Synthesis and Characterization of Cu(II), Ni(II) and Co(II) Based Schiff Base Complexes

N-(3-Bromo-4-hydroxy-5-methoxybenzylidene)-4-Bromobenzenamine was synthesized. This was further used to synthesize Co(II), Ni(II) and Co(II) based metal complexes and characterized by FT-IR, Elemental analysis, ESI Mass and UV spectroscopy


INTRODUCTION
A large number of Schiff bases and their complexes have been studied for their interesting and importantproperties, e.g., their ability to reversibly bind oxygen [1], catalytic activity in hydrogenation of olefins [2] andtransfer of an amino group [3], photochromic properties [4], and complexing ability towards some toxic metals [5]. The high affinity for the chelation of the Schiff bases towards the transition metal ions is utilized in preparingtheir solid complexes. The condensation of >C=O group compound with varied primary amine or amino compound on elimination of water molecule forms a weakly basic compound known as an imine or an anil or an azomethine which is commonly known as Schiff base, named honor Schiff [6] who synthesized such compound. Extensive investigation in the field of Schiff bases, have been reported by Bayer [7].
In specially, Cu(II) complexes with diverse drugs have been the subject of a large number of research studies [23,24], presumably due to the biological role of Cu(II) and its synergetic activity with the drug [25]. The antifungal and antibacterial properties of a range of Cu(II) complexes have been evaluated against several pathogenic fungai and bacteria [26][27][28]. For many years it has been believed a trace of Cu(II) destroys the microbe, however, recent mechanisms becomes activated oxygen in the surface of metal Cu kills the microbe because Cu(II) activity is weak.

1. Materials
All the chemicals were purchased from Loba chemical Pvt. Ltd. and used without purification.

Method
Synthesis of N-(3-Bromo-4 hydroxy-5-methoxybenzylidene)-4-Bromobenzenamine: In R.B.F. 0.01 M of 3-bromo-4-hydroxy-5-methoxybenzalde was dissolved in 10 ml methanol and then 0.01 M 4-bromo aniline was added with stirring and 4-5 dropsof glacial acetic acid was added. Then reaction mixture was refluxed in water bath for 12 hours. Pour this reaction mixture in the crushed ice, Product is precipitated out. It was filtered and crystallized from methanol (Scheme 1).
Reaction Scheme 1

3. Synthesis of metal complexes
Mixture of metal chloride solution (0.01 mole) and Schiff base (0.02 mole) was dissolved in methanol and stirred at 350 °C for about 48 hours.After completion of the reaction mixture was allowed to stand at room temperature for one hour. Then the product was filtered and washed with little quantity of methanol (Scheme 2). 1 H NMR spectra were recorded on BRUCKER Av spectrophotometer (300MHz) using TMS as an internal reference. FT-IR spectra were recorded on SHIMADZU FT -IR 8400 spectrophotometer on KBr pellets. Mass spectra were recorded on GCMS QP-2010 gas Chromatograph SHIMADZU. UV -Visible spectra were recorded in DMSO Solution on a SHIMADZU UV mini -1240 Spectrophotometer. TLC was performed on silica gel-G using ethyl acetate: hexane solvent system.

RESULTS AND DISCUSSION
The ligands have reacting system containing N and O sosituated as to form heterocyclic ring with metal ion.
The absorption spectra of ligand in UV visible region show three bands at 215-235, 264-280 nm and 340-368 nm. These are attributed to n → π* and π→ π* transition. Cu complex is insoluble in water and difficultly soluble in alcohol' chloroform and carbon tetrachloride. Cu complex show all the three characteristics of the ligand system and two bands due to d-d transition of the metal ion. The position of the ligand bands are shifted which may be due to their interaction of the ligand with metal ion. Thus three spin allowed transition are expected. All are d-d transitions and hence would be Laporteforbidden. The band corresponding to 2 Eg ← 2 B1g transition would have overlapped with the strong charge transfer band of the spectra. Thus it indicates D 4h.
The magnetic moment of the Cu complex is 2.05 B.M. This value is greater than spin only value for unpaired electron (1.73 B.M.) The excess value is considered to be due to spin orbital coupling.
Ni complex is insoluble in water and difficultly soluble in alcohol. The absorption band at 540-580. It is fully filled up to a 1g orbital. The excitation of one of the a 1g electron to International Letters of Chemistry, Physics and Astronomy Vol. 31 b 1g orbital leads to 3 B 1g and 1 B 1g terms but the transition from to is spin forbidden and hence band at 640-685 nm is attributed to the transition. The other band at 540-580 nm is attributed to the extinction coefficient of these two bands are large in spite of the Laporte -forbidden. It is the because of the extensive mixing of the metal 'd' orbitals and the ligand orbitals.

CONCLUSION
In the present work, coordination chemistry of a Schiff base ligand obtained from the reaction of 3-bromo-4-hydroxy-5-methoxybenzaldehyde and 4-bromoaniline is decribed. The metal complexes of Cu, Co and Ni have been synthesized using the Schiff base ligand in good to moderate yield. The synthesized metal complex are characterized by spectral and nalytical data.