Synthesis of thiosemicarbazone derivatives of benzo-15-crown-5 and their anion recognition properties

Article abstract of DOI:10.1080/10426500701681631

A series of thiosemicarbazone derivatives of benzo-15-crown-5 were synthesized efficiently at room temperature using hydrogenchloride acid (HCl) as catalyst. Their anion recognition properties of a, b and c were studied, the result show they exhibit highly selective binding and sensing of F-, MeCO2- and n-C3H7CO2- in CH3CN (F- > n-C3H7CO2- > MeCO2- ? Cl-, Br- and I-). Especially receptor c shows different UV-Vis spectrum of F- from MeCO2-and C3H7CO2-, in addition to the color of the solution change from colorless to yellow upon the addition of F-, these two points make it suitable to be used as colorimetric anion sensor to identify fluoride anion from other halide anions and carboxylate anions by naked-eye. The connection between receptor and anion is by hydrogen bonding interactions, the binding ratio is 1:1, which have been confirmed by UV-vis inspection spectra in CH3CN and 1HMR in DMSO-d6. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/10426500701681631

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Phosphorus, Sulfur, and Silicon
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Synthesis of
Thiosemicarbazone Derivatives
of Benzo-15-crown-5 and Their
Anion Recognition Properties
Yan-Qing Zhou a b , Tai-Bao Wei a & You-Ming Zhang a
a College of Chemistry and Chemical Engineering,
Gansu Key Laboratory of Polymer Materials ,
Northwest Normal University, Lanzhou , Gansu, P. R.
China
b Lanzhou Petrochemical College of Vocational
Technology, Lanzhou , Gansu, P. R. China
Published online: 04 Jun 2008.
To cite this article: Yan-Qing Zhou , Tai-Bao Wei & You-Ming Zhang (2008) Synthesis
of Thiosemicarbazone Derivatives of Benzo-15-crown-5 and Their Anion Recognition
Properties, Phosphorus, Sulfur, and Silicon and the Related Elements, 183:6,
1478-1488
To link to this article: http://dx.doi.org/10.1080/10426500701681631
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Phosphorus, Sulfur, and Silicon, 183:1478–1488, 2008
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500701681631
Synthesis of Thiosemicarbazone Derivatives of
Benzo-15-crown-5 and Their Anion Recognition
Properties
Yan-Qing Zhou,1,2 Tai-Bao Wei,1 and You-Ming Zhang1
1College of Chemistry and Chemical Engineering, Gansu Key
Laboratory of Polymer Materials, Northwest Normal University,
Lanzhou, Gansu, P. R. China
2Lanzhou Petrochemical College of Vocational Technology, Lanzhou,
Gansu, P. R. China
A series of thiosemicarbazone derivatives of benzo-15-crown-5 were synthesized ef-
ficiently at room temperature using hydrogenchloride acid (HCl) as catalyst. Their
anion recognition properties of a, b and c were studied, the result show they exhibit
highly selective binding and sensing of F−, MeCO− and n-C H CO− in CH CN
3
7
3
2
2
(F− > n-C H CO− > MeCO− >> Cl−, Br−− and I−). Especially receptor c shows dif-
3
7
2
2
ferent UV-Vis spectrum of F−from MeCO and C H CO−, in addition to the color
3
7
2
2
of the solution change from colorless to yellow upon the addition of F−, these two
points make it suitable to be used as colorimetric anion sensor to identify fluoride
anion from other halide anions and carboxylate anions by naked-eye. The connec-
tion between receptor and anion is by hydrogen bonding interactions, the binding
ratio is 1:1, which have been confirmed by UV-vis inspection spectra in CH CN and
3
1HMR in DMSO-d .
6
Keywords Anion recognition; synthesis; thiosemicarbazone derivatives of Benzo-15-
crown-5
INTRODUCTION
The design and synthesis of efficient artificial receptors for selective
binding of biologically or environmentally important anionic species
is an important work with many applications such as sensors, homo-
geneous catalysis, and membrane transport1. It is noteworthy that
Received 10 July 2007; accepted 4 August 2007.
This work was supported by NSFC (20671077),the Natural Science Foundation of
Gansu province(3ZS061-A25-027,3YS051-A25-010) and Lanzhou Petrochemical College
of Vocational Technology (K07-3), who are gratefully acknowledged.
Address correspondence to You-Ming Zhang, College of Chemistry and Chemi-
cal Engineering, Northwest Normal University, Lanzhou, 730070, Gansu, P.R. China.
E-mail: zhangnwnu@126.com
1478

Thiosemicarbazone Derivatives of Benzo-15-crown-5
1479
thioureas are good hydrogen-bond donors and are excellent receptors
for Y-shaped anions such as carboxylate through the formation of two
hydrogen bonds1,2,3.However, during our study, we find the title com-
pounds exhibit specific UV-Vis spectrum of fluoride anion, a sphere an-
ion, yet this substrate is crucial for biological processes, and the color of
the solutions change from colorless to yellow, which show that they can
be used as a powerful naked-eye sensor for fluoride anion. Herein, we
report the synthesis and anion recognition properties of these highly
selective and sensitive anion receptors to continue and develop our pre-
vious work on the synthesis and crystal structure of crown ether.4,5
SCHEME 1
RESULTS AND DISCUSSION
Synthesis of a-i
The synthetic route is shown in Scheme 1. In general, thiosemicar-
bazones are prepared under refluxing solvent for several hours, how-
ever, in this reaction, we find the 4-acetyl benzo-15-crown-5 react with
thiosemicarbazides using concentrated hydrogenchloride (HCl) as cat-
alyst at room temperature to afford the target products almost in quan-
titative yield within an hour, in addition, the products, which need only
a simple washing with 10ml ethanol three times, can be used to char-
acterize (Table I). In order to find out the most ideal reaction condition,
we selected a as an example to study the influence of catalyst on this
reaction. Then two experiments were carried out at room temperature
with AcOH as catalyst and without any catalyst separately. After12h,
the reaction catalyzed by AcOH began,but it did not go to completion
after 24h and gave the product in 11% yield, the reaction without any
catalyst did not take place at all after 24 h. Apparently, the HCl is an
efficient catalyst for this reaction.

1480
Y.-Q. Zhou et al.
TABLE I The Reaction Time, Yield, and Melting Points of a–i
Entry
R
Time/yield (%)
M.p. (◦)
a
b
c
d
e
f
g
h
i
C6H5
4-FC6H4
1 h
98
100
100
96
99
94
90
95
85
114
1 h
1 h
1 h
1 h
1 h
1 h
1 h
1 h
166–168
156–158
108–110
160–161
156–158
168–170
182–183
165–167
4-CH3CH2OC6H4
2-CH3OC6H4
2-CH3C6H4
3-CH3C6H4
4-CH3C6H4
2-ClC6H4
4-ClC6H4
UV-vis Absorption Spectra
The effect of various anions as N(C4H9)
+
salt on absorption spec-
4
trum of c (2.0 × 10−5 M) was examined in CH3CN, and result are shown
in Figure1. Spectrum (c) is measured in the absence of anions, where
c has a UV-vis spectrum with λmax at 323nm, which can be assigned as
an intramolecular charge transfer absorption band. As shown in spec-
trum (Cl−), (Br −) and (I−), c does not show any obvious spectral change
even in the presence of 50 equiv. of Cl−, Br−, and I−. By contrast, sig-
nificant changes are observed in the presence of 50 equiv. of MeCO−2 ,
n-C3H7CO− and F−, as shown in spectrum (MeCO−), n-C3H7CO− and
2
2
(F−), in fac2t, there are some differences among them: after F−is added,
FIGURE 1 UV-vis absorption spectra of c recorded in CH3CN (2.0 × 10−5 M)
after the addition of 50 equivalents of representative anions.

Thiosemicarbazone Derivatives of Benzo-15-crown-5
1481
FIGURE 2 UV-vis absorption spectra of c in CH3CN (2.0 × 10−5 M) upon the
addition of various equivalents of Bu4N+F−: 0, 0.5, 6.0, 12, 20, 40, 60, 80, 100,
120, and 140.
the peak at 323 nm produces a hypsochromic shift (from 323 to 305 nm),
a new peak appears at 379 nm, and the color of the solution changes
from colorless to yellow obviously, however, addition of MeCO−2 and n-
C3H7CO− cause a very small hypsochromic shift (from 323 to 322nm),
2
no new peak appears and no clear color change is found. It is apparent
that the specific spectra property and the resulting color change of re-
ceptor c upon the addition of F− under the solution-phase conditions
can be used as colorimetric anion sensor.
The binding properties of c with F−, MeCO2− and n-C3H7CO− were
2
further assessed by UV-vis spectroscopy. Figure 2 show the dependence
of UV-vis spectra of c in CH3CN on the concentration of F−. Increasing
the concentration of F− the peak at 323 nm decreases, and produces a
significant hypsochromic shift from 323 to 305 nm, at the same time,
a new peak at 379 nm appears, which is ascribed to the formation of
the complex between c and F−, and produces a bathochromic shift from
379 to 386 nm, indicating that the combination of c with F− promotes
the charge transfer interaction, and two clear isosbestic points appear
at 280 nm and 347 nm, respectively. A Job plot experiment was con-
ducted, the result show the absorption of c-F− complex approaches a
maximum when the molar fraction of [F−]/([c]+[ F−]) is about 0.5 (Fig-
ure 3), indicating that 1:1 complex is formed. The association constant
(Kass) calculated according to the titration experiment is 1890 (Table
II). The satisfactory result of the nonlinear curve fitting (the correlation
coefficient R>0.99) confirms further the 1:1 binding ratio6 (Figure 4).

1482
Y.-Q. Zhou et al.
FIGURE 3 Job’s plot between receptor c and Bu4N+ F− in CH3CN. [c] + [F−]
= 4.0 × 10−5M.
Differently, less hypsochromic shift (from 323 to 322 nm) are seen upon
the addition of excess MeCO−2 , no new peak appears, no obvious color
changes, but two clear isosbestic points appears at 275nm and 350nm,
the binding ratio between receptor c and MeCO−2 is still 1:1, the asso-
ciation constant is 1680 (Figure 5). n-C3H7CO− shows the same prop-
erties as MeCO−2 , two clear isosbestic points 2appears at 279nm and
348nm, its association constant is 1740 (Figure 6). From these asso-
ciation constants data and Figure1, we draw the conclusion that the
binding ability o−f receptor c recognizes anions in the following order :
F− > n-C3H7CO > MeCO2− >> Cl−, Br− and I−.
2
In the case of receptor b, the addition of MeCO−2 and n-C3H7CO−
show the similar tendency with F−, all of the three anions cause th2e
TABLE II Association Constants Kass((mol L−1 −1) for Receptor a,
)
Receptor b and Receptor c with Anions and Their Correlation
Coefficients R
Receptor a
Receptor b
Receptor c
Anion
F−
Kass
R
Kass
R
Kass
R
4310
3400
3240
0.9988
0.9993
0.9990
4590
4330
3580
0.9918
0.997
0.9987
1890
1740
1680
0.9995
0.9994
0.9983
n-C3H7CO−
2
CH3CO−
2

Thiosemicarbazone Derivatives of Benzo-15-crown-5
1483
FIGURE 4 Plot of absorbance change of receptor c vs. equivalents of Bu4N+
F− added (the hollow spheres are the fitting curve).
color of the solution change from colorless to yellow. For receptor a,
the addition of n-C3H7CO− show the similar tendency with F−, and
2
the color of the solution change from colorless to yellow, the addition
of MeCO−2 show the similar tendency with that of receptor c, and no
obvious color changes is found.
FIGURE 5 UV-vis absorption spectra of c in CH3CN (2.0 × 10−5 M) upon the
addition of various equivalents of Bu4N+MeCO2−: 0, 0.75, 2.0, 5.0, 10, 20, 30,
40, 60, 80, 110, 130, 150, 200, and 250.

1484
Y.-Q. Zhou et al.
FIGURE 6 UV-vis absorption spectra of c in CH3CN (2.0 × 10−5 M) upon the
addition of various equivalents of Bu4N+C3H7CO2−:0, 0.5, 6.0, 15, 30, 50, 80,
110, 140, 200, and 250.
Mechanism of Recognition
Receptor b was selected as a model to study the mechanism of recog-
nition between receptors and anions. The color of the solution b+ F−
is yellow; however, as a protic solvent methanol was added gradually,
the yellow color of the solution faded, at the same time, the absorbance
of the solution b+ F− at 323nm went back to the value of receptor b
and the peak of complex b- F− at 369 nm disappeared. The reason is
that the addition of methanol resulted in the hydrogen bond between
NH of thiourea and anions replaced by a new hydrogen bond between
NH of thiourea and methanol, in view of this point, the hydrogen bonds
between NH of thiourea and anions come into being.
In order to reveal the forming of the hydrogen bond, a 1HNMR
1
titration experiment was carried out. HNMR spectroscopy of b was
recorded in DMSO-d6 (1.0 × 10−2 mol·L−1) after the addition of 1.0
equivalent of representative anions. Addition of F−, n-C3H7CO2− and
MeCO−2 to compound b caused the NH proton signals of thiourea group
to be changed. Upon addition of F− and n-C3H7CO−, the NH peaks
2
of the thiourea disappeared. In the case of MeCO−2 , NH(adjacent to
imine) disappeared, another NH showed a downfield shift from 9.9 to
10.0ppm. These results illustrate that the connection between receptor
b and those anions was by hydrogen bonding interactions.

Thiosemicarbazone Derivatives of Benzo-15-crown-5
1485
CONCLUSION
We have succeeded in preparing a new class of receptors that exhibit
−
–
highly selective binding and sensing of F−, n-C3H7CO and MeCO2 in
CH3CN, the highly sensing properties and unique co2lor change upon
addition of F− of receptor c make it can be explored as a colorimetric
sensor for F− in application.
EXPERIMENTAL
Melting points were determined in open capillaries and are uncorrected.
IR spectra were recorded in KBr on a Digilab FTS-3000 spectropho-
1
tometer and HNMR spectra on an mercury plus-400MHz or mercury
plus-300MHz Varian instrument using CDCl3 or DMSO-d6 as solvent
and TMS as internal reference. Elemental analysis was determined on
PE-2400 CHN instrument. UV-vis spectra were taken on an Agilent-
8453 spectrometer.
Materials
The thiosemicarbazides have been prepared by following the method of
Shukla et al.7 and 4-acetyl benzo-15-crown-5 has been prepared by fol-
lowing the method of Lai-xin Zhang8. The anionic substrates were used
as the tetrabutylammonium salts, which were analytical reagents. The
CH3CN was refluxed with K2CO3, KMnO7and then P2O5. All other com-
mercially available reagents were used without further purification.
Synthesis of a–i
This reaction was carried out by adding a thiosemicarbazide (2 mmol),
4-acetyl benzo-15-crown-5 (2 mmol) and 1–2 drops of HCl to a round-
bottomed flask containing 20 ml ethanol and a magnetic stirring bar
and stirred at room temperature. Several minutes later, substantial
precipitation took place. In order to make it completed, the reaction
lasted for 1 h. When the reaction finished, the precipitation was filtered
and washed with 10 ml ethanol three times. By this simple treatment,
pure product, Suitable for characterization, was obtained.
a (C23H29N3SO5)
Elemental analysis, found: C 60.28, H 6.72, N 9.31; Calc: C 60.11,
H 6.36, N 9.14%. IR: 3439,3283 (N-H), 3060,3026 (Ar-H), 2925 (CH3),
2866 (CH2), 1596 (C=N), 1551, 1516 (Ar), 1272, 1059 (Ar O CH2),
1
1183 (C=S), 1131 (CH2 O CH2), cm−1. HNMR (CDCl3), δH: 2.3 (s,

1486
Y.-Q. Zhou et al.
3H, CH3), 3.75–4.21 (m, 16H, 4 × OCH2CH2O), 6.87–7.69 (m, 8H,
Ar-H), 8.69 (s, 1H, NH), 9.34 (s, 1H, NH).
b (C23H28N3SO5F)
Elemental analysis, found: C57.75, H 6.04, N 8.82; Calc: C 57.85, H
5.91, N 8.79%. IR: 3445, 3293 (N-H), 3080 (Ar-H), 2924 (CH3), 2866
(CH2), 1605 (C=N), 1545,1512 (Ar), 1273, 1057 (Ar O CH2), 1188
(C=S), 1133 (CH2 O CH2), cm−1. 1HNMR (DMSO-d6), δH: 2.35 (s, 3H,
CH3), 3.62–4.15 (m, 16H, 4 × OCH2CH2O), 6.94-7.61 (m, 7H, Ar-H),
9.99 (s, 1H, NH), 10.50 (s, 1H, NH).
c (C25H33N3SO6)
Elemental analysis, found: C 59.70, H 6.57, N 8.42; Calc: C 59.62,
H 6.6, N 8.34%. IR: 3441, 3225 (N-H), 3080 (Ar-H), 2930 (CH3), 2974,
2866 (CH2), 1595 (C=N), 1539,1512 (Ar), 1272, 1046 (Ar O CH2), 1180
1
(C=S), 1136 (CH2 O CH2), cm−1. HNMR (DMSO-d6), δH: 1.31–1.35
(t, 3H, CH3), 2.34 (s, 3H, CH3), 2.49–2.50(d, 2H, OCH2 ), 3.55–4.15
(m, 16H, 4 × OCH2CH2O), 6.89-7.61 (m, 7H, Ar-H), 9.87 (s, 1H, NH),
10.36 (s, 1H, NH).
d (C24H31N3SO6)
Elemental analysis, found: C 58.92, H 6.50, N 8.68; Calc: C 58.88, H
6.38, N 8.58%. IR: 3375, 3249 (N-H), 3073 (Ar-H), 2999,2990 (CH3), 2871
(CH2), 1647 (C=N), 1602, 1540,1510 (Ar), 1274, 1052 (Ar O CH2),
1
1190 (C=S), 1150(CH2 O CH2), cm−1. HNMR (DMSO-D6), δH: 2.37
(s, 3H, CH3), 3.89(s, 3H, -OCH3) 3.62–4.14 (m, 16H, 4 × OCH2CH2O),
6.94–7.51 (m, 7H, Ar-H), 10.19 (s, 1H, NH),10.71 (s, 1H, NH).
e(C24H31N3SO5)
Elemental analysis, found: C 60.79, H 6.64, N 8.93; Calc: C 60.87,
H 6.59, N 8.87%. IR: 3439, 3304 (N-H), 3078 (Ar-H), 2927 (CH3), 2866
(CH2), 1589 (C=N), 1551, 1514 (Ar), 1273, 1057 (Ar O CH2), 1171
(C=S), 1131(CH2 O CH2), cm−1
.
1HNMR (CDCl3), δH: 2.31 (s, 3H,
CH3), 2.36 (s, 3H, CH3) 3.76–4.19 (m, 16H, 4 × OCH2CH2O), 6.86–
7.86 (m, 7H, Ar-H), 8.74 (s, 1H, NH), 9.18 (s, 1H, NH).
f (C24H31N3SO5)
Elemental analysis, found: C 60.92, H 6.76, N 8.94; Calc: C 60.87,
H 6.59, N 8.87%. IR: 3454, 3276 (N-H), 3079 (Ar-H), 2920 (CH3), 2866
(CH2), 1609 (C=N), 1554, 1514 (Ar), 1273, 1057 (Ar O CH2), 1110
(C=S), 1136(CH2 O CH2), cm−1. 1HNMR (DMSO-D6), δH: 2.32 (s, 3H,

Thiosemicarbazone Derivatives of Benzo-15-crown-5
1487
CH3), 2.35 (s, 3H, CH3) 3.61–4.15 (m, 16H, 4 × OCH2CH2O), 6.94–
7.59 (m, 7H, Ar-H), 9.93 (s, 1H, NH), 10.45 (s, 1H, NH).
g (C24H31N3SO5)
Elemental analysis, found: C 60.81, H 6.73, N 8.90; Calc: C 60.87,
H 6.59, N 8.87%. IR: 3443, 3285 (N-H), 3081, 3021 (Ar-H), 2926 (CH3),
2866 (CH2), 1591 (C=N), 1544, 1517 (Ar), 1272, 1059 (Ar O CH2),
1
1180 (C=S), 1136(CH2 O CH2), cm−1. HNMR (CDCl3), δH: 2.30 (s,
3H, CH3), 2.37 (s, 3H, CH3) 3.76–4.21 (m, 16H, 4 × OCH2CH2O),
7.20–7.32 (m, 7H, Ar-H), 8.68 (s, 1H, NH), 9.24 (s, 1H, NH).
h(C23H28N3SO5Cl)
Elemental analysis, found: C 56.00, H 5.61, N 8.62; Calc: C 55.92, H
5.71, N 8.51%. IR: 3437, 3261 (N-H), 3077 (Ar-H), 2928 (CH3), 2867
(CH2), 1597 (C=N), 1543,1515 (Ar), 1274, 1057 (Ar O CH2), 1185
(C=S), 1130(CH2 O CH2), cm−1. 1HNMR (DMSO-D6), δH: 2.38 (s, 3H,
CH3), 3.62–4.14 (m, 16H, 4 × OCH2CH2O), 6.96–8.12 (m, 7H, Ar-H),
10.08 (s, 1H, NH), 10.81 (s, 1H, NH).
i (C23H28N3SO5Cl)
Elemental analysis, found: C 56.04, H 5.63, N 8.64; Calc: C 55.92, H
5.71, N 8.51%. IR: 3460, 3285 (N-H), 3079 (Ar-H), 2923 (CH3), 2865
(CH2), 1590 (C=N), 1532,1513 (Ar), 1273, 1059 (Ar O CH2), 1191
(C=S), 1129(CH2 O CH2), cm−1
.
1HNMR (CDCl3), δH: 2.29 (s, 3H,
CH3), 3.76–4.21 (m, 16H, 4 × OCH2CH2O), 6.86–7.65 (m, 7H, Ar-H),
8.80 (s, 1H, NH), 9.30 (s, 1H, NH).
BINDING STUDIES
UV-vis spectral studies of the three receptors using CH3CN as solvent
were carried out by addition of anions to a 2.0 × 10−5 M solution of
receptor. The job plot study was performed on a total concentration of
1
4.0 × 10−5M in CH3CN. The HNMR study was recorded by adding
equivalent amounts of anions to receptor b in DMSO-d6(mercury plus-
300MHz Varian instrument).
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