Spectral, Magnetic and Biological Studie on Some Bivalent 3d Metal Complexes of Hydrazine Derived Schiff-Base Ligands

Metal(II) complexes of hydrazine derived Schiff-base ligands of the type M(L)2Cl2 where M = Co, Cu, Ni and Zn and L = L1 and L2 have been prepared and characterised by molar conductance, magnetic moment, elemental analysis and electronic, IR, H-NMR and 13C spectral data.The different modes of chelation of the ligands and their comparative biological properties against different bacterial species are reported.


INTRODUCTION
In view of the promising roleS,2 of Schiff-bases as ligands in metal coordination chemistry, we have commenced a research program3-8 to study the ligational and biological behaviour of difterent Schiff-base ligands.The present work,with the same idea has been undertaken and extended to the hitherto less investigated Schiff-base ligands derived from hydrazines and their complexes with 3d metal ions.These studies might permit us to report a variety in coordination behaviour of hydrazines.
Many reportsg-12 on coordination properties of acyl and aroyl hydrazines have appeared.We have already reported3 pyrrolyl, thienyl and furanyl derived hydrazines and their 3d metal complexes and in continuation to the same, now, wish to report the synthesis,structural studies and biological behaviour of 3d metal ions such as Co, Cu, Ni & Zn on the title ligands L and L 2. All the chemicals used were of Analar Grade.Metal ions were used as their chloride salts.Conductance and magnetic measurements were made on a YSI model-32 conductivity bridge and Gouy balance, respectively.IR spectra were recorded on a Ro Hitachi spectrophotometer. H-NMR spectra of the ligands in DMSO-d were obtained on Ro Perkin-Elmer spectrometer.13C NMR spectra of the ligands were obtained on a Brucker 250 MHz instrument.Electronic spectra were studied in DMF on a Hitachi double-beam U-2000 model spectrophotometer using glass cells of cm thickness.Elemental analysis of C, H & N were determined on a Coleman automatic analyser.AII melting points were taken on a Gallenkamp melting point apparatus and are uncorrected.All the complexes were analysed for their metal contents employing standard literature procedures4 after decomposing the organic matter at first with a mixture of conc HNO3 and HCI and then with conc H2SO,.Chloride was estimated as AgCI and nitrogen as microanalytically. Antibacterial studies were carried out with the help of the Microbiology Laboratory, Department of Microbiology,Qaide Azam Medical College, Bahawalpur.These studies were done on wild pathogenic bacterial species collected from urine and blood samples of infected patients admitted in Bahawal Victoria Hospital, Bahawalpur. Preparation of the Ligands N-3-(Indolylmethylene) phenyl hydrazine (L). Indole-3-carboxaldehyde(0.4 g, 0.01 tool)in ethanol (15 mL) was added to an ethanolic solution (20 mL) of phenyl hydrazine (0.7 g, 0.01 mol).Then 2-3 drops of conc.H2SO, were added and mixture refluxed for lb. The reactant mixture on cooling gave a yellow solid product which was filtered, washed with ether and dried. It was crystallised in hot aqueous ethanol to give L (72 %). The same method was adopted using the same molar ratio of respective reagents for the preparation of L2 (75 %).

RESULTS AND DISCUSSION
The Schiff-base ligands were prepared by the same method reported earlier5-8.The structural determination of these ligands was done with the help of their spectral and analytical data. The IR spectra of the free ligands (Table 1)  stretching and similarly, the appearance of a new band at 1625 cmdue to az.omethine(-C -N) linkage provided a strong evidence for the formation of ligands L and L2.Also H-NMR and 3C spectral data (Table 1)  The comparative studies of the IR spectra of the ligands and their metal complexes indicated that the ligands are coordinated to the metal atom possibly in three ways a) The bands at 3215 and 3100 cm-1 attributed to(-NH2) and (-NH) modes in the spectra of the ligands suffer a negative shift indicating the involvement of this group.
b) The band in the spectra of the ligand at 1625 cmdue to the azomethine (-C N) linkage is also shifted towards lower frequency side by 5-10 cmrespectively, suggesting the ligand to be coordinated to the metal atom through azomethine nitrogen.
c) The new band appearing in the spectra of the metal (11) complexes and not observed in the spectra of ligands at 515-520 cm-assigned15 to M-N mode respectively indicated that the heteroatom X (Fig 2) is also coordinated to the metal(ll) ions. The above observations gave a conclusive evidence of the coordination between metal(ll) ions and the ligands possibly through NH or X, NH2 and C N (azomethine) groups. Zahid H. Chohan and Syed K.A. Sherazi
On the basis of the above observations,it isproposed that all the metal complexes show an octahedral geometry in which the two ligands behaving as tridentate accommodate themselves around the metal ion in such a way that a stable chelate ring is formed (Fig 2) attaininga stable configuration of a metal(ll) complex. The uncomplexed ligands in comparison to their metal complexes were tested for their antibacterial activity against bacterial species such as Staphylococcus aureus, Pseudomonas aeruginosa, K/ebsie//a pneumonae and Proteus vu/garus.The antibacterial activity was tested at concentration 30 Ig / 0.01 mL in DMF by a method deviced and reported by us elsewhere28-31. The results of these studies reproduced in table 3 show that the ligands and all their metal complexes are biologically active against one or more bacterial species. In comparison, the metal complexes have shown to be more antibacterial than the uncomplexed ligands.