Synthesis of Schiff base Metal Complexes with Motivating Scavenging Potential Studies

Cite this article: Al-Azawi K, AL-Duhaidahawi DL, Al-Amiery A, Kadhum AAH. Synthesis of Schiff base Metal Complexes with Motivating Scavenging Potential Studies. Free Radicals and Antioxidants. 2019;9(1):1-4. ABSTRACT Objective: Schiff’s base complexes can be important substitutes for some antioxidant drugs because they have a carbon-nitrogen (N-C) double bond with the ability to push the electrons into the transition metal. Methods: A series of Schiff base metal complexes have been synthesized by the condensation of MCl2.nH2O (M = Co, Ni, Cu) with 1-(2hydroxybenzylideneamino) quinolin-2(1H)-one. Results: The Schiff base and it metal complexes have been characterized by various instrumental techniques like element chemical analysis, molar conductance, magnetic susceptibility measurements and spectral studies. The investigated complexes were subjected to antioxidant studies. The investigated complexes showed an excellent activities as antioxidant as compared to the parent Schiff base and standard compound. Conclusion: The data showed that transition metal complexes have significant improved antioxidant activity than Schiff base.


INTRODUCTION
Schiff bases have a broad applications in various areas like medical chemistry, organic and inorganic chemistry.The medicinal utilization and applications Schiff bases and their metal complexes are of growing clinical and commercial significance.Schiff bases were selected significance in medical and pharmacological domain due to an expansive range of biological activities such as anti-inflammatory, 1,2 analgesic, 3,4 antimicrobial, 5 antispasmodic, 6 tuberculosis, 7 anticancer, 8 antioxidants, 9,10 anthelmintic. 11,12The antioxidant performance of N-amino quinoline-2-one metal complexes versus, hydrogen peroxide radicals was not described.In our potential on behalf of the development of complexes based therapeutic agents and according to the curative, employment of us and as the duration of previous investigations, [13][14][15][16][17][18][19][20] herein, the spectroscopic characterizations to the prepared complexes of N-aminoquinoline-2-one with 2-hydroxybenzaldehyde was reported.The metal complexes were evaluated for their antioxidant performance.Firstly, we utilized 1-(2hydroxybenzylideneamino) quinolin-2(1H)-one as a ligand (Figure 1) for the preparation of complexes (Figure 2).

MATERIALS AND METHODS
This study was done in the applied science department at the university of technology in Iraq.All chemical used were of reagent grade (supplied by either Merck or Fluka) and used as supplied.Melting points were determined on SMP40 melting point apparatus and were uncorrected.The IR spectra of the compounds were recorded on a shimadzu FT-IR-8300 spectrometer as KBr and CsI disks.The UV spectra were performed on Cintra5-Gbes scientific equipment.Magnetic susceptibility measurement for complexes were obtained at room temperature using (Magnetic susceptibility Balance Model MSB-MKI).Flame atomic absorption of elemental analyzer, shimadzu AA-670 was used for metal determination.Elemental micro analysis, was carried out using C.H.N elemental analyzer model 5500-Carlo Erba instrument.

Synthesis of Schiff base
A mixture of N-aminoquinolone (0.8 g, 0.005 mol) and the (0.005 mol) 2-hydroxybenzaldehyde, was refluxed in absolute ethanol 25 ml for 6-8 h.The reaction mixture was cooled and the product obtained was recrystallized from ethanol, the melting point was 240.filtration, then washed with ethanol and dried under vacuum for 4 h.All these complexes were analyzed by using different available techniques, the physical proportion of 1-((2-hydroxybenzylidene)amino)quinolin-2(1H)-one and its metal complexes are listed in Table 1.

Synthesis of complexes
Study of complexes formation in solution: Complexes of ligands with metal ions were studied in solution using ethanol (or DMF) as solvents, in order to determine (M:L) ratio in the complex following molar ratio method (Sulekh et al. 2007). 21A series of solution were prepared having a constant concentration 10G3 M of metal ion and ligand.The [M/L] ratio was determined from relationship between absorption of the absorbed light and mole ratio of [M/L].The results of complexes formation in ethanol were listed in Table 1.

Antioxidant activity H 2 O 2 scavenging activity assay
The scavenging activity of 1-((2-hydroxybenzylidene)amino)quinolin-2(1H)-one metal complexes, Compound 1, Compound 2 and Compound 3 has been estimated based on Fenton reaction. 22Different strengths (250, 500 and 1000 µ/mL) of Compound 1, Compound 2 and Compound 3 Complexes, 0.1mL of 7.5 mM, O-phenanthroline, 0.5 ml of 0.2 M phosphate buffer (pH 6.6), 0.1 mL of 7.5 mM ferrous sulfate and 0.1 mL of H 2 O 2 (0.1%) were combined and diluted up to 3 mL with DW (distilled water).Incubation at 30 o C for 30 min and the absorbance was evaluated at 510 nm.The hydroxyl radical scavenging activity of complexes and ascorbic acid were estimated using Equation 1.
where Ao is control absorbance and A1 is the sample absorbance.

Statistical analysis
The data obtained were displayed as the means ± SD, with an analytical significance of the variations, was defined using ANOVA with the SPSS software program.Values were demonstrated meaningful at P< 0.05.The significances are displayed as the means ± SD (n= 3).

Results
Removing free radicals is the agent of cancer prevention.3][24] The hydrogen radical contribution will remove odd electrons which responsible for reactivity of radical. 25,26In an earlier decade, free radicals are the most exciting subject, specialists due to influences in biological systems.It had been shown that radicals assume a significant role in aging and specific diseases. 27rget complexes were tested for scavenging activity using hydrogen peroxide assay.Complexes demonstrate great scavenging activity (Figure 3).

Discussion
Figure 3 demonstrate that the three complexes have the abilities to be perfect scavengers H 2 O 2 .At a lower concentration of 250 μg/mL we detected a concentration dependent reduction in H 2 O 2 activity.Good suppression activities have been displayed for Ni-complex and Co-complex (44.38 ± 1.00 and 42.11 ± 1.50).On the hand, Cu-complex with a high concentration has been shown at 1000 µ/mL as in Figure 3.The perfect scavenging activity was presented by Cu-complex (76.93 ± 1.50).
Vitamin C has been utilized as control with an inhibition percentage of 73.85 ± 1.00.
The mechanism for the action of metal complexes as antioxidants, as displayed in Figure 4, depend on the azomethine or imine (-C=N) hydrogen's atoms, which may under the impact of resonance and inductive forces in addition to metal effect.The resonance influence of the azomethine hydrogen's fragments enables the liberation of hydrogen, whereas the inductive influence drives the electrons to an azomethine-free, causing stability of the complexes.

Figure 2 :
Figure 2: The chemical structures of metal complexes.

Figure 3 :
Figure 3: The antioxidant activities of tested complexes and control.

Figure 4 :
Figure 4: The postulated mechanism for using of metal complexes as antioxidants.