SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF N-(2-{[(2E)-2-(2- HYDROXYBENZYLIDENE)HYDRAZINYL]CARBONYL}-PHENYL)BENZAMIDE (HL) AND ITS Co(II), Fe(III), Cu(II) AND Zn(II) COMPLEXES. X-RAY CRYSTAL STRUCTURE OF HL

N-(2-{[(2E)-2-(2-hydroxybenzylidene)hydrazinyl]carbonyl}phenyl)benzamide (HL) and its Co(II), Fe(III), Cu(II) and Zn(II) perchlorate complexes were synthesized. The structures of HL and its complexes were confirmed on the basis of elemental analysis and FT-IR, FT-Raman, H-NMR spectra. TGA, magnetic moment and molar conductivity measurements were carried out for the complexes. In addition, the crystal structure of HL was determined by X-ray diffraction at room temperature. It crystallizes in the monoclinic, space group C2/c and Z=4. HL has an interesting structure due to the presence of two intramolecular hydrogen bonds. It behaves as a bidentate ligand through the C=N nitrogen and OH oxygen atoms in its chelate complexes that they have 1:2 M:L (metal:ligand) ratio. The Fe(III), Cu(II) and Zn(II) complexes, [Fe(HL)(L)(H2O)2](ClO4)2, [Cu(HL)2](ClO4)2∙3H2O, [Zn(HL)2](ClO4)2·H2O are 2:1 electrolytes whereas the Co(II) complex, [Co(HL)(L)(H2O)]ClO4·H2O, is 1:1 electrolyte according to the molar conductivity data.


INTRODUCTION
Benzamide and its analogues have various application in synthesis of heterocyclic ring skeletons and are used as intermediate in the synthesis of 2,3-disubstituted quinazolin-4(3H)-one heterocycles [1]. In addition, benzamides are identified as important structural unit present in many compounds having potential biological activities, which are extracted from natural sources. For example, molecules, like proteins which play an essential role in almost all biological processes such as enzymatic catalysis (nearly all known enzymes are proteins), transport/storage (haemoglobin), immune protection (antibodies) and mechanical support (collagen). The benzamide derivatives are also useful for modulation of numerous metabolic functions including regulation of carbohydrate, protein and lipid metabolism, regulation of normal growth and/or development, influence on cognitive function, resistance to stress and mineralocorticoid activity [2,3].
Structural characterization of benzohydrazides is important to comprehend their effect mechanisms because of their considerable biological effects. Recently, the crystal structures of hydrazone compounds have been widely studied [18][19][20][21].
In our previous study, the crystal structure of 2-amino-N'-[(1Z)-1-(4-chlorophenyl)ethylidene]benzohydrazide was reported [22]. The structure of the compound also was characterized by elemental analysis, MS, FT-IR and NMR spectroscopic techniques. In this study, we synthesized and characterized N- Figure 1), a new benzohydrazide derivative, and its Co(II), Fe(III), Cu(II) and Zn(II) complexes. The structure of the compounds is characterized by the analytical data and FT-IR, FT-Raman, NMR spectroscopy. TGA, magnetic moment and molar conductivity measurements were carried out for the complexes. In addition, the crystal structure of HL is determined by X-ray diffraction analysis.

Chemicals and apparatus
All chemicals and solvents were of reagent grade from Sigma-Aldrich, Merck, Alfa Easer, Carlo Erba and Acros Organics and they were used without further purification.
Elemental analysis data were obtained with a Thermo Finnigan Flash EA 1112 analyzer. Molar conductivity of the complexes was measured on a WTW Cond315i conductivity meter in DMF at 25 ºC. Magnetic moment measurements for the paramagnetic complexes were carried out on a Sherwood Scientific apparatus (MK1) at room temperature by Gouy's method. FT-IR spectra were recorded on a Bruker Optics Vertex 70 spectrometer using ATR (Attenuated Total Reflection) techniques. The FT-Raman spectra were also recorded in the same instrument with a R100/R RAMII Raman module equipped with Nd:YAG laser source operating at 1064 nm line with 200 mW power and a spectral resolution of ±2 cm -1 . Thermogravimetric (TG) study was made on a TG-60WS Shimadzu, with a heating rate of 10 ºC/min under flowing air at the rate of 50 mL/min. 1 H-NMR spectra were run on a Varian Unity Inova 500 NMR spectrometer in CDCl 3 .

Synthesis of the compounds N-(2-{[(2E)-2-(2-Hydroxybenzylidene)hydrazinyl]carbonyl}phenyl)benzamide (HL).
To the well stirred solution of salicylaldehyde (0.1 mL, 0.8196 mmol) in dry ethanol (10 mL) was added 2-3 drops of sulfuric acid (98%) and stirred with gentle heating for 30 min followed by addition of ethanolic solution of 2-phenyl-4H-3,1-benzoxazin-4-one (0.2 g, 7.84 mmol, Scheme 1). The mixture was further refluxed with continuous stirring for one hour; the progress of the reaction was monitored with TLC upon completion of the reaction. The mixture was allowed to cool to room temperature, and was then poured into ice cold water. The product precipitated was filtered, washed with 5% cold NaHCO 3 solution, dried and recrystallized from ethanol (239 mg). Yield benzamide (HL).

Crystallography
Suitable crystal was selected for data collection which was performed on a Bruker SMART APEX CCD area-detector diffractometer with graphite monochromated Mo-Kα radiation (λ = 0.71073 Å) at 251 o C (298 K). The structures were solved by direct methods using SHELXS-97 and refined by full-matrix least-squares methods on F using SHELXL-97 [23]. All nonhydrogen atoms were refined with anisotropic parameters. The H atoms of C atoms were located from different maps and then treated as riding atoms with C-H distances of 0.96 -0.97 Å. H atoms treated by a mixture of independent and constrained refinement. For the structure solution, 9402 reflections were collected, 3530 were unique (R int = 0.066); equivalent reflections were merged. Lorentz-polarization and absorption corrections were applied using Bruker SAINT [24] and SADABS [25] software. The crystal structure was deposited at the Cambridge Crystallographic Data Centre under the following deposition number: CCDC 1538433.

Discussion of the ligand structure
Synthesis of the ligand (HL) was given in Scheme 1. The structure of HL was confirmed by the characteristic absorption peaks of amide in IR region, D 2 O exchangeable amide proton peak in the 1 H-NMR region and further confirmation was done on the basis of molecular ion peak in EI-MS, FAB-MS and Mass fragmentation pattern. It is important to note that HL did not cyclize further under the selected reaction conditions.
In addition to spectroscopic proof of the structure, crystals of HL were obtained and the absolute structure was determined with the help of X-ray crystallography, which confirmed the formation and reactivity of the open chain products.
The crystal data and details of data processing are given in Table 1. Table 2 contains the hydrogen bond geometry parameters. Selected bond lengths and angles are given in Table 3; some torsion angles are given in Table 4. The ORTEP III drawing of HL is given in Figure 2 and the unitcell packing diagram with the intermoleculer H-bonding is given in Figure 3. There are two intra-and three inter-molecular hydrogen bonds in the HL molecule ( Table  2). The intermolecular hydrogen bonding distances are 1.99, 2.60 and 2.46 Å, for N2H2A···O1, C4H4···O3 and C17H17···O2, respectively. The intermolecular H-bonding values for C4-H4···O3 and C17-H17···O2 (2.60 and 2.46 Å, respectively) are higher than the ordinary intermolecular H-bonding lengths as expected due to very weak electron-withdrawing characteristic of the aromatic CH hydrogen atoms. The crystal structure is stabilized by the intermolecular hydrogen bondings. The intramolecular hydrogen bonding distances, (N1H1A···O2: 1.97(2) Å; O3H3A···N3: 1.85(3) Å), are in agreement with the literature data [21,[26][27][28][29][30]. The intramolecular hydrogen bonds cause forming almost two more rings in the molecule. It is expected that the intramolecular hydrogen bonds affect the physical properties of HL, significantly. It is not a very common feature that there are hydrogen bonds in a molecule more than one.
The C=O bond lengths are very close to each other: 1.231 (3) [32][33][34]. The room temperature magnetic moment value of Co(II) complex, 3.31 BM, lower than the spin-only value for high spin and higher than the spin-only value for low spin configurations. This may be considered as a spin equilibrium between two spin states [35] and it can be attributed a square pyramidal geometry for this complex nearly [36,37].
The experimental data of the Co(II) and Fe(III) complexes suggest us monodeprotonated structure in contradistinction to the Cu(II) and Zn(II) complexes. The dark color of the complexes, especially the Fe(III) and Co(II) complexes, shows that there are charge transfer transitions ligand to metal ions through phenolic oxygen atom, O→M [38,39].

Thermogravimetric analysis
The major features of the thermal analysis of the complexes are given in Experimental section. TGA curves of the Co(II) and Zn(II) complexes are given in Figure 4. The decomposition points of the complexes are in the 180  273 o C range. In this range, explosions were occurred in the Fe(III) and Cu(II) complexes due to presence of the perchlorate anion. Because of the explosion, TGA analysis could not be performed for these complexes fully. However, we could detect the coordinated and uncoordinated water molecules in the complexes by means of TGA. The uncoordinated lattice water molecules were lost through evaporation from 50 to 100 ºC (dehydration) in the Cu(II) and Zn(II) complexes whereas the coordinated water molecules (aqua) were removed at temperatures near 150 ºC in the Fe(III) and Co(II) complexes. The full TGA data of the Co(II) and Zn(II) complexes could be obtained without explosion (Figure 4) between 40 and 800 o C. Thermal degradation of the complexes occurred at three stages. Firstly, uncoordinated lattice water left at the 50 -100 ºC range as mentioned above. At the second stage, a considerable weight losses observed between 200 and 400 ºC can be explained in terms of cleavage of hydroxyl, NHs and carbonyl groups. Above 500 ºC, all other organic parts of complexes are oxidized to carbon dioxide and water. Complete decomposition of the complexes continues up to 600 ºC probably to the forming of MO. Molecular weight ratio of the amount of metal oxide shows very good agreement for the proposed structures according to the TGA data in the Co(II) and Zn(II) complexes.

H-NMR Spectra
1 H-NMR spectral data of the ligand and the Zn(II) complexes are given in Experimental Section. The phenolic OH and CH=N protons give singlet at 11.10 and 9.17 ppm, respectively, in the ligand. In the Zn(II) complex, the OH signal shifted to 11.94 ppm from 11.10 ppm; the CH=N proton shifted to 9.64 ppm from 9.17 ppm with respect to the ligand. These data showed that the phenolic OH oxygen and the CH=N nitrogen atoms coordinated to the Zn(II) ion, and the OH proton did not remove on complexation (The other data such as elemental analysis, molar conductivity, also confirm that the OH proton does not remove on complexation). The hydrazine (-CO-NH-N=C) and benzamide (-CO-NH-Ph) NH protons of the ligand appear at 11.19 ppm as a singlet, respectively. These NH protons exhibit different behavior in the Zn(II) complex: The NH proton of hydrazine that neighbor to the coordinated imine nitrogen (-NH-CH=N) gives a singlet at 11.69 (from 11.19), whereas the benzamide NH proton (far from the coordinated imine nitrogen) is slightly affected from coordination (it gives a singlet at 11.10 ppm). This observation is considered as an additional evidence for CH=N nitrogen atom coordination.

Vibrational Spectroscopy
FT-IR and FT-Raman spectral data of the compounds are given in Experimental section. The FT-IR spectra of the ligand and the complexes are given in Figure 5. FT-Raman spectra of HL and the Zn(II) complex were shown in Figure 6. We could not get the FT-Raman spectra of the Cu(II), Co(II) and Fe(III) complexes (Raman inactive).
In the IR spectra of the ligand, the medium bands at 1650 and 1667 cm -1 must belong to the C=O groups. The corresponding wavenumbers in the complexes are detected at the 1617 -1736 cm -1 range. In the Raman spectra, the 1653 cm -1 and 1667 cm -1 bands can be assigned for the ν(C=O) group of the ligand and the Zn(II) complex, respectively. The medium (IR) and strong (Raman) bands between 1604 -1616 cm -1 are attributed to the aromatic ring (CC) frequencies. There are no considerable changes in these frequencies on complexation as expected. Similarly the (CN) asymmetric stretching frequency of the ligand is appeared at 1519 cm 1 , and it was detected at the 1582 -1590 cm 1 range in the complexes. This considerable shifting shows that the coordination occurs through the C=N nitrogen atom.
The strong bands between 761 and 744 cm -1 (in the ligand: 758 cm -1 ), and the strong or medium bands at the 830 -730 cm -1 range are due to the out-of-plane deformation bands for the aromatic C-Hs. The bands at 3284 cm -1 (w, br) and 3198 cm -1 (m, br) can be attributed to (OH) and (NH) in the ligand, respectively. These bands shifted to the 3322 -3361 cm -1 and 3187 -3266 cm -1 ranges in the complexes, respectively.
In the FT-IR spectra of all the complexes, the new strong band between 1105 and 1152 cm -1 can be assigned to the stretching vibrations of the uncoordinated perchlorate anion, (Cl=O). In addition, the medium bands in the complexes near 620 cm -1 are due to ν 4 mode of perchlorate anion [40][41][42].
The broad band between 3000-2500 cm -1 in the complexes should be belonged to the hydrogen bonding because of the coordinated and uncoordinated (lattice) water molecules. The characteristic (C-H) modes of ring residues are observed in the range of 3054 -3095 cm -1 , in the FT-IR and FT-Raman spectra of the compounds (Figures 5 and 6). HL and its complexes.
Raman spectra of HL and its Zn(II) complex.

CONCLUSION
Benzamide and its analogues have various applications in synthesis of heterocyclic ring skeletons and are used as intermediate in the synthesis of some heterocycles. In addition, some extracted from plants having potential biological activities.
Benzamide and its analogues have various applications in synthesis of heterocyclic ring some heterocycles. In addition, some In this study, a new benzamide derivative, N-(2-{[(2E)-2-(2-hydroxybenzylidene)hydrazinyl]carbonyl}phenyl)-benzamide (HL) and its complexes with Co(ClO 4 ) 2 , Fe(ClO 4 ) 3 , Cu(ClO 4 ) 2 and Zn(ClO 4 ) 2 were synthesized and characterized. In addition, the crystal structure of HL is determined by X-ray diffraction at room temperature. According to the analytical and spectral data, HL behaves as a bidentate in the chelate complexes; and the complexes have 1:2 M:L ratio. According to the molar conductivity measurements in DMF, the Fe(III), Cu(II) and Zn(II) complexes are 2:1 electrolytes whereas the Co(II) complex can be considered as 1:1 electrolyte.
As a conclusion, the structures in Figure 7 can be proposed for the complexes. It can be proposed a tetrahedral geometry for the Cu(II) and Zn(II) complexes; distorted octahedral and square pyramidal geometries for the Fe(III) and Co(II) complexes, respectively [43][44][45][46][47]. In addition, the ball-stick structure for the Cu(II) and Zn(II) complexes is shown in Figure 8.

ACKNOWLEDGEMENT
This work was supported by the Scientific Research Projects Unit of Istanbul University and TUBITAK-BIDEB.