Theoretical Studies of Structure , Spectroscopy , and Properties of a NewHydrazine Derivative

We will report a combined experimental and theoretical study on molecular structure, vibrational spectra, and energies of (E)1-(2,4-dinitrophenyl)-2-[(4-methylphenyl)methylidene]hydrazine (1). e molecular geometry and vibrational frequencies and energies in the ground state are calculated by using HF and DFT levels of theory with 6-311G basis sets.e calculated HOMO and LUMOenergies also con�rm that charge transfer occurswithin themolecule.eharmonic vibrational frequencieswere calculated, and the scaled values have been compared with experimental FTIR and FT-Raman spectra. e observed and the calculated frequencies are found to be in good agreement. e experimental spectra also coincide satisfactorily with those of theoretically constructed bar-type spectrograms.


Introduction
e properties of hydrazides and hydrazones are of interest due to their biological activities and their use as metal extracting agencies [1].e hydrazones derivatives are used as fungicides and in the treatment of diseases such as tuberculosis, leprosy, and mental disorders.e complexes of various hydrazones are reported to act as inhibitors of enzymes [2].Many substituted hydrazides are employed in the treatment of psychotic and psychoneurotic conditions.Carboxylic acid hydrazides are known to exhibit strong antibacterial activities which are enhanced by complexation with metal ions.Chemistry of Schiff bases has been intensively investigated in recent years, owing to their coordination properties and diverse applications.Schiff base hydrazones are widely used in analytical chemistry as a selective metal extracting agent as well as in spectroscopic determination of certain transition metals [3][4][5][6].Schiff bases play an important role in inorganic chemistry as they easily form stable complexes with most transition metal ions in the periodic table.e development of the �eld of bioinorganic chemistry has increased the interest in Schiff base complexes, since it has been recognized that many of these complexes may serve as models for biologically important species [7][8][9][10][11].Schiff base metal complexes have been widely studied because they have industrial, fungicide, antibacterial, anticancer, and herbicidal applications [12,13].
However, the detailed ab initio and DFT (LSDA) with 6-311G comparative studies on the complete FTIR spectra of compound (1) have not been reported so far.In this study, molecular geometry, optimized parameters, and vibrational frequencies are computed and the performance of the computational methods for the ab initio and DFT (LSDA) levels with the 6-311G basis sets is compared.e HOMO represents the ability to donate an electron, LUMO as an electron acceptor represents the ability to obtain an electron.e HOMO and LUMO energy calculated by the ab initio and DFT (LSDA) levels with the 6-311G basis sets.

Experimental
2.1.Computational Details.All calculations were performed using the Gaussian 03 program on a Windows-XP operating PC.e molecular structure of the title compound in the ground state is computed by performing the ab initio and DFT (LSDA) with the 6-311G basis sets.

Results and Discussion
3.1.Molecular Geometry.e molecular structure of compound (1) belongs to C1 point group symmetry.e optimized molecular structure of title molecule is obtained from Gaussian 03W and Gaussview programs are shown in Figure 1.e optimized structural parameters of compound (1) calculated by the ab initio and DFT (LSDA) levels with the 6-311G basis sets are listed in Table 1.

Vibrational Analysis.
Vibrational spectroscopy was extensively used in organic chemistry for the identi�cation of functional groups of organic compounds, the study of molecular conformations, reaction kinetics, and so forth.e observed and calculated data of the vibrational spectrum of compound (1) are given in Table 2. e suggested reason was that the result obtained by the calculation was harmonic oscillation frequency, while the experimental value contained the anharmonic oscillation frequency.Assignment of compound systems could be proposed on the basis of frequency agreement between the computed harmonics and the observed fundamental modes.e calculated infrared spectra for different methods of compound (1) are presented in Figure 2. Correlation graphs between the scaled calculated and observed results for the assigned fundamentals in the region 4000-500 cm −1 are shown in Figure 3.
Comparing the observed and calculated frequencies shows that the results of our computations are in good agreement with the experiment.
In the spectrum of ligand, the strong IR absorption at 3447 cm −1 is due to N-H frequency.e calculated stretching vibration modes of the N-H band for compound (1) with ab initio and DFT (LSDA) levels with the 6-311G basis sets are 3814 and 3353 cm −1 (unscaled), respectively.Obviously, LSDA functional gives results in closest agreement with the observed frequencies over the other methods surveyed.e experimental C=N bands were observed at 1591 cm −1 as sharp bands.e calculated stretching vibration mode of the C=N band for compound (1) with HF and LSDA methods at 6-311G basis set was somewhat shied to the higher frequency appearing at 1792 and 1608 cm −1 , respectively.e FT-IR spectrum showed absorption bands at 1092 cm −1 which were assigned to N-N and calculated theoretically by HF/LSDA at 1145 and 1066 cm −1 for compound (1).
As can be seen from Figure 3, experimental fundamentals have a good correlation with LSDA/6-311G.120.9 120.9 C26-C28-C31 120.9 120.8As a result, the fundamental vibrational are in good consistency with the experimental results and are found a good agreement above the predicated literature.

Orbital Analysis.
e UV-Vis spectral analysis of compound (1) has been calculated by TD-HF/6-311G and TD-LSDA/6-311G methods along with measured UV-Vis data which are summarized in Table 3. e UV-Vis spectrum of compound (1) is shown in Figure 4 as measured in acetonitrile solution.Both the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) are the main orbitals that take part in chemical stability.e HOMO represents the ability to donate an electron, LUMO as an electron acceptor represents the ability to obtain an electron.e HOMO and LUMO energy calculated by the ab initio and DFT (LSDA) levels with the 6-311G basis set Figure 5. is electronic absorption corresponds to the transition from the ground to the �rst excited state and is mainly described by one electron excitation from the highest occupied molecular or orbital (LUMO).e HOMO is located over the group, and the HOMO → LUMO transition implies an electron density transfer to ring from chlorine and partially from ring.e HOMO energy calculated by LSDA/6-311G method is higher than by HF method.e biggest LUMO energy value is 0.10537 a.u.obtained using HF/6-311G.e biggest value of energy gap (ΔE) between HOMO and LUMO  energies is −0.17595 a.u.obtained at LSDA/6-311G whereas the smallest one is −0.47583 a.u.obtained at HF/6-311G.e total energies are found to decrease with increase of basis set dimension.

F 1 :F 2 :
Molecular structure and atom numbering scheme adopted in this study for(1).Calculated infrared spectra of compound (1).

F 3 :
Scaled calculated vibrational frequencies in comparison to the experimental obtained data and correlation coefficients for compound(1).

F 5 :
e atomic orbital compositions of the frontier molecular orbital for compound(1).