Colorimetric sensing of cyanide anions in aqueous media based on functional surface modification of natural cellulose materials

Article abstract of DOI:10.1016/j.tet.2011.04.061

The synthesis of two new water soluble azo dyes and their optical response to different anions is reported herein. Solution studies in water indicate that cyanide induces a colour change in these dyes, whereas no changes are observed in the presence of ot

Full text of DOI:10.1016/j.tet.2011.04.061

Tetrahedron 67 (2011) 4939e4947
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Colorimetric sensing of cyanide anions in aqueous media based on functional
surface modification of natural cellulose materials
,
b
,
a,b
Jalal Isaad a , Ahmida El Achari
*
a University Lille Nord de France, F-5900 Lille, France
b ENSAIT, GEMTEX Laboratory, F-59056 Roubaix, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 3 March 2011
Received in revised form 4 April 2011
Accepted 15 April 2011
Available online 21 April 2011
The synthesis of two new water soluble azo dyes and their optical response to different anions is re-
ported herein. Solution studies in water indicate that cyanide induces a colour change in these dyes,
whereas no chꢀanges are observed in the presence of other anions, such as CH3COOHꢀ; HSO4ꢀ;
ClOꢀ3 ; ClOꢀ4 ; Cl ; Brꢀ; H2POꢀ4 ; S2Oꢀ3 ; Fꢀ; NOꢀ3 ; Iꢀ; NO2ꢀ; SO32ꢀ; S2ꢀ; C2O24ꢀ; SO42ꢀ; N3ꢀ; SCNꢀ; Fꢀ;
CO23ꢀ; HCO23ꢀ: In the second part of the paper, we report the incorporation of one of these dyes onto
cellulosic fibres. The dye-sensitized cellulose materials were immersed in solutions of different anions
Keywords:
Azo dye
Chemosensing
Chemical grafting
Cellulose
and their response studied. The material is able to detect cyanide about 0.01e0.07
mM in aqueous
solution with high selectivity over other anions.
Ó 2011 Elsevier Ltd. All rights reserved.
Cyanide
1. Introduction
the strategies used for the development of anionic chemosensors,
the most simple involves the design of molecules that change
colour following an alteration in their molecular structure due to
their contact with anions. In this case, the selectivity of the che-
mosensor towards an anion is related to the fact that anionic spe-
cies have differentiated capabilities to interact with the receptor
site in the chemosensor, for instance, through hydrogen bonding. In
spite of these developments there are still relatively few examples
of selective probes for cyanide owing to high interference from
other anions, in particular, fluorides.22,23 Another drawback with
most of the current methods is that the detection needs to be
carried out in organic solvents (or mixtures of organic solvents and
water), which limits their application to the analysis of ‘real’ sam-
ples that are often aqueous solutions. Therefore, the development
of selective and efficient methodologies for detecting cyanide from
aqueous media is in great demand. Recently we are developed
a new generation of water soluble chemosensor able to detect the
cyanide anion in pure water.24 The water solubility of this new
chemosensor generation was obtained by glyco conjugation of the
starting organic chemodosimeter with the usual carbohydrates23
following the general structure of the water soluble colouring
agents reported previously.25 Other various methods based on the
functional modification of nanocrystalline TiO2 films or membrane
anchored with azo dye,26 quantum dots,27 supported materials28 or
polymers29 to specifically react with cyanide have been reported.
However, the development of facile, low-cost, highly sensitive and
practical cyanide chemosensors that function in aqueous media
Due to the important roles of the anions played in the biological
processes, the recognition and sensing of anions has received
considerable attention over recent years.1e12 In addition, there is
interest in finding better and more efficient ways of detecting an-
ions that can be potentially harmful to the environment or human
health. One such anion is cyanide, which is lethal to humans at
concentrations of 0.5e3.5 mg per kg of body weight.13 Conse-
quently, the presence of this anion in drinking water (1.9 mM as
maximum concentration)13 can pose a very serious risk to human
health. It is therefore evident that reliable and efficient ways of
detecting the presence of cyanide in water are needed. Although
highly effective experimental protocols and detection techniques
cyanide ions have been reported,14,15 aqueous media, which are
common in biological systems, often collapse their sensing func-
tions. Because these anions are relatively small and are strongly
solvated in protic solvents, interaction between these anions and
anion sensors is hampered.16,17 Therefore, much more powerful
hosteguest interactions are required to develop anion sensors that
work in aqueous media. In this sense, many optical chemosensors
have been developed to perform selective anion detection visually
and, in addition, to allow the quantification of such species.18e21 of
* Corresponding author. Tel.: þ33 0320258936; fax: þ33 0320272597; e-mail
address: jalal.isaad@ensait.fr (J. Isaad).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.04.061

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J. Isaad, A. El Achari / Tetrahedron 67 (2011) 4939e4947
H
still remains a challenge. Practical heavy anion sensors that allow
on-site, real time detection without using any spectroscopic in-
struments have received a great deal of attention. In particular,
colorimetric sensors26e28 are extremely attractive because of the
ease of observation with the naked eye. The colour change of these
sensitizer materials in the presence of parts per million concen-
trations of cyanide salt was observed. However, the naked-eye
detection of parts per billion level of cyanide in aqueous solution
has not been achieved without the use of spectrophotometers due
to the low surface area of flat TiO2 film used for anchoring dye
molecules.26 In order to develop a simple material able to detect the
cyanide anions in pure aqueous media, our idea consist of the in-
corporation of the adequate cyanide chemodosimeter into the
natural fibres. For this purpose, our attention was focused to the
cellulose as a support to incorporate the chemosensors that are not
soluble in water via chemical grafting (Fig. 1). The final function-
alized cellulose was then exposed to the aqueous solutions of var-
ious anions to investigate its selectivity and sensitivity towards
cyanide anions.
OH
OH
O
N
B
N
OH
a
3
NH2
OH
O
N
OH
O
OH
N
1
a
H
O
OH
B
OH
OH
O
2
Scheme 1. Synthesis of chemosensors 2 and 3. Reagent and conditions: (a) NaNO2, HCl
1 N, water, 0 ꢁC to rt, 3 h.
firstly chemically modified by coupling with glucose and glycerol,
to make them water soluble, as reported in our previous studies.24
The chemical modification of the dyes 2 and 3 is carried by an es-
terification coupling of the carboxylic group (COOH) of the dyes 2, 3
and the primary alcohol group (eOH) of the protected glucose 4 and
the protected glycerol 530 to afford the protected azo dyes 6 and 7,
respectively. Finally, a simple deprotection of 6 and 7 by TFA 90%
solution at room temperature affords the water soluble chemo-
sensors 8 and 9 (Scheme 2).
The Table 1 reports the UVevis data and the measured water
solubility of all synthesized dyes.
The results reported in Table 1 show that lmax does not exhibit
any significant shift after the chemical modification of the starting
dyes 2 and 3, by glyco conjugation with glucose or glycerylation
with glycerol moiety. Also, molar extinction coefficient values can
be considered almost constant, only very small differences being
detected. Thus, derivatization of the carboxylic function in prepared
dyes 2 and 3 does not affect the UVevis spectrum as these groups
are far from the chromophore.
2.2. Absorption spectral characteristics of chromogenic
probes 8 and 9 in water
The ability of 8 and 9 to complex with anions was explored with
UVevis absorption spectrometry in pure water. Among the elevꢀen
anions tested in water solution CH3COOHꢀ; HSO4ꢀ; ClO3ꢀ; ClO4 ;
Clꢀ; Brꢀ; H2PO4ꢀ; S2O3ꢀ; Fꢀ; NOꢀ3 ; Iꢀ; NO2ꢀ; SO23ꢀ; S2ꢀ; C2O24ꢀ
;
SO24ꢀ; N3ꢀ; SCNꢀ; Fꢀ; CO32ꢀ; HCO23ꢀ and CNꢀ as their sodium salts,
8 and 9 responded to only CNꢀ resulting in a colour change from
colourless to yellow for 8 and from green/yellow to colourless for 9
(Fig. 2), indicating that probes 8 and 9 can serve as a ‘naked-eye’
cyanide indicators in pure water. The absorption profiles of the
sensors showed a remarkably higher selectivity for cyanide over
the other anions in water. This colour change was also confirmed by
UVevis spectroscopy study. The treatment of the dyes 8 and 9 with
a solution of cyanide caused a lmax shift of the chromogenic probes
from 357 nm to 432 nm for 8 and from 412 nm to 351 nm for 9.
The strong nucleophilicity of cyanide in water seems to be the
major contributor to the high selectivity of 8 and 9 for cyanide in
water (Scheme 3).
Fig. 1. Schematic representation of cyanide sensing using functionalized natural cel-
lulose substance.
2. Results and discussions
2.1. Syntheses of chemosensors 2 and 3
The synthesis of the azoic dyes 2 and 3 is shown in Scheme 1.
The treatment of 4-amino-benzoic acid 1 with NaNO2 in acidic
medium afford its corresponding diazonium salt, which treated by
phenyl boronic acid or salicylaldehyde to afford the azo dyes 2 and
3, respectively in high yield.
In order to investigate and compare the chemosensing proper-
ties and the detection limit of the synthesized chromogenic probes
2 and 3 in pure water solution and when these chemosensors are
supported on the cellulose material, these organic compounds are
However, anion, such as Fꢀ and AcOꢀ should interact with the
aqueous medium through H-bonding, and this solvation leads to
a decrease in their basicity, thus, resulting in the poor deprotona-
tion reaction as reported in our previous studies.24

J. Isaad, A. El Achari / Tetrahedron 67 (2011) 4939e4947
4941
OH
N
O
OH
O
OH
O
H
OH
H
O
O
H
O
O
O
a
b
O
O
O
+
N
O
O
O
N
N
4
O
N
N
6
O
OH
OH
OH
O
8
O
HO
O
OH
2
HO
OH
B
HO
HO
OH
O
HO
OH
B
N
HO
B
N
O
O
O
O
a
b
O
N
O
+
N
O
O
HO
5
N
N
9
7
OH
3
Scheme 2. Synthesis of the water soluble chemosensors 8 and 9. Reagent and conditions: (a) SOCl2, DCM, rt, 2 h (b) TFA 90%, rt, 3 h.
Table 1
Spectroscopic solubility data of the synthesized dyes
2.3. Sensitivity and detection limit in solution
Dyes
lmax
Log 3max
Solubilitya
[g/L]
Once the anion selectivity of 8 and 9 in water was established, it
was of interest to determine the sensitivity and the detection limit of
these two chromogenic probes. The detection limit31 was calculated
by measuring the absorbance changes by increasing the amount of
cyanides (from 0 to 1 equiv). To determine the binding stoichiom-
etry, a Job’s plot of (AꢀA0) versus equivalent of the cyanide ion was
established. Fig. 3 show a near linear correlation between intensity
difference absorption (AꢀA0) and CNꢀ concentration in water at
(MeOH) [nm]
(Mꢀ1 cmꢀ1
)
2
3
6
7
8
9
357
411
357
412
358
422
4.3921
4.3222
4.3951
4.3254
4.3991
4.3287
Insoluble
Poorly soluble at 60 ꢁC
Insoluble
Insoluble
67.54
70.45
a
The solubility was measured at room temperature.
Fig. 2. (a) The absorbance response of the solution containing chemosensor 8 and 9 in pure water (10ꢀ4 M) at room temperature and at pH¼7 in the presence of 3.10ꢀ4 M various
anions.

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J. Isaad, A. El Achari / Tetrahedron 67 (2011) 4939e4947
H
OH
N
O
OH
CN
O
O
O
CN
H
O
O
-
O
H
CN
H
O
Water
O
O
O
O
N
O
N
N
N
OH
OH
N
OH
OH
OH
8
OH
HO
OH
OH
OH
HO
HO
CN
HO
HO
HO
OH
NC
CN
B
N
B
HO
HO
3CN-
O
O
Water
O
O
N
N
N
9
Scheme 3. Proposal mechanism for 8 and 9 towards CNꢀ
.
Fig. 3. The plot of AꢀA0 versus equivalent of [CNꢀ] for the titration of 8 (a) and 9 (b) (10ꢀ5 M) with CNꢀ (0e1 equiv) in water at 25 ꢁC and at pH¼7.
room temperature, which indicates one to one binding between the
esterification of 10 or 11 and the hydroxyl groups of cellulose fibre
in DMSO as solvent at 100 ꢁC allows the incorporation of the dyes
10 or 11 on the cellulose materials.
probe and cyanide.
The Table 2 reports the detection limit31 of chromogenic probes
8 and 9.
The presence of graft dyes on the surface of the treated cotton
fabric samples has been also identified by IR(ATR) spectroscopy.
The FTIR spectra of the biosourced and grafted cellulose are shown
in Fig. 4. The eOH stretching vibration of the biosourced cellulose
occurs at 3397.07 cmꢀ1 and the broad CeH stretching band appears
from 2800 to 3000 cmꢀ1 region, these eOH and eCH are common
in the spectrum a, b and c in Fig. 4. In the grafted cotton, the eOH
band has undergone a shift towards 3411.08 cmꢀ1. It can also be
observed that the hydroxyl band intensity of the grafted cellulose
was considerably less than that of the pure cellulose. This may be an
indication of the possible participation of the hydroxyl groups in
the chemical modification. This can be further supported by the
decreased peak about 1163 cmꢀ1, which can be assigned to the CeO
stretching vibration of the eCH2OH group. However, if the cellulose
fabric was exposed to the treatment by the dyes 2 and 3, a new peak
appeared at around 1750 cmꢀ1, these are from the esterification
reaction of the hydroxyl group of the cellulose material and the
carboxylic group of the dyes 2 and 3 via the formation of ester
group. Therefore the peaks appeared at 1732.54 cmꢀ1 (in the case of
Ad Mat-1) and at 1731.33 cmꢀ1 (in the case of Ad Mat-2) corre-
sponds to the C]O stretching of ester group.
Table 2
Detection limit of chromogenic probes 8 and 9
Chromogenic probes
Detection limit
8
9
0.39
0.37
m
m
M
M
According to the World Health Organization (WHO), cyanide
concentrations lower than 1.9 mM are acceptable in drinking
water,13 which meant that our water soluble chemosensors 8 and 9
based colorimetric method are sensitive enough to monitor cyanide
concentration in drinking water.
2.4. Functional surface modification of natural cellulose
Once the anion-sensing properties of 8 and 9 were established
in solution, it was of interest to incorporate these dyes onto nano
structured natural cellulose fibre. The resulting functionalized
cellulose by organic dyes can be exposed to aqueous solutions of
the cyanide anions to be detected. Scheme 4 shows the synthesis
strategy to functionalize the cellulose fabrics by the chromogenic
probes 2 and 3. Compounds 2 and 3 are first treated with SOCl2 to
afford its corresponding acyl chlorides 10 and 11. Then, a simple
The functionalized cellulose materials are then exposed to
aqueous solutions of various anions (the same as those used in
solution) and the optical changes of the modified textile are in-
vestigated. An initial qualitative naked-eye study indicated that the

J. Isaad, A. El Achari / Tetrahedron 67 (2011) 4939e4947
4943
Scheme 4. Functionalization of the cellulose fabrics. Reagents and conditions: (a) SOCl2, DCM, rt, 2 h (b) DMSO, 100 ꢁC, 1.5 h.
chemosensor materials only changed colour in the presence of
cyanide anions (Fig. 5). The colour change of the sensor material is
due to the selective coordination of cyanide with the chromogenic
probes receptors of dye 2 and 3. Depending on the concentrations
of the CNꢀ solutions, the sensor material showed an obvious colour
change within 1e10 min. However, a closer inspection of the sys-
tem showed that in the presence of cyanide, not only does the
adsorbed dye change colour, but it also desorbs from the cellulose
chemosensors. This was confirmed by measuring the UVevis ab-
sorption spectrum of the sensitized cellulose materials in the
presence of increasing amounts of cyanide (Fig. 6c).
S2ꢀ; C2O24ꢀ; SO24ꢀ; N3ꢀ; SCNꢀ; Fꢀ; CO23ꢀ; HCO32ꢀ (1 mM), it showed
the same colour change as well as the band shift in the absorption
spectra (from 351 nm to 426 nm for Ad Mat-1 and from 412 nm to
351 nm for Ad Mat-2). These results indicate the high selectivity
of the chemosensor modified filter paper for the detection of
CNꢀ from mixed aqueous solutions of various anions.
To establish the sensitivity of Ad Mat-1 and Ad Mat-2 to cy-
anide and the detection limit of the system, the absorbance of the
functionalized cellulose materials at different cyanide concen-
trations was recorded (Fig. 7). Plotting
us to calculate the detection limit to be 0.011
and 0.075 M for Ad Mat-2 (see Supplementary data). The dif-
D
A versus [CNꢀ] allowed
M for Ad Mat-1
m
As displayed in Fig. 6a, the chemosensor modified cellulose
materials underwent an obvious colour change from green/yellow
to yellow/orange for 8 after being dipped into cyanide aqueous
solutions. Because of the high surface areas of functionalized cel-
lulose material, as expected, the colour change could be clearly
seen by naked eye inspection. Also, lmax shift of the sensitized Ad
Mat-1 from 351 to 426 nm (Fig. 6b). The 75 nm hypsochromic shift
indicates that cyanide anions react via nucleophilic substitution
with its aldehyde receptor on the chromogenic group 8. However,
no colour change was observed for Ad Mat-1 upon exposing it
to aqueous solutions of other anions, such as CH3COOHꢀ; HSO4ꢀ;
m
ference between the detection limit of cyanide anions in solution
and on solid support may be explained by the large surface area
of the solid support, which facilitates the contact between the
receptor site and the cyanide anions. The choice of the textile
support is crucial to develop a functional material able to detect
cyanide in pure water, in this sense; this support must be hy-
drophilic material to facilitate the reaction between cyanide and
chemosensor incorporated on the fabric. The cotton is a very
interesting choice because of its hydrophilic character and its
natural availability.
To investigate the pH effect in the sensing ability of the sensi-
tised materials, Ad Mat-1 and Ad Mat-2 are immersed in aqueous
solutions of different acidity (namely, pH 5, 9 and 11) and left in
such solutions for some time. As shown in Fig. 8, a constant de-
crease in the intensity of the lmax of the materials was observed at
pH 11 with time.
ClOꢀ3 ; ClOꢀ4 ; Clꢀ; Brꢀ; H2POꢀ4 ; S2Oꢀ3 ; Fꢀ; NO3ꢀ; Iꢀ; NO2ꢀ; SO32ꢀ
;
S2ꢀ; C2O24ꢀ; SO24ꢀ; N3ꢀ; SCNꢀ; Fꢀ; CO23ꢀ; HCO32ꢀ in a large excess
as shown in Fig. 6a. These anions did not cause any hypsochromic
shift of the initial 351 nm adsorption band of the chemosensor
functionalized filter textile (Fig. 6b). Furthermore, the colouration
response in the presence of CNꢀ is not influenced by addition of
other anions. Upon exposing the Ad Mat-1 or Ad Mat-2 to
aqueous solutions of CNꢀ (10 mM) mixed with CH3COOHꢀ;
The decrease in the intensity of the lmax of the Ad Mat-1 and Ad
Mat-2 materials observed at pH 11 can be explained by the de-
sorption of the dyes from the materials due to the saponification of
HSOꢀ4 ; ClOꢀ3 ; ClO4ꢀ; Clꢀ; Brꢀ; H2PO4ꢀ; S2Oꢀ3 ; Fꢀ; NO3ꢀ; Iꢀ; NO2ꢀ; SO32ꢀ
;

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J. Isaad, A. El Achari / Tetrahedron 67 (2011) 4939e4947
Fig. 4. FTIR transmission spectra of (a) the scoured cotton fabric and (b) the functionalized cotton fabric Ad Mat-1 (c) the functionalized cotton fabric Ad Mat-2.
Fig. 5. Schematic representation of CNꢀ sensing using dyes modified natural cellulose substance.

J. Isaad, A. El Achari / Tetrahedron 67 (2011) 4939e4947
4945
Fig. 6. Colour change of the chemosensor-modified cellulose fibre upon exposure to aqueous solutions of different anions ꢀ1 mM (a). Solid UVevis spectra of the chemosensors ꢀ2-
modified cellulose fibre after dipping in aqueous solutions at pH¼7 of different anions (b). Absorption spectra of the chemosensor ꢀ2-modified cellulose fibre upon contact with
increase amount of aqueous solution of CNꢀ
.
0,0005
0,0005
0,00045
0,0004
0,00035
0,0003
0,00025
0,0002
0,00015
0,0001
0,00005
0
Ad Mat-1
Ad Mat-2
0,00045
0,0004
0,00035
0,0003
0,00025
0,0002
0,00015
0,0001
0,00005
0
-0,2
0
0,2
0,4
0,6
0,8
1
-0,2
0
0,2
0,4
0,6
0,8
1
CN- eq
CN- eq
Fig. 7. Normalised absorption spectra of Ad Mat-1 and Ad Mat-2 immersed in aqueous solutions of cyanide at different concentrations.
the esteric groups at pH¼11. Therefore, the sensitised materials, Ad
Mat-1 and Ad Mat-2 can be used for cyanide detection in water at
5<pH<11.
3. Conclusions
Two new water-soluble dyes (8 and 9) are prepared, and
their optical responses to anions are studied both in pure water.
The water solubility is obtained by the incorporation of the
water soluble molecules (glucose end glycerol) on the starting
organic dyes and its corresponding water soluble derivatives
present very high chemo selectivity towards cyanide anions in
water. Organic compounds 2 and 3 were then grafted on natural
cellulose fibres and its optical properties studied. Immersion of
these functionalized textiles in an aqueous solution of cyanide
induced a colour change that can be used for the detection of
cyanide down to 0.01e0.07
mM. These easy-to-use materials
also showed also a high degree of cyanide selectivity in aqueous
medium.
Fig. 8. Plot showing the reduction in intensity of the lmax absorption for the Ad Mat-1
and Ad Mat-2 materials as a function of pH.

4946
J. Isaad, A. El Achari / Tetrahedron 67 (2011) 4939e4947
4. Experimental section
m/z¼271.21 [Mþ1]þ. C14H10N2O4 (270.06): calcd C, 62.22; H, 3.73;
N, 10.37, found, C, 62.31; H, 3.79; N, 10.42.
4.1. Materials and instrumentations
4.3.2. Synthesis of 4-((4-boronophenyl)diazenyl)benzoic acid (3). The
product 3 was prepared according to the general procedure A
using the following quantities: 4-amino benzoic acid (1.00 g,
7.29 mmol), phenyl boronic acid (0.88 g, 7.29 mmol), NaNO2
(0.56 g, 8.74 mmol), in HCl 1 N/water (10 mL), to afford 3 (1.51 g,
ꢀ
TLC was carried out on silica gel pre-coated plates (Merck; 60 A
F254) and spots located with (a) UV light (254 and 366 nm), (b)
ninhydrin (solution in acetone), (c) fluorescamine, (d) I2 or (e)
a basic solution of permanganate [KMnO4 (3 g), K2CO3 (20 g) and
NaOH (0.25 g) in water (300 mL)]. Flash column chromatography
(FCC) was carried out on Merck silica gel 60 (230e400 mesh)
according to Still et al.32 1H and 13C NMR spectra were recorded at
200 MHz with Varian spectrometers in deuteriated solvents and
are reported in parts per million (ppm) with the solvent resonance
used as the internal reference. Mass spectra were recorded with
a Thermo Fisher LCQ fleet ion-trap instrument (the spectra repor-
ted were also using the ESIþc technique). Elemental analysis was
carried out with a PerkineElmer 240C Elemental Analyzer. Trans-
mission mode spectra (32 scans, 4 cmꢀ1 resolution) were measured
with KBr pellets of finely cut and ground fabrics. FTIR ATR spectra
(216 scans, 4 cmꢀ1 resolution) were collected with a MIRacle, single
reflection horizontal ATR accessory (PIKE instruments) having
a diamond ATR crystal fixed at incident angle of 45ꢁ. UVevis spectra
were recorded with a Cary-4000 Varian spectrophotometer. The
compound 5 was prepared following the procedures reported in
the literatures.30
77%). 1H NMR (200 MHz, DMSO-d6):
d
¼8.40e8.21 (AA’XX’ system,
4H), 8.12 (s, 2H), 8.02e7.94 (AA’XX’ system, 4H) ppm. 13C NMR
(50 MHz, DMSO-d6):
d
¼169.7, 157.5, 152.9, 133.5, 132.6, 130.4,
123.7, 122.8, 108.9, ppm. MS (ESI): m/z¼271.17 [Mþ1]þ.
C13H11BN2O4 (270.08): calcd C, 57.82; H, 4.11; N, 10.37, found, C,
57.89; H, 4.17; N, 10.41.
4.4. General procedure B: synthesis compounds 6 and 7
A mixture 2 or 3 (1 mol) and SOCl2 (1 mol) in dry DCM (2 mL)
was stirred under a hydrogen atmosphere at room temperature for
1 h. The solvent evaporated in vacuo to give the crude product,
which was coupled, without purification, with the protected glu-
cose 4 or the protected glycerol 5 (1 mol) in THF as solvent. The
formed products are isolated by flash chromatography to afford the
corresponding dyes 6 or 7.
4.4.1. Synthesis of compound 6. The product 6 was prepared
according to the general procedure B using the following quanti-
ties: dye 2 (1.00 g, 3.70 mmol), SOCl2 (0.44 g, 3.70 mmol), 4 (0.96 g,
3.70 mmol), in THF (10 mL), to afford 6 (1.53 g, 81%). Rf 0.53 (EtOAc/
4.2. Preparation of chromogenic probes titration solutions
PE: 2/3). 1H NMR (200 MHz, DMSO-d6):
d¼10.27 (s, 1H), 8.36e8.22
Stock solutions (1 mM) ꢀof the tetrabutylammonium salts
NOꢀ3 ; Iꢀ; NOꢀ2 ; SO32ꢀ; S2ꢀ; C2O24ꢀ; SO24ꢀ; Nꢀ3 ; SCNꢀ; Fꢀ; CO32ꢀ; HCO23ꢀ
in water were prepared. Stock solutions of chemodosimeter
(0.1 mM) were prepared in water. Test solutions were prepared by
(AA’XX’ system, 4H), 8.10 (m, 2H), 7.23 (m, 1H), 5.53 (d, 1H,
J1,2¼5.1 Hz, H-1), 5.31 (s, 1H, PhOH), 4.62 (dd, 1H, J2,3¼2.4 Hz,
J3,4¼7.8 Hz, H-3), 4.33 (dd, 1H, H-2), 4.22 (dd, 2H, J4,5¼1.8 Hz,H-4),
4.19 (m, 2H, H-6a, H-6b), 4.01 (ddd, 2H, J5,6a¼6.6 Hz, J5,6b¼4.4 Hz,
H-5), 1.46, 1.41, 1.34, 1.33 [4s, each 3H, 2ꢃ C(CH3)2] ppm. 13C NMR
of
CH3COOHꢀ; HSO4ꢀ; ClO3 ; ClO4ꢀ; Clꢀ; Brꢀ; H2PO4ꢀ; S2O3ꢀ; Fꢀ;
placing 4e40 mL of the probe stock solution into a test tube, adding
(50 MHz, DMSO-d6):
d
¼193.4, 165.5, 164.2, 157.3, 145.8, 132.7, 130.9,
an appropriate aliquot of each anion, and diluting the solution to
4 mL with water. In the case of Ad Mat-1 and Ad Mat-2 titration,
a fragment of these textiles were immersed in stock solutions of
each anions for 1e10 min (1 mM) and dried under air flux. All the
experiments were carried out at 20ꢂ2 ꢁC.
130.4, 124.2, 122.6, 118.4, 116.6, 96.1 (C-1), 70.9 (C-2), 70.5 (C-4),
70.3 (C-3), 65.8 (C-5), 63.7 (C-6), 25.8, 25.7, 24.8, 24.3 [4ꢃ C(CH3)2]
ppm. MS (ESI): m/z¼513.28 [Mþ1]þ. C26H28N2O9 (512.18): calcd C,
60.93; H, 5.51; N, 5.47, found, C, 60.97; H, 5.56; N, 5.51.
4.4.2. Synthesis of compound 7. The product 7 was prepared
according to the general procedure B using the following quanti-
ties: dye 3 (1.00 g, 3.71 mmol), SOCl2 (0.45 g, 3.70 mmol), 4 (0.97 g,
3.70 mmol), in THF (10 mL), to afford 6 (1.61 g, 87%). Rf 0.49 (EtOAc/
4.3. General procedure A: synthesis compounds 2 and 3
PE: 2/3). 1H NMR (200 MHz, DMSO-d6):
d
¼8.41e8.22 (AA’XX’ sys-
To a solution 4-amino benozoic acid (1 mol) in 15 mL of water/
HCl 1 N: 15/1.5, a solution of NaNO2 (1.4 mmol) in water (2 mL)
was added dropwise at 0 ꢁC and the resulting mixture was stirred
for 30 min. The diazonium salt solution previously prepared was
added dropwise to the solution of salicaldehyde or phenyl boronic
acid (1 mol) in methanol (3 ml) and the combined solutions were
maintained at 0 ꢁC for 6 h with stirring. After this time, the pH
was adjusted to 8 and the resulting mixture was diluted with
chloroform (20 ml), the formed product was isolated by filtration
and washed with chloroform to afford the corresponding azo dyes
2 or 3.
tem, 4H), 8.12 (s, 2H), 8.03e7.93 (AA’XX’ system, 4H), 4; 51e4.30
(m, 3H), 3.94e3.89 (m, 2H), 1.25 (s, 6H) ppm. 13C NMR (50 MHz,
DMSO-d6):
d
¼166.6, 157.4, 152.6, 133.7, 132.6, 130.8, 123.5, 122.7,
118.5, 108.8, 75.7, 67.9, 64.6, 26.1 ppm. MS (ESI): m/z¼385.23
[Mþ1]þ. C19H21BN2O6 (384.15): calcd C, 59.40; H, 5.51; N, 7.29;
found, C, 59.45; H, 5.56; N, 7.32.
4.5. General procedure C: deprotection of compounds 6 and 7
A solution of 6 or 7 (1 mol) in 90% aqueous CF3COOH (18 mL)
was stirred at room temperature for 2 h and the red-violet reaction
mixture was concentrated under diminished pressure and re-
peatedly co-evaporated with toluene (4ꢃ30 mL) to afford the wa-
ter-soluble dyes 8 and 9.
4.3.1. Synthesis
4-((3-formyl-4-hydroxyphenyl)diazenyl)benzoic
acid (2). The product 2 was prepared according to the general
procedure A using the following quantities: 4-amino benzoic acid
(1.00 g, 7.29 mmol), salicaldehyde (0.89 g, 7.29 mmol), NaNO2
(0.56 g, 8.74 mmol), in HCl 1 N/water (10 mL), to afford 2 (1.24 g,
4.5.1. Synthesisofcompound 8. The product 8 was prepared according
to the general procedure C using the following quantities: dye 6
(1.00 g, 1.96 mmol), to afford 8 (0.79 g, 95%). 1H NMR (200 MHz,
62%). 1H NMR (200 MHz, DMSO-d6):
d
¼10.28 (s, 1H), 8.37e8.22
(AA’XX’ system, 4H), 8.09 (m, 2H), 7.29 (m, 1H), 5.31 (s, 1H) ppm.
13C NMR (50 MHz, DMSO-d6):
¼193.9, 169.4, 164.3, 157.3, 145.6,
132.9, 130.9, 130.2, 124.5, 122.7, 118.4, 116.3 ppm. MS (ESI):
d
DMSO-d6):
d
¼10.26 (s, 1H), 8.36e8.23 (AA’XX’ system, 4H), 8.11 (m,
2H), 7.22 (m, 1H), 5.82 (d, 1H, J¼9.3 Hz), 5.76 (m, 1H), 5.56 (m, 2H),

J. Isaad, A. El Achari / Tetrahedron 67 (2011) 4939e4947
4947
5.33 (s, 1H, PhOH), 5.24 (dd, 1H, J¼10.2, 3.3 Hz), 4.2 (m, 2H) ppm. 13
C
3. Suksai, C.; Tuntulani, T. Top. Curr. Chem. 2005, 255, 163e198.
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NMR (50 MHz, DMSO-d6): see Table 3 for glycidic moiety and
d
¼193.7,
165.6, 164.2, 157.6, 145.6, 132.7, 130.8, 130.6, 124.4, 122.5, 118.6,
116.9 ppm. MS (ESI): m/z¼433.25 [Mþ1]þ. C20H20N2O9 (432.12): calcd
C, 55.56; H, 4.66; N, 6.48, found, C, 55.61; H, 4.69; N, 6.52.
9. Wiskur, S. L.; Aıt-Haddou, H.; Lavigne, J. J.; Anslyn, E. V. Acc. Chem. Res. 2001, 34,
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Table 3
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nacorsi T. Eur. Pat. Appl. EP 2 085 434 A1, 2008. (b) Bianchini, R.; Catelani, G.;
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13C NMR spectroscopic data (
glucoyl derivatives
d, ppm) for the glycide portions for deprotected 3-O-D-
Dyes
C-1
C-2
C-3
C-4
C-5
C-6
8-
8-
a
a
p
p
92.4
92.4
72.1
72.1
81.9
82.0
72.1
72.1
70.0
70.0
61.2
61.3
4.5.2. Synthesis of compound 9. The product 9 was prepared
according to the general procedure C using the following quanti-
ties: dye 7 (1.00 g, 2.60 mmol), to afford 9 (0.83 g, 92%). 1H NMR
(200 MHz, DMSO-d6):
2H), 8.01e7.91 (AA’XX’ system, 4H), 4.52e4.29 (m, 2H), 3.91e3.61
(m, 3H), 3.56 (s, 2H) ppm. 13C NMR (50 MHz, DMSO-d6):
157.3, 152.6, 133.8, 132.5, 130.7, 123.6, 122.7, 118.6, 108.9, 70.6, 65.9,
63.6 ppm. MS (ESI): m/z¼345.22 [Mþ1]þ. C16H17BN2O6 (344.12):
calcd C, 55.84; H, 4.98; N, 8.14; found, C, 55.88; H, 5.03; N, 8.19.
d¼8.42e8.22 (AA’XX’ system, 4H), 8.12 (s,
d
¼166.5,
Acknowledgements
ThisworkisfinanciallysupportedbyGEMTEXLaboratorydFrance.
We thank Mr. ChristianCatel (technicianof GEMTEX laboratory) for its
kind disponibility.
26. (a) Gimeno, N.; Li, X.; Durrant, J. R.; Vilar, R. Chem.dEur. J. 2008, 14, 3006e3012;
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Chem. Commun. 2005, 2790e2792.
Supplementary data
27. Touceda-Varela, A.; Stevenson, E. I.; Galve-Gasion, J. A.; Dryden, D. T. F.; Mar-
eque-Rivas, J. C. Chem. Commun. 2008, 1998e2000.
Supplementary data related to this article can be found online at
doi:10.1016/j.tet.2011.04.061.
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