Thermal properties and DNA-binding studies of a new kind of acyl hydrazone compounds containing imidazole ring

Article abstract of DOI:10.1016/j.tca.2014.01.022

Three new acyl hydrazone compounds C₁₂H₁₂N ₄O₃ (I), C₁₂H₁₄N₄O ₄ (II) and C₁₆H₁₆N₄O₃ (III) are synthesized and characterized by elemental analysis and single-crystal X-ray diffraction. The crystal structural analyses show that the three compounds crystallize in the monoclinic crystal lattice. Their thermal decomposition processes under nitrogen and air are studied by TG-DTG, the sequence of the thermostability for three compounds at each condition is the same: III > I > II. The interaction modes of the three compounds with CT-DNA are investigated by UV-Vis absorption, showing hyperchromic and hypochromic effects. The thermogenic curves of the three compounds reacting with CT-DNA are measured by microcalorimetry, indicating that they are all endothermic reaction and the reaction times are within 10-30 min.

Full text of DOI:10.1016/j.tca.2014.01.022

Thermochimica Acta 582 (2014) 17–24
Contents lists available at ScienceDirect
Thermochimica Acta
journal homepage: www.elsevier.com/locate/tca
Thermal properties and DNA-binding studies of a new kind of acyl
hydrazone compounds containing imidazole ring
Jingwen Ren, Xiangrong Liu∗, Zaiwen Yang, Shunsheng Zhao
College of Chemistry and Chemical Engineering, Xi’an University of Science and Technology, Xi’an 710054, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Three new acyl hydrazone compounds C12H12N4O3 (I), C12H14N4O4 (II) and C16H16N4O3 (III) are synthe-
sized and characterized by elemental analysis and single-crystal X-ray diffraction. The crystal structural
analyses show that the three compounds crystallize in the monoclinic crystal lattice. Their thermal
decomposition processes under nitrogen and air are studied by TG-DTG, the sequence of the ther-
mostability for three compounds at each condition is the same: III > I > II. The interaction modes of
the three compounds with CT-DNA are investigated by UV–Vis absorption, showing hyperchromic and
hypochromic effects. The thermogenic curves of the three compounds reacting with CT-DNA are mea-
sured by microcalorimetry, indicating that they are all endothermic reaction and the reaction times are
within 10–30 min.
Received 25 November 2013
Received in revised form 9 January 2014
Accepted 25 January 2014
Available online 11 March 2014
Keywords:
Acyl hydrazone
Crystal structure
Thermal stability
DNA-binding mode
Microcalorimetry
© 2014 Elsevier B.V. All rights reserved.
1. Introduction
reaction times for the three compounds with CT-DNA are measured
by microcalorimetry.
Imidazole compounds have aroused wide public concern due
to their high biological activity in many application fields, such
as medical chemistry, pesticide chemistry, natural products and
so on. Many of the substituted imidazoles are known as herbi-
cides, fungicides, antibacterial, antitumor, pesticides and plant
growth regulators [1–9]. Acyl hydrazone compounds containing
CONHN CH group reduce the toxicity brought to biological
organism caused by the NH2 group of hydrazides structure. More-
over, they also enhance the affinity between receptors because of
the participation of both oxygen atom and nitrogen atom in the
formation of hydrogen bond in the organism, thus make the hydra-
zones have the unique physiological activities of anti-TB germs,
other anti-inflammatory and bactericidal activity [10–25].
2. Experimental
2.1. Materials and instruments
All chemicals were used as commercially obtained without
further purification. The CT-DNA was purchased from Sigma com-
pany. The CT-DNA was dissolved in Tris–HCl buffer (0.01 mol L−1
,
pH = 7.90) and its purity was checked from the absorbance ratio
A260/A280. For all the solutions, the ratio was in the range of 1.8–1.9.
The crystal structures of three compounds were determined
using a BRUKER SMART APEX II CCD diffractometer equipped
with graphite monochromator Mo-K˛ radiation (ꢀ = 0.71073 nm).
Elemental analyses for carbon, hydrogen and nitrogen were car-
ried out on a Perkin-Elmer 2400-II analyzer. UV–Vis spectra were
recorded in DMF at 1.0 × 10−4 mol L−1 (200–500 nm) by a TU-1900
UV–Vis spectrophotometer. Thermal data were collected on a MET-
TLER TOLEDO TG-DSC1 HT instrument under nitrogen and under
air at three heating rates of 5, 10 and 15 ◦C min−1 from 30 ◦C
to 800 ◦C. Thermogenic curves were measured by Setaram C80
microcalorimeter.
In this paper, we introduce the group of imidazole into acyl
hydrazone compounds according to the superposition principle
[26]. Three new imidazole-containing compounds are synthesized
by using 1H-imidazole-4-carboxylic acid ethyl ester, hydrazine
hydrate,
2-hydroxy-3-methoxy-benzaldehyde,
3-hydroxy-4-
methoxy-benzaldehyde and 2-hydroxy-1-naphthaldehyde, which
are characterized by elemental analysis and single-crystal X-ray
diffraction. Their thermal behaviors are studied by TG-DTG. The
interaction modes of the three compounds with CT-DNA are
investigated by UV–Vis absorption. The thermogenic curves and
2.2. Synthesis of three compounds
2.2.1. Synthesis of 1H-imidazole-4-carboxylic acid hydrazide
The 1H-imidazole-4-carboxylic acid ethyl ester (0.7010 g,
5.00 mmol) was dissolved in the nonaqueous alcohol (10.00 mL)
∗
Corresponding author. Tel.: +86 13659205872.
E-mail address: xkchemistry@163.com (X. Liu).
0040-6031/$ – see front matter © 2014 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.tca.2014.01.022

18
J. Ren et al. / Thermochimica Acta 582 (2014) 17–24
Table 1
Crystallographic data for I, II and III.
Empirical formula
Formula weight
Crystal system
Space group
a/nm
C12H12N4O3(I)
260.26
Monoclinic
P2 1/n
C12H12N4O3·H2O(II)
C15H12N4O2·CH3OH(III)
278.27
312.33
Monoclinic
P2 1/n
4.8068(15)
Monoclinic
P2 1/c
8.9110(12)
25.225(16)
b/nm
8.104(5)
12.503(4)
12.8341(17)
c/nm
27.848(14)
90
122.02(4)
90
4827(5)
16
1.433
21.707(7)
90
94.508(6)
90
1300.5(7)
4
1.421
14.313(2)
90
106.969(2)
90
1567.7(4)
4
1.325
˛/(◦)
ˇ/(◦)
ꢁ/(◦)
Volume/nm3
Z
Density (calculated)/(mg m−3
Crystal size/mm
)
0.34 × 0.25 × 0.15
0.37 × 0.28 × 0.20
0.35 × 0.26 × 0.18
ꢂ range for data collection
Reflections collected/unique
Goodness-of-fit on F2
0.95–25.10
1.88–25.10
2.18–25.09
22,994/8556 [R(int) = 0.1168]
1.081
6378/2310 [R(int) = 0.0421]
1.041
7619/2788[R(int) = 0.0205]
1.033
Final R indices [I ≥ 2ꢃ(I)]
R1 = 0.1765, wR2 = 0.5259
R1 = 0.2469, wR2 = 0.5777
R1 = 0.0502, wR2 = 0.1084
R1 = 0.0800, wR2 = 0.1242
R1 = 0.0406, wR2 = 0.1153
R1 = 0.0500, wR2 = 0.1243
R indices (all data)
and treated with 80% hydrazine hydrate (5.00 mL). The mixture was
stirred and heated at 80 ◦C on a water bath for 4 h. After the night,
white crystals were collected by filtration, washed with nonaque-
ous alcohol and dried. Yield: 39.0%, m.p. 204–205 ◦C.
3. Results and discussion
3.1. Crystal structures of compounds I–III
Compounds I–III were crystallized in the monoclinic crystal lat-
tice system in the centrosymmetric P2 1/n, space group with Z = 16,
4 and 4, respectively. In compound I, the asymmetric unit contains
four molecules. The perspective views of the molecular structures
of three compounds are represented in Figs. 1–3. From Fig. 1, it can
be seen that this molecular has a 5-member ring and a 6-member
ring. The band length of O(3) C(9) is 1.222 nm, which is the typ-
ical C O double bond. It indicates that the compound includes a
keto group. The N(1) C(8) (1.267 nm) is shorter than the N(2) C(9)
(1.427 nm), showing there is a typical C N double bond between
C(8) and N(1). The dihedral angle of N(2) N(1) C(8) C(6) is 171.7◦
and N(1) N(2) C(9) C(10) is 172.8◦, indicating that the 5-member
ring and the 6-member ring are not in the same plane. The crys-
tal structure of I shown in Fig. 4 is stabilized by weak interaction
of intermolecular and intramolecular hydrogen bonds. There are
three kinds of hydrogen bonds: N H. . .O, O H. . .N and O H. . .O
between one molecule and the adjacent layer which make the crys-
tal structure more stable.
2.2.2. Synthesis of acyl hydrazones
A solution of 2-hydroxy-3-methoxy-benzaldehyde (0.0760 g,
0.50 mmol) in methanol (5.00 mL) was added to a solution of
1H-imidazole-4-carboxylic acid hydrazide in methanol (5.00 mL).
After heating for 3 h on the water bath at 70 ◦C, the color of
reaction mixture changed from colorless transparent to yellow.
The resultant solution of 1H-imidazole-4-carboxylic acid (2-
hydroxy-3-methoxy-benzylidene)-hydrazone (compound I) was
left unperturbed to allow for slow evaporation of the solvent. Yel-
low single crystals, suitable for X-ray diffraction analysis, were
formed after a week.
The similar procedures were followed for synthesis of 1H-
imidazole-4-carboxylic acid (3-hydroxy-4-methoxy-benzylidene)-
hydrazone (compound II) and 1H-imidazole-4-carboxylic acid (2-
hydroxy-naphthalen-1-ylmethylene)-hydrazone (compound III).
The synthesis routes of the compounds are summarized by
Scheme 1.
3.2. Thermal behaviors
Compound I: Yield: 47.5%, m.p. 247–248 ◦C. Anal. calcd for
C
12H12N4O3: C 55.39, H 4.62, N 21.54; found C 54.88, H 4.70, N
22.24.
Compound II: Yield: 69.0%, m.p. 226–228 ◦C. Anal. calcd for
3.2.1. Thermal decomposition processes of compounds I–III under
nitrogen
The TG curves of three compounds under nitrogen at the heat-
ing rate of 15 ◦C min−1 are represented in Fig. 5. The DTG curves of
three compounds under nitrogen at the heating rate of 5, 10 and
15 ◦C min−1 are shown in Figs. 6–8. The main thermal decomposi-
tion processes under nitrogen for three compounds are described
in Fig. 9.
C12H12N4O3·H2O: C 51.80, H 5.04, N 20.14; found C 52.03, H 5.12,
N 20.99.
Compound III: Yield: 70.4%, m.p. 253–254 ◦C. Anal. calcd for
C15H12N4O2·CH3OH: C 61.54, H 5.13, N 17.95; found C 62.03, H
5.20, N 17.33.
It can be seen from Figs. 5 and 6, compound I undergoes one
major stage of weight loss during 30–800 ◦C, and the endother-
mic peak is in the temperature of 325.98 ◦C at the heating rate of
15 ◦C min−1. The value of the weight loss at this stage is 49.63%
(Calcd. 47.83%), and the lost group is shown in Fig. 9. In Figs. 5 and 7,
two stages of weight loss of compound II can be clearly discerned
under the heating rate of 15 ◦C min−1. The first step starts from
130 ◦C and ends at 204 ◦C with the sum loss of 6.67% which should
be assigned to one lattice water (Calcd. 6.47%). The second stage
occurred at 306.46 ◦C with the mass loss of 43.09% (Calcd. 44.56%),
which is shown in Fig. 9. In the TG and DTG curves of compound
III, as described in Figs. 5 and 8, two mass loss stages are observed.
The decomposition of III starts at 109 ◦C and ends at 148 ◦C with a
2.3. X-ray crystallography
The crystal data and the cell parameters for I–III are given in
Table 1. The structures were solved with direct methods using the
program SHELXS-97 and refined by full-matrix least-squares meth-
ods against F2 using the program SHELXL-97 [27]. The hydrogen
atoms were fixed at calculated position, and their positions were
refined with a riding model. The non-hydrogen atoms were located
with difference Fourier synthesis and hydrogen atoms were gener-
ated geometrically. The largest residual peak and hole in the final
difference Fourier diagram have no chemical significance.

J. Ren et al. / Thermochimica Acta 582 (2014) 17–24
19
HO
OHC
OCH3
HO
OCH3
HN N
O
HN
N
( I )
OH
OCH3
OH
OCH3
H3CH2C
OHC
HN N
O
NHNH2 MeOH
NH2NH2 H2O
EtOH, 80ºC, 4h
O
HN
HN
HN
HN
( II )
N
70ºC, 3h
N
N
O
O
OHC
HO
HN N
O
( III )
N
HO
Scheme 1. The synthesis routes of compounds I–III.
Fig. 1. Molecular structure of I.
weight loss of 5.73%. It may indicate the loss of lattice methanol.
The second step starts from 260 ◦C and remains level at 405 ◦C. In
this temperature region, the sum of weight loss is 68.10% (Calcd.
68.20%) and the decomposition process is represented in Fig. 9.
3.2.2. Thermal decomposition processes of compounds I–III under
air
The TG curves of three compounds under air at the heating rate
of 15 ◦C min−1 are represented in Fig. 10. The DTG curves of three
Fig. 2. Molecular structure of II. The solvent is omitted for clarity.

20
J. Ren et al. / Thermochimica Acta 582 (2014) 17–24
Fig. 3. Molecular structure of III. The solvent is omitted for clarity.
compounds under nitrogen at the heating rate of 15 ◦C min−1 are
shown in Fig. 11.
methods of Kissinger and Ozawa [28] are listed in Tables 2 and 3,
respectively. The different heating rate (ˇ) and corresponding
peak temperature value (Tp) on DTG curve were substituted into
Kissinger formula (1) and Ozawa formula (2), apparent activation
energy values E˛ and the pre-exponential factor A were calculated
by least-square method fitting in the computer.
Comparing Figs. 5 and 10, it can be seen clearly that the decom-
position processes under nitrogen and air from 30 to 400 ◦C are
similar, but from 400 to 700 ◦C, there appear obvious weight losses
for all the compounds under air and the three compounds are com-
pletely decomposed nearly at 700 ◦C. For compounds decomposed
under nitrogen, the weight percentages have no change during the
temperature range of 400 to 700 ◦C, and there still have residues
up to 800 ◦C. This is because oxygen is adequate under the air
condition. No matter in nitrogen or air flow, the maximum decom-
position peak temperatures of the three compounds shown in Figs.
6, 7, 8 and 11 are almost the same. It indicates that the thermal sta-
bilities for all the compounds are in agreement at both conditions.
ꢀ
ꢁ
ꢂ
ꢂ
ꢃ
ˇ
Tp2
AR
Ea
Ea
ln
= ln
−
(1)
(2)
RTP
ꢃ
AEa
Ea
lgˇ = lg
− 2.315 − 0.4567
RG(˛)
RTP
It can be seen from the Tables 2 and 3 that the apparent acti-
vation energy values E˛ and the linear correlation coefficient r
for compounds calculated by two methods are approximate. The
sequence of E˛ for three compounds at each condition is III > I > II,
so the sequence of their thermostabilities is the same.
3.2.3. Kinetic calculation
The kinetic parameters of main decomposition processes for
three compounds under nitrogen and under air obtained by
Fig. 4. View of the hydrogen bonds of compound I.

J. Ren et al. / Thermochimica Acta 582 (2014) 17–24
21
Table 2
Kinetic parameters of main thermal decomposition of compounds I–III under nitrogen.
Compound
ˇ/(◦C min−1
)
Tp/◦C
Kissinger
Ozawa
Ea/(kJ mol−1
)
lgA
r
Ea/(kJ mol−1
)
r
C12H12N4O3(I)
5.00
10.00
15.00
305.23
313.59
325.98
138.8
10.200
−0.9640
141.3
−0.9684
−0.9879
−0.9919
C
12H14N4O4(II)
5.00
10.00
15.00
285.02
301.46
306.46
121.9
165.0
8.989
−0.9860
−0.9909
124.9
166.2
C16
H16N4O3(III)
5.00
10.00
15.00
311.43
324.58
329.18
12.420
-1
-1
-1
311.43°C
324.58°C
329.18°C
I
.
.
.
5°
10°
15°
-1
0.0200
100
.
β
II
III
0.0175
0.0150
0.0125
0.0100
0.0075
0.0050
0.0025
0.0000
90
80
70
60
50
40
30
20
10
72.33%
71.11%
43.09%
49.63%
68.10%
68.10%
5.73%
0
100 200 300 400 500 600 700 800
0
100 200 300 400 500 600 700 800
Temperature (°C)
Temperature (°C)
Fig. 5. TG curves of compounds I–III under nitrogen.
Fig. 8. DTG curves of the compound III under nitrogen.
-1
-1
-1
OCH3
HO
0.016
0.014
0.012
0.010
0.008
0.006
0.004
0.002
0.000
-0.002
.
5°
325.98°C
305.23°C
313.59°C
HN
O
N
N
HN
HN
.
49.63%
49.79%
48.50%
I
(Calcd. 47.83%)
.
N
N
OH
49.63%
HN
O
43.09%
(Calcd. 44.56%)
OCH3
II
HN
O
N
68.10%
(Calcd. 68.20%)
HN
III
N
0
100 200 300 400 500 600 700 800
HO
Temperature (°C)
Fig. 9. Illustration of main thermal decomposition processes for three compounds
under nitrogen.
Fig. 6. DTG curves of the compound I under nitrogen.
110
0.0105
0.0090
0.0075
0.0060
0.0045
0.0030
0.0015
0.0000
306.46°C
-1
-1
-1
I
.
.
.
-1
5°
10°
15°
285.02°C
301.46°C
100
90
80
70
60
50
40
30
20
10
0
β = 15 °C⋅min
II
III
47.24%
39.62%
43.09%
62.54%
41.08%
40.37%
6.67%
0
100 200 300 400 500 600 700 800
Temperature (°C)
0
100 200 300 400 500 600 700 800
Temperature (°C)
Fig. 7. DTG curves of the compound II under nitrogen.
Fig. 10. TG curves of compounds I–III under air.

22
J. Ren et al. / Thermochimica Acta 582 (2014) 17–24
-8
0.020
0.018
0.016
0.014
0.012
0.010
0.008
0.006
0.004
0.002
0.000
-0.002
3.5x10
328.81°C
589.02°C
-1
-8
β = 15°C⋅min
3.0x10
1
1
-
I
-8
0
1
2.5x10
318.63°C
300.22°C
II
ε
7
0
1
-8
III
.
1
ε
2.0x10
+
5
-
x
-8
0
1
1.5x10
0
1
8
6
2
2
.
5
111.41°C
185.86°C
4
8
.
+
-8
9
x
=
0
1
1.0x10
y
:
9
I
4
I
6
.
I
3
606.96°C
634.36°C
=
y
-9
I:
5.0x10
0.0
-4
-4
-4
-4
0.0
1.0x10
2.0x10
3.0x10
4.0x10
-1
0
100 200 300 400 500 600 700 800
CDNA(mol
⋅
L )
Temperature (°C)
Fig. 13. Plot of CDNA/(εa − εf ) versus CDNA
.
Fig. 11. DTG curves of the compounds I–III under air.
3.3. Interaction of CT-DNA with the three compounds
small hypsochromic shift due to addition of successive amounts of
CT-DNA. A strong hyperchromic effect was observed for increasing
concentrations of CT-DNA at 260 nm. As there is a bathochromic
shift in position of absorption bands, it can be inferred that the
compound exhibits intercalation binding to CT-DNA. After bind-
ing to the base pairs of DNA, the ␲* orbital of the intercalated
compound I could couple with ␲ orbit of the base pairs, thus,
decreasing the ␲–␲* transition energies [29–31]. For compound
II, there is hypochromic effect for increasing concentration of CT-
DNA at 322 nm, and for compound III, there are hypochromic
effect for increasing concentrations of CT-DNA at 324 nm and
359 nm, respectively. As there is no change in position of absorp-
tion bands (bathochromic or hypsochromic shift), it can be inferred
that compounds II and III exhibit electrostatic binding interactions
to CT-DNA [32].
3.3.1. Electronic absorption titration
Electronic absorption spectroscopy is an efficient method to
examine the binding mode of DNA with compounds. The UV–Vis
spectra of I–III with CT-DNA were done in Tris buffer from 200 to
500 nm. The absorption spectra of compounds I–III were recorded
for a fixed concentration of compounds (1.0 × 10−4 mol L−1) with
increasing concentrations of CT-DNA (0–300 ␮L) in Fig. 10. Hyper-
chromism and hypochromism have been attributed to the presence
of synergic non-covalent interactions: external contact (electro-
static binding), hydrogen bonding, groove surface binding (major
or minor) along outside of DNA helix and intercalation. For I, in
Fig. 12a, an isosbestic point at 290 nm was observed and a dis-
tinct charge transfer band appeared at 300 nm. This band showed a
0.5
b
322nm
0.6
-4
-1
.
) mol L
1. II (1.0×10
a
1
-4
-1
.
1. I ( 1.0x10 ) mol L
290nm
1
7
2. 1+DNA (50μL)
3. 2+DNA (50μL)
4. 3+DNA (50μL)
5. 4+DNA (50μL)
6. 5+DNA (50μL)
7. 6+DNA (50μL)
0.4
0.3
0.2
0.1
0.0
2. 1+DNA (50μL)
3. 2+DNA (50μL)
4. 3+DNA (50μL)
5. 4+DNA (50μL)
6. 5+DNA (50μL)
7. 6+DNA (50μL)
0.5
0.4
0.3
0.2
0.1
0.0
7
7
1
250
300
350
400
450
250
300
350
400
450
Wavelength(nm)
Wavelength(nm)
0.30
c
-4
-1
.
) mol L
1. III (1.0×10
1
2. 1+DNA (50μL)
3. 2+DNA (50μL)
4. 3+DNA (50μL)
5. 4+DNA (50μL)
6. 5+DNA (50μL)
7. 6+DNA (50μL)
0.25
0.20
0.15
0.10
0.05
324nm
359nm
7
0.00
250
300
350
400
450
Wavelength (nm)
Fig. 12. (a) UV–Vis absorption spectra of CT-DNA interaction with I. (b) UV–Vis absorption spectra of CT-DNA interaction with II. (c) UV–Vis absorption spectra of CT-DNA
interaction with III.

J. Ren et al. / Thermochimica Acta 582 (2014) 17–24
23
Table 3
Kinetic parameters of main thermal decomposition of compounds I–III under air.
Compound
ˇ/(◦C min−1
)
Tp/◦C
Kissinger
Ozawa
Ea/(kJ·mol−1
)
lgA
r
Ea/(kJ·mol−1
)
r
C12H12N4O3(I)
5.00
10.00
15.00
298.29
311.43
318.63
141.5
10.57
−0.9996
143.7
−0.9997
C
12H14N4O4(II)
5.00
10.00
15.00
279.97
293.07
300.22
133.0
176.4
10.20
13.47
−0.9996
−1.0000
135.4
177.1
−0.9996
−1.0000
C16
H16N4O3(III)
5.00
10.00
15.00
311.54
322.26
328.81
The intrinsic binding constants Kb for compounds I–III were
evaluated from the collected absorbance data of the titration curve
at the specified wavelength and the formula (3), where CDNA repre-
sents the concentration of DNA, εf, εa, and εb refer to the extinction
coefficient for the free compound, for each addition of DNA to
the compound and for the compound in the fully bound form,
respectively [33]. When CDNA/(εa − εf) is plotted versus CDNA, three
straight lines and their equations are obtained as presented in
Fig. 13.
0.15
0.10
0.05
0.00
-0.05
-0.10
3.1min
17.3min
T= 25oC
ΔH= 3.39 kJ⋅mol-1
CDNA
CDNA
1
=
+
(3)
εa − εf
εb − εf
Kb(εb − εf )
3.6min
20 40
The binding constants Kb of I, II and III obtained by the ratio of
the slope to the intercept are 4.44 × 105 L mol−1, 4.24 × 106 L mol−1
and 8.54 × 106 L mol−1, respectively. Therefore, the results indicate
that the interactions of three compounds with CT-DNA are strong
[32].
0
60
80
100 120 140
Time (min)
Fig. 15. Thermogenic curve of compound II with CT-DNA.
0.08
0.06
3.3.2. Microcalorimetry studies
Microcalorimetry is an important tool for the study of both ther-
modynamic and kinetic properties of biological molecules by virtue
of its general applicability, high accuracy and precision [34–40].
Recently, this method has yielded useful data on the interactions
between DNA and DNA-targeting molecules [41].
T= 25°C
ΔH= 4.49 kJ⋅mol-1
0.04
4.1min
27.2min
0.02
Figs. 14–16 show thermogenic curves for compounds I–III to CT-
DNA at 25 ◦C. The processes are all endothermic reaction. For I, an
endothermic peak appears at 5.2 min and the reaction time lasts
from 3.1 min to 34.2 min, indicating that the interaction between
I and CT-DNA is very rapid. The enthalpy change is 3.57 kJ mol−1
(ꢄH = 3.57 kJ mol−1) by calculating the peak area. The thermogenic
curves of II and III are almost the same with I. Both of them present
the endothermic reaction, their enthalpy changes are 3.39 kJ mol−1
0.00
-0.02
-0.04
6.0min
-0.06
0
20
40
60
80
100 120 140
Time (min)
Fig. 16. Thermogenic curve of compound III with CT-DNA.
0.12
3.1min
34.2min
and 4.49 kJ mol−1. The thermogenic curves indicate that there are
interactions between three compounds and CT-DNA.
0.09
0.06
0.03
0.00
-0.03
-0.06
4. Conclusions
T= 25°C
ΔH= 3.57 kJ⋅mol
Three novel acyl hydrazone compounds C12H12N4O3 (I),
C12H14N4O4 (II) and C16H16N4O3 (III) have been synthesized and
characterized. We obtained the single crystal structures of three
compounds which crystallize in the monoclinic space group. The
sequences of apparent activation energy values of thermal decom-
position and thermostabilities for three compounds under nitrogen
and air are III > I > II. The UV–Vis results show that compound I
exhibits intercalation binding to CT-DNA, while II and III exhibit
electrostatic binding interactions to CT-DNA. The thermogenic
curves of compounds I–III reacting with CT-DNA indicate that
-1
5.2min
20
0
40
60
80
100
120
140
Time (min)
Fig. 14. Thermogenic curve of compound I with CT-DNA.

24
J. Ren et al. / Thermochimica Acta 582 (2014) 17–24
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Supplementary material
Crystal and structure refinement data for compounds I,
II and III are summarized in CCDC 920578, 949989 and
949990, respectively. These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/data request/cif, by email-
ing data request@ccdc.cam.ac.uk, or by contacting The Cambridge
Crystallographic Data Center, 12 Union Road, Cambridge, CB2 1EZ,
UK. Fax: +44 1223 336033.
Acknowledgement
Financial supports from the National Natural Science Founda-
tion of China under grant nos. 21073139, 21103135and 21301139
are gratefully acknowledged.
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Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
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