Bismuth ions selective fluorescent chemosensor based on rhodamine-B

Article abstract of DOI:10.14233/ajchem.2016.19264

A new rhodamine-based compound (L1) has been synthesized and applied as an "off-on" chemosensor for Bi³⁺. The complexation behaviour of chemosensor with different metal ions including Bi³⁺ ions in EtOH/H²O (4:1, v/v) was studied on UV-visible absorption spectra and fluorescent spectra. Results showed that the chemosensor (L1) is highly selective for Bi³⁺ over other cations such as Hg²⁺, Fe²⁺, Mn²⁺ and Ca²⁺. This selectivity can be attributed to the photoinduced electron transfer mechanism (PET) of the sensor in the presence of Bi³⁺. The complex solution (L1-Bi³⁺) exhibited reversibility with EDTA.

Full text of DOI:10.14233/ajchem.2016.19264

Asian Journal of Chemistry; Vol. 28, No. 2 (2016), 287-290
A
SIAN
J
OURNAL OF HEMISTRY
C
http://dx.doi.org/10.14233/ajchem.2016.19264
Bismuth Ions Selective Fluorescent Chemosensor Based on Rhodamine-B
*
LIANWEI YU, JIANFEI TIAN and FULI TIAN
College of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot 010021, P.R. China
*Corresponding author: E-mail : ftian@imu.edu.cn; 2803546043@qq.com
Received: 20 April 2015;
Accepted: 19 June 2015;
Published online: 3 November 2015;
AJC-17592
A new rhodamine-based compound (L1) has been synthesized and applied as an “off-on” chemosensor for Bi3+. The complexation
behaviour of chemosensor with different metal ions including Bi3+ ions in EtOH/H2O (4:1, v/v) was studied on UV-visible absorption
spectra and fluorescent spectra. Results showed that the chemosensor (L1) is highly selective for Bi3+ over other cations such as Hg2+, Fe2+,
Mn2+ and Ca2+. This selectivity can be attributed to the photoinduced electron transfer mechanism (PET) of the sensor in the presence of
Bi3+. The complex solution (L1-Bi3+) exhibited reversibility with EDTA.
Keywords: Rhodamine-B, Fluorescent chemosensor, Bismuth ions.
sensor has been synthesized by connecting the rhodamine
derivatives with 2,2’-dipicolylamine through an amido group
bridge [12,13], which shows very high sensitivity and selec-
tivity toward Bi3+ over other metal ions.
INTRODUCTION
The design and synthesis of functional fluorescence
probes for metal ions are of growing interest because of their
potential application in biomedical and environmental chemo-
sensors as well as molecular logic devices [1-3]. Although
considerable efforts have been devoted to the elaboration of
luminescence sensors for various metal ions in the last two
decades, there are only a handful of reports on Bi3+ fluorescent
chemosensors [4,5]. Bismuth ions have been widely applied
to the biological preparation, low-temperature alloys, inorganic
materials modification and the preparation of new materials
such as magnetism and optics recently. Many techniques are
available for determining bismuth concentration in samples
such as gravimetric method, volumetric method and atomic
absorption spectrophotometry, but these methods are both
complicated and costly compared with fluorescence determi-
nation [6,7]. Therefore, the design of a reliable and sensitive
analytical method to efficiently evaluate the Bi3+ level in
environmental and biological systems is highly desirable [7].
So far, various fluorophores with different excitation and
emission wavelengths have been employed to develop various
chemical sensors with superior properties for the detection of
metal ions [8].Among the fluorophores developed, rhodamine
and its derivatives are highly favourable because of their high
absorption coefficients, high fluorescence quantum yields and
long absorption and emission wavelengths. As we know, 2,2’-
dipicolylamine (DPA) is also used as a receptor to bind certain
metal ions [9,10]. Based on both rhodamine and 2,2’-dipicolyl-
amine remarkable properties [11], a novel fluorescent chemo-
EXPERIMENTAL
All chemicals used in the experiments were of analytical
grade and purchased from commercial suppliers. The UV-
visible spectra were recorded on a Hitachi U-3900 spectro-
photometer and fluorescence spectra were recorded with a
Hitachi F-7000 spectrophotometer with excitation at 371 nm
1
(slit width, 5 mm). H NMR spectra were recorded at room
temperature on a Bruker Avance-500 NMR spectrometer.
Synthesis and characterization of compound 1: To a
solution of rhodamine-B (3.8 g, 7.95 mmol) in 100 mL of
ethanol was added ethane-1,2-diamine (5 mL, 75 mmol). The
mixture was refluxed for 12 h and was then taken to dryness
under vacuum. The residue was dissolved in CH2Cl2 and then
washed with H2O and brine respectively. The organic layer
was dried with MgSO4. After the removal of the solvent, flash
chromatography (silica gel; MeOH/CH2Cl2, 3:97, v/v) of the
1
residue gave compound 1 as a yellow solid. H NMR (500
MHz, CDCl3) δ 7.90 (dd, J = 5.7, 3.0 Hz, 1H), 7.46-7.42 (m,
2H), 7.11-7.07 (m, 1H), 6.43 (d, J = 8.8 Hz, 2H), 6.37 (d, J =
2.5 Hz, 2H), 6.28 (d, J = 2.6 Hz, 1H), 6.26 (d, J = 2.6 Hz, 1H),
3.33 (q, J = 7.3 Hz, 8H), 3.19 (t, J = 6.5 Hz, 2H), 2.43 (t, J =
6.6 Hz, 2H), 1.56 (s, 2H), 1.16 (t, J = 7.1 Hz, 12H).
Synthesis and characterization of compound 2: 2-
Chloroacetyl chloride (2 mL, 20.9 mmol) was dissolved in
chloroform (10 mL) and added dropwise to a cooled and stirred

288 Yu et al.
Asian J. Chem.
solution of compound 1 (2.6 g, 5.03 mmol) and pyridine
(0.43 mL, 5.2 mmol) in chloroform (10 mL) within 1 h. After
the reaction solution was stirred for 2 h at room temperature,
the solvent was removed under reduced pressure and the white
powder was washed with dichloromethane and diethyl ether.
1H NMR (500 MHz, CDCl3) δ 7.93 (dd, J = 5.9, 2.7 Hz, 1H),
7.73 (s, 1H), 7.46 (dd, J = 5.0, 3.5 Hz, 2H), 7.08 (dd, J = 5.8,
2.6 Hz, 1H), 6.44 (d, J = 8.8 Hz, 2H), 6.38 (s, 2H), 6.28 (d, J
= 8.0 Hz, 2H), 3.93 (s, 2H), 3.34 (q, J = 6.9 Hz, 10H), 3.09 (d,
J = 4.8 Hz, 2H), 1.17 (t, J = 7.0 Hz, 12H).
Synthesis and characterization of L1: Compound 2
(0.56 g, 1.01 mmol), 2,2’-dipicolylamine (DPA) (0.19 mL, 1
mmol), N,N-diisopropylethylamine (0.18 mL, 1.01 mmol) and
potassium iodide (4 mg) were dissolved in acetonitrile (30 mL),
stirred and refluxed for 12 h under nitrogen atmosphere. The
mixture was cooled to room temperature and the solvent was
removed under reduced pressure to obtain yellow oil, which was
purified by silica gel column chromatography using chloroform/
methanol (30:1, v/v) as eluent to afford product (Scheme-I).
1H NMR (500 MHz, CDCl3) δ 7.93 (dd, J = 5.9, 2.7 Hz, 1H),
7.73 (s, 1H), 7.46 (dd, J = 5.0, 3.5 Hz, 2H), 7.08 (dd, J = 5.8,
2.6 Hz, 1H), 6.44 (d, J = 8.8 Hz, 2H), 6.38 (s, 2H), 6.28 (d, J
= 8.0 Hz, 2H), 3.93 (s, 2H), 3.34 (q, J = 6.9 Hz, 10H), 3.09 (d,
J = 4.8 Hz, 2H), 1.17 (t, J = 7.0 Hz, 12H).
2
1
0
Hg2+
Al3+,Ag+,Ba2+,Ca2+,Cd2+,Co2+,Fe2+
,
K+,Mg2+,Mn2+,Na+,Ni2+,Pb2+,Sn2+,Sr2+
Zn2+,Blank
,
Bi3+
200
300
400
500
Wavelength (nm)
Fig. 1. UV-visible absorption spectra of chemosensor L1 (5 µM) in absence
and presence of different metal ions (50 µM) at room temperature
and 310 nm, respectively. The position of absorption band
remained unchanged with the various metal ions, however a
new absorption band at 385 nm was formed with Bi3+.
Fluorescence studies of chemosensor: The fluorescence
behaviour of chemosensor (L1) was investigated in Hitachi
F-7000 fluorescence spectrometer upon the addition of various
metal ion solution. Chemosensor (L1) did not show any signi-
ficant quenching alone when the excitation wavelength was at
317 nm. After the addition of Hg2+, Al3+, Bi3+, Ag+, Ba2+, Ca2+,
Cd2+, Co2+, Fe2+, K+, Cu2+, Mg2+, Mn2+, Na+, Ni2+, Pb2+, Sn2+,
Sr2+ and Zn2+ (Fig. 2), chemosensor (L1) did not exhibit any
significant fluorescent quenching (except Al3+, Sn2+, Cu2+ and
Bi3+ ions). Only in case of Bi3+ ions it exhibited a clear fluorescent
quenching (about 15-fold) (Fig. 2). Interferences of cations
had been investigated by treating chemosensor L1 with 10
equiv. of Bi3+ in the presence of 10 equiv. of other metal ions.
RESULTS AND DISCUSSION
UV-visible studies of chemosensor with various metal
ions: UV-visible absorption spectra of chemosensor (L1) in
the presence of various metal ions Hg2+, Al3+, Bi3+, Ag+, Ba2+,
Ca2+, Cd2+, Co2+, Fe2+, K+, Mg2+, Mn2+, Na+, Ni2+, Pb2+, Sn2+,
Sr2+ and Zn2+ (conc. of 50 µM) were recorded in EtOH/H2O
(4:1, v/v) using a Hitachi U-3900 spectrophotometer. As seen
in Fig. 1, the absorption spectrum of chemosensor L1 exhibited
a broad absorption band at 230 nm, two weak bands at 275
O
O
O
NH2
C
N
Cl
OH
Cl
ethane-1,2-diamine
Cl-
+
EtOH,Reflux
Py
N
N
O
N
N
O
1
N
O
O
O
O
N
Cl
N
N
H
H
N
N
DPA
KI/DIEA/CH3CN
N
N
N
N
N
O
O
2
L1
Scheme-I

Vol. 28, No. 2 (2016)
Bismuth Ions Selective Fluorescent Chemosensor Based on Rhodamine-B 289
3500
Hg2+
3500
3000
2500
2000
1500
1000
500
3000
L
Ag+
Al3+
Ba2+
Bi3+
Ca2+
Cd2+
Co2+
Cu2+
Fe2+
K+
2500
3000
2000
Mg2+
1500
1000
500
0
Mn2+
Na+
Ni2+
2000
1000
0
Pb2+
Sn2+
Sr2+
Zn2+
0.0 0.5 1.0 1.5 2.0 2.5 3.0
3+
Bi /L1
0
350
400
450
500
550
600
Wavelength (nm)
350
400
450
500
550
Fig. 2. Fluorescence emission spectra of L1 (5 µM) in EtOH/H2O (4:1,
v/v) in the presence of different metal ions (50 µM) such as Hg2+,
Al3+, Bi3+, Ag+, Ba2+, Ca2+, Cd2+, Co2+, Fe2+, K+, Cu2+, Mg2+, Mn2+,
Na+, Ni2+, Pb2+, Sn2+, Sr2+ and Zn2+. Excitation wavelength was at
371 nm and emission maximum was 418 nm
Wavelength (nm)
Fig. 4. Fluorescence emission spectra of L1 upon addition of Bi3+ (0.0,
0.025, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, 1.5,
2.0, 2.5, 3.0 equiv.) with an excitation of 317 nm
As shown in Fig. 3, the response of chemosensor (L1) for Bi3+
O
in the presence of competing metal ions were not affected.
NH
N
Bi3+
3500
3000
2500
2000
1500
1000
500
N
O
N
N
O
N
N
O
NH
O
N
N
Bi3+
N
N
O
N
N
Fig. 5. Proposed binding mechanism of the chemosensor 1 with Bi3+
0
none Ag +Ba2+Ca2+Cd2+Co2+Cu2+Fe2+Hg2+K+Mg2+Na+Ni2+Sn2+Sr2+Zn2+
Fig. 3. Selectivity of L1 for Bi3+ ions in the presence of other competitive
metal ions in (5 µM), excitation wavelength and emission maximum
are 371 and 418 nm, respectively. Blue bars represent fluorescent
intensity after the addition 50 µM of the appropriate metal ion (Hg2+,
Al3+, Bi3+, Ag+, Ba2+, Ca2+, Cd2+, Co2+, Fe2+, K+, Cu2+, Mg2+, Mn2+,
Na+, Ni2+, Pb2+, Sn2+, Sr2+ and Zn2+) in a 50 µM solution of L1. Red
bars represent the subsequent addition of same equiv. of Bi3+ ions
in each of the samples
4000
3500
L1
L1+Bi3+
Li+Bi3++EDTA
3000
2500
2000
1500
1000
500
Sensitivity of L1 for bismuth ions was examined with the
titration of different concentration of Bi3+ ions (0.0, 0.025,
0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.5, 1.8, 2.0,
2.5 and 3.0 equiv.) at 418 nm (Fig. 4). The fluorescence
intensity gradually decreased with increasing the concentration
of Bi3+. As shown in Fig. 4, the fluorescence intensity of L1
didn’t reduce any more when the {[Bi3+]/[L1]} was at a molar
ratio of 1. Hence, it is concluded that the binding ratio between
the chemosensor and Bi3+ was 1:1.
0
350
400
450
500
550
600
Wavelength (nm)
Fig. 6. Fluorescent emission spectra of L1 (10 µM) in the presence of Bi3+
ions (1.0 equiv.) or EDTA (0.6 equiv.) in EtOH/H2O (4:1, v/v)
Binding mode of chemosensor: The proposed binding
mechanism is shown in Fig. 5.As can be seen, Bi3+ is bound to
the amide oxygen and the nitrogen atom of 2,2’-dipicolylamine.
The reversibility nature of chemosensor L1 was showed
by the titration of EDTA with fluorescent chemmosensor
(L1+Bi3+), results are shown (Fig. 6) that chemosensor L1 in
(L1+Bi3+) was replaced by EDTA and formed (EDTA+Bi3+).
Therefore, fluorescent chemosensor L1 could be recyclable
simply through treatment with a proper reagent such as EDTA.
The effect of different solvents DMSO, THF, DMF, aceto-
nitrile, dichloromethane and methanol on the detection of Bi3+
ions by L1 had been explored and the results were showed in
Fig. 7, it can be seen that the fluorescence is changed variously

290 Yu et al.
Asian J. Chem.
promising to evaluate the Bi3+ level in environmental and
biological systems.
1200
1000
800
600
400
200
0
MeCN
DMSO
DCM
DMF
EtOH
THF
ACKNOWLEDGEMENTS
This work was financially supported by the National
Nature Science Foundation of China (No. 21265010).
REFERENCES
MeOH
1. Z.-X. Han, B.-S. Zhu, T.-L. Wu, Q.-Q. Yang, Y.-L. Xue, Z. Zhang and
X.-Y. Wu, Chin. Chem. Lett., 25, 73 (2014).
2. T. Yu, J. Meng, Y. Zhao, H. Zhang, X. Han and D. Fan, Spectrochim.
Acta A Mol. Biomol. Spectrosc., 78, 396 (2011).
3. M. Hranjec, E. Horak, M. Tireli, G. Pavloviæ and G. Karminski-Zamola,
Dyes Pigments, 95, 644 (2012).
4. M.X. Wang, X.M. Meng, M.Z. Zhu and Q.X. Guo, Chin. Chem. Lett.,
19, 977 (2008).
5. Q. Liu, G.-P. Li, D.-J. Zhu, L. Xue and H. Jiang, Chin. Chem. Lett., 24,
479 (2013).
6. V.K. Gupta, A.K. Singh and L.K. Kumawat, Sens. Actuators B, 204,
507 (2014).
350
400
450
500
550
600
Wavelength (nm)
Fig. 7. Solvent effect on fluorescent intensity of L1 probe in different
solvent DMSO, DMF, DCM, methanol, THF and aetonitrile, ethanol
7. L. Zhu, C.Y. Gu, Y. He and G. Wang, J. Lumin., 153, 439 (2014).
8. Y. Liu, E.-B.Yang, R. Han, D. Zhang, Y.Ye andY.-F. Zhao, Chin. Chem.
Lett., 25, 1065 (2014).
9. Y.-Y. Wu, Y. Chen, W.-H. Mu, X.-J. Lv and W.-F. Fu, J. Photochem.
Photobiol. Chem., 272, 73 (2013).
due to different solvents. The best result was observed with
ethanol.
Conclusion
In conclusion, a bismuth-sensitive fluorescent chemosensor
was synthesized, which showed high sensitivity and selectivity
toward Bi3+ over other competitive metal ions. The presence
of metal ions such as Hg2+, Al3+, Ag+, Ba2+, Ca2+, Cd2+, Co2+,
Fe2+, K+, Cu2+, Mg2+, Mn2+, Na+, Ni2+, Pb2+, Sn2+, Sr2+ and Zn2+
had little influence on the selectivity and sensitivity of Bi3+.
The fluorescent nature of L1-Bi3+ complex goes to “turn-off”
in presence of Bi3+ and EDTA. This type of sensor design is
10. H.G. Lee, J.H. Lee, S.P. Jang, I.H. Hwang, S.-J. Kim, Y. Kim, C. Kim
and R.G. Harrison, Inorg. Chim. Acta, 394, 542 (2013).
11. C. Gao, X. Jin, X. Yan, P. An, Y. Zhang, L. Liu, H. Tian, W. Liu, X. Yao
and Y. Tang, Sens. Actuators B, 176, 775 (2013).
12. C.-Y. Li, C.-X. Zou, Y.-F. Li, J.-L. Tang and C. Weng, Dyes Pigments,
104, 110 (2014).
13. X.-H. Yang, S. Li, Z.-S. Tang, X.-D. Yu, T. Huang and Y. Gao, Chin.
Chem. Lett., 26, 129 (2015).