Synthesis, spectroscopic characterization and thermal studies of (E,E)-2-hydroxy-3-methoxybenzaldehyde azine

Article abstract of DOI:10.14233/ajchem.2014.15932

Hydrazone, (E,E)-2-hydroxy-3-methoxybenzaldehyde azine was synthesized and its spectroscopic characterization was studied via IR, ¹H NMR, MS and XRD. Its fluorescence activity and thermal stability were also analyzed.

Full text of DOI:10.14233/ajchem.2014.15932

Asian Journal of Chemistry; Vol. 26, No. 4 (2014), 1095-1098
http://dx.doi.org/10.14233/ajchem.2014.15932
Synthesis, Spectroscopic Characterization and Thermal Studies of
(E,E)-2-Hydroxy-3-methoxybenzaldehyde Azine
1,2
1
1,*
RONG ZHOU , HUAIBO ZOU and GUANGQUAN MEI
1Key Laboratory of Jiangxi University for Applied Chemistry & Chemical Biology, Yichun University, Jiangxi Province, P.R. China
2College of Chemistry & Bioengineering, Yichun University, Jiangxi Province, P.R. China
*Corresponding author: Tel/Fax: +86 795 3200655; E-mail: yc_mgq@163.com
Received: 18 June 2013;
Accepted: 28 August 2013;
Published online: 15 February 2014;
AJC-14706
Hydrazone, (E,E)-2-hydroxy-3-methoxybenzaldehyde azine was synthesized and its spectroscopic characterization was studied via IR,
1H NMR, MS and XRD. Its fluorescence activity and thermal stability were also analyzed.
Keywords: Hydrazone, Spectroscopic characterization, XRD, Thermal analysis.
INTRODUCTION
EXPERIMENTAL
Hydrazones contain the azomethine group (–RC=N–) and
usually formed by the condensation of a primary amine with
an active carbonyl compound1. Hydrazones are widely used
as intermediates in synthesis2, and in particular in hydrazone
Schiff base ligands, which are among others employed in
dinuclear catalysts3. In analytical chemistry, the formation of
hydrazones was extensively used as ideal reagents in detection,
determination and isolation of compounds containing the
carbonyl group or transition metals determinations4,5.
Furthermore, hydrazones demonstrate many bioactivities
in the treatment of several diseases, therefore, a number of
hydrazide-hydrazone derivatives have been claimed to possess
interesting antibacterial6-7, antifungal8-9, anticonvulsant10, anti-
inflammatory11, antimalarial12, and antituberculosis activities13.
Hydrazones have also been used for different purposes such
as herbicides, insecticides14-15 and plant growth regulators16.
This paper contains the synthesis, characterizations and thermal
stability of the hydrazone, (E,E)-2-hydroxy-3-methoxy-
benzaldehyde azine (Scheme-I).
2-Hydroxy-3-methoxybenzaldehyde (Fluka) and hydra-
zine hydrochloride (Fluka) were used as received. Analytical
grade ethanol was used as solvent.
Synthesis of (E,E)-2-hydroxy-3-methoxybenzaldehyde
azine: The (E,E)-2-hydroxy-3-meth-oxybenzaldehyde azine
was prepared by the condensation reaction of 2-hydroxy-3-
methoxybenzaldehyde (1.52 g, 1 mmol) and hydrazine
hydrochloride (0.34 g, 1 mmol) in ethanol (30 mL). The
reaction mixture was refluxed and stirred at 70 °C for 24 h.
The resulting clear solution was kept in air and, after several
minutes, yellow crystals were formed at the bottom of the
vessel. The crystals were isolated, washed three times with
ethanol and dried in an infrared-xay vacuum oven at 55 °C
(yield 72 %).
The IR spectra (4000-400 cm-1) were recorded as KBr
pellets on a TG-209/Vector-22 spectrometer. 1H NMR spectra
was elucidated using a Bruker Avance AV 400 MHz 1H NMR
spectrometer. The solvent used was DMSO-d6 and the chemical
shifts were given in ppm in using TMS as the internal standard.
The 1H NMR spectra were taken at 25 °C. Mass spectra was
obtained on a Agilent GC-MS 5975C instrument at 70 eV.
XRD was obtained on a SMART APEXII Single-Crystal
Diffractometer. The fluorescence spectra was obtained on a
Varian LS55 fluorescence spectrometer. The solvent used was
DMSO. Thermal analysis and differential thermogravimetric
(TGA-DTG) analyses were carried out in temperature range
from 25 to 600 °C in nitrogen atmosphere by TGA-Q50 thermal
analyzer. The experimental conditions were: aluminium crucible
with 1 mg of sample, nitrogen atmosphere (nitrogen flow
H3CO
OH
N
N
HO
OCH3
Scheme-I: (E,E)-2-Hydroxy-3-methoxybenzaldehyde azine

1096 Zhou et al.
Asian J. Chem.
50 mL/min) and heating rate of 20 °C/min. Differential scan-
ning calorimetric (DSC) analyses were carried out in temperature
range from 25 to 500 °C in nitrogen atmosphere by DSC-Q20
analyzer. The experimental conditions were: aluminium
crucible with 2 mg of sample, nitrogen atmosphere (nitrogen
flow 50 mL/min) and heating rate of 10 °C/min.
Mass Spectroscopy: The most significant m/z peaks in
Fig. 3 of mass spectrum of the hydrazone are given in Table-1.
TABLE-1
MASS SPECTRUM (m/z) OF THE (E,E)-2-HYDROXY
-3-METHOXYBENZALDEHYDE AZINE
Origin
C16H16N2O4
m/z
300
283
150
135
108
80
RESULTS AND DISCUSSION
[C16H15N2O3]+
[C8H8NO2]+
[C7H5NO2]+
[C6H4O2]+
[C5H4O]+
The IR spectrum (Fig. 1) shows a broad band at 3470 cm-1,
which may be assigned to the -OH. The bands appeared at
around 3000 cm-1 are assigned to the phenyl group and the
strong intensity peak at 1615 cm-1 belongs to ν(C=N), sugges-
ting that the condensation was carried out and producted the
hydrazone. The peak at 1257 cm-1 is the usual mode of C-O
bending vibration. Bands appearing at 1577, 1460, 777, 731
cm-1 are the usual modes of phenyl ring vibrations.
[C3O]+
52
The (E,E)-2-hydroxy-3-methoxybenzaldehyde azine
show one peak at m/z 300 assigned to the C16H16N2O4 molecu-
lar ion. It also shows a series of peaks i.e. m/z (%): 300 (81.55),
283 (26.46), 150 (50.34), 135 (65.40), 80 (51.35) and 52 (100)
corresponding to various fragments. Their signals give an idea
about the formation of the hydrazone (Scheme-II).
X-ray structure: The X-ray structure of the (E,E)-2-
hydroxy-3-methoxybenzaldehyde azine is shown in Fig. 4 and
selected metric parameters are listed in Table-2. The whole
molecule is to be almost planar. There are two half-molecules
in the asymmetric unit, the mid-points of the N-N bonds lie
on centers of symmetry. The molecular structure is stabilized
by an intermolecular O–H···N hydrogen bond which forms a
six-membered ring.
Other X-ray crystallographic data are shown below:
Monoclinic, space group P2(1)/n, a = 5.9986(6), b = 18.3183
(19), c = 6.8263(7) Å; α = 90, β = 107.093(3), γ = 90°; V =
716.97(13) Å3; Z = 4; Dcalc. = 1.391 mg m-3, F(000) = 316;
µ(Mo-Kα)= 0.71073; T = 293 (2) K.
Fluorescence spectroscopy: Fig. 5 shows the fluore-
scence spectra in the range 200-500 nm of the hydrazone in
DMSO (1 × 10-4 mol L-1). The emission spectrum indicates a
peak at 275 nm due to π-π* transition, with the red shift deriving
from the resonance donating effect of both –OH and –OCH3
groups in the phenyl ring and another broad peak at 425 nm is
due to n-π* transition.
Fig. 1. Infrared spectrum of the (E,E)-2-hydroxy-3-methoxybenzaldehyde
azine
The 1H NMR spectrum of the hydrazone (Fig. 2) show a
singlet band at 3.83 ppm that was assigned to the proton of
–OCH3 group. The multiplet signals at 6.87-7.29 ppm were
attributed to the protons of aromatic rings. The signal of the
azomethine group was observed at 8.97 ppm, which could
further prove the formation of the hydrazone and the signal of
the –OH was found at 10.85 ppm.
1100
1000
900
800
700
600
500
400
300
200
100
0
-100
11.0 10.5 10.0 9.5
9.0
8.5
8.0
7.5
7.0
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0 .-0.5
f1 (ppm)
1
Fig. 2. H NMR spectral of the (E,E)-2-hydroxy-3-methoxybenzaldehyde azine

Vol. 26, No. 4 (2014)
Synthesis and Thermal Studies of (E,E)-2-Hydroxy-3-methoxybenzaldehyde Azine 1097
Fig. 3. Mass spectrum of the (E,E)-2-hydroxy-3-methoxybenzaldehyde azine
Scheme-II: Fragment patterns of the (E,E)-2-hydroxy-3-methoxy-benzaldehyde azine

1098 Zhou et al.
Asian J. Chem.
The DSC curve (Fig. 7) indicates that the melt point of the
hydrazone is 185-187 °C and the maximum peak at 205 °C in
DSC is observed by endothermic reaction.
Fig. 4. Molecular structure of the (E, E)-2-hydroxy-3-methoxyben-
zaldehyde azine
TABLE-2
SELECTED BOND LENGTHS AND BOND
ANGELS FOR THE COMPOUND
Bond
N1-N1A
N1-C7
Bond length (Å)
1.402(3)
1.281(2)
1.448(2)
1.370(3)
1.400(2)
1.393(2)
1.377(2)
1.402(2)
1.402(2)
Bond
C7-N1-N1A
N1-C7-C6
C1-C6-C7
C5-C6-C7
C1-C6-C5
C6-C5-C4
C5-C4-C3
C 4 - C 3 - C 2
C3-C2-C1
Bond angle (°)
112.97(18)
122.22(16)
119.12(16)
121.51(16)
119.37(16)
119.41(16)
120.02(16)
120.45(17)
120.12(17)
C7-C6
C(1)-C(2)
C(1)-C(6)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(5)-C(6)
Temperature (°C)
Fig. 7. DSC of the (E,E)-2-hydroxy-3-methoxybenzaldehyde azine
Conclusion
In summary, the (E,E)-2-hydroxy-3-methoxybenzal-
dehyde azine was synthesized by the condensation reaction in
a relatively good yield. Its spectroscopic characterizations were
1
analyzed in terms of IR, H NMR, MS, XRD, fluorescence
spectrometry and the thermal stability was also studied.
ACKNOWLEDGEMENTS
The authors gratefully acknowledged the National Natural
Science Foundation of China (21261024), Jiangxi Department
of Education (GJJ11704, GJJ12603), the Natural Science
Foundation of Jiangxi Province (20132BAB203002) and Key
Laboratory of Jiangxi Province for Research on Active Ingre-
dients in Natural Medicines (China) for financial support.
Wavelength (nm)
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Fig. 6. TG-DTG of the (E,E)-2-hydroxy-3-methoxybenzaldehyde azine