Synthesis, Characterization, Thermochromism, and Photochromism of Aromatic Aldehyde Hydrazone Derivatives

Article abstract of DOI:10.1155/2016/8460462

The Schiff bases N-(5-phenylthiazole-2-yl)-2-hydroxylnaphthaldehydehydrazone (1), N-(4′-chloro-5-phenylthiazole-2-yl)-2-hydroxylnaphthaldehydehydrazone (2), and N-(4′-nitro-5-phenylthiazole-2-yl)-2-hydroxylnaphthaldehydehydrazone (3) were synthesized. The

Full text of DOI:10.1155/2016/8460462

Hindawi Publishing Corporation
Journal of Chemistry
Volume 2016, Article ID 8460462, 8 pages
http://dx.doi.org/10.1155/2016/8460462
Research Article
Synthesis, Characterization, Thermochromism, and
Photochromism of Aromatic Aldehyde Hydrazone Derivatives
ShaoPing Zhu, Yuan Chen, Jun Sun, YuTing Yang, and ChuanJun Yue
School of Science, Changzhou Institute of Technology, 1 Wushan Street, Changzhou, Jiangsu 213002, China
Correspondence should be addressed to ShaoPing Zhu; zhushaoping18@163.com
Received 26 April 2016; Revised 5 July 2016; Accepted 27 July 2016
Academic Editor: Davut Avci
Copyright © 2016 ShaoPing Zhu et al. is is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the orꢀiginal work is properly cited.
e Schiff bases N-(5-phenylthiazole-2-yl)-2-hydroxylnaphthaldehydehydrazone (1), N-(4 -chloro-5-phenylthiazole-2-yl)-2-
hydroxylnaphthaldehydehydrazone (2), and N-(4ꢀ-nitro-5-phenylthiazole-2-yl)-2-hydroxylnaphthaldehydehydrazone (3) were
synthesized. ese compounds were characterized by using IR, 1H NMR, 13C NMR, and MS. e photochromism of the
compounds was investigated by IR and UV-visible spectrometry which is time variable under irradiation of 254 nm UV light.
e thermochromism of the compounds was studied using temperature-variable IR, UV-visible spectrometry, TG, and differential
scanning calorimetry (DSC). e results suggested that compound 2 showed thermochromism properties and compounds 2 and
3 displayed photochromism properties. e relationship between the substituents species and photochromic or thermochromic
properties of these compounds was revealed as well.
1. Introduction
In this study, three Schiff bases (1–3) were synthesized
(Scheme 1). e thermochromism or photochromism of the
compounds were also studied. e results suggested that
although the compounds (1–3) were all o-hydroxyl Schiff
bases, compound 1 showed no thermochromism or photo-
chromism, so o-hydroxyl was not the only factor work for the
thermochromic or photochromic properties; the substituent
species on the phenyl ring had great effect on such properties.
Of the many Schiff bases, o-hydroxylnaphthaldehydehydra-
zone had been found to be unique classes of Schiff bases
with reversible thermochromism, photochromism, and other
interesting properties. It was known that Schiff bases expe-
rience reversible phototransformations or thermal transfor-
mations between two forms, in particular, between enol-
imine form and keto-amine form [1]. e tautomerism of the
Schiff bases played an important role in their photochromic
and thermochromic characteristics [2, 3]. When heated or
receiving ultraviolet radiation, the hydrogen atom of the
O-H or N-H transferred and attached to the N atom of
C=N or O atom of C=O (Scheme 2) leading to ꢀ-ꢀ charge
transfer. e tautomerization between enol-imine and keto-
amine achieved by proton migrating thermally or through
irradiation induction, so orthohydroxyl played an important
part on both thermochromism and photochromism of such
Schiff bases [4, 5]. A link between molecular planar structures
and thermochromism or photochromism has been proposed
[6, 7]. Planarity of the molecule made it possible for the
proton to transfer with small energy requirement [8, 9]. Sub-
stituents on the aromatic ring might also have an influence on
the proton transfer [10, 11].
2. Experimental
2.1. Materials and Methods. All the required chemicals were
purchased from Sinopharm Chemical Reagent Co., Ltd, and
were used without further purification. Melting points of the
compounds were determined on SGWX-4 digital micromelt-
ing point apparatus. FT-IR spectra were recorded on a
ermo Scientific System 2000 FT-IR spectrometer. NMR
spectra were recorded on AVANCE III NMR spectrometer
in deuterated DMSO with TMS as an internal standard at
1
300 MHz for H and for 75 MHz for 13C. LC mass spectra
were recorded on SHIMADZU, LCMS-2020 MS instrument
with resolution >40000 FWHM. e UV-visible spectra

2
Journal of Chemistry
S
NNHCNH2
OH
OH
CHO
CH
O
3
2
16ꢀ
13
17ꢀ
18
11
S
12
1
OH
R
CCH2Br
CH
NNH
4
NH2CSNHNH2
5
10
R
14 15
6
9
16 17
7
8
a
R: = 1: H; 2: Cl; 3: NO2
Scheme 1
OH
O
S
Compound 2
Compound 3
S
CH
NNH
CH
HNHN
N
R
R
N
Enol-imine
Keto-amine
Scheme 2: Tautomerism of aromatic aldehyde hydrazones.
were measured using a TU-1901 ultraviolet spectrophotome-
ter. DSC analysis was performed by a DZ3335 differential
scanning calorimeter (DSC) and TG analysis was detected
by a STA449-F5TAQ600 analyzer. ZF-6 UV-light analyzer
(254 nm, 365 nm) was used as the radiation source.
Ar-H and thiazole-H, resp.); 1H NMR (DMSO-d6, 300 MHz,
ppm) ꢂ: 12.29 (s, 1H, OH), 11.02 (s, 1H, N-H), 8.97 (s, 1H,
H-C=N), 8.74–8.71 (d, 1H, thiazole-H), 7.89–7.86 (t, 4H,
naphthalene-H), 7.62–7.57 (m, 1H, naphthalene-H), 7.46–7.43
(d, 1H, naphthalene-H), 7.41–7.40 (d, 2H, benzene-H),
7.37–7.30 (m, 2H, benzene-H), 7.25–7.22 (d, 1H, benzene-H).
13C-NMR (75 MHz, DMSO-d6, ppm): ꢂ 168.2 (C ), 156.9
2.2. General Procedure for the Synthesis of Aromatic Aldehyde
Hydrazone Derivatives. To a 250 mL three-neck round flask
containing 182 mg (2 mmol) of aminothiourea in 25 mL
ethanol (80%), 344 mg (2 mmol) of 2-hydroxy-1-naphthalde-
hyde was dissolved in 20 mL absolute ethanol. en 2 mL of
glacial acetic acid was added. e resulting mixture was mag-
netically stirred and refluxed for 4 hours. e solution was
poured into a beaker and laid in ice baths for 2 hours to pre-
cipitate. e solid was recrystallized from ethanol-DMF (vol-
ume ratio, 1 : 1) and dried at 40∘C; 461 mg golden yellow solid
(yield: 94%) was obtained. e solid was 2-hydroxy-1-naph-
thaldehydethiosemicarbazone (a).
12
(C ), 150.5 (C ), 141.8 (C ), 134.8 (C ), 132.4 (C ), 131.5
2
11
14
13
15
(C ), 129.3 (C , C ꢀ ), 129.1 (C , C ꢀ ), 128.6 (C ), 128.2 (d, ꢃ
18
17
17
16
16
1
= 86.3, C , C ), 126.1 (C ), 123.9 (C ), 123.4 (C ), 118.7 (C ),
5
10
4
3
6
9
110.6 (C ), 103.61 (C ); ESIMS calculated for C H N OS:
7
8
20 15
3
345.42, found ꢄ// = 346.10 [M+H]+, ꢄ// = 368.10 [M+Na]+,
ꢄ// = 344.05 [M-H]+.
N-(4ꢀ-Choro-5-phenylthiazole-2-yl)-2-hydroxylnaphthalde-
hydehydrazone (2). 277 mg, yield 73%, gray purple crystal,
m.p. 302–304∘C. IR (KBr, ]/cm−1): 3333 (]O-H), 3112 (]N-H),
2921, 2851 (stretching vibration of Ar-H and thiazole-H,
resp.), 1629 (]C=N), 1600, 1580, 1560, 1490 (Ar; thiazole ring),
1469, 1419 (rocking vibration of Ar-H and thiazole-H, resp.),
1399 (]C-OH), 779, 739 (out-of-plane ring bending vibration of
Ar-H and thiazole-H, resp.). 1H NMR (DMSO-d6, 300 MHz,
ppm) ꢂ: 12.27 (s, 1H, OH), 10.94 (s, 1H, N-H), 8.96 (s, 1H,
H-C=N), 8.77–8.74 (s, 1H, thiazole-H), 7.92–9.86 (t, 4H,
naphthalene-H), 7.62–7.57 (t, 1H, naphthalene-H), 7.50–7.48
(d, 1H, naphthalene-H), 7.44–7.42 (d, 1H, benzene-H), 7.40–
7.37 (d, 2H, benzene-H), 7.25–7.22 (d, 1H, benzene-H), 706
245 mg (1 mmol) of compound a was dissolved in 25 mL
absolute ethanol, and 199 mg (1 mmol) ꢁ-bromoacetophe-
none or 244 mg (1 mmol) 2-bromo-4ꢀ-chloroacetophenone
or 245 mg (1 mmol) ꢁ-bromo-4-nitroacetophenone in 10 mL
ethanol was added, respectively.
e reaction mixture was refluxed for 30 minutes. e
mixture became clear in a moment. Five minutes later, a
great deal of solid appeared. Solid (compound 1, 2, or 3)
was obtained afer suction filtration and recrystallized with
ethanol-DMF (volume ratio, 1 : 1).
(]C-Cl). 13C-NMR (75 MHz, DMSO-d6, ppm): ꢂ 173.0 (C ),
18
161.6 (C ), 154.6 (C ), 146.5 (C ), 138.6 (C ), 137.3 (C ),
12
2
11
14
13
137.1 (C , C ꢀ ), 136.3 (C , C ꢀ ), 134.0 (C ), 133.8 (C ), 133.4
2.3. Spectral Data
17
17
16
16
15
1
(C ) 132.9 (C ), 132.5 (C ), 128.6 (C ), 128.1 (C ), 123.5 (C ),
5
10
4
3
6
9
N-(5-Phenylthiazole-2-yl)-2-hydroxylnaphthaldehydehydra-
zone (1). 250 mg, yield 72.6%, bright yellow solid, m.p.
200–202∘C. IR (KBr, ]/cm−1): 3320 (]O-H), 3111 (]N-H), 3073,
2971 (stretching vibration of Ar-H and thiazole-H, resp.),
1619 (]C=N), 1611, 1581, 1491, 1480 (Ar; thiazole ring), 1409,
1349 (rocking vibration of Ar-H and thiazole-H, resp.), 1319
(]C-OH), 756, 733 (out-of-plane ring bending vibration of
115.3 (C ), 109.1 (C ). ESIMS calculated for C H N OSCl
7
8
20 14
3
379.86, found ꢄ// = 380.00 [M+H]+, ꢄ// = 378.00 [M-H]+,
ꢄ// = 402.05 [M+Na] +.
N-(4ꢀ-Nitro-5-phenylthiazole-2-yl)-2-hydroxylnaphthaldehyde-
hydrazone (3). 306 mg, yield 78.4%, shallow orange crystal,
m.p. 257–259∘C. IR (KBr, ]/cm−1): 3309 (]O-H), 3118 (]N-H),

Journal of Chemistry
3
60
50
40
30
20
10
2921, 2851 (Ar-H, thiazole-H), 1619 (]C=N), 1601, 1580, 1499,
1469 (Ar; thiazole ring), 1521, 1330 (stretching vibration
of the nitro group), 1439, 1419 (rocking vibration of Ar-H
or thiazole-H), 1371 (]C-OH), 777, 746 (out-of-plane ring
1
bending vibration of Ar-H and thiazole-H, resp.). H NMR
(DMSO-d6, 300 MHz, ppm) ꢂ: 12.36 (s, 1H, OH), 10.89 (s,
1H, N-H), 8.96 (s, 1H, H-C=N), 8.82–8.80 (d, 1H, thiazole-
H), 8.32–8.29 (d, 2H, naphthalene-H), 8.16–8.13 (d, 2H,
naphthalene-H), 7.89–7.86 (d, 2H, naphthalene-H), 7.77 (s,
1H, benzene-H), 7.62–7.57 (t, 1H, benzene-H), 7.42–7.37 (t,
1H, benzene-H), 7.25–7.22 (d, 1H, benzene-H). 13C-NMR
(75 MHz, DMSO-d6, ppm) ꢂ: 168.6 (C ), 156.9 (C ), 149.1
200∘C
∘
3333
140 C
90∘C
60∘C
25∘C
18
12
(C ), 146.7 (C ), 141.9 (C ), 141.0 (C ), 132.5 (C , C ꢀ ),
2
11
14
13
17
17
131.5 (C , C ꢀ ), 129.3 (C ), 128.7 (C ), 128.2 (C ), 126.9
4000
3500
3000
2500
2000
1500
1000
500
16
16
15
1
5
Wavenumber (cm−1
)
(C ), 124.6 (C ), 123.9 (C ), 123.7 (C ), 118.6 (C ), 110.6
10
4
3
6
9
(C ), 108.6 (C ); ESIMS calculated for C H N O S 390.42,
7
8
20 14
4
3
(a)
found ꢄ// = 391.10 [M+H]+, ꢄ// = 388.95 [M-H]+, ꢄ// =
D
413.25 [M-Na]+.
60
50
40
30
E
756cm−1
A
695cm−1
3. Results and Discussion
C
B
3.1. ermochromism
652
3.1.1. IR Spectroscopic and TG Studies. e color of com-
pound 2 changed from gray purple to brown afer being
heated to 229∘C and restored the original color afer cool-
ing. To investigate the thermochromism of the compounds
thoroughly, KBr tablets of 1–3 were heated to certain tem-
peratures on the electric hot plate; then the IR spectra were
measured promptly. e IR spectra of 2 were shown in
Figure 1(a). Compound 2 had the characteristic stretching
band of hydroxyl group (O-H) at 3333 cm−1. When com-
pound 2 was heated to 140∘C, the absorption peak intensity
of hydroxyl group absorption peak decreased partly the result
of a conversion of the hydroxyl group to the carbonyl group
(Scheme 2). When the temperature reached 200∘C, the band
almost disappeared. When compound 2 was heated to 60∘C,
a small absorption peak appeared at 1763 cm−1. is was due
to the stretching vibration of the carbonyl of the keto-amine,
which was produced from enol-imine of compound 2 on
heating [12–14].
750
700
650
600
550
500
Wavenumber (cm−1
)
140∘C (D)
25∘C (A)
60∘C (B)
90∘C (C)
200∘C (E)
(b)
Figure 1: e IR spectra of compound 2 on heating in the whole
spectra range investigated (a) and in the narrowed range (b).
In fingerprint region (Figure 1(b)), small new absorption
peaks appeared at 756 cm−1 and 695 cm−1, while the peak
at 652 cm−1 diminished. All of these changes were ascribed
to the bending vibration of the C-H bond of the losing
aromaticity ring of the keto-amine [12–14].
Figure 2 was the TG curve of compound 2. e TG curve
suggested that there was a loss weight in the beginning of
the test. e loss weight had relations to the loss of the
crystal water in the molecule. Because the band of crystal
water in IR spectra overlapped that of hydroxyl group, the
reduction of the intensity at 3333 cm−1 in Figure 1(a) was
about more than the loss of crystal water. Similar intensity
changes could be observed in Figure 7. By photoirradiation,
the absorption peak intensity at 3333 cm−1 of unheated
compound 2 became smaller gradually without the loss of
crystal water. So the intensity decreased partly because of
the tautomerism and Figure 4 confirmed the discussion as
well. e band at 3333 cm−1 in Figure 1(a) almost disappeared
when temperature rose to 200∘C. It was still the result of
the loss of the crystal water and tautomerism. All the crystal
water lost at this moment and maybe most enol-imine form
of compound 2 changed to enol-amine form.
When the temperature rose to 337∘C, compound 2 lost
weight again because it started to decompose.
3.1.2. e DSC Measurement. e DSC curves of compounds
1–3 were shown in Figure 3. Compound 2 exhibited three
endothermic peaks at 229∘C, 303∘C, and 343∘C, respectively.
e first endothermic peak at 229∘C corresponded to color
change temperature; the second and the third endothermic
peak corresponded to the melting point and decomposition
temperature, respectively. e results further confirmed that
compound 2 showed thermochromism. e melting point

4
Journal of Chemistry
0.30
0.25
0.20
0.15
0.10
0.05
0.00
100
90
80
70
60
50
337∘C
378
484
0
100 200 300 400 500 600 700 800 900
300
400
500
600
700
Temperature (∘C)
Wavelength (nm)
100∘C
30∘C
50∘C
70∘C
90∘C
Figure 2: e TG curve of compound 2.
110∘C
Cool down to 30∘C
2
0
Figure 4: e UV-vis spectra of compound 2 on heating.
343
303
229
201
Figure 4 showed the UV-visible absorption spectra
change of compound 2 on heating. e yellow DMF solu-
tion of compound 2 (concentration: 1.0 × 10−5 mol/L, path
length: 1 cm) transformed to light orange. e intensity of
the absorption peak at 378 nm decreased, and a new band
appeared at 484 nm. e absorption peak intensity of the
new band became greater with temperature rising. e heated
solution was lef to rest for enough time to cool down to
room temperature, and the color of the solution came back to
yellow. UV-visible absorption spectra were tested again. e
result was showed in Figure 4 as well. e absorption curve
of the cooled compound 2 was compared with that of the
unheated compound 2 and they agreed well. ese indicated
that compound 2 had reversible thermochromism.
−2
−4
−6
−8
602
258
0
100
200
300
T (
400
500
600
700
∘C)
Compound 1
Compound 2
Compound 3
3.2. Photochromism
Figure 3: e DSC curves for compounds 1–3.
3.2.1. UV-Visible Spectroscopic Studies. Figures 5 and 6
showed the UV-visible absorption spectra changes of com-
pounds 2 and 3 upon irradiation of 254 nm UV light, respec-
tively. e yellow DMF solution of compound 2 (concentra-
tion: 1.0 × 10−5 mol/L, path length: 1 cm) transformed to pale
orange under the UV light. e intensity of the absorption
peak at 378 nm decreased and a new band appeared at 480 nm
which kept increasing as the exposure time went on.
peaks for compounds 1 and 3 were 201∘C and 258∘C, respec-
tively. ere was another endothermic peak at 602∘C for
compound 3 which was a decomposition peak.
3.1.3. UV-Visible Spectroscopic Studies. e UV-visible spec-
tra of orthohydroxylated Schiff bases existing mainly as enol-
e orange red DMF solution of compound 3 trans-
imine structure indicated the presence of bands at <400 nm.
However, the compounds existing as either keto-amine or
mixture of enol-imine/keto-amine forms showed a new band
at >400 nm [15]. Photochromism or thermochromism was
the phenomenon of chromatic change due to the reversible
photoisomerization or thermomerization between the two
tautomers which showed different absorption bands and
absorbance changes of the bands [16–20].
formed to orange yellow under the UV light (concentra-
tion: 1.0 × 10−5 mol/L, path length: 1 cm). Furthermore, the
intensity of the absorption peak at 469 nm became smaller,
while the absorption peak at 377 nm increased gradually.
e changes of the absorption peaks of compounds 2 and 3
supported that the two compounds underwent tautomerism.
Because the ratio of keto-amine form of compound 2
increased under UV irradiation, the absorbance of the peak

Journal of Chemistry
5
60
50
40
30
20
10
0
0.30
0.25
0min
20min
40min
0.20
0.15
0.10
0.05
0.00
378
60min
80min
120 min
3333
480
4000
3500
3000
2500
2000
1500
1000
500
Wavenumber (cm−1
)
300
400
500
600
700
Wavelength (nm)
Figure 7: e IR spectra of compound 2 afer a period of exposure
to UV light.
90min
0min
30min
60min
120 min
Restoration
60
50
40
30
20
10
Figure 5: e UV-vis spectra of compound 2 afer a period of
exposure to UV light.
377
0.25
0.20
0.15
0.10
0.05
0.00
469
3309
0
4000 3500 3000 2500 2000 1500 1000 500
Wavenumber (cm−1
)
60min
0min
40min
120 min
Figure 8: e IR spectra of compound 3 afer a period of exposure
300
400
500
600
700
800
to UV light.
Wavelength (nm)
120 min
0min
40min
80min
Restoration
Meanwhile, the color of the solutions was nearly back, so both
of compounds 2 and 3 were reversible photochromic.
Figure 6: e UV-vis spectra of compound 3 afer a period of
exposure to UV light.
3.2.2. IR Spectroscopic Studies. e IR spectra of 2 and 3
were taken on each exposure time by the 254 nm UV light.
e time-variable behavior of the IR spectra of compounds
2 and 3 exposure to UV light was shown in Figures 7
and 8, respectively. In Figure 7, e hydroxyl group (O-H)
stretching band was observed at 3333 cm−1 for compound 2.
Upon irradiation with ultraviolet (UV) light, the intensity of
the stretching band decreased. It was confirmed that the enol-
imine form of compound 2 changed partially to keto-amine,
while in Figure 8 the hydroxyl group (O-H) stretching band
of compound 3 at 3309 cm−1 became greater which confirmed
that part of the keto-amine turned to enol-imine form when
exposed to UV light.
at greater than 400 nm increased. For the same reason, the
ratio of the enol-imine form of compound 3 increased while
the keto-amine decreased afer irradiation of UV light [21].
e UV light was removed afer the solutions exposure
to it for two hours. e solutions were let to stand for 24
hours and the UV-visible spectra of the compounds were
detected again. e spectra of the restored compounds 2
and 3 were also showed in Figures 5 and 6, respectively.
e absorption curves were of close resemblance to the
spectra of the compounds without irradiation with UV light.

6
Journal of Chemistry
0.25
0.20
0.15
0.10
0.05
0.00
0.25
0.20
0.15
0.10
0.05
0.00
378
378
469
469
300
400
500
600
700
300
400
500
Wavelength (nm)
Compound 3
600
700
Wavelength (nm)
Compound 3
Compound 1
Compound 2
Compound 1
Compound 2
Figure 10: e UV-vis spectra of compounds 1, 2, and 3 exposure to
UV light for 120 min.
Figure 9: e UV-vis spectra of compounds 1, 2, and 3.
3.3. e Effect of Substituents on ermochromism or Pho-
tochromism. Based on what had been discussed above, com-
pounds 2 and 3 showed thermochromism and compound 2
exhibited photochromism, both phenomena being associated
with an intramolecular proton transfer which led to the
tautomerism between the enol-imine and the keto-amine [7].
But compound 1 had no similar properties. Orthohydroxyl
was essential for the intramolecular proton transfer. Com-
pounds 1, 2, and 3 were all orthohydroxyl Schiff bases and
their structures were similar except for the difference in the
substituents on the phenyl groups, so the substituent species
effected the proton transfer as well.
Figures 9 and 10 were the UV-vis spectra of compounds
1–3 and those of the compounds exposure to the UV
light for two hours, respectively. e results showed that
compound 1 existed as enol-imine form and changed little
afer irradiation. Compound 2 existed as enol-imine form
and transformed to keto-amine form, and the conversion
(ꢁ ꢅ =ꢆ%−ꢆ0%)/ꢆ0%; ꢁ was conversion; ꢆ0% and ꢆ% were
the absorbance of a compound before and afer irradiation
by UV light) was nearly 11% at 378 nm. As for compound 3,
the conversion of keto-amine to enol-imine was about 36% at
469 nm.
changed to a much more stable benzene ring. Furthermore,
the benzene ring and C=N formed conjugated system and the
whole molecule became more stable. So the proton transfer
could take place [20, 22–29].
e paranitro group made less charge population on N
atom of amino group due to inductive effect and the shared
electron pair deviate from H atom and turn to N atom which
is advantageous to the hydrogen proton on N atom going
away.
e substituent of compound 2 was a chlorine atom
which was also an electron- withdrawing group. e com-
pound tended to turn enol-imine into keto-amine form.
Whatever the direction of the tautomerism, intramolecular
proton in compounds 2 and 3 transferred more readily than
compound 1.
4. Conclusion
Investigations of three naphthaldehyde hydrazone derivatives
were conducted. It was found that not all of the o-hydroxyl
Schiff bases exhibited thermochromism and photochromism.
Compounds 1, 2, and 3 had similar structures, but the
substituted species on phenyl ring were different. Compound
2 showed thermochromism and compounds 2 and 3 showed
photochromism. As for compound 1, it showed no such
properties. So the substituted species was a very important
prerequisite in these properties. Results of UV-visible and
IR analyses showed that compound 2 existed as enol-imine
form. Heated to a certain temperature or exposed to UV light
for a period of time, it partially transformed to keto-amine.
Part of the keto-amine tautomer of compound 3 changed
to enol-imine tautomer upon UV-light irradiation. Of these
three compounds, the electron-withdrawing substituents on
the benzene ring seemed to help the tautomerism.
Hammett parameters (paranitro: +0.778, para-Cl: +0.227,
H: 0.0) were important basis for judging substituents effects
on the reaction of benzene ring. For example, the alkalinity
of p-nitroaniline was weaker than aniline due to the charge
population on N atom being less and proton capacity weak-
ened since the nitro group was a strong electron-withdrawing
group. But p-nitroaniline and p-nitrophenylhydrazine were
only alkaline which accept proton rather than lose proton.
But here it was evident that the molecule of compound 3
was a system containing several aryl rings and amino group
was not isolated. If the proton on N atom could transfer, a
double bond formed between the N atom and the neigh-
boring C atom. Meanwhile, the unsaturated cyclic ketone

Journal of Chemistry
7
Additional Points
[11] L. Kong, X. Ju, Y. Zhang, J. Zhao, and J. Xu, “Substituent effect of
a donor unit on electrochemical and opto-electronic properties
of ambipolar benzotriazole-based polymers,” Iranian Polymer
Journal, vol. 25, no. 5, pp. 443–454, 2016.
All additional information pertaining to characterization of
the complexes using ESI-MS technique (Figures S1, S1’, and
S1”; S4, S4’, and S4”; S7, S7’, and S7”), 1H NMR (Figures S2, S5,
and S8), and 13C NMR (Figures S3, S3’; S6; and S9) is given in
Supplementary Material available online at http://dx.doi.org/
10.1155/2016/8460462.
[12] L. J. Bellamy, e Infrared Spectra of Complex Molecules,
Chapman and Hall, London, UK, 1980.
[13] J. P. Charles, Aldrich Library of FT-IR Spectra, Aldrich Chemical
Co, Milwaukee, Wis, USA, 1985.
[14] L. V. Daimay, B. C. Norman, G. F. William et al., e Handbook
of Infrared and Roman Characteristic Frequencies of Organic
Molecules, Academic Press, San Diego, Calif, USA, 1990.
Competing Interests
¨
¨
¨
[15] H. Unver, M. Yıldız, A. Kiraz, and O. Ozgen, “Spectroscopic
studies and crystal structure of (Z)-6-[(2- hydroxyphenylam-
ino)methylene]-2-methoxycyclohexa-2,4-dienone,” Journal of
Chemical Crystallography, vol. 39, no. 1, pp. 17–23, 2009.
e authors declare that they have no competing interests.
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