T. Tunç et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 127 (2014) 490–497
491
compounds can be used to identify the aldehydes and ketones from
Experimental
which the hydrazones have been formed. Hydrazones are more
efficient than oximes in this reaction, because their greater molec-
ular weight causes a lower solubility in most solvents. Therefore,
they can be easily isolated and recrystallized [1]. Hydrazones are
also useful for the synthesis of metal complexes as they easily form
stable complexes with most transition metal ions. Therefore,
hydrazones and their metal complexes have gained a special
attraction and growing interest in chemistry and biology, analyti-
cal chemistry. Also, hydrazones possessing an azomethine
ANHN@CHA proton constitute an important class of compounds
for new drug development [2]. Also, hydrazones have been inten-
sively investigated mostly for pharmacological applications due
to their potential application as anticancer, antiviral, antibacterial,
and antifungal agents [3–9]. Moreover, aromatic hydrazone mole-
cules dispersed in a binder polymer are used as the main constitu-
ent of electro photographic photoreceptors of laser printers due to
their excellent hole-transporting properties and relatively simple
synthesis [10].
General procedures and materials
2-Hydrazinobenzoic acid and 4-methylbenzaldehyde were
purchased from Aldrich and used without further purification.
Ethanol and dioxan were purchased from Carlo Erba. All other
chemical substances used were reagent-grade commercial prod-
ucts. The IR spectra were recorded on a THERMO NICOLAT 6700
ATR spectrophotometer by using KBr disk in the range 4000–
400 cmꢃ1. The electronic spectra in the 200–780 nm range were
obtained on a Shimadzu UV-1240 spectrophotometer using meth-
anol as the solvent. Elemental analyses for (C, H, N) were per-
formed using a LECO CHNS 932 elemental analyzer. 1H NMR
spectra were performed on a Bruker AVANCE DPX-300 MHz and
Mass spectra were recorded using an Agilent 1100 MSD mass
spectrometer.
Synthesis of compound MCH
In this study, a new Schiff-base complex N-(4-Methylbenzylid-
ene)-N0-(2-carboxyphenyl) hydrazine (MCH) has been synthesized
and its structure was determined using the X-ray diffraction
method. This compound is also characterized by elemental analy-
sis, FT-IR, 1H NMR and UV–Vis spectroscopy techniques. In the
conformational analysis, the minimum energy conformational
geometries were performed with the help of potential energies
barrier by B3LYP/6-31 G basis set. In addition, we performed
the structural and vibrational properties of the MCH molecule
by means of DFT calculations using the B3LYP functional with
6-311++G** basis set. The complete assignment of the bands
observed in the vibrational spectra were performed taking into
account the natural internal coordinates for the more stable
structures by using the harmonic force field with the Scaled
Quantum Mechanics Force Field (SQMFF) methodology. The
experimental and theoretical results were compared with each
other.
The title compound, MCH, was prepared as shown in Scheme 1.
For synthesis of the MCH, a solution of 4-methylbenzaldehyde (1)
(2.403 g, 0.02 mol) in hot methanol (50 ml) was added dropwise to
a solution of 2-hydrazinobenzoic acid (2) (3.77 g, 0.02 mol) in hot
methanol–dioxane mixture (100:20 ml) and a little 5%HCl with
constant stirring. Since condensation reaction was carried out in
acidic conditions, synthesis was made at about pH 4–5 [21]. The
procedure was completed in approximately 30 min. The resulting
pale yellow Schiff base (3) was left on the bench for 3 days and
then was filtered. The precipitate formed was filtered and the res-
idue was dissolved in hot methanol under the reflux for 3 h. and
kept in cupboard for 2 days for recrystallization and then was fil-
tered. Also, a structure unsubstituted, N-benzlidene-N0-phenyl
hydrazine (BPH) was synthesized in the same way for clarification
of substituent effects of MCH. Experimental data of MCH Schiff
base is given in Table S2.
X-ray diffraction study
Computational detail
The crystal and instrumental parameters used in the unit-cell
determination and data collection are summarized in Table 1.
Diffraction measurements were made at room temperature on a
four-circle Rigaku R-AXIS RAPID-S diffractometer (equipped
with a two-dimensional (2D) area IP detector). The graphite-
All calculations were performed at density functional theory
[11,12] using Gaussian 09 program [13], invoking gradient geom-
etry optimization [14]. Geometry optimization, Harmonic vibra-
tional spectra, NMR and UV–Vis spectra were performed using
the Becke’s three parameter hybrid functional, a combination that
gives rise to the well known B3LYP method with 6-311++G(d,p)
basis set [15–18]. Later, based on the SQMFF procedure [19], the
harmonic force fields for the more stable conformer were evalu-
ated at the same theory level. The theoretical vibrational spectra
of the title compound were interpreted by means of TEDs using
the SQM program [20]. Only the total energy distribution (TED)
components ꢂ10% was considered to perform the final
assignment.
monochromatized Mo K
scans technique with
a
radiation (k = 0.71073 Å) and oscillation
D
x = 5° for one image were used for data
collection. The lattice parameters were determined by the least-
squares methods on the basis of all reflections with F2 > 2 (F2). Inte-
r
gration of the intensities, correction for Lorentz, and polarization
effects, and cell refinement were performed using Crystal – Clear
(Rigaku/MSC, Inc., The Woodlands, TX) software [22]. The structures
were solved by direct methods using SHELXS-97 [23] and refined by
a full matrix least-squares procedure using the program SHELXL-97
[24]. All non-hydrogen atoms were refined with anisotropic dis-
placement parameters and hydrogen atoms were included in their
idealized positions and refined isotropically. An ORTEP [25] drawing
of the molecule with 50% probability displacement thermal ellip-
soids and atom-labeling scheme are shown in Fig. 1.
The aim of the conformational analysis of the MCH molecule is
to provide a model for the molecular structure. The energy barrier
of the rotation around the C1AC2, N2AC8, C8AC5, N1AN2, C9AN1 and
C14AC15 bond were calculated for by B3LYP/6-31G(d,p) basis set.
All dihedral angles were varied from 0° to 360° by steps of 10°.
All potential energy barriers are given in Fig. S1. The most stable
geometry is shown in Fig. S1. The optimized geometric parameters
(bond lengths, bond angles and dihedral angles) of the ground state
are given in Table S1.
Results and discussion
Then, the optimized molecular structure, vibrational normal
modes, nuclear magnetic resonance spectra and UV–Vis spectra
were calculated for ground state in the B3LYP with
6-311++G(d,p) basis sets.
Vibrational spectra
Table 2 lists the results of three DFT calculations of the normal
modes of vibration that were performed using the Gaussian 09 [13]