Salicylaldehyde-indole-2-acylhydrazone: A simple, colorimetric and absorption ratiometric chemosensor for acetate ion

Article abstract of DOI:10.1080/10610278.2012.758368

A simple anion receptor (i.e. salicylaldehyde-indole-2-acylhydrazone) was synthesised and its recognition properties were investigated by naked-eye observation, UV-vis titration spectra, ¹H NMR spectroscopy and DFT calculations. The obtained results indicated that this receptor could realise the selective colorimetric sensing and absorption ratiometric response towards AcO^- in CH₃CN-DMSO medium, by virtue of threefold intermolecular hydrogen bonding interactions formed with phenolic OH, indole NH and amide NH.

Full text of DOI:10.1080/10610278.2012.758368

This article was downloaded by: [Pennsylvania State University]
On: 12 June 2013, At: 11:59
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,
37-41 Mortimer Street, London W1T 3JH, UK
Supramolecular Chemistry
Publication details, including instructions for authors and subscription information:
http://www.tandfonline.com/loi/gsch20
Salicylaldehyde-indole-2-acylhydrazone: a simple,
colorimetric and absorption ratiometric chemosensor
for acetate ion
Xiao-ping Bao a , Peng-cheng Zheng a , Yong Liu a , Zan Tan a , Yu-hui Zhou b & Bao-an Song a
a Center for Research and Development of Fine Chemicals, Key Laboratory of Green
Pesticide and Agricultural Bioengineering, Ministry of Education, Guizhou University,
Guiyang, 550025, P. R. China
b Department of Chemistry, Guizhou University, Guiyang, P. R. China
Published online: 16 Jan 2013.
To cite this article: Xiao-ping Bao , Peng-cheng Zheng , Yong Liu , Zan Tan , Yu-hui Zhou & Bao-an Song (2013):
Salicylaldehyde-indole-2-acylhydrazone: a simple, colorimetric and absorption ratiometric chemosensor for acetate ion,
Supramolecular Chemistry, 25:4, 246-253
To link to this article: http://dx.doi.org/10.1080/10610278.2012.758368
PLEASE SCROLL DOWN FOR ARTICLE
Full terms and conditions of use: http://www.tandfonline.com/page/terms-and-conditions
This article may be used for research, teaching, and private study purposes. Any substantial or systematic
reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to
anyone is expressly forbidden.
The publisher does not give any warranty express or implied or make any representation that the contents
will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should
be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims,
proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in
connection with or arising out of the use of this material.

Supramolecular Chemistry, 2013
Vol. 25, No. 4, 246–253, http://dx.doi.org/10.1080/10610278.2012.758368
Salicylaldehyde-indole-2-acylhydrazone: a simple, colorimetric and absorption ratiometric
chemosensor for acetate ion
Xiao-ping Baoa*, Peng-cheng Zhenga, Yong Liua, Zan Tana, Yu-hui Zhoub and Bao-an Songa*
aCenter for Research and Development of Fine Chemicals, Key Laboratory of Green Pesticide and Agricultural Bioengineering, Ministry
of Education, Guizhou University, Guiyang 550025, P. R. China; bDepartment of Chemistry, Guizhou University, Guiyang, P. R. China
(Received 6 July 2012; final version received 2 December 2012)
A simple anion receptor (i.e. salicylaldehyde-indole-2-acylhydrazone) was synthesised and its recognition properties were
investigated by naked-eye observation, UV–vis titration spectra, 1H NMR spectroscopy and DFT calculations. The obtained
results indicated that this receptor could realise the selective colorimetric sensing and absorption ratiometric response
towards AcO2 in CH3CN–DMSO medium, by virtue of threefold intermolecular hydrogen bonding interactions formed
with phenolic OH, indole NH and amide NH.
Keywords: anion recognition; colorimetric sensing; absorption ratiometry; acetate ion
1. Introduction
wavelength, the absorption ratiometric method provides
more reliable quantitative information since it employs the
ratio of absorption intensity at two different wavelengths
as a function of analyte concentration, thereby a built-in
correction for adverse environmental effects is obtained.
Bearing the above considerations in our mind, in this
article we studied the recognition and sensing properties of
salicylaldehyde-indole-2-acylhydrazone towards different
anions. To our delight, a selective colorimetric sensing and
absorption ratiometric response were seen upon addition
of AcO2 to the solution of the receptor.
Anions play a very important role in many chemical and
biological processes, thereby development of anion
chemosensors capable of selective recognition and sensing
of the specific anions has been becoming a research focus
in the field of supramolecular chemistry (1–5). Among
common anions, fluoride and acetate ions are of particular
interest to chemists because the amount of fluoride intake
in the human body is closely related with some diseases
(such as nephrolithiasis and kidney failure) (6, 7), and
carboxylate ions are pivotal components of many human
metabolic processes (8). Compared with numerous
selective sensors for F2, the examples of selective sensing
of AcO2 are relatively limited to date (9–17). Moreover,
almost all the reported AcO2 chemosensors were
completely relied on NH functionality; nevertheless, it
had been validated that OH group, indole NH and amide
NH in the Salmonella typhimurium sulphate-binding
protein could work in concert to efficiently bind SO422
in nature (18). Many anion receptors bearing indole NH
and amide NH had been developed (19–26); to our
surprise, there was little example of cooperative use of the
above-mentioned three groups for construction of anion
receptors (27).
2. Results and discussion
2.1 Synthesis of salicylaldehyde-indole-2-
acylhydrazone (the receptor)
Salicylaldehyde-indole-2-acylhydrazone was synthesised
(see Scheme 1), and its structure was characterised by 1H
and 13C NMR, MS, IR and elemental analysis. In order to
evaluate the effect of phenolic OH on anion recognition
properties, benzaldehyde-indole-2-acylhydrazone was
also prepared as a reference compound.
Generally, a good anion chemosensor should produce
easy-to-detect signal changes (e.g. colour, fluorescent and
electrochemical changes) after complexation with specific
anions. Relative to fluorescent and electrochemical
sensors, colorimetric chemosensors have unique advan-
tages as they can immediately provide qualitative
information without resorting to any expensive equipment
(28). In addition, compared with the usual detection
method utilising an absorbance value at a single
2.2 UV–vis titration spectra and colorimetric sensing
Recognition properties of the receptor towards different
anions were firstly studied in CH3CN–DMSO (99.5/0.5,
v/v) through UV–vis titration spectra. The receptor
exhibited three characteristic absorption peaks at 308, 333
and 349 nm along with a very weak shoulder peak around
380 nm in the absence of anions. Upon addition of
increasing amount of AcO2, a moderate decrease in the
*Corresponding authors. Email: baoxp_1980@yahoo.com.cn; songbaoan22@yahoo.com
q 2013 Taylor & Francis

Supramolecular Chemistry
247
CHO
R
O
O
N2H4 • H2O
reflux
O
NH
N CH
OCH3
NHNH2
EtOH/reflux
Cat. HOAc
N
N
H
N
H
H
R
R=OH the receptor
R=H reference compound
Scheme 1. Synthesis of the receptor and reference compound.
absorbance of the three characteristic peaks along with an
obvious absorbance increase in the absorption band
centred at 380 nm were simultaneously discovered (see
Figure 1). In addition, a clear isosbestic point emerged at
350 nm, indicating the existence of only two absorbing
species in the mixed solution (29). Noticeably, the
colourless receptor solution was gradually changed into
greenish-yellow upon addition of AcO2. Interestingly, the
above colour change was reversed after addition of several
drops of water to the titrated solution, which fully proved
that the above binding was reversible in essence.
The 1:1 stoichiometry for the receptor–AcO2 complexa-
tion was determined by Job’s plot method (see Figure 2).
Gratifyingly, a good linear relationship was obtained
between the A380/A308 ratio and the concentration of AcO2
within the range of 0–32 mM (see Figure 3), thus enabling
the receptor to work as an absorption ratiometric
chemosensor for the quantitative detection of AcO2.
Different with AcO2, addition of F2 to the receptor
solution promoted a modest enhancement in the
absorbance at 333 and 349 nm (see Figure 4). Furthermore,
the UV–vis spectral changes at 308 and 380 nm were
similar but weaker than those in the presence of AcO2.
Noticeably, no perceptible colour change was detected
under the range of fluoride concentration we used (0–6.4
equiv.).
Addition of 4.0 equiv. of H2PO24 , Cl2, Br2, I2, NO23
and HSO24 triggered a little or negligible changes in the
UV–vis spectra of the receptor (see Figure 5), suggesting
that very weak or no binding interactions occurred. The
colorimetric responses of the receptor towards different
anions were displayed in Figure 6, a visible colour change
was found only in the case of AcO2, so the receptor could
act as a selective colorimetric chemosensor for detecting
the AcO2. Due to the subtle differences in the basicity and
surface charge density among F2, AcO2 and H2PO42,
1.0
0.20
0.9
0.18
0.16
0.8
0.14
0.12
0.7
0.10
0.6
0.08
0.06
0.5
0.04
0.02
0.4
0.00
0
1
2
3
4
5
0.3
Equiv of acetate
0.2
0.1
0.0
300
350
400
Wavelength (nm)
450
500
Figure 1. UV–vis absorption spectra of the receptor (20 mM) in CH3CN–DMSO (99.5/0.5, v/v) upon titration with Bu4NþAcO2 (0–
4.6 equiv.). Inset: the nonlinear curve fitting of DA380 vs. equivalents of the added AcO2.

248
X.-P. Bao et al.
0.5
0.4
0.3
0.2
0.1
0.0
0.0
0.2
0.4
0.6
0.8
1.0
[R]/([R]+[AcO–])
Figure 2. Job’s plot of the receptor and AcO2 with a total concentration of 100 mM.
0.22
0.20
0.18
0.16
0.14
0.12
y=0.0057*x + 0.0385
R=0.9895
0.10
0.08
0.06
0.04
0.02
-5
0
5
10
15
[AcO–] (µM)
20
25
30
35
Figure 3. A linear relationship between the A380/A308 ratio (for the receptor) and the concentration of AcO2 from 0 to 32 mM.
it was generally difficult to discriminate them from each
other (30). However, the above aim could be realised to
some extent on the basis of the different colour responses
and absorption profiles of the receptor in the presence of
these three anions.
the careful observation of the obtained titration curves and
colour change, three obvious features could be observed
from the deprotonation event caused by OH2: (i) a
significant decrease in the absorbance at 308, 333 and
349 nm and a sharp increase in the peak intensity at 375 nm
were found, which was obviously different with the
observed spectral changes in Figures 1 and 4; (ii) a distinct
new absorption peak at 375 nm evolved upon the addition
of OH2, different with the appearance of a broad and
In order to judge the nature of absorption spectral
changes of the receptor induced by AcO2/F2 (complexa-
tion or deprotonation), the UV–vis titration of the receptor
with Bu4NþOH2 was also carried out (see Figure 7). After

Supramolecular Chemistry
249
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0.16
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0.00
0
1
2
3
4
5
6
7
Equiv of fluoride
300
350
400
Wavelength (nm)
450
500
Figure 4. UV–vis absorption spectra of the receptor (20 mM) in CH3CN–DMSO (99.5/0.5, v/v) upon titration with Bu4NþF2 (0–6.4
equiv.). Inset: the nonlinear curve fitting of DA380 vs. equivalents of the added F2.
1.0
0.8
0.6
0.4
AcO–
–
Free receptor, Cl–, Br–,
F–
H2PO4
0.2
0.0
I–, HSO4–, NO3
–
300
350
400
Wavelength (nm)
450
500
Figure 5. UV–vis absorption spectra of the receptor (20 mM) in CH3CN–DMSO (99.5/0.5, v/v) upon titration with different anions
(4.0 equiv.).
unstructured absorption band from 350 to 450 nm upon
addition of AcO2/F2; (iii) colourless receptor solution
was changed into brightly yellow (not greenish-yellow
induced by AcO2). The above phenomena (especially the
first one (31)) sufficiently attested that hydrogen-bonding
complexation between the receptor and AcO2/F2 was
responsible for the spectral changes in Figures 1 and 4,
instead of the deprotonation event. Last but not least, the
observed consistent spectral changes throughout the entire
titration process using AcO2/F2 also stated that only one
interaction process took place. Remarkably, the UV–vis
spectral changes of the receptor upon addition of excessive
F2 were nearly identical to those triggered by OH2 (see
Figure 8), implying that the deprotonation event indeed
happened in such a case. Interestingly, no deprotonation
was seen upon titration with excessive AcO2 (up to 48

250
X.-P. Bao et al.
Figure 6. Colour change of the receptor (200 mM) in CH3CN–DMSO (99.5/0.5, v/v) in the presence of 6.0 equiv. different anions (from
left to right: free receptor, þF2, þCl2, þBr2, þI2, þNO23 , þHSO24 , þH2PO24 , þAcO2).
(see Figure 9), suggesting that phenolic OH of the receptor
was indispensable for realising effective anion binding.
1.2
1.0
0.8
0.6
0.4
0.2
0.0
2.3 Determination of association constants (Ka)
In a supramolecular system with the formation of a 1:1
binding complex, the association constant (Ka) could be
determined through the method of nonlinear curve fitting
using the following equation (34):
A ¼ A0 þ ½ðAlim 2 A0Þ=2C0ꢀ{ðCH þ CG þ 1=KaÞ
2
1=2
2 ½ðCH þ CG þ 1=KaÞ 2 4CHCGꢀ
}
300
350
400
450
500
Wavelength (nm)
where A is the absorbance of the whole system, A0 is the
absorbance of free receptor, CH is the concentration of
receptor compound, CG is the concentration of guest anion
and Ka is the association constant. The obtained Ka and R
(correlation coefficient) from the above equation were listed
in Table 1. Excellent correlation coefficients (R . 0.99)
established the formation of a 1:1 complex between the
receptor and AcO2/F2 (35–39). The value of Ka for AcO2
(4.10 £ 104 M21) was nearly sixfold larger than that for F2
(5.92 £ 103 M21), which may be due to the stronger
Figure 7. UV–vis absorption spectra of the receptor (20 mM) in
CH3CN–DMSO (99.5/0.5, v/v) upon titration with Bu4NþOH2
(0–9.4 equiv.).
equiv.). The special stability of the species [HF22 ] in
CH3CN (32, 33) was the main reason for the F2-induced
deprotonation.
Unexpectedly, there was no detectable interaction
between reference compound and all the tested anions
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Addition of excessive
of F (12, 16, 20, 24,
28, 32 equiv)
–
Free receptor
300
350
400
450
500
Wavelength (nm)
Figure 8. UV–vis absorption spectra of the receptor (20 mM) in CH3CN–DMSO (99.5/0.5, v/v) upon titration with excessive F2.

Supramolecular Chemistry
251
1.0
0.8
0.6
0.4
0.2
0.0
Free reference compound, +F–,
+Cl–, +Br–, +I–, +NO3–, +HSO4
,
–
–
+AcO–, +H2PO4
250
300
350
Wavelength (nm)
400
450
Figure 9. UV–vis absorption spectra of reference compound (20 mM) in CH3CN–DMSO (99.5/0.5, v/v) upon addition of different
anions (1.6 equiv.).
Table 1. Association constants (Ka/M21) and correlation coefficients (R) of the receptor with different anions in CH3CN–DMSO
(99.5/0.5, v/v).
Anionsa
AcO2
F2
H2PO24
Other anions
NSCd
b
Ka
R
(4.10 ^ 0.19) £ 104
(5.92 ^ 0.89) £ 103
NDc
2
0.9997
0.9981
2
a Anions were used as their tetra-n-butylammonium salts.
b Values of Ka were determined by UV–vis titration spectra.
c The spectral changes were too small to calculate Ka accurately.
d No spectral changes were observed.
hydrogen-bonding accepting ability of AcO2 and the better
shape complementarity for the receptor and AcO2.
Figure 10). The receptor displayed three sharp peaks at
12.16, 11.85 and 11.19 ppm, attributed to indole NH,
amide NH and phenolic OH, respectively. Upon addition
of 1.0 equiv. of AcO2, these three peaks completely
disappeared and no detectable chemical shift changes
appeared for other protons. Obviously, the added AcO2
was complexed by the receptor via threefold hydrogen-
bonding interactions, contributing from indole NH,
amide NH and phenolic OH.
2.4 1H NMR titration spectra
In order to disclose the concrete binding sites within the
receptor, the 1H NMR titration of the receptor with
AcO2 was conducted in DMSO-d6 as an example (see
2.5 DFT calculations
According to the DFT calculations (see Figure 11), indole
NH, amide NH and phenolic OH formed H-bonds with
AcO2 ion (1.69, 1.67 and 2.44 A, respectively). In
˚
addition, it was worth mentioning that an intramolecular
H-bond presumably existed between the imine nitrogen
and phenolic hydroxyl proton.
Based on the above studies, a possible binding model
between salicylaldehyde-indole-2-acylhydrazone and
AcO2 was proposed in Scheme 2.
Figure 10. Partial 1H NMR spectra of the receptor (6.4 mM) in
DMSO-d6 upon addition of AcO2. (a) þ0 equiv.; (b) þ1.0 equiv.

252
X.-P. Bao et al.
Elementar Vario-III CHN analyzer. UV–vis spectra were
recorded on TU-1900 spectrophotometer (Beijing Purkinje
General Instrument Co., Beijing, China).
4.2 Synthesis
4.2.1 Synthesis of indole-2-acylhydrazine
Indole-2-acylhydrazine was prepared according to the
previous literature (40).
4.2.2 Synthesis of the receptor (salicylaldehyde-indole-
2-acylhydrazone)
Figure 11. Calculated structure (B3LYP/6-31(d)) of the
receptor–AcO2 complex.
Indole-2-acylhydrazine (88 mg, 0.5 mmol), salicylalde-
hyde (53 ml, 0.55 mmol) and two drops of acetic acid were
dissolved in 25 ml ethanol. The above mixed solution was
heated to reflux for 5 h and then cooled to room
temperature. The formed precipitate was filtered off and
washed with ethanol to afford the receptor. Yield: 110 mg
3. Conclusions
In summary, salicylaldehyde-indole-2-acylhydrazone was
found to provide the selective colorimetric sensing and
absorption ratiometric response towards biologically
importantly AcO2 in CH3CN–DMSO (99.5/0.5, v/v)
medium, which were driven by threefold intermolecular
hydrogen-bonding interactions. The ease of synthesis of
indole-2-acylhydrazone compounds provides the possi-
bility to develop more elaborate and preorganised neutral
anion receptors with a better affinity and selectivity.
1
(79%), mp: . 250oC. H NMR (500 MHz, DMSO-d6): d
12.16 (s, 1H), 11.85 (s, 1H), 11.19 (s, 1H), 8.66 (s, 1H),
7.70 (d, J ¼ 8.0 Hz, 1H), 7.61 (d, J ¼ 7.5 Hz, 1H), 7.49 (d,
J ¼ 8.5 Hz, 1H), 7.33 (s, 1H), 7.31(d, J ¼ 8.0 Hz, 1H),
7.24 (t, J ¼ 7.5 Hz, 1H), 7.08 (t, J ¼ 7.5 Hz, 1H),
6.96 2 6.93 (m, 2H). 13C NMR (125 MHz, DMSO-d6): d
158.0, 157.8, 147.8, 137.5, 131.9, 130.1, 129.8, 127.5,
124.6, 122.4, 120.6, 119.9, 119.4, 116.9, 113.0, 104.4. FT-
IR (KBr): 3294, 1653, 1616, 1539, 1267, 752 cm21. MS
(ESI): 302.1 (M þ Naþ), 318.3 (M þ Kþ). Anal. Calcd for
C16H13N3O2 C 68.81, H 4.69, N 15.05. Found: C 68.65, H
4.83, N 15.22.
4. Experimental
4.1 General
Acetonitrile was refluxed over CaH2 and then distilled for
use in the titration experiments. All the anions were
utilised as their tetra-n-butylammonium salts. Other
chemicals were purchased as analytical grade reagents
and used directly. Melting points were determined on a
XT-4 binocular microscope (Beijing Tech Instrument Co.,
Beijing, China). IR spectra were recorded on a Shimadzu
IRPrestige-21 spectrometer in KBr disc. 1H and 13C NMR
spectra were measured on a JEOL-ECX 500 NMR
spectrometer at room temperature using TMS as an
internal standard. Mass spectra were recorded on Agilent
LC/MSD. Elemental analysis was performed on an
4.2.3 Synthesis of reference compound (benzaldehyde-
indole-2-acylhydrazone)
A similar synthetic method was utilised to prepare the
reference compound by the reaction of indole-2-acylhy-
1
drazine with benzaldehyde. mp: 195 2 198oC. H NMR
(500 MHz, DMSO-d6): d 11.94 (s, 1H), 11.82 (s, 1H), 8.47
(s, 1H), 7.78 2 7.68 (m, 3H), 7.49 2 7.47 (m, 4H), 7.33
(s, 1H), 7.24 (t, J ¼ 7.5 Hz, 1H), 7.08 (t, J ¼ 7.5 Hz, 1H).
13C NMR (125 MHz, DMSO-d6): d 158.3, 147.7, 137.4,
134.8, 130.6, 130.5, 129.4, 127.6, 127.5, 124.5, 122.3,
O
O
H
C
N N
H
CH3CN
H2O
CH N NH
AcO–
HN
N
H
H
O
OH
O–
O
the receptor (colorless)
H-bond complex (pale yellow)
Scheme 2. A possible binding model between the receptor and AcO2.

Supramolecular Chemistry
253
(18) He, J.J.; Quiocho, F.A. Science 1991, 251, 1479–1481.
(19) Chang, K.-J.; Chae, M.K.; Lee, C.; Lee, J.-Y.; Jeong, K.-S.
Tetrahedron Lett. 2006, 47, 6385–6388.
(20) Bates, G.W.; Triyanti; Light, M.E.; Albrecht, M.; Gale,
P.A. J. Org. Chem. 2007, 72, 8921–8927.
120.6, 112.9, 104.2. FT-IR (KBr): 3308, 1636, 1603, 1545,
1246, 745, 689 cm21. MS (ESI): 286.1 (M þ Naþ). Anal.
Calcd for C16H13N3O C 72.99, H 4.98, N 15.96. Found: C
72.75, H 5.15, N 16.23.
(21) Bates, G.W.; Gale, P.A.; Light, M.E. Chem. Commun.
2007, 2121–2123.
´
(22) Zielinski, T.; Dydio, P.; Jurczak, J. Tetrahedron 2008, 64,
568–574.
Acknowledgement
Financial support from National Natural Science Foundation of
China (No. 21161005) is deeply acknowledged.
(23) Caltagirone, C.; Gale, P.A.; Hiscock, J.R.; Hursthouse,
M.B.; Light, M.E.; Tizzard, G.J. Supramol. Chem. 2009, 21,
125–130.
ˇ ˇ
(24) Makuc, D.; Lenarcic, M.; Bates, G.W.; Gale, P.A.; Plavec,
J. Org. Biomol. Chem. 2009, 7, 3505–3511.
References
´
(25) Dydio, P.; Zielinski, T.; Jurczak, J. Chem. Commun. 2009,
4560–4562.
(1) Suksai, C.; Tuntulani, T. Chem. Soc. Rev. 2003, 32,
192–202.
(2) Gunnlaugsson, T.; Glynn, M.; Tocci, G.M.; Kruger, P.E.;
Pfeffer, F.M. Coord. Chem. Rev. 2006, 250, 3094–3117.
(3) Beer, P.D.; Gale, P.A. Angew. Chem. Int. Ed. 2001, 40,
486–516.
(26) Caltagirone, C.; Mulas, A.; Isaia, F.; Lippolis, V.; Gale,
P.A.; Light, M.E. Chem. Commun. 2009, 6279–6281.
(27) Bao, X.P.; Zhou, Y.H.; Yu, J.H. J. Lumin. 2010, 130,
392–398.
(4) O’Neil, E.J.; Smith, B.D. Coord. Chem. Rev. 2006, 250,
3068–3080.
(28) Kumari, N.; Jha, S.; Bhattacharya, S. J. Org. Chem. 2011,
76, 8215–8222.
(5) Beer, P.D.; Bayly, S.R. Top. Curr. Chem. 2005, 255,
125–162.
´
(29) Vazquez, M.; Fabbrizzi, L.; Taglietti, A.; Pedrido, R.M.;
Gonzalez-Noya, A.M.; Bermejo, M.R. Angew. Chem. Int.
´
(6) Singh, P.P.; Barjatiya, M.K.; Dhing, S.; Bhatnagar, R.;
Kothari, S.; Dhar, V. Urol. Res. 2001, 29, 238–244.
(7) Cittanova, M.-L.; Lelong, B.; Verpont, M.-C.; Geniteau-
Legendre, M.; Wahbe, F.; Prie, D.; Coriat, P.; Ronco, P.M.
Anesthesiology 1996, 84, 428–435.
(8) Gunnlaugsson, T.; Davis, A.P.; O’Brien, J.E.; Glynn, M.
Org. Lett. 2002, 4, 2449–2452.
(9) Hu, S.; Guo, Y.; Xu, J.; Shao, S. Org. Biomol. Chem. 2008,
6, 2071–2075.
(10) Qiao, Y.H.; Lin, H.; Shao, J.; Lin, H.K. Chin. J. Chem.
2008, 26, 611–614.
(11) Shao, J.; Wang, Y.; Lin, H.; Li, J.; Lin, H. Sens. Actuators B
2008, 134, 849–853.
(12) Joo, T.Y.; Singh, N.; Lee, G.W.; Jang, D.O. Tetrahedron
Lett. 2007, 48, 8846–8850.
(13) Goswami, S.; Chakrabarty, R. Tetrahedron Lett. 2009, 50,
5994–5997.
Ed. 2004, 43, 1962–1965.
(30) Peng, X.; Wu, Y.; Fan, J.; Tian, M.; Han, K. J. Org. Chem.
2005, 70, 10524–10531.
(31) Duke, R.M.; McCabe, T.; Schmitt, W.; Gunnlaugsson, T.
J. Org. Chem. 2012, 77, 3115–3126.
(32) Ashokkumar, P.; Ramakrishnan, V.T.; Ramamurthy, P.
J. Phys. Chem. B 2011, 115, 84–92.
(33) Wang, L.; He, X.; Guo, Y.; Xu, J.; Shao, S. Org. Biomol.
Chem. 2011, 9, 752–757.
(34) Valeur, B.; Pouget, J.; Bourson, J.; Kaschke, M.; Ernsting,
N.P. J. Phys. Chem. 1992, 96, 6545–6549.
(35) Wu, F.Y.; Li, Z.; Wen, Z.C.; Zhou, N.; Zhao, Y.F.; Jiang,
Y.B. Org. Lett. 2002, 4, 3203–3205.
(36) Bourson, J.; Pouget, J.; Valeur, B. J. Phys. Chem. 1993, 97,
4552–4557.
(37) Lu, Q.-S.; Dong, L.; Zhang, J.; Li, J.; Jiang, L.; Huang, Y.;
Qin, S.; Hu, C.-W.; Yu, X.-Q. Org. Lett. 2009, 11,
669–672.
(38) Bao, X.; Zhou, Y. Sens. Actuators B 2010, 147, 434–441.
(39) Cort, A.D.; Forte, G.; Schiaffino, L. J. Org. Chem. 2011, 76,
7569–7572.
(14) Helal, A.; Kim, H.-S. Tetrahedron 2010, 66, 7097–7103.
(15) Hu, Z.-Q.; Wang, X.-M.; Feng, Y.-C.; Ding, L.; Li, M.; Lin,
C.-S. Chem. Commun. 2011, 47, 1622–1624.
(16) Huang, W.; Lin, H.; Lin, H. Sens. Actuators B 2011, 153,
404–408.
(40) Zhao, H.; Burke, Jr., T.R. Tetrahedron 1997, 53,
4219–4230.
(17) Mahapatra, A.K.; Hazra, G.; Roy, J.; Sahoo, P. J. Lumin.
2011, 131, 1255–1259.