Fluorescence sensing of iodide and bromide in aqueous solution: Anion ligand exchanging and metal ion removing

Article abstract of DOI:10.1039/c2nj40102a

A new rhodamine-based fluorescent probe RSP was facilely synthesized. Interestingly, the RSP-Hg-ClO₄ ensemble can serve as a selective fluorescent probe for iodide and bromide based on metal ion removal and anion ligand exchanging, which is a novel rhodamine-based fluorescence sensing mechanism. Moreover, RSP can recognise Hg²⁺ selectively in 99% aqueous solution. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2012.

Full text of DOI:10.1039/c2nj40102a

View Online / Journal Homepage
NJC
Accepted Manuscript
This is an Accepted Manuscript, which has been through the RSC Publishing peer
review process and has been accepted for publication.
Accepted Manuscripts are published online shortly after acceptance, which is prior
to technical editing, formatting and proof reading. This free service from RSC
Publishing allows authors to make their results available to the community, in
citable form, before publication of the edited article. This Accepted Manuscript will
be replaced by the edited and formatted Advance Article as soon as this is available.
New Journal of Chemistry
An international journal of the chemical sciences
www.rsc.org/njc
Volume 34 | Number 12 | December 2010 | Pages 2685–3016
To cite this manuscript please use its permanent Digital Object Identifier (DOI®),
which is identical for all formats of publication.
More information about Accepted Manuscripts can be found in the
Information for Authors.
Please note that technical editing may introduce minor changes to the text and/or
graphics contained in the manuscript submitted by the author(s) which may alter
content, and that the standard Terms & Conditions and the ethical guidelines
that apply to the journal are still applicable. In no event shall the RSC be held
responsible for any errors or omissions in these Accepted Manuscript manuscripts or
any consequences arising from the use of any information contained in them.
ISSN 1144-0546
PERSPECTIVE
Kaisa Helttunen and
Patrick Shahgaldian
Self-assembly of amphiphilic
calixarenes and resorcinarenes in water
1144-0546(2010)34:12;1-1
www.rsc.org/njc
Registered Charity Number 207890

Page 1 of 5
New Journal of Chemistry
View Online
A new rhodamine-based fluorescent probe RSP for Hg2+ was facilely synthesized. Interesting,
RSP-Hg-ClO4 ensemble can serves as a fluorescent probe for iodide and bromide by metal ion
removing and anion ligand exchanging, which was a novel rhodamine-based fluorescence sensing
mechanism.

New Journal of Chemistry
Page 2 of 5
Dynamic Article Links ►
NJC
View Online
Cite this: DOI: 10.1039/c0xx00000x
www.rsc.org/njc
LETTER
Fluorescence sensing of iodide and bromide in aqueous solution: anion
ligand exchanging and metal ion removing
Lin Xu, Yufang Xu, Weiping Zhu, Zheng Xu, Mengjie Chen and Xuhong Qian*
Received (in XXX, XXX) Xth XXXXXXXXX 2011, Accepted Xth XXXXXXXXX 2011
5
DOI: 10.1039/b000000x
verified by 1H NMR, 13C NMR and HRMS (ESI, Fig. S1).
A new rhodamine-based fluorescent probe RSP was facilely
synthesized. Interesting, RSP-Hg-ClO4 ensemble can serve as
a selective fluorescent probe for iodide and bromide base on
metal ion removing and anion ligand exchanging, which was a
10 novel rhodamine-based fluorescence sensing mechanism.
Moreover, RSP can recognise Hg2+ selectively in 99%
aqueous solution.
The specific detection of anions is an active field of research
because of their important roles in biological, industrial and
15 environmental processes.1 Among anions, iodide is of particular
interest due to its essential role in normal growth, development
and functioning of brain and body.2 Abnormal iodide level in the
thyroid gland can lead to major health concerns. In addition,
elemental iodine is frequently involved in organic synthesis,
20 including medicine and dyes.3
Along with iodide, bromide is widely present in either natural
environment or in biological fluids such as saline, salt well, urine,
serum and saliva of organism.4 Bromide plays important roles in
the areas of environmental, biological and chemical systems.5
25 However, chronic toxicity from bromide can cause bromism,
bromide toxicity can also lead to a type of skin eruption.6
Therefore, there is a great need of quantification and monitoring
iodide and bromide.
To date, fluorescent sensing techniques enabling to the
30 determination of iodide and bromide are of considerable
significance owing to their high sensitivity, simplicity and realꢀ
time detection. Nevertheless, relatively few examples of
fluorescent sensors for iodide and bromide were reported7 based
on two recognition strategies including hydrogenꢀbonding and
35 metalꢀcoordination. Since iodide and bromide have the large
ionic radius, low charge density and low hydrogen bonding
ability, it is challenging to develop specific probes for either
entities based on hydrogenꢀbonding. Therefore, we plan to
untilize the latter binding strategy for iodide and bromide probe
40 development.
50
Scheme 1 Synthesis of RSP
As a rhodamine B derivative with a spirolactam group, the free
RSP remained nearly colorless in ethanolꢀwater (40:60, v/v, 10
mM TrisꢀHClO4, pH 7.4) system. Upon addition of 1 equiv. of
55 Hg(ClO4)2 to a solution of RSP, the absorption at around 563 nm
and fluorescence intensity at 592 nm were significantly enhanced,
along with an obvious color change from colorless to purple, this
indicated the opening of the spirolactam ring (Fig. S3, ESI). We
then studied the selectivity of RSP-Hg2+ ensemble towards
60 various anions. Upon addition of 20 equiv. of various anions to
the solutions of RSP-Hg2+ ensemble, respectively, only iodide
caused significantly decreasing of the absorption at around 563
nm and the fluorescence at 592 nm along with the color change
from purple to nearly colorless instantaneously (Fig. 1), ATP and
65 PPi induced a slight quenching of fluorescence intensity, however
less than 30% of drop caused by iodide. Interesting, bromide
caused about 40% increase of the fluorescence at 592 nm.
Therefore, RSP- Hg2+ ensemble is a selective colorimetric
“naked eye” and fluorescence “onꢀoff” probe for iodide in
70 aqueous solution, further, RSPꢀHg2+ ensemble can also be used as
a selective fluorescence probe for bromide.
The UVꢀvis and fluorescence titration was carried out by
gradual addition of various concentrations of Iꢀ and Brꢀ (Fig. 2;
Fig. S4, ESI). Upon addition of 0~2 equiv. of Iꢀ, caused the
75 increasing of the absorption at around 563 nm and the
fluorescence at 592 nm. If additional Iꢀ was added, significantly
decreasing of the absorption and the fluorescence were observed.
However, upon addition of Brꢀ, the fluorescence at 592 nm was
In this paper, we report a new rhodamine derivative RSP,
which was facilely synthesized from rhodamine B through three
steps (see Scheme 1). Rhodamine B was chosen as fluorophore
by virtue of its excellent photophysical properties such as good
45 photostabilty, longꢀwavelength absorption and emission.8 Besides,
it is a convenient platform to construct colorimetric “naked eye”
and/or fluorescence “offꢀon” probes taking advantage of the
opening of the spirolactam ring. The structure of RSP was
This journal is © The Royal Society of Chemistry [2011]
Journal Name, [year], [vol], 00–00 | 1

Page 3 of 5
New Journal of Chemistry
View Online
ligand exchanges from ClO4ꢀ to Iꢀ. Addition of another 2 equiv. of
35 Iꢀ to the solution of RSPꢀHg(ClO4)2, further enhancement of
fluorescence was observed. It is likely that the heavyꢀatom effect
0.6
0.5
0.4
0.3
0.2
0.1
0.0
a)
of Hg2+ was partly inhibited due to Hg2+
ꢀ
Iꢀ backꢀbonding, which
ꢀ
is not present between Hg2+ and ClO4 . Recently, Wong9 reported
a probe, upon Hg2+ ion binding, the fluorescence increased but
40 also little quenching due to the heavyꢀatom effect of Hg2+.
Further addtion of Iꢀ beyond 2 equiv. leads to the extrapolation of
Hg2+ from the RSPꢀHg2+ complex and hence fluorescence
intensity of the solution decreases due to the restoration of the
nonꢀfluorescent lactam form, whose formation was confirmed by
45 ESIꢀMS. However, addition of excess Brꢀ up to 20 equiv. was not
able to remove Hg2+ from the RSPꢀHg2+ ligand, this is in
agreement with the more poor affinity of Brꢀ to Hg2+ than Iꢀ. This
is also verified by the obersvation that addition of Brꢀ up to 5
equiv. to the solution of [RSP+Hg2++Iꢀ] nearly did not result in
50 any fluorescence change (ESI, Fig. S7). This is an interesting
reslut that addition of anion to the sensorꢀmetal ionꢀanion
ensemble lead to the further increasing of fluorescence intensity
based on anion exchanging mechanism (Scheme 2).
[RSP@Hg2+],
other anions
I-
475 500 525 550 575 600 625 650 675
Wavelength (nm)
Br-
200
b)
150
100
50
[RSP@Hg],
other anions
-
200
I
200
a)
I-
160
120
150
80
40
0
540 560 580 600 620 640 660 680
100
50
0
0
Wavelength (nm)
0
5
10
15
20
25
30
[I-]/10-5
M
Fig. 1 The absorption (a) and fluorescence spectra (b) of RSPꢀHg2+ (10
ꢁM RSP and 10 ꢁM Hg2+) in the presence of 200 ꢁM of various anions as
ꢀ
5
Fꢀ, Clꢀ, Brꢀ, Iꢀ, ATP, AMP, PPi, H2PO4 , PO43ꢀ, OHꢀ, AcOꢀ, SO42ꢀ, HCO3ꢀ,
ꢀ
2ꢀ
NO3 , HPO4 in TrisꢀHClO4 aqueous buffer (10 mM, pH 7.4, containing
40% ethanol as a coꢀsolvent). (λex = 530 nm; slit widths: 2.5 nm, 5 nm).
Inset: The photographs showed (a) the color change and (b) the
fluorescent change (irradiated at 365 nm) of [RSP@Hg2+] (10 ꢁM RSP
550
575
600
625
650
675
Wavelength (nm)
10 and 10 ꢁM Hg2+) in the presence of 200 ꢁM of various anions. From left
to right: RSPꢀHg2+, ATP, PPi, Iꢀ, Brꢀ, OHꢀ, SO4
.
2ꢀ
200
150
100
50
b)
Br-
180
170
160
150
140
130
increased untill to equilibrium.
To further test the interference for other anions on the
determination of Iꢀ, the competition experiments were carried out.
15 Fig. S5 indicated that all other anions show no obvious
interference for Iꢀ detection.
0
2
4
6
8
10 12 14 16 18 20
[Br-]/(10-5M)
A tentative detection mechanism was proposed to explain the
aforementioned results and shown in Fig. 3. Upon addition of 1
equiv. of Hg(ClO4)2 to the solution of RSP, significant
20 enhancement in fluorescence intensity was observed (Fig. 4).
Clearly, coordination of the RSP to the Hg2+ induced the opening
of the fiveꢀmembered spirolactam ring. Hg2+ is a heavy metal ion
and known to quench the fluorescence. However, it is obvious
that this quenching effect9 is overwhelmed by the drastic
25 fluorescence enhancement by the formation of a strongly
fluorescent xanthene moiety. The fourth coordination site of Hg2+
0
540
560
580
600
620
640
660
680
Wavelength (nm)
55
Fig. 2 The fluorescence spectra of (a) RSPꢀHg2+ (10 ꢁM RSP and 10
ꢁM Hg2+) upon addition of Iꢀ (10~300 ꢁM) and (b) fluorescence spectra of
RSPꢀHg2+ (10 ꢁM RSP and 10 ꢁM Hg2+) upon addition of Brꢀ (10~200
ꢁM) in TrisꢀHClO4 aqueous buffer (10 mM, pH 7.4, containing 40%
60 ethanol as a coꢀsolvent). (λex = 530 nm; slit widths: 2.5 nm, 5 nm). Inset:
Fluorescence intensity at 592 nm of RSPꢀHg2+ as a function of (a) [Iꢀ]
and (b) [Brꢀ].
ꢀ
was occupied by ClO4 as evidenced by the ESIꢀMS (ESI, Fig.
S11). Addition of the Brꢀ to the solution of RSPꢀHg(ClO4)2 leads
to further enhancement in fluorescence intensity and the ligand
ꢀ
30 exchanges from ClO4 to Brꢀ was proved by ESIꢀMS (ESI, Fig.
Generally, addition of metal ion to the solution of free
rhodamineꢀbased probe, the fluorescence intensity was
65 significantly enhanced, further additon of anion or small
molecular which has stronger binding capacity of the metal ion to
S11). Similar to Brꢀ, upon introduction of 2 equiv. of Iꢀ to the
solution of RSPꢀHg(ClO4)2, further enhancement in fluorescence
intensity was also observed, it might be also attributed to the
2
| Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [2011]

New Journal of Chemistry
Page 4 of 5
View Online
aqueous solution. Rational analysis of the sensing mechanism of
rhodamineꢀmetal ion ensemble, concomitantly, fluorescent 35 RSP-Hg2+ ensemble to iodide and bromide based on anion
the ensemble solution induced the metal ion removal from the
intensity of the solution return to be weak. However, in this work,
addition anion to the rhodamineꢀmetal ion ensemble induced
stronger fluorescent base on anion exchanging, it may be could
serve as a novel approach for designing of rhodamineꢀbased
fluorescent probe for anion (Scheme 2).
exchanging and metal ion removal was given. This sensing
mechanism may be could serve as a novel approach for designing
of rhodamineꢀbased fluorescent probe for anion.
5
Fig. 3 Proposed binding mode of [RSP@Hg2+] with Brꢀ and Iꢀ.
40
Scheme 2 Conventional approach and new approach in this work
RSP + 1 equiv. Hg2+ + 2 equiv. I-
RSP + 1 equiv. Hg2+ + 20 equiv. Br-
RSP + 1 equiv. Hg2+ + 2 equiv. I- + 5 equiv. Br-
Experimental
200
Synthesis of chemosensor RSP
150
Rhodamine B hydrozide (1): In this work, 1 was synthesized
RSP + 1 equiv. Hg2+
according to the reference.10 To a 50 mL flask, rhodamine B (480
100
45 mg, 1.0 mmol) was dissolved in 12 mL ethanol. 1.2 mL (excess)
hydrazine hydrate (85%) was then added. After the addition, the
mixture was heated to reflux for 2 h. The solution changed from
dark purple to light orange and became clear. Then the mixture
was cooled and solvent was removed under redured pressure. 1 M
50 HCl (about 20 mL) was added to the solid in the flask to generate
a clear red solution. After that, 1 M NaOH (about 28 mL) was
added slowly with stirring until the pH of the solution reached
9~10. The resulting precipatate was filtered and washed 3 times
with 6 mL water, and then dired in air. The product was then
55 chromatographed on silica gel using dichloromethane/methanol
30: 1 (v/v) as eluant to afford 370 mg (81%) 1 as pink solid.
50
RSP + 1 equiv. Hg2+ + 20 equiv. I-
RSP
0
550
600
650
700
750
800
Wavelength (nm)
10
Fig. 4 The fluorescence spectra of RSP (10 ꢁM) in the presence of
various ions in TrisꢀHClO4 aqueous buffer (10 mM, pH 7.4, containing
40% ethanol as a coꢀsolvent). (λex = 530 nm; slit widths: 2.5 nm, 5 nm).
To develop more wider practice of RSP, the selectivity of
2: Compound 1 (0.64 mmol, 300 mg) was dissolved in 10 mL
absolute methanol, then 2ꢀpyridinecarbaldehyde (0.64 mmol, 68
mg) was added. And then the mixture was heated to reflux and
60 stirred for 6 h. After that, white precipitates obtained were filtered
off, washed with methanol to give of compound 2 (333 mg, 93%)
15 RSP to metal ions in water (10 mM HEPES, pH 7.4 ) was also
measured. As shown in Fig. S8, upon addition of Hg2+ to a
solution of RSP, the absorption at around 563 nm and the
fluorescence at 592 nm were significantly enhanced along with
the color change from nearly colorless to pink instantaneously,
20 presumably as a result of the spirolactam ringꢀopened RSP. By
contrast, the other ions (even excess) had almost no influence on
the fluorescence spectra. Therefore, RSP was a highly selective
fluorescence “offꢀon” probe for Hg2+ in 99% aqueous solution.
In conclusion, we have reported a fluorescent probe RSP,
25 which could sensitively and selectively recognize Hg2+ in 99%
aqueous solution. Interestingly, Based on the RSPꢀHgꢀClO4
ensemble, addition of iodide less than 2.0 equiv. induced the
fluorescence further increased and more iodide induced the
fluorescence quenching selectively by removing of Hg2+ from the
30 RSPꢀHgꢀClO4 ligand, however, addition of bromide induced the
fluorescence further increased by exchanging of anion ligand
1
as a white solid. H NMR (CDCl3, 400 MHz): δ 1.15 (t, J = 6.4
Hz, 12H), 3.29ꢀ3.34 (m, 8H), 6.24ꢀ6.26 (dd, J1 = 8.8 Hz, J2 = 2.0
Hz, 2H), 6.47 (d, J = 2.4 Hz, 2H), 6.57 (d, J = 8.8 Hz, 2H), 7.12
65 (d, J = 6.8 Hz, 2H), 7.43ꢀ7.51 (m, 2H), 7.58ꢀ7.61 (m, 1H), 8.02
(d, J = 7.2 Hz, 2H), 8.44 (s, 1H), 8.46 (s, 1H). 13C NMR (CDCl3,
100 MHz): δ 12.64, 44.30, 65.86, 98.32, 105.65, 108.03, 120.53,
123.54, 123.59, 123.72, 127.59, 128.10, 128.24, 133.70, 136.04,
146.11, 148.95, 149.00, 152.49, 152.95, 154.68, 165.42.
70
RSP: Compound 2 (0.55 mmol, 300 mg) and Lawesson’s
reagent (0.55 mmol, 222 mg) were dissolved in dry benzene (15
mL), and the reaction mixture was refluxed for 24 h under N2
atmosphere. After removal of benzene under reduced pressure,
the product was then chromatographed on silica gel using
ꢀ
from ClO4 to Brꢀ. Therefore, RSPꢀHgꢀClO4 ensemble can serves
75 dichloromethane/methanol 60: 1 (v/v) as eluant to afford 99 mg
as a selective fluorescent probe for iodide and bromide in
This journal is © The Royal Society of Chemistry [2011]
Journal Name, [year], [vol], 00–00 | 3

Page 5 of 5
New Journal of Chemistry
View Online
10 Y. Xiang, A. Tong, P. Jin and Y. Ju, Org. Lett., 2006, 8, 2863.
1
(32%) RSP as orange solid. H NMR (CDCl3, 400 MHz): δ 1.15
(t, J = 6.4 Hz, 12H), 3.29ꢀ3.34 (m, 8H), 6.24ꢀ6.26 (dd, J1 = 8.8
Hz, J2 = 2.0 Hz, 2H), 6.80 (d, J = 8.8 Hz, 2H), 7.16 (t, J = 5.2 Hz,
1H), 7.28 (m, 1H), 7.47 (t, J = 4.8 Hz, 2H), 7.68 (t, J = 7.6 Hz,
1H), 8.14 (d, J = 8.0 Hz, 1H), 8.19 (t, J = 5.2 Hz, 1H), 8.65 (s,
1H), 8.67 (s, 1H). 13C NMR (CDCl3, 100 MHz): δ 12.61, 44.44,
63.46, 97.56, 108.36, 110.36, 121.75, 122.63, 124.53, 127.08,
127.95, 130.18, 132.51, 135.17, 136.25, 148.21, 149.55, 151.88,
153.73, 155.36, 158.96, 173.36. HRMS (ES+): Calcd for
5
10 ([M+H])+, 562.2641, found, 562.2636.
Acknowledgements
We are grateful for the financial support from National Basic
Research Program of China (973 Program, 2010CB126100), the
China 111 Project (Grant B07023). We also thank Professor
15 Youjun Yang of ECUST for discussions and suggestions.
Notes and references
Shanghai Key Laboratory of Chemical Biology, State Key Laboratory of
Bioreactor Engineering, School of Pharmacy, East China University of
20 Science and Technology, Shanghai, 200237, China.
Fax: +86 21 6425 2603; Tel: +86 21 6425 3589;
E-mail: xhqian@ecust.edu.cn
† Electronic supplementary information (ESI) available: Synthetic details
and spectroscopic data. See DOI:
25
1
(a) R. MartínezꢀMáñez and F. Sancenón, Chem. Rev., 2003, 103,
4419; (b) Z. Xu, S. K. Kim and J. Yoon, Chem. Soc. Rev., 2010, 39,
1457; (c) L. A. Joyce, S. H. Shabbir and E. V. Anslyn, Chem. Soc.
Rev., 2010, 39, 3621; (d) R. M. Duke, E. B. Veale, F. M. Pfeffer, P.
E. Kruger and T. Gunnlaugsson, Chem. Soc. Rev., 2010, 39, 3936;
(e) M. E. Moragues, R. MartínezꢀMáñez and F. Sancenón, Chem.
Soc. Rev., 2011, 40, 2593; (f) M. Wenzel, J. R. Hiscock and P. A.
Gale, Chem. Soc. Rev., 2012, 41, 480.
30
35
40
45
50
55
60
2
(a) K. Wygladacz and E. Bakker, Analyst, 2007, 132, 268; (b) T. K.
Malongo, S. Patris, P. Macours, F. Cotton, J. Nsangu and J. M.
Kauffmann, Talanta, 2008, 76, 540.
N. Singh and D. O. Jang, Org. Lett., 2007, 9, 1991.
J. Shao, Y. H. Qiao, H. Lin and H. K. Lin, J. Incl. Phenom.
Macro.,2008, 62, 99.
J. Liao, H. Sihler, L. G. Huey, J. A. Neuman, D. J. Tanner, U. Friess,
U. Platt, F. M. Flocke, J. J. Orlando, P. B. Shepson, H. J. Beine, A. J.
Weinheinmer, S. J. Sjostedt, J. B. Nowak, D. J. Knapp, R. M.
Staebler, W. Zheng, R. Sander, S. R. Hall and K. Ullmann, J.
Geophys. Res., 2011, doi:10.1029/2010JD014788.
B. R. Taylor, R. Sosa and W. J. Stone, Am. J. Med., 2010, 123, 11.
(a) A. Corma, M. S. Galletero, H. Garcia, E. Palomares and F. Rey,
Chem. Commun., 2002, 1100; (b) H. A. Ho and M. Leclerc, J. Am.
Chem. Soc., 2003, 125, 4412; (c) H. Kim and J. Kang, Tetrahedron
Lett., 2005, 46, 5443; (d) M. Vetrichelvan R. Nagarajan and S.
Valiyaveettil, Macromolecules, 2006, 39, 8303; (e) H. Li, C. Han
and L. Zhang, J. Mater. Chem., 2008, 4543; (f) H. Okamoto, H.
Konishi, M. Kohno and K. Satake, Org. Lett., 2008, 10, 3125; (g) K.
Ghosh and T. Sen, Tetrahedron Lett., 2008, 49, 7204; (h) W. Lin, L.
Yuan, X. Cao, B. Chen and Y. Feng, Sens. Actuators B Chem. 2009,
138, 637; (i) J. S. Mendy, M. A. Saeed, F. R. Fronczek, D. R.
Powell and M. A. Hossain, Inorg. Chem., 2010, 49, 7223; (j) H. J.
Jung, N. Singh, D. Y. Lee and D. O. Jang, Tetrahedron Lett., 2010,
51, 3962; (k) H. Wang, L. Xue and H. Jiang, Org. Lett., 2011, 13,
3844; (l) J. Zhang, X. Xu, C. Yang, F. Yang and X. Yang, Anal.
Chem., 2011, 83, 3911.
3
4
5
6
7
8
9
H. N. Kim, M. H. Lee, H. J. Kim, J. S. Kim and J. Yoon, Chem. Soc.
Rev., 2008, 37, 1465.
C. Wang and K. M. C. Wong, Inorg. Chem., 2011, 50, 5333.
4
| Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [2011]