Synthesis , Characterization , Antimicrobial New 2,2'-[(1E,2E)-ethane-1,2-diylidenedi(2E)hydrazin-1-yl-2-ylidene]bis (5-methyl-1,3,4-oxadiazole) and their transition metal complexes

        Transition metal complexes of new legend 2,2'-[(1E,2E)-ethane-1,2-diylidenedi(2E) hydrazin-1-yl-2-ylidene] bis (5-methyl-1,3,4-oxadiazole) with some transition metal ion such as Cr3, Co3+, Ni2+  were synthesis ,characterization by magnetic susceptibility measurements, conductance, elemental analyses, 1HNMR, IR, and mass  spectra. The electrolytic behavior were confirmed from their conductance. data spectral study of transition metal complexes suggest octahedral geometry for  Cr3+, Co3+ ion , square planer geometry for Ni2+.The effective magnetic moment of cobalt complex is 0.91 that mean the Co2+ oxidation to Co3+. The complexes and ligand were tested against two types of bacteria (Staphylococcus aureus, Escherichia coli) all prepared complexes showed good biological activity. 
 


Measurements
Elemental microanalysis CHN were carried out on a Thermofinigan flash analyzer, the FTIR spectra in the range (200-4000) cm -1 were recorded as CsI discs using a Shimadzu FTIR spectrophotometer, molar conductance measurements were made in anhydrous DMSO at 25 o C using Inolabcond 720.The 1 H NMR spectra were recorded on a Mercury-300BB NMR 300 spectrometer, relative to the internal standard tetramethylsilane (TMS), DOSO-d6 used as solvent. Melting points were determined in open capillary tubes using an electro thermal melting point /SMP3 apparatus. Mass spectra were recorded in the range (0-800) m/e on a 5973 network mass selective detector. Balance Magnetic susceptibility were recorded inModel MSB-MKI.

Results & Discussion
The physical properties of ligand and its complexes are presented in table 1. Elemental microanalysis CHN shown in table 2.

Infra-Red Spectroscopy
Infrared spectroscopy is one of the most commonly used tools for the detection of functional groups in pure compounds and complexes. The spectra for L shows a characteristic stretching absorption bands at (3452, 3421, 2934, 1523, 1627, 1475,1365, 1025,) cm -1 assigned to υ(N-H) ,ʋ(N-H) , ʋ(N-H) , ʋ(C=N), ʋ(C=N) (Field et al. 2012), symmetrical and Asymmetrical C-O-C stretching respectively (Huang et al. 2003) . The C=N and C-O-C are important to predict the bonding mode of the ligand ,these bands shift higher wavenumber in the spectra of complexes compare with ligand, observed changes are the evidences of complexation had happened . The IR data of the ligand and complexes are shown in Table (3) and figure (8), (9) and (10) . The Table lists the stretching frequency (υ) for some of the characteristics groups exhibited by the ligand and complexes.

Mass spectra 3.3.
The mass spectra of the ligand and its transition metal complex were recorded at room temperature ,The mass spectrum of the ligand shows a molecular ion peak [M0] at m/z =250 . The fragmentation pathways of ligand give the peaks at different mass numbers at m/z = (218,167, 136, 125, 98 and 83) Respectively. The intensity of these peaks reflects the stability and abundance of the ions . as shown in Figure (12-17) and (Scheme 2). The complex [Cr(L) Cl 2 ]Cl showed a molecular ion peak at m/z [M0]= (659) which is equivalent to molecular mass of the complex. This complex shows another a fragmentation peak with loss of chlorine atom at Table 1. conductance, physical properties data of the ligand and its complexes .   (345)and (309). the mass spectra of the complexes shown in figure(12), (13), (14),(15) .

Magnetic susptibility
The value of the effective magnetic moment of the complexes is tabulated in table 1 by using Balance Magnetic susceptibility. The Results are shown in the table above all the complexes given low value of effective magnetic moment. Chromium ion Cr 3+ shows the highest value (4.28) M.B due to the presence of three single electrons compare the low value (0.91) M.B for Co 3+ ion and (0.42) M.B for nickel ion Ni 2+ because there is no single electron for cobalt ion Co 3+ and nickel ion Ni 2+ . We conclude that the ligand works as strong ligand (strong field).

Biological Study
The ligand and its transition metal complexes were evaluated for antimicrobial activity against gram positive bacteria such as Staphylococcus aureus and gram negative bacteria Escherichia coli, by using agar well diffusion method. All the microbial cultures were adjusted to 0.5 McFarland standard, dimethyl sulphoxide (DMSO) were used to prepared all the test solution. The area of inhibition was measured in millimeter. nutrient agar used as culture medium (Balouiri et al. 2016) , the values of the investigated compounds are tabulated in Table.4.The observe result showed transition metal complexes enhanced antimicrobial activity than that of free ligand. This result can be due to the greater lipophilic nature of the complexes and favors its permeation through the lipoid layers of the bacterial membranes. The activity of transition metal complexes can be expound on the basis of Overton's concept and Chelation theory (Chen et al. 2007).