An efficient colorimetric and absorption ratiometric anion sensor based on a simple azo-azomethine receptor

Article abstract of DOI:10.1016/j.ica.2018.04.027

An efficient colorimetric and absorption ratiometric azo-azomethine receptor N'-((E)-2-hydroxy-5-((E)-(4-nitrophenyl)diazenyl)benzylidene)picolinohydrazide (L) based on phenolic and acyl hydrazine binding units was synthesized and characterized by FT-IR, ¹H NMR, ¹³C NMR and HRMS method. The optical response of L towards different anions was studied by colorimetric, UV–vis and ¹H NMR titration method. The results revealed that L had a selective colorimetric sensing ability for biologically important F^?, AcO^? and H₂PO₄^? by changing color from pale yellow to blue by naked-eye. Interestingly, the sensor L demonstrated an absorption ratiometric response towards F^? (1:2 complex) and H₂PO₄^? (1:1 complex) during the recognition process. The detection limit of the sensor L towards F^?, AcO^? and H₂PO₄^? was estimated to be 2.94 μM, 4.12 μM and 12 μM respectively. The recognition mechanism was attributed to hydrogen bonding and subsequent deprotonation process according to ¹H NMR titration experiments.

Full text of DOI:10.1016/j.ica.2018.04.027

Inorganica Chimica Acta 479 (2018) 148–153
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Research paper
An efficient colorimetric and absorption ratiometric anion sensor based
on a simple azo-azomethine receptor
Zheng Li a, , Shujun Wang a, Liwei Xiao a, Xiaolong Li b, , Xuemin Jing a, Xiaoxia Peng a, Lilei Ren a
⇑
⇑
a College of Chemistry and Materials Science, Langfang Normal University, Langfang 065000, PR China
b School of Chemistry and Chemical Engineering, Shaanxi University of Science and Technology, Xi’an 710021, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
An efficient colorimetric and absorption ratiometric azo-azomethine receptor N’-((E)-2-hydroxy-5-((E)-
(4-nitrophenyl)diazenyl)benzylidene)picolinohydrazide (L) based on phenolic and acyl hydrazine bind-
ing units was synthesized and characterized by FT-IR, 1H NMR, 13C NMR and HRMS method. The optical
response of L towards different anions was studied by colorimetric, UV–vis and 1H NMR titration method.
The results revealed that L had a selective colorimetric sensing ability for biologically important FÀ, AcOÀ
and H2POÀ4 by changing color from pale yellow to blue by naked-eye. Interestingly, the sensor L demon-
strated an absorption ratiometric response towards FÀ (1:2 complex) and H2PO4À (1:1 complex) during
the recognition process. The detection limit of the sensor L towards FÀ, AcOÀ and H2PO4À was estimated
Received 22 January 2018
Received in revised form 30 March 2018
Accepted 16 April 2018
Keywords:
Colorimetric
Absorption ratiometric
Anion sensor
Azo-azomethine
to be 2.94
bonding and subsequent deprotonation process according to 1H NMR titration experiments.
Ó 2018 Elsevier B.V. All rights reserved.
lM, 4.12 lM and 12 lM respectively. The recognition mechanism was attributed to hydrogen
1. Introduction
at two different wavelengths as a function of analyte concentra-
tion. However, traditional sensors often depend on a single wave-
length for quantitative analysis. In the last few decades, a number
of azo-based colorimetric sensors for anions have been reported
[14,15]. Velmathi et al. [16] reported a azo-schiff base receptor
containing a phenolic OH unit for selective sensing of FÀ/AcOÀ with
the formation of a 1:1 stoichiometric complex. Hamid et al. [17]
developed diaminomaleonitrile-based azo receptors and they
formed 1:1H-bonded complexes with FÀ in CH3CN solution.
Rezaeian et al. [18] prepared a new chromogenic azo-azomethine
sensor containing active phenolic sites for biologically important
anions such as FÀ, AcOÀ and H2POÀ4 over other anions which
formed a 1:2 stoichiometric complex. To the best of our knowl-
edge, there was no example of offering colorimetric and absorption
ratiometric responses upon addition of anions by integrating acyl
hydrazine NAH and phenolic OH units into a single anion receptor.
Herein, as a part of our ongoing research, we designed and syn-
thesized a new azo-azomethine receptor (as shown in Fig. 1)
equipped with nitro-azobenzene group as signal subunit and phe-
nolic OH & hydrazide NAH as binding units. The sensing ability of L
towards different anions was investigated by means of naked-eye,
UV–vis spectroscopy as well as by 1H NMR titration method. Inter-
estingly, the sensor L demonstrated a good selectivity towards FÀ
and AcOÀ (1:2 complex) and H2POÀ4 (1:1 complex) along with a
vivo color change and absorption ratiometric responses during
the recognition process.
Anions play an essential role in the field of biology, industry and
environmental science [1,2]. Therefore, More and more attention
has been laid over the last few decades on the development of
anion sensors [3–5]. Among all the anions, fluoride, acetate and
dihydrogenphosphate ions receive the most concerns due to their
crucial roles in a broad range of chemical and biological processes
[6,7]. For instance, fluoride ion is biologically active and utilised for
the treatment of osteoporosis, dental care, anesthetics and psychi-
atric drugs [8,9] Acetate ions also play an important role in living
system as acetyl coenzyme A. In addition, the production of acetic
acid from the fermentation process is the main ingredient present
in vinegar used in foods [10,11]. Similarly, phosphate and its ana-
logs play a vital role in signal transduction, energy storage and
gene construction in biological systems [12,13]. Accordingly, the
design and preparation of effective sensors for biologically relevant
anions with high selectivity is urgently needed.
Compared with fluorescent and electrochemical sensors, colori-
metric sensors have some obvious advantages, such as its conve-
nience, low cost and good visualization. On the other hand,
ratiometric sensors could provide more reliable quantitative infor-
mation since they utilize the ratio of absorption/emission intensity
⇑
Corresponding authors.
E-mail addresses: lizheng1105@tju.edu.cn (Z. Li), lixiaolong@sust.edu.cn (X. Li).
https://doi.org/10.1016/j.ica.2018.04.027
0020-1693/Ó 2018 Elsevier B.V. All rights reserved.

Z. Li et al. / Inorganica Chimica Acta 479 (2018) 148–153
149
Fig. 1. Synthesis of the sensor L.
2.3.2. UV–vis titration of L with FÀ, AcOÀ and H2PO4À
To each three 3.0 mL of the stock solution was added 3–30
2. Experimental section
l
L of
the tetrabutylammonium of fluoride ion, acetate ion and dihydro-
gen phosphate ion(10 mM). After mixing them for a few seconds,
UV–vis titration spectra were taken at room temperature.
2.1. Materials and methods
Picolinic acid, hydrazine hydrate, p-nitroaniline, salicylic alde-
hyde, tetra-n-butyl-ammonium (TBA) salts (FÀ, ClÀ, BrÀ, IÀ, NO3–,
H2POÀ4 , HSO4À, ClOÀ4 , AcOÀ) were purchased from Sigma-Aldrich
and used without further purification. Other reagents were pur-
chased from commercial source and used as received.
Melting points were determined on a Beijing X-4 microscopic
melting point apparatus without correction (Beijing Tech Instru-
ment Co., China). Infrared spectrum were recorded on a Shimadzu
IR Prestige-21 spectrometer in KBr disk. UV–vis absorption spectra
were recorded on a UV-2550 spectrophotometer in the region 300–
600 nm. High-resolution mass spectra (HRMS) were measured by
using a Shimadzu LCMS-IT-TOF spectrometer. 1H NMR and 13C
NMR spectra were recorded on a Bruker 400 spectrometer (Bruker
BioSpin Gmbh, Rheinstetten, Germany) and used tetramethylsilane
as internal standard substance.
2.3.3. 1H NMR titration of L with FÀ, AcOÀ and H2POÀ4
Seven NMR tubes of L (14.5 mg, 0.05 mmol) with seven differ-
ent equiv (0, 0.5, 1.0, 1.5, 2.0, 3.0 and 4.0 equiv) of the tetrabuty-
lammonium salts (FÀ, AcOÀ and H2POÀ4 ) were dissolved in
DMSO d6 (0.6 mL). After shaking them for a minute, there 1H
NMR spectra were taken.
3. Results and discussion
3.1. Synthesis and characterization
The sensor L has been synthesized via condensation reaction of
azo-coupled precursors with pyridine-2-carbohydrazine in abso-
lute ethanol in good yield. The sensor L was characterized by FT-
IR, HRMS and 1H NMR method. The appearance of a new
t(C@N)
2.2. Synthesis of the sensor L
absorption at 1612 cmÀ1 clearly indicated that a new Schiff base
compound has been formed. Two absorption bands appeared at
3448 and 3259 cmÀ1 were assigned to the O–H and NAH stretch-
ing vibrations respectively (Fig. S1). The IR spectra of L exhibits
peaks at 1674 cmÀ1 was attributed to C@O stretching vibration.
In the 1H NMR, the signal at 12.66 ppm and 12.09 ppm were
assigned to the –OH and –NH group separately. The peak at 8.98
ppm confirmed the presence of –CH@N group [23–25] (Fig. S2).
The M+1 (protonated molecular ion) peak of the high resolution
mass spectrum (HRMS) confirmed the molecular formula of L
(C19H15O4N6) without any ambiguity (Fig. S4).
Pyridine-2-carbohydrazine was synthesized according to litera-
ture method [19]. Azo-coupled salicylaldehyde precursor was pre-
pared according to the well-known literature procedure [20–22].
Pyridine-2-carbohydrazine(1.44 g, 0.0105 mol) and azo-cou-
pled salicylaldehyde precursor (2.71 g, 0.01 mol) were dissolved
in 30 mL absolute ethanol followed by the addition of few drops
of glacial acetic acid to the reaction mixture. Then the reaction
mixture was refluxed for 5 h under stirring. After cooling to room
temperature, the mixture was filtered, washed with absolute etha-
nol, dried in vacuum to obtain red powder. Yield: 82%. m.p. 298–
300 °C. FT-IR(KBr, cmÀ1): 3448(AOH), 3259(NAH), 1674(C@O),
1612(C@N), 1587(Ar, C = C), 1511, 1335(–NO2), 748(Ar-H)
(Fig. S1). 1H NMR (400 MHz, DMSO) d 12.66 (s, 1H), 12.09 (s, 1H),
8.95 (s, 1H), 8.75 (d, J = 4.3 Hz, 1H), 8.39 (d, J = 8.6 Hz, 2H), 8.20
(d, J = 1.3 Hz, 1H), 8.16 (d, J = 7.7 Hz, 1H), 8.10 (d, J = 7.6 Hz, 1H),
8.04 (d, J = 8.6 Hz, 2H), 7.95 (d, J = 8.7 Hz, 1H), 7.78–7.59 (m, 1H),
7.15 (d, J = 8.7 Hz, 1H) (Fig. S2). 13C NMR (101 MHz, DMSO): d
161.97(s), 161.06(s), 155.79(s), 149.57(s), 149.06(s), 148.43(s),
148.27(s), 145.62(s), 138.51(s), 127.67(s), 127.12(s), 125.45(d),
124.90(s), 123.65(d), 123.36(s), 120.34(s), 118.06(s) (Fig. S3).
3.2. Colorimetric and UV–vis studies
To investigate the sensing ability of the sensor L towards vari-
ous anions, the colorimetric and UV–vis studies were carried out
in CH3CN solution. Before the addition of different anions (FÀ,
ClÀ, BrÀ, IÀ, NO3–, AcOÀ, HSO4À, H2PO4À, ClO4À), the solution of free L
was pale yellow and displayed two bands at 316 and 378 nm
which were attributed to
and the chromophore respectively (as shown in Figs. 2 and 3).
p
?
p
⁄ transitions of salicylhydrazone
HRMS: m/z calcd for
391.1174 (Fig. S4).
C
19H14N6O4: [M+H]+ 391.1149; found:
Upon addition of 10 equiv different anions, only the relatively basic
2.3. Sensing experiments
2.3.1. UV–vis spectrum of L with various anions
Stock solution of the sensor L was prepared in CH3CN solution
and the final concentration was 20
lM. To a 3.0 mL of the stock
solution was added 60 L CH3CN solution of each anion (10 mM).
l
After shaking them for a few seconds, UV–vis spectra of L were
taken at room temperature.
Fig. 2. Color changes of the probe L (20
lm) in CH3CN solution upon addition of
10.0 equiv of different anions (FÀ, ClÀ, BrÀ, IÀ, NO3–, AcOÀ, HSO4À, H2PO4À, ClOÀ4 ).

150
Z. Li et al. / Inorganica Chimica Acta 479 (2018) 148–153
1/(A-A0) against 1/[FÀ]2 showed
a good linear relationship
(R@0.9932) (Fig. 5) according to the Benesi-Hildebrand equation
[28,29], proving that L bound to fluoride ion in a 1:2 stoichiometry
with a binding constant of 6.85 Â 108 MÀ2
.
Interestingly, the ratio of the absorbance (A576/A378) also dis-
played a good linear relationship against the concentration of FÀ
ranging from 0 to 5 Â 10À4 M (Fig. 6), which provided a absorption
ratiometric method to quantitative detection of FÀ. In addition, the
detection limit (LOD) of L for FÀ was calculated to be 2.94 Â 10À6
M
(Fig. S5) according to 3
r method (LOD = 3r/S, where r was the
standard deviation of blank measurements and S was the slope
between intensity versus sample concentration [30]).
Similar spectral changes were observed when addition of AcOÀ
to CH3CN solution of L (Fig. 7). The plot of 1/(A À A0) against 1/
[AcOÀ]2 also showed an excellent linear relationship (R =
0.99929) according to the Benesi-Hildebrand equation(Fig. 8),
which proved a 1:2 stoichiometry between L and AcOÀ with the
binding constant of 1.54 Â 109 MÀ2. Uv–vis spectra of the sensor
L upon addition of H2POÀ4 was shown in Fig. 9, which was similar
to that of the addition of FÀ and AcOÀ. However, a linear fitting
1/(A À A0) against 1/[H2POÀ4 ] was achieved (R = 0.99804), which
Fig. 3. UV–vis changes of the probe L (20 lm) in CH3CN solution upon addition of
10.0 equiv of different anions (FÀ, ClÀ, BrÀ, IÀ, NO3–, AcOÀ, HSO4À, H2PO4À, ClOÀ4 ).
anions like FÀ, AcOÀ and H2POÀ4 induced a color change from pale
yellow to blue, which was due to the deprotonation of phenolic
hydroxyl and/or hydrazide NAH. Consistent with the color change,
the intensity of the band centered at 378 nm decreased upon addi-
tion of these three anions. Furthermore, the absorption band disap-
peared when 10.0 equiv FÀ, AcOÀ and H2PO4À were added
accompanied by the increase of the absorbance at 576 nm, 567
nm and 572 nm respectively. No distinct spectral and color
changes were observed when the same amount of other anions
were added. Therefore, the results indicated that the sensor L can
serve as a colorimetric probe for FÀ, AcOÀ and H2PO4À.
To further investigate the binding characteristics of the sensor
L, the UV–vis spectroscopic titrations upon the addition of FÀ, AcOÀ
and H2POÀ4 were carried out in CH3CN solution. With the addition
of incremental amounts of fluoride ion, the absorption band at 316
nm and 378 nm decreased gradually accompanied with incremen-
tal growth of the absorbance at 576 nm and appearance of a new
band centered at 426 nm (as shown in Fig. 4). A distinct isosbestic
point was observed at 409 nm, which indicated an equilibrium
between L and its fluoride ion complex [26,27]. The plot of
Fig. 5. Benesi-Hildebrand plot (k = 576 nm) of the probe L and FÀ.
Fig. 4. UV–vis spectral changes of the probe L (20 lm) in CH3CN solution upon
addition of 0–5.0 equiv of FÀ. The inset was the absorbance of L at 576 nm against
Fig. 6. Plot of the absorbance ratio at 576 and 378 nm (A576/A378) of the probe L as a
function.
the added FÀ.

Z. Li et al. / Inorganica Chimica Acta 479 (2018) 148–153
151
indicated the formation of a 1:1 complex between L and H2PO4À
with the binding constant of 2.37 Â 103 MÀ1 (Fig. 10).
Similar to fluoride ion, there also existed a good linear relation-
ship between A572/A378 and the concentration of H2POÀ4 (Fig. 11). In
addition, the detection limit of sensor L for AcOÀ and H2PO4À was
calculated to be 4.12 Â 10À6 M and 1.2 Â 10À5 M, respectively
(Figs. S6 and S7).
3.3. Detection mechanism
In order to have a better understanding of the binding mecha-
nism between the sensor L and anions, 1H NMR titration experi-
ments were conducted in DMSO d6 (Fig. 12). As depicted in
Fig. 12, in absence of any anions, the peak at 12.66 ppm was
assigned to the phenolic hydroxyl group (Ha) which appeared at
a down field due to the formation of intramolecular hydrogen
bonding with imine nitrogen. The signal at 12.09 ppm was attrib-
uted to the amide NAH proton (Hb). The peak at 8.95 ppm (Hc)
was due to the proton of –CH@N of L. Upon addition of 0.5 equiv
fluoride ion, the signal at 12.66 ppm(Ha) was diminished and it dis-
appeared completely when 1.0 equiv FÀ was added due to the
Fig. 7. UV–vis spectral changes of the probe L (20 lm) in CH3CN solution upon
addition of 0–2.0 equiv of AcOÀ. The inset was the absorbance of L at 567 nm
against the added AcOÀ.
Fig. 10. Benesi-Hildebrand plot (k = 572 nm) of the probe
concentration.
L
and H2POÀ4
Fig. 8. Benesi-Hildebrand plot (k = 567 nm) of the probe L and AcOÀ.
Fig. 9. UV–vis spectral changes of the probe L (20 lm) in CH3CN solution upon
addition of 0–5.0 equiv of H2POÀ4 . The inset was the absorbance of L at 572 nm
Fig. 11. Plot of the absorbance ratio at 572 and 378 nm (A572/A378) of the probe L as
a function.
against the added H2POÀ4 .

152
Z. Li et al. / Inorganica Chimica Acta 479 (2018) 148–153
Fig. 12. 1H NMR spectra of L with FÀ in DMSO-d6.
enhancement of acidity of O–H proton because of the presence of
azophenyl unit in the sensor L [31,32]. Similarly, the amine NAH
proton (Hb) also got deprotonated and disappeared after the addi-
tion of 0.5 equiv F-which is caused by the highly electron-with-
drawing carbonyl group [33]. Simultaneously, up field shift was
observed for imine (Hc) attributed to the increase in the electron
density around aromatic system [16]. However, the signal of Hd
exhibited reverse shift toward downfield by 0.09 ppm. However,
we did not observe any signal for HFÀ2 , which may be due to its
instability in a highly polar solvent like DMSO [34,35]. In addition,
the aromatic proton signals showed upfield shift which can be
attributed to the negative electron transfer on to the p-conjugated
system causing shielding effect [36]. On the further addition of 1.0
equiv FÀ, the development trend of chemical shift did not change.
Furthermore, upon addition of 2.0– 4.0 equiv FÀ, a tiny new peak at
15.4 ppm indicating the existence of trace amounts of the anionic
form of amide proton [37]. 1H NMR titration of L in the presence of
AcOÀ and H2POÀ4 as their TBA salts induced similar shift patterns
Fig. 13. A possible binding model between L and FÀ and AcOÀ in CH3CN solution.

Z. Li et al. / Inorganica Chimica Acta 479 (2018) 148–153
153
Fig. 14. A possible binding model between L and H2POÀ4 in CH3CN solution.
(as shown in Figs. S8 and S9). The above observations clearly reveal
References
that the sensor L underwent the deprotonation process in recog-
nizing the three anions.
[1] P.A. Gale, S.E. García-Garrido, J. Garric, Chem. Soc. Rev. 37 (2008) 151.
[2] M. Wenzel, J.R. Hiscock, P.A. Gale, Chem. Soc. Rev. 41 (2012) 480.
[3] I. Ravikumar, P.S. Lakshminarayanan, P. Ghosh, Inorg. Chim. Acta 363 (2010)
2886.
According to the obtained UV–vis and 1H NMR titration exper-
iments, the proposed mechanism for detection of FÀ, AcO- and
H2POÀ4 by L was shown as Figs. 13 and 14.
[4] K. Flídrová, M. Tkadlecová, K. Lang, et al., Dyes Pigments 92 (2012) 668.
[5] Z.M. Dong, W. Wang, Y.B. Wang, et al., Inorg. Chim. Acta 461 (2017) 8.
[6] S. Ghosh, M.A. Alam, A. Ganguly, et al., Inorg. Chim. Acta 429 (2015) 39.
[7] D. Udhayakumari, S. Velmathi, Sens. Actuators B 209 (2015) 462.
[8] S. Kumar, R. Saini, D. Kaur, Sens. Actuators B 160 (2011) 705.
[9] X. Zhuang, W. Liu, J. Wu, et al., Spectrochim. Acta A 79 (2011) 1352.
[10] Q.Q. Wang, V.W. Day, K. Bowmanjames, Chem. Sci. 2 (2011) 1735.
[11] A.S. Murugan, E.R.A. Noelson, J. Annaraj, Inorg. Chim. Acta 450 (2016) 131.
[12] X. Bao, Y. Zhou, B. Song, Sens. Actuators B 171 (2012) 550.
[13] S. Sen, M. Mukherjee, K. Chakrabarty, et al., Org. Biomol. Chem. 11 (2013)
1537.
[14] S. Ghosh, M.A. Alam, A. Ganguly, et al., Spectrochim. Acta A 149 (2015) 869.
[15] N. Maurya, S. Bhardwaj, A.K. Singh, Sens. Actuators B 229 (2016) 483.
[16] V. Reena, S. Suganya, S. Velmathi, J. Fluorine Chem. 153 (2013) 89.
[17] H. Khanmohammadi, V. Arab, K. Rezaeian, et al., J. Mol. Struct. 1129 (2017)
169.
[18] K. Rezaeian, H. Khanmohammadi, Spectrochim. Acta A 133 (2014) 31.
[19] I. Miwa, T. Tsugawa, K. Koyasu, et al., Pharmacology 52 (1996) 314.
[20] C. Meckert, Molecules 8 (2003) 894.
[21] H. Khanmohammadi, K. Rezaeian, M.M. Amini, et al., Dyes Pigments 98 (2013)
557.
[22] H. Dinçalp, F. Toker, Inci Durucasu, et al., Dyes Pigments 75 (2007) 11.
[23] S.G. Dogaheh, H. Khanmohammadi, E.C. Sañudo, Spectrochim. Acta A 179
(2017) 32.
4. Conclusions
In summary, we designed and synthesized an efficient colori-
metric and absorption ratiometric azo-azomethine based anion
chemosensor L containing phenolic OH and acyl hydrazine NHs
as binding units. The sensor L had a selective colorimetric sensing
ability for FÀ, AcOÀ and H2POÀ4 by naked eye. Interestingly, the sen-
sor L demonstrated a highly selective ability towards FÀ and AcOÀ
(1:2 complex) and H2POÀ4 (1:1 complex) along with a absorption
ratiometric responses. The selectivity of sensor toward different
anions can be attributed to the guest basicity and structural geom-
etry. The recognition mechanism was further investigated by 1H
NMR titration method. The 1H NMR titration confirmed that the
optical response was ascribed to the formation of hydrogen bond
between binding units and studied anions followed by deprotona-
tion process.
[24] Z. Shaghaghi, Spectrochim. Acta A 131 (2014) 67.
[25] R.M. Duke, T. Gunnlaugsson, Tetrahedron Lett. 52 (2011) 1503.
[26] Y.J. Chang, S.S. Wu, C.H. Hu, et al., Inorg. Chim. Acta 432 (2015) 25.
[27] Y. Shiraishi, H. Maehara, T. Hirai, Org. Biomol. Chem. 7 (2009) 2072.
[28] Y. Shiraishi, M. Itoh, T. Hirai, Tetrahedron 67 (2011) 891.
[29] J. Chen, C. Liu, J. Zhang, et al., Chem. Commun. 49 (2013) 10814.
[30] C. Jin, M. Zhang, C. Deng, et al., Tetrahedron Lett. 54 (2013) 796.
[31] Y. Wu, V. Papper, O. Pokholenko, et al., J. Fluoresc. 25 (4) (2015) 961.
[32] A. Okudan, S. Erdemir, O. Kocyigit, J. Mol. Struct. 1048 (2013) 392.
[33] H. Khanmohammadi, K. Rezaeian, A. Abdollahi, Spectrochim. Acta
(2015) 405.
[34] A. Satheshkumar, E.H. El-Mossalamy, R. Manivannan, et al., Spectrochim. Acta
A 128 (2014) 798.
Acknowledgements
The authors acknowledge the financial support from the Pro-
jects of Education Department of Hebei Province, China)
(ZD2016046, QN20170129), Self-finance Project of Science and
Technology Bureau of Langfang City, Hebei Province, China
(2017011007) and Science and Technology Research Projects of
Langfang Normal University (LSLB201704).
A 139
[35] C.P. And, A.K. Yatsimirsky, J. Org. Chem. 73 (2008) 2275.
[36] R.M. Duke, J.E. O’Brien, T. Mccabe, et al., Org. Biomol. Chem. 6 (2008) 4089.
[37] D.E. Gómez, L. Fabbrizzi, M. Licchelli, et al., Org. Biomol. Chem. 3 (2005) 1495.
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at https://doi.org/10.1016/j.ica.2018.04.027.