PHYSICO-CHEMICAL STUDY OF FUROSEMIDE SALICYLDEHYDE SCHIFF BASE COMPLEX WITH Hg ( II ) . AND Ag ( I ) METAL IONS

In the present paper, we describe the synthesis and characterization of metal complexes of Hg (II) and Ag (I) using Schiff base ligand salicyldehydefurosemide. Furosemide (FSD) is a diuretic drug and it is used to increase the rate of urination through kidneys. Analytical data and stoichiometry suggest ligand metal ratio as 2:1 for Hg complex and 1 : 1 for Ag complex. The structure assigned to the complexes, synthesized via Schiff base formation is supported by infra-red spectral studies.


INTRODUCTION
Schiff base and their metal have been the subject of intensive research due to their novel structural features and their industrial and biological importance and hence have well been studied in past [1][2][3][4][5][6][7] .Survey of Literature reveals some studies on pharmacological activities of metal complexes of Schiff base.We report herein the synthesis and characterization of some bipositive 3d metal ion chelats of Furosemide-Schiff base.In continuation of our previous work on metal complexes of established drugs [8][9][10][11] the synthesis and structural studies of Furosemide-Hg and Furosemide-Ag complexes are described below.

EXPERIMENTAL
Pure sample of furosemide (FSD) molecular formula C12H11N2O5S, molecular wt.330.75, was obtained from Geno Pharmaceuticals Private Limited, Goa.Metal salts were of Qualigen chemicals.Solvents used were methyl alcohol and acetone which were of analytical grade.
Equimolar solutions of pure drug (0.01 M) and salicyldehyde (0.01 M) were taken in methanol-water mixture (50:50 ratio).Both the solutions were mixed and refluxed for three hours.The reaction mixture was kept overnight.Light yellow crystals of furosemide-Schiff base were formed in the reaction mixture, which was washed with 50:50 mixture of methanol: water, filtered, dried and weighed.Melting point was recorded.

Ligand-Metal ratio and stoichiometry :
To confirm the ligand metal ratio, conductometric titrations using monovariation method were carried out on Systronics conductometer and dip type electrode.Titrations were carried out at 21°C and 20°C respectively for HgCl2 and AgNO3.0.01M solution of furosemide-Schiff base was prepared in 60 : 40 mixtures of acetone and water, diluted to 200 ml with same solvent.This Schiff base solution was titrated against 0.02M metal solutions using monovariation method.3] The stability constants and free energy changes were calculated.

Synthesis of complexes :
For the synthesis of complexes of furosemide-Hg and furosemide-Ag, 0.006 M ligand solution was prepared in 60:40 mixture of acetone water and refluxed for four hours with 0.003M solution of HgCl2 and 0.006M solution of AgNO3.The refluxed solutions were kept for two days.Solid crystalline compounds appeared in the solutions.Complexes of furosemide-Hg and furosemide-Ag were washed with 60:40 mixture of acetone: water, filtered, dried and weighed.Melting points were recorded.

RESULTS AND DISCUSSION
Conductometric studies monovariation method and Job's method of continuous variation modified by Turner and Anderson indicate the formation of 2:1 (L: M) complex of Schiff base of furosemide with Hg and formation of 1:1 (L: M) complex of Schiff base of furosemide with Ag lons.
Analytical data of these complexes are in agreement with the composition (C19H14C1N2O6S)2 Hg and (C19H14C1N2O6S) Ag.
Proposed structure was further supported by IR spectral data [14][15][16][17][18] .Bands observed in the IR spectra of FSD-SA-Hg and FSD-SA-Ag at 1172 cm -1 and 1163 cm -1 are characteristic of SO2-N group.Absorption band at 1411 cm -1 and 1420cm -1 shows the presence of chelate ring.Frequency at 664 cm -1 and 680cm -1 is characteristics of M-O linkage.Bands at 582cm -1 and 579 cm -1 are because of M-N linkage.Frequencies at 789 cm -1 and 880 cm -1 indicate the S-N linkage.
The disappearance of frequencies of phenolic -OH in complex supports its involvement in complexation.
All these evidences support the proposed structure of the prepared complexes.

Table 1 .
Synthesis and Physico-chemical Characteristics of Complexes

Table 2 .
Analytical data of Complexes C:\Aftab1.PM5\33 Structure of Furosemide Schiff base silver complex Structure of Furosemide Schiff base (FSD-SB)