingly, the reported Fe3þ-selective fluorescent
sensors are relatively rare [31e41] despite the widespread appli-
cations of Fe3þ. Fe3þ is a biologically essential element and provides
the oxygen-carrying capacity of heme and acts as a cofactor in
many enzymatic reactions [42]. Fe3þ plays an important role in
many biological processes at the cellular level ranging from oxygen
metabolism to DNA and RNA synthesis [43]. Iron is indispensable
for most organisms, and both its deficiency and excess result in
various pathological disorders [44]. In addition, there are very rare
examples those that exhibit selective Fe3þ-amplified emission
[31e36] though it is generally believed that chemosensors with
fluorescent Fe3þ-chemosensors, especially those that exhibit
selective Fe3þ-amplified emission.
Therefore, we are motivated to design and synthesize a novel
molecular system which can sense Fe3þ against environmental and
biological samples. Because polyphenyl derivatives are easy to
synthesize and their structures are relatively simple, they may be
ideal molecular chemosensors [45]. It is a pity that there are very
rare examples about such compounds applied in the detection of
metal ions except our previous work about two polyphenyl
derivatives (compounds 1 and 2 in Fig. 1) in the detection of Zn2þ
,
Cu2þ, and Fe3þ [46,47]. As for compound 1, Zn2þ made the rotation
of CeC among the aromatic rings inhibited while Cu2þ made
electron and/or energy transfer happen, which resulted in the
emission intensity of 1 changing differently [46]. As for compound
2, the paramagnetic property and unfilled d shell of Fe3þ led to the
possibility of electron and/or energy transfer with organic fluo-
rophores opening a non-radiative deactivation channel, resulting
in the emission intensity of 2 decreasing. If the electrophilic
group pyridyl ring was replaced with electron-donating group
aniline, that is, what influence on the emission spectra of 4-
* Corresponding authors. Department of Chemistry, Zhengzhou University,
Zhengzhou 450001, China. Tel./fax: þ86 371 67781205.
E-mail addresses: lizx@zzu.edu.cn (Z. Li), yumm@zzu.edu.cn (M. Yu).
0143-7208/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.dyepig.2011.11.007

Z. Li et al. / Dyes and Pigments 94 (2012) 60e65
61
(7,10-diphenylfluoranthen-8-yl)benzenamine (3) (compound 3 in
Fig. 1 and 2) will be when different metal ions were added into the
solution of compound 3? This question was answered in this
manuscript.
2. Experiment
2.1. Materials and methods
All chemicals were purchased from commercial suppliers and
used without further purification. All reactions were performed
under an argon atmosphere with the solvents purified with stan-
dard methods.
1H and 13C-NMR spectra were recorded on a Bruker 400 spec-
trometer. Chemical shifts are reported in ppm using tetrame-
thylsilane (TMS) as the internal standard. Mass spectra were
obtained on high resolution mass spectrometer (IonSpec4.7 Tesla
FTMS-MALDI/DHB).
Fig. 2. X-ray crystal structure of 3. Hydrogen atoms are omitted for clarity.
All spectral characterizations were carried out in HPLC-grade
solvents at 20 ꢁC within a 10 mm quartz cell. UVevis absorption
spectra were measured with a TU-1901 double-beam UVevis
Spectrophotometer, and fluorescence spectra were determined on
a Hitachi F-4500 spectrometer. The fluorescence quantum yield
was measured at 20 ꢁC with quinine bisulfate in 1 M H2SO4
(Vfr ¼ 0.546) selected as the reference.
2.4. Synthesis of 7,9-diphenyl-8H-cyclopenta[l]acenaphthylen-8-
one (6)
Acenaphthenedione (546.5 mg, 3 mmol) were added into the
ethanol (5 mL) solution of 1,3-diphenylacetone (630.8 mg, 3 mmol)
under heating and stirring. Under refluxing and stirring, the
ethanol solution (2 mL) of KOH (94.1 mg) was dropwised in the
above mixture. After reacting 5 min, the product was obtained after
the above solution was cooled for 12 h and was filtrated. The yield:
1.038 g, 90%. Characterization of compound 6: 1H-NMR: dH
(400 MHz; CDCl3; Me4Si) 8.08 (m, 2H), 7.87 (m, 6H), 7.61 (m, 2H),
7.55 (m, 4H), and 7.43 (m, 2H). 13C-NMR: dC (100 MHz, CDCl3):
154.21, 132.14, 131.54, 131.44, 129.07, 128.58, 128.42, 128.29,
127.75 121.66, and 120.93.
2.2. Synthesis of 4-dimethylsilanylethynyl-phenylamine (4)
Triethylamine (2.5 mL), p-iodoaniline (1.0237 g, 467.4 mmol),
CuI (0.0901 g, 0.473 mmol), Pd(PPh3)2Cl2 (0.1651 g, 0.235 mmol),
and ethynyl-trimethyl-silane (0.8 mL, 562 mmol) were added in
THF under argon atmosphere and the above mixture was refluxed
for 5 h. The crude product was obtained by reduced pressure
distillation and the final product (654.9 mg) was gained by column
chromatography over silica gel column using dichloromethane/
light petroleum (2:1) as eluent. The yield was 74.5%. Compound 4-
dimethylsilanylethynyl-phenylamine was directly used in the
formation of 4-ethynyl-phenylamine without characterization.
2.3. Synthesis of 4-ethynyl-phenylamine (5)
4-dimethylsilanylethynyl-phenylamine (0.9078 g, 479.5 mmol)
and methanol solution of KOH (0.4374 g/8.2 mL) were added in
30 mL THF and the mixture was stirred for 5 h at room temperate.
The crude product was obtained from the concentration in vacuum
and extraction with ethyl acetate. The final product (280.5 mg) was
obtained by column chromatography over silica gel column using
dichloromethane/light petroleum (2:1) as eluent. The yield was
50%. Characterization of compound 4-ethynyl-phenylamine: 1H-
NMR: dH (400 MHz; CDCl3; Me4Si) 7.30 (m, 2H), 6.61 (m, 2H), 3.83
(s, 2H), and 2.98 (s, 1H). 13C-NMR: dC (100 MHz, CDCl3): 147.04,
133.48, 114.60, 111.32, 84.42, and 74.92.
Fig. 1. Molecular structures of compounds 1, 2, and 3.
Scheme 1. Synthetic route of compound 3.

62
Z. Li et al. / Dyes and Pigments 94 (2012) 60e65
column chromatography (200e300 mesh), using a CH2Cl2ehexane
(1:1) mixture as eluent (2.1805 g, 65%). Characterization of
compound 3: HRMS (EI) calcd. for C34H23N [M], 445.1830; found,
445.1824. 1H-NMR: dH (400 MHz; CDCl3; Me4Si) 7.73 (m, 4H), 7.54
(m, 3H), 7.41 (m, 6H), 7.31 (m, 4H), 7.03 (m, 2H), 6.67 (m, 1H), 6.52
(m, 2H), and 3.60 (s, 2H). 13C-NMR: dC (100 MHz, CDCl3): 144.54,
140.93, 138.23, 135.11, 133.11, 130.36, 129.14, 127.15, 126.52, 123.26,
122.70, and 114.50.
3. Results and discussion
Using DielseAlder reaction, a fluorescent chemosensor 4-(7,10-
diphenylfluoranthen-8-yl)benzenamine (3), as a dual-emission
Fe3þ sensor, was synthesized according to Scheme 1 and modi-
fied methods [48e54]. Upon addition of FeCl3 into the ethanol
solution of 3, it exhibits a great increase of emission intensity (I/
I0 ¼ 8) against environmental and biological samples. Moreover, the
fluorescence signals can be restored by the addition of orthophe-
nanthroline solution into the mixture solution of 3 and FeCl3.
Further experiments demonstrate that Fe(NO3)3 have the similar
influence as FeCl3 while Fe2(SO4)3 has no influence on the emission
spectra of 3.
Fig. 3. Changes in absorption spectra of 3 (8.3 ꢂ 10ꢀ6 M) in ethanol upon addition of
Fe3þ. The final ratio of Fe3þ to 3 is 1.6 equiv.
The absorption spectra of compound 3 (8.3 ꢂ 10ꢀ6 M) in ethanol
reveals four bands at 206, 235, 300, and 376 nm (molar extinction
coefficient ε206 ¼ 8.37 ꢂ 104 Mꢀ1 cmꢀ1, ε235 ¼ 7.92 ꢂ 104 Mꢀ1 cmꢀ1
,
ε300 ¼ 3.59 ꢂ 104 Mꢀ1 cmꢀ1, and ε376 ¼ 1.26 ꢂ 104 Mꢀ1 cmꢀ1). These
bands may be assigned to electron transition from
p to p*. The
addition of 1.6 equiv of FeCl3 (Fe3þ, 1.3 ꢂ 10ꢀ5 M), led to the great
increase of the original absorbance (ε206 ¼ 1.48 ꢂ 105 Mꢀ1 cmꢀ1
,
ε235 ¼ 1.60 ꢂ 105 Mꢀ1 cmꢀ1, ε300 ¼ 7.54 ꢂ 104 Mꢀ1 cmꢀ1, and
ε376 ¼ 5.96 ꢂ 104 Mꢀ1 cmꢀ1) (Fig. 3). Such absorption change may
be ascribed to the newly formed complex and the absorption of
Fe3þ in the UVevis region [47].
Compound 3 exhibits relatively weak fluorescence emission at
550 nm in ethanol upon excitation at 360 nm (Fig. 4) (Vfr ¼ 0.055)
[55]. Upon titration of Fe3þ (1.3 ꢂ 10ꢀ5 M), the fluorescence of 3 was
significantly enhanced (Vfr ¼ 0.133, I/I0 ¼ 75.4) with fluorescence
emission wavelength change from 557 nm to 450 nm (Fig. 3),
indicating an efficient Fe3þ-selective dual-emission behavior. The
increased emission intensity is probably due to the complex of Fe3þ
and 3, in which, the coordination of Fe3þ and 3 inhibits the photo-
induced electron transfer (PET) from electron-donating group
aniline to electron-receptor 7,10-diphenyl-fluoranthenyl group
(Fig. 5) [54]. Fig. 6 demonstrates the relationship between the
concentration of Fe3þ and the emission intensity at special wave-
length. The detection limit on fluorescence response of the sensor
to Fe3þ is 2.49 ꢂ 10ꢀ7 M. A Job’s plot indicated that 3 chelated Fe3þ
with 2:1 stoichiometry (Fig. 7).
Fig. 4. Changes in fluorescence emission spectra of 3 (8.3 ꢂ 10ꢀ6 M) in ethanol upon
addition of Fe3þ with excitation at 360 nm. The final ratio of Fe3þ to 3 is 1.6 equiv. Inset:
fluorescence emission spectra of 3 in ethanol (lex ¼ 360 nm).
2.5. Synthesis of 4-(7,10-diphenylfluoranthen-8-yl)
benzenamine (3)
A stirred mixture of 4-ethynylaniline (1.0506 g, 6 mmol)
and 7,9-diphenyl-8H-cyclopenta[l]acenaphthylen-8-one (2.6708 g,
7.5 mmol) in degassed o-xylene (25 mL) was refluxed for 15 h. The
solvent was removed under vacuum. The solid was purified by
The experiments of the counterion effect on the selective
properties of Fe3þ (Fig. 8) were also measured. Addition of ferric
Fig. 5. Proposed process of 3 in sensing of Fe3þ
.

Z. Li et al. / Dyes and Pigments 94 (2012) 60e65
63
Fig. 6. Emission intensity of compound 3 (8.3 ꢂ 10ꢀ6 M in ethanol) at 450 nm (black
Fig. 9. Fluorescent responses of 3 (8.3 ꢂ 10ꢀ6 M in ethanol) upon addition of different
metal salts (0.4 equiv.) (lex ¼ 360 nm). I and I0 represent the emission intensity at
450 nm. The metal salts represent NaCl, MgCl2, KCl, CaCl2, CrCl3, MnCl2, CoCl2, NiCl2,
CuCl2, ZnCl2, CdCl2, and HgCl2. Inset: solution color change upon addition of Fe3þ [56].
dot) as a function of addition of Fe3þ with excitation at 360 nm.
sulfate made the fluorescence of compound 3 change very little,
and ferric nitrate had similar influence as that of ferric chloride.
The specificity of the chemosensor 3 toward Fe3þ was deter-
mined next, as shown in Figs. 9 and 10. Upon addition of the same
amount of the various metal ions (3.3 ꢂ 10ꢀ6 M), respectively, only
Fe3þ enhanced the emission of 3 (I/I0 ¼ 8.4). However, under
identical conditions, nearly no fluorescence intensity changes were
observed in emission spectra with Naþ, Mg2þ, Kþ, Ca2þ, Cr3þ, Mn2þ
,
Co2þ, Ni2þ, Cu2þ, Zn2þ, Cd2þ, and Hg2þ. That is, sensor 3 can readily
distinguish Fe3þ from environmentally and biologically relevant
metal ions by fluorescent spectra.
The competition experiments were also conducted for
3
(Fig. 11). When 0.4 equiv of Fe3þ was added into the solution of 3 in
the presence of 10 equiv of other ions, similar fluorescence spectra
change was displayed to that with Fe3þ ion only. Because the
amount of Naþ, Mg2þ, Kþ, and Ca2þ is much more than Fe3þ bio-
logically, it is necessary to measure the disturbance when the
amount of these metal ions is much higher than that of Fe3þ. The
measurement experiments show that no fluorescence change was
Fig. 7. Job plot for determining the stoichiometry of 3 and Fe3þ ion in ethanol. The
variation of the emission intensity at 450 nm were measured as a function of molar
ratio XM ([3]/([Fe3þ] þ [3])).
Fig. 10. Fluorescence spectra changes of 1 (8.3 ꢂ 10ꢀ6 M) upon addition of different
metal ions (FeCl3, NaCl, MgCl2, KCl, CaCl2, CrCl3, MnCl2, CoCl2, NiCl2, CuCl2, ZnCl2, CdCl2,
and HgCl2, 1.3 ꢂ 10ꢀ5 M) in ethanol.
Fig. 8. Fluorescence emission spectra of 3 (8.3 ꢂ 10ꢀ6 M) in ethanol upon addition of
different ferric salts (1.3 ꢂ 10ꢀ5 M) with excitation at 360 nm.

64
Z. Li et al. / Dyes and Pigments 94 (2012) 60e65
Acknowledgments
We are grateful for the financial supports from the NSFC
(50903075 and 50873093) and Key Laboratory of Photochemical
Conversion and Optoelectronic Materials.
Supplementary data
Crystallographic data have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication no.
CCDC 835066. Crystallographic data is available.
Appendix. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.dyepig.2011.11.007.
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Fig. 11. Fluorescence change that occurs upon addition of Fe3þ (3.3 ꢂ 10ꢀ6 M) to the
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ground cation to Fe3þ is 10) (lex ¼ 360 nm). I and I0 represent the emission intensity at
450 nm. The metal salts represent NaCl, MgCl2, KCl, CaCl2, CrCl3, MnCl2, CoCl2, NiCl2,
CuCl2, ZnCl2, CdCl2, and HgCl2.
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