Synthesis, Characterization and Biological Activity of Schiff Bases Chelates with Mn(II),Co(II),Ni (II),Cu(II) and Hg(II)

In this paper, some series of new complexes of Mn(II), Co(II), Ni (II) Cu(II) and Hg(II) are prepared from the Schiff bases (L 1 ,L 2 ). (L 1 ) derived from 4-aminoantipyrine and O-phenylene dia mine then (L 2 ) derived from (L 1 ) and 2-benzoyl benzoic acid. Structural features are obtained from their elemental microanalyses, molar conductance, IR, UV–Vis , 1 H, 13 CNMR spectra and magnetic susceptibility. The magnetic susceptibility and UV–Vis, IR spectral data of the ligand (L 1 ) complexes get square–planar and tetrahedral geometries and the complexes oflig and (L 2 ) get an octahedral geometry. Antimicrobial examinations show good results in the sharing complexes.

Now there are new studies attracting the attention of biochemists around new types of Schiff bases derivative from 4-aminoantipyrineand its complexes, generally because of their use in the assortment of applications in analytical biological, pharmacological, clinical areas and especially chemotherapeutic applications [1][2][3]. The precedent literatureex plains increasing activity for organic compounds used drugs when they are treated as metal complexes [4][5][6]. In the 1980s some investigations show that the interaction of little molecules with DNA are very necessary for the styling of new kinds of molecules such as pharmaceutical [7] and their transition metal complexes which have chemical nuclease activity; it is studying the technicality of DNA with transition metal complexes and the interaction model [8]. The reconnoitring of metal complexes and their application in antineoplastic, bioengineering and molecular biology medication have become hotspots in recent years [9]. 4aminoantipyrine ligand has become a flexible system by condensation with a set of reagents such as carbazides, aldehydes, thiosemicarbazides and ketones etc [10]. This paper reports synthesis and characterization of new Schiff bases ligands derived from 4-

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aminoantipyrine and their complexes with Mn(II), Co(II), Ni (II) Cu(II) and Hg(II). Chemicals 4-aminoantipyrine,O-Phenylen ediamine and 2-benzoyl benzoic acid and several metal(II) chlorides are Merck compounds .Glacial acetic acid reagent and trade solvents are distilled and they are used for the synthesis of all compounds.

Instrumentation
Electronic spectra are recorded using UV-Vis. spectrophotometer type CECIL, England, by using quartz cell has path length (1cm) in range

Biological Activity
We studied effects of biological screening for the compounds by testing in vitro against the bacteria: (Escherichia coli), (Staphylococcus aureus), (Bacillus subtilis) and (Pseudomonas aeruginosa) by the welldiffusion method at 25°C [10]. The well is filled with the test solution (10 -3 M) is prepared by dissolving the compounds in DMSO using a micropipette and the plate is incubated for 24hs. Using agar nutrient as the medium inoculated with microorganisms. During this time, the test solution spread and the evolution of the inoculated bacteria are affected.

FT-IR Spectra
The value of the IR spectra of two ligands and their complexes are listed in Table (2). The bands in spectra of the ligands and complexes are compared and considered. The IR spectra of ligand (L 1 ) displays a strong peak at 1622 cm -1 refers to ν(C=N) azo methane group. This peak shifts to lower energy region by (13-9) cm -1 in the complexes [11]. It suggests bonding through (C=N) nitrogen. The sharp peaks around 3427 and 3342 cm -1 in the spectra of (L 1 ) has been assigned to amine groups. In the complexes Table (3) the IR spectra show characteristic peaks in the region 3390-3360 and 3286 -3257 cm -1 which are lower in comparison with free NH 2 . Hence, it can be concluded that the nitrogen atoms of the amino groups are involved in metal coordination [12]. In all complexes, new band in there gion (565-545) cm -1 are due to the formation of ν(M-N) band. The IR spectrum of Schiff base(L 2 ) shows two strong bands at 1647 and 1624 cm -1 referring to ν(C=N) groups. In IR spectra of metal complexes; they shift down (7-36 cm -1 ) due to chelating coordination of the (C=N) nitrogen's to the central metal ion. The appearance of broad peak at 3446 cm -1 in the ligand (L 2 ) has been given to ν(OH) carboxylic group. In the complexes spectra this band disappeared, supporting the idea that the ligand chelated during deprotonated oxygen of (COOH) [13]. The υ asym. (COO -) and υ sym. (COO -) stretching vibrations of the (carboxylate O) are observed at (1436,1319) cm -1 for the free ligand (L 2 ), these stretching vibrations are shifted to higher or lower frequencies at (1450-1471) cm -1 and (1327-1392) cm -1 for all the complexes, (Δυ asym. -Δυ sym. )= (123-79) cm -1 , supporting the notion that the ligand coordinate during deprotonated O of carboxylate [14].In all complexes, new peaks in range (565-545) cm -1 and (486-447) cm -1 referred to the fashioning of ν(M-N) and ν(M-O) bands respectively [15]. NMR Spectra 1 HNMR spectrum of (L 1 ) in DMSOd 6 Figure( [15,16,7].The 13 CNMR spectrum of L 1 in DMSO-d 6 Figure( [16,9].The 13 C NMR spectrum of L 2 in DMSO-d 6 Figure( Table(4b) solution shows the signals at: (9.13 for =C-CH 3 group);( 34.70 for N-CH 3 group); (40.59 for DMSO); ( 110.18 for =C-N); (123.90~135.89) to 4 benzene rings) and( 140.48 for C=C in antipyrine ).The peak observed at 167.17 is due to the acidic COOH group present in the 2benzoyle benzoic acid. The peak observed at (164.89) was attributable to the C=N imine group [15,10].

Electronic Spectra
The (UV-Vis) spectrum for the (L 1 ), exhibits two high intense absorption peaks at (243 nm) and (289 nm), assigned to (π→π*) transition respectively [17], Table (5). The (UV-Vis) spectrum of [Co(L 1 )] Cl 2 complexexhibits three peaks, the first high broad peak at (261 nm) is due to the (L.F), while the second weak peak at (347nm) is due to the (C.T). The third peak at (467 nm) is assigned to 4 A 2 (F) → 4 T 1 (F) transition and magnetic moment µ eff = 2.41 B.M at room temperature, the low value of the magnetic moments suggest low spin [12,18] a coordination number of four for the central Co (II) ion and obtaining a square planar geometry.[Cu(L 1 )]Cl 2 complex exhibits three peaks , the first high broad peak at (251 nm) is due to the L.F , while the second band at (357 nm) is due to the (C.T) .The third weak peaks at (633 nm), which assigned to 2 T 2 → 2 E, transition. Cu (II) complex shows a value of µ eff =1.73 μ B . The observed magnetic moments of Cu (II) showing 1 unpaired electron with paramagnetic kind and propos a square plane geometry in terms of Jahn-Teller effect [13].[Ni(L 1 )]Cl 2 complex, exhibits four peaks, the first high peak at (271nm) is due to the ligand field, while the second middle broad peak at (354 nm) is due to (C.T). The third and fourth weak peaks at (514nm) and at (630nm) can be assigned to the 1 A 1 g→ 1 A 2 g ( 2 ) and 1 A 1 g→ 1 B 1 g ( 1 ) transitions respectively. Magnetic susceptibility of Ni(II) complex diamagnetic, a coordination number of four for the central Ni(II) ion and attaining square planar geometry [14].
[Mn(L 1 )]Cl 2 complex, exhibits three peaks, the first high band at (258 nm)is due to (L.F) and the second peak at (304 nm) is due to the (C.T) transition, the three weak peak at (514 nm) can be assigned to the 6 A 1 → 4 T 1 ( 3 ), transition. Magnetic moment µ eff = 4.58 B.M at room temperature, this low value the magnetic moments suggest high spin [15] a coordination number of four for the central manganese (II) ion and attaining a tetrahedral geometry.
[Hg(L 1 )]Cl 2 complex does not appear any band in the visible region, shows apeak at (269nm) is due to (L.F) absorption, and therefore the bands appear at (310and 385) nm in the spectrum of the complex could be attributed to the (C.T) transition. Magnetic susceptibility measurements for Hg (II) (d 10 ) show diamagnetic as perspective from their electronic arranging [16]. The (UV-Vis) spectrum for the (L 2 ), exhibits two small absorption peaks at (264nm) and, and high intense absorption peak at ((297 nm) assigned to (π→ π*)transition respectively [17].[Co(L 2 )]complex, exhibits three peaks, the first high intense peak at (277nm) is due to the (L.F), while the second peak at(365nm) is due to the (C.T).The third weak peak at  1 = (410nm) assigned to 4 T 1g(F) → 4 T 1 g (P) .The room temperature magnetic moment (µ eff =5.42B.M) corresponded to a high spin octahedral symmetry [12,17].[Cu(L 2 )] complex, exhibits three peaks, the first and second high intense peaks at (272 nm) and(323 nm) are due to the (L.F) and (C.T) transitions. The third and fourth weak peaks at (417nm) and (937nm)are assigned to ( 2 B 1 g→ 2 B 2 g) and ( 2 B 1 g → 2 A 1 g) transitions.
[Ni(L 2 )]complex, exhibits five peaks , the first and second high intense peak at (276 nm) and (356 nm)is due to the (L.F), while the third peak at (408 nm). The fourth and fifth peaks at (734 nm) and (887 nm) which assigned to ( 3 A 2 g (F) → 3 T 1 g (F) (ν 2 )) (d-d), and ( 3 A 2 g (F) → 3 T 2 g (F) (ν 1 )) (d-d), transitions, respectively in an octahedral geometry. The complex exhibit a value of µ eff = 2.82 B.M, which suggests an octahedral geometry around the central Ni ion [19]. [Mn(L 2 )]complex, exhibits four peaks, the first and second high peaks at (275nm) and (331nm) are due to (L.F) and (C.T)transition. The fourth-week peak at (396nm) and (957 nm) can be assigned to the 6 A 1 g (F) → 4 T 2 g (G) ( 3 ) and 6 A 1 g (F) → 4 T 2 g (G) ( 2 )transitions. Magnetic moment µ eff = 4.72 B.M at room temperature, this low data of the magnetic moments suggest high spin [20] a coordination number of 6 for the central manganese (II) ion and attaining [an octahedral geometry]. [Hg(L 2 )] complex exhibits two high peak at (212 nm) is due to the (L.F), while the second peak at (350 nm) is due to the, in an octahedral geometry. There is no ligand field stabilisation activtiy Hg (II) ions because of its completed (d 10 ) shell. This metal ion is diamagnetic and does not possess any d-d transition [21]  Antibacterial Activities: Tetradent and hexadentate Schiff base ligands (L 1 ,L 2 ) and the Mn(II),Cu(II), Ni(II),Co(II), and Hg(II) complexes showed biological activities against the four types of bacterial Figure (6&7), Table (6). On the comparing the antimicrobial activities of the Schiff base ligands and their complexes with those of normal bacteria, it was shown that the complexes had reasonable activity as compared to the normal but all the metal complexes were larger active than their free ligands. The maximum inhibition zone of the metal complexes than the free ligand can be expounded based on the chelation theory and the overtone concept. The overlap of the ligand orbital and the partial sharing of the positive charge of the metal ion with given groups are on account of reduced the polarity of the metal ion in upon chelation [22]. Furthermore, this enhances the blocking of the metal binding sites and the penetration of the complexes into lipid membranes in the enzymes of bacteriathat rises the delocalization of the π-electrons above the full chelating ring [23].

Conclusion:
A tetradentate Schiff base ligand (L 1 ) formed from the condensation of 4aminopridine and O-phenylenediamine and a hexadentate Schiff base ligand (L 2 ) formed from the condensation of (L 1 ) and 2-benzoyl benzoic acid are synthesised and characterised. The metal complexes with Ni (II) , Hg (II) ,Co (II) , Cu (II) and Mn (II) ions with the ligands(L 1 )and(L 2 ) are synthesised and characterised . The bonding of the ligand in the metal complexes and the thorough geometry has been concluded on the basis of various spectroscopic mechanics. The relative in vitro antimicrobial results suggest that all complexes display a significant antimicrobial activity as compared to the ligand, L 1 , L 2 and their Ni (II) , Hg (II) ,Co (II) ,Mn (II)