Novel N2O2 Schiff base derived from 1,2-Hydrazinedicarboximidamide and its complexes with Cu(II), Co(II), Ni(II), Mn(II) and Cr(III): Synthesis and characterization

The synthesis of a (1,2-Hydrazinedicarboximidamide) was identified in this paper and condensing it with 2-4dihydroxybenzaldehyde to form tetradentate ligand (L). This ligand used to prepare five metal complexes as chloride salts [Cu2(L)Cl2](1), [Co2(L)Cl2](2), [Ni2(L)Cl2](3), [Mn2(L) Cl2](4) and [Cr2(L)Cl2](5) in an ethanolic medium. Dimethyl formamide (DMF) prepared complexes solutions to applied it as electrolytes. The structures were confirmed by several spectroscopic and analytical techniques indicating that metal complexes are more likely to have tetrahedral-coordinated geometry. Thus, these structures indicated the ligand show similar actions as tetradentate linked to metal ion by nitrogen (azomethine) and the negative charge of oxygen atoms from hydroxyl in 2-4dihydroxybenzaldehyde.


INTROdUCTION
Metal complexes of azomethine ligands have acquired more attention due to their easy synthesis, their stereo-electronic structures, and outstanding biological activities 1 , catalytic activities 2,3 , Synthesis and design of transition metal ion complexes get together. Continued interest of Schiff base ligands consideration of the possibility of earning multiple structures scientific research involving catalysts 4 , material science 5 , optic applications 6 , medical chemistry 7 . Synthetic ingenuity leading to variety in structural arrangement in space considered as the gateway factors, which attending wide deal of benefit to azomethane ligands in coordination chemistry. Furthermore, their individual self-assembling behavior, result to the modeling of different supramolecular structural design, have assisted them to have the status of special ligand configuration 8 . Schiff bases are believed to be "privileged ligands" due to their easily synthesis by the reaction between aldehyde and primary amine. The Ligands of Schiff base are eligible to linked with several metal ions and to confirm them in many oxidation states 9 . Tetradentate Schiff bases with a (N 2 O 2 ) donation atoms to coordinate with several metal ions, and this has confirmed by many papers 10 .
Rather significant advantage was the azomethine group (C = N) in the configuration of the Schiff bases for the lone pair of electrons on a nitrogen atom sp2-hybridized orbital 11 . They show premium benefits for several fields, such as speeding up the organic synthesis reaction as a catalyst, chemistry of transition metals, industrial, biological, pharmacological and optical sensor properties 12 .

Synthesis of (1,2-Hydrazinedicarboximidamide) (A)
It was prepared by reaction of thiourea (24.57 g, 0.3228 mol) and hydrazine hydrate (8 g, 0.16 mol) in ethanol (100 cm 3 ) by refluxing for 3 h with stirring. The product was cooled at room temperature and filter it to get hydrazide 13 . The recommended structure for the synthesis ligand(A) was given in Fig. 1 and some physical properties were showed in Tables 1.

Synthesis of the Schiff base ligand (L)
L was synthesis by dissolving (0.039 mol, 5.52 g) of 2-4dihydroxybenzaldehyde in (25 mL) of ethanol and adding about (3-2) drops of glacial acetic acid and stirred for 10 min to ensure the formation of the carbonium ion, then (0.0096 mol, 1.2 g) of compound A dissolved in (15 mL) of ethanol was slowly and step by step added while refluxing. After completing the addition process, the mixture left for (5 h) in an inert atmosphere of Akron gas. The reaction was followed up using layer chromatography 14 . The suggested structure for the prepared ligand(L) was showed in Fig. 2 and some physical properties were listed in Tables 1.

Synthesis of the Schiff base complexes
Complexes of the ions Mn (II), Co (II), Ni (II), Cu (II), Cr (III) were prepared with the Schiff bases of (L) by dissolving (0.149 g, 0.001 mol) of ligand (Dissolved L in (2: 3: 3 mL) of solvents (DMF: EtOH: MeOH)) respectively with ( (3 hours). with the presence of supplying of Argon gas to the reaction, a colored precipitate was observed after which the solution was filtered and the crystals were washed with diethyl ether and then the product was allowed to dry at room temperature 15 . The prepared Complexes structure was suggested in Fig. 3

RESULTS
Identification and characterization of synthetic Schiff base and it's complexes were confirmed by many techniques like by the FTIR, UV-Vis, 1 H-NMR, 13 C-NMR,ESI-Mass, molar conductivity and magnetic properties to proven the chemical structure of the prepared Schiff base and it's complexes.

IR spectra of the ligands and complexes
The IR bands of the ligands and it's complexes are given in Table 2. The most notation divergence in the IR figure of the ligand (L and complexes (L 3 -Cu, L 3 -Co,L 3 -Mn,L 3 -Ni,L 3 -Cr) was the moving of C=N stretching frequencies to smaller frequencies cause to metal-ligand coordination 16 . The ligand (L) show vibration of azomethine at 1633 cm -1 was Shifted to a greater frequencies in the complex (L-Cu) due to back donation and decreasing the planar specialty after complexation 17 and the azomethine vibration was shifted for a less frequencies in the complexes(L-Co, L-Mn,L-Ni,L-Cr ) due to decreasing the double bonding property after complex 18 . The absorption bands in the spectra of complexes(L-Cu) (L-Co), (L-Mn),(L-Ni) and (L-Cr ) at 3363 cm -1 , 3344 cm -1 , (3348-3336 cm -1 ), 3367 cm -1 and 3385 cm -1 respectively were attributed to OH.

UV-Visible spectra of the ligands and complexes
The electronic spectra (UV-Vis) data of the ligands and its complexes are shown in Table 3 and The π band of the ligands L at 282 nm is assigned to phenyl of 2,4-dihydroxybenzaldehyde π→π* transition 19 . The azomethine group in these ligands was appeared two bands is because of the π→π* and n→π* 19 . These two bands were moved to higher wavelengths in the complexes.  H-NMR, 13 C-NMR spectra of the ligands: The 1 H-NMR spectra of the ligand L was recorded in DMSO. Using 400 MHZ, and it appeared a many of characteristic signals of the ligand as shown in Table 4. The signals due to the aromatic protons were observed in the range d = 7.53 -6.32 ppm. The signal observed in the d = 9.90 ppm was attributed to the azomethine protons in the molecule 21 . 13 C-NMR spectra of the ligand was recorded in DMSO. Using 100MHZ and it showed a number of identification signals of ligand as shown in Table 5 17 , the signals assigned the aromatic carbon were shown in the range d = 102.19 -132.18ppm. The signal observed in the d 165.16ppm was due to azomethine carbon in the molecule and the signals observed in d 163. 25 ppm was attributed to carbon guanidine group 22 .

Molar conductivity
The measurements of Conductivity were completed at room temperature of 10 -3 M in DMF solvent to proven the charge order of metal complexes. The values of conductivity for the prepared metal complexes Co (II), Cu (II), Mn(II), Ni(II) and Cr(III) were found to be 82.1, 80.2, 89.5, 79.7 and 78.2 Ohm -1 cm 2 mol -1 respectively. So that, the suggestion for the complexes were electrolytes 24 due to the Chlorate ions outside the coordination sphere in solution and they were separate gradually in the DMF solvent. which is more convenient with the SP 3 geometry while Cr Complex computed 3.932 BM which is more convenient with the tetrahedral geometry 25 too.

dISCUSSION
The L ligand and its metal complexes of Cu(II), Co(II), Mn(II), Ni(II) and Cr(II) have been structurally proven by several techniques. The stoichiometry of metal ligand in all these complexes clarify that analytical data is 2:1. In DMF solvent appeared all these complexes are electrolytes. That ligand showed the spectral data deal as neutral and tetradentate coordinating through nitrogen atom of the azomethine and oxygen atoms of hydroxyl group of the 2-4dihydroxybenzaldehyde. Depending on all information that gotten from technique like molar conductance, magnetic and spectral data, lead to considerable opinion that complexes wer assigned to be in tetrahedral geometry (SP 3 ).