SYNTHESIS, CHARACTERIZATION AND ANTIBACTERIAL STUDIES ON DIVALENT TRANSITION METAL COMPLEXES OF HYDRAZINE WITH ARYL SUBSTITUTED ACETIC ACIDS

Metal phenylacetate Sesquihydrazinate hydrates of the formula M(PhAc)2.1.5N2H4.H2O where M=Co,Ni or Cd and Metal phenoxyacetate Sesquihydrazinate hydrates M(PhOAc)2.1.5N2H4.H2O Where M=Co, Ni , Cd or Mn have been prepared and characterized by analytical, IR spectral and thermal studies. The composition of complexes have been determined by analytical studies. Infrared spectral data indicate that the bidentate bridging by hydrazine molecules and monodentate coordination by carboxylate ions to the cental metal ion. Thermogravimetry (TG) and differential thermal analyses (DTA) in air have been used to study the thermal behaviour of the complexes. The simultaneous TG-DTA curves of all the complexes in air resultedin the formation of respective metal or metal oxide as final residue. These complexes decompose exothermically either in single step or decompose through respective metal carboxylate intermediates. The antibacterial activity of the prepared complexes screened against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Proteus mirabilis.


INTRODUCTION
Hydrazine is a versatile ligand and forms a wide variety of complexes with various metal ions. The monodentate and bridging bidentate coordination of the hydrazine molecule on complexation has been well documented in the literature (Braibanti et al., 1968). The emerging interest in these hydrazine complexes is mainly due to their structure and thermal behaviour. Hydrazine carboxylates of the transition metal ions with variety of acids have been reported.
In this context, we present some new metal hydrazine complexes with aromatic carboxylic acids namely phenylacetic acid and phenoxyacetic acid.

Preparation of M(PhAc)2.1.5N2H4.H2O where M=Co,Ni or Cd
The Cobalt, Nickel and Cadmium complexes were prepared by the addition of an aqueous solution (50 ml) of hydrazine hydrate (0.2 ml, 0.004 m) and phenylacetic acid (0.5 g, 0.0036 m) to the corresponding aqueous solution (50 ml) of metal nitrate hydrates (Co(NO3)2.6H2O,0.5 g, 0.0017 m, Ni(NO3)2.6H2O,0.5 g, 0.0017 m, Cd(NO3)2.4H2O, 0.5 g, 0.0016 m). The mixture was stirred well to get a clear solution. This solution was concentrated on a water bath to 20ml and it was kept for complexation. After 15 minutes complex was formed. It was filtered and washed by using water, alcohol and diethyl ether and air dried.

Quantitative methods
The hydrazine content in the complexes was determined by titration using KIO3 as the titrant (Von Burg and Stout, 1991). The percentage of metals in the complexes was estimated by the standard methods given in the Vogel's textbook (Von Burg and Stout, 1991).

Infrared spectrum
The infrared spectrum of the solid precursor sample was recorded by the KBr disc technique using a Perkin Elmer 597/1650 spectrophotometer.

Thermal analysis
The simultaneous TG-DTA experiment was carried out in Shimadzu DT40, Stanton 781 and STA 1500 thermal analyzer. Thermal analysis was carried out in air at the heating rate of 10°C per minute using 5-10 mg of the sample. Platinum cups were used as sample holders and alumina as reference. The temperature range was ambient to 700°C.

Biological assay
The antibacterial activities of the prepared complexes were determined by the disc diffusion method. The bacteria were cultured in nutrient agar medium and used as inoculum for the study. The antibacterial activity of the synthesized compounds of 25μg, 50μg, 100μg and 200μg concentrations were tested against Staphylococcus aureus, Escherichia

PhOAc -Phenoxyacetate
These are in good agreement with proposed formulae of the complexes.

FT-IR spectral analysis
The hydrated derivatives displayed a broad band in the region 3625-3282 cm -1 due to O-H stretching shows the presence of water molecule. The absorption band in the region 3246-3224 cm -1 .This is due to the N-H stretching frequency of N2H4. The complexes show asymmetric and symmetric stretching frequencies of COOin the region 1610-156cm -1 and 1392-1338 cm -1 respectively. The Δγ(γasym-γsym) of COOin range >222 cm -1 confirms the monodendate coordination of carboxylate anion. In the complexes, the N-N stretching is seen in the range 983-943 cm -1 confirming the bridging bidentate coordination of hydrazine (Sivasankar and Govindrajan, 1996). The IR spectra of the prepared complexes are displayed in Fig. 1-8. Table 2. FT-IR spectral data of the prepared complexes.

Co(PhAc)2.1.5N2H4.H2O
This complex undergoes two step decomposition. The TG curve shows 14% mass loss in the temperature range 175-245 o C which coincides with the calculated mass loss for the formation of Co(PhAc)2 with loss of hydrazine and water molecule. The higher temperature decomposition indicates that coordinated water molecule. This intermediate further decomposes in the temperature range 245-500 o C to give CoO,as the final product. DTA shows exotherm corresponding to the above two stages at 220 and 440 o C, respectively. The TG-DTA pattern of this complex is given in Fig.9.

Cd(PhOAc)2.1.5N2H4.H2O
This DTA curves reveal three peaks corresponding to three step decomposition of the complex as shown by TG. The first endothermic peak at 140 o C is assigned to the loss of molecule of water. The second step corresponds to the decomposition of the intermediate, Cd(PhOAc)2.1.5N2H4 to yield 230 and 465 o C, respectively. The TG-DTA pattern of this complex is given in Fig. 11.   Fig. 11. Ni(PhAc)2.1.5N2H4.H2O

Coordination geometry
The analytical and physico chemical studies suggest that, in these complexes ,the hydrazine molecules are present as a bidentate bridging ligand. The phenylacetate and phenoxyacetate ions are seen to present as a monodentate ligand (Figs. 12 and 13) as evidented from IR spectra. From TG-DTA analysis we confirmed that water molecule is present as a coordinated one. The complexes are isolated only as a polycrystalline powders. Hence, without crystal structure, it is very difficult to predict the environment of the metal in the complexes. Sixcoordination has been tentatively proposed for all the complexes with octahedral stereochemistry. The insoluble nature of these complexes conforms to the polymeric structure.  The complexes of phenylacetic and phenoxyacetic acid have been screened to evaluate their antibacterial activities against (A) Staphylococcus aureus, (B) Escherichia coli, (C) Pseudomonas aeruginosa, (D) Proteus mirabilis, respectively at two different concentrations (Fig.  14). The radius of the zone of inhibition was measured in millimeter. Cefepimetazobactum were used as a standard control and is tabulated as follows. (9) -standard (-) -no activity From the result, it has been observed that there is a concentration dependent percentage inhibition in the tested compounds. The activities of the complexes have been compared with the activity of standard antibiotics (Cefepimetazobactum) and it has been found that all the complexes showed good activities but compound Mn(PhOAc)2 . l.5.N2H4.H2O has no activity against all the four microorganisms. The results suggest that the antibacterial activity of complexes prepared from both phenylacetic acid phenoxyacetic acid are almost same. This may be due to structural relaitivity between them. activity of the complexes against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Proteus mirabilis were also carried out.

CONCLUSION
The IR spectral data indicates that the binding of hydrazine to a metal ion is a bidentate fashion. Carboxylate ligands are monodentatively coordinated to the central metal ion. The broad peak around 3625-3282 cm -1 indicates the presence of water molecule. The prepared complexes undergo two or three step decomposition to form metal oxide as the final product. The higher temperature dehydration indicates that the presence of water molecule as coordinated one.