Research Journal of Chemical Sciences ______________________________________________ ISSN 2231-606X Vol. 4(2), 1-6, February (2014) Res. J. Chem. Sci. International Science Congress Association 1 Spectrophotometric Method for determination of Copper (II) using p-Chlorobenzaldehyde -4-(2’-carboxy-5-sulphophenyl)-3-thiosemicarbazone [p-CBCST] Patel N.C.* andBhavesh A. Patel Department of Chemistry, SIR P. T. Sarvajanik College of Science, Surat-395009, INDIAAvailable online at: www.isca.in, www.isca.me Received 3rd April 2013, revised 25th January 2014, accepted 7th February 2014Abstract p-Chlorobenzaldehyde-4-(2’-carboxy-5’-sulphophenyl)-3-thiosemicarbazone [p-CBCST] is spectrophotometric reagent for copper (II) in DMF. Reaction between metal ion and p- Chlorobenzaldehyde -4-(2’-carboxy-5’-sulphophenyl)-3-thiosemicarbazone [p-CBCST] forming a pale yellow colored complex in the pH range 3.0-4.5. The complex shows maximum absorption at 325 nm. The molar absorptivity found to be 5.137×103 lit. mol.-1 cm.-1. The complexes have been characterized on the basis of elemental analysis, UV, IR, NMR spectra. p-CBCST is found to be a selective and strong chelating agent for copper. The 1:2 metal:ligand ratio of complex found from the mole ratio and the slope ratio method and the Job’s method of continuous variation. The stability constant of the complex found to be 1.184 × 1012. Keywords: - Chlorobenzaldehyde, thiosemicarbazone, p-CBCST. Introduction Thiosemicarbazone compounds give antifungal and antibacterial activity with different transition metal ions. Thiosemicarbazone are known as analytical reagents1-7. Thiosemi-carbazones are also found to have biological activity. Thiosemicarbazone9-12and its metal complexes are known for its biological application and the great medicinal value including antibacterial, antifungal, antimalarial, antitumor and antiviral activity12-19. Patric Raymond P20 and et al studied the role of binary complex for its physiological activity of substances in storage and transport. Copper and nickel metal react directly with thiosemicarbazide in organic solvents to get corresponding metal complexes and the resultant complexe has been successfully applied in the determination of copper content in brass and bronze powder21, 22. In the view of these finding, we report the use of p- chlorobenzaldehyde -4-(2’-carboxy-5’-sulphophenyl)-3-thiosemicarbazone23 (p-CBCST) as a spectrophotometric reagent for copper (II). Material and Methods All the reagents used were of AR grade and were used without further purification. Salts were obtained from BDH. The reagent p- Chlorobenzaldehyde -4-(2’-carboxy-5’-sulphophenyl)-3-thiosemicarbazone (p-CBCST) [M.P. 198ºC] was prepared by condensation of p-chlorobenzaldehyde with 4-(2’-Carboxy-5’-sulphophenyl)-3-thiosemicarbazide by using the reported procedures24. 2.17 gm (0.01 mole) 5-sulphoanthranilic acid, 30 ml ethanol and 20 ml ammonium hydroxide were mixed and cooled below 20ºC. 8 ml carbon disulphide was then added with continuous stirring for 15 minutes. It was then allowed to stand for 1 hr. then 4 ml of ClCHCOONa and 14 ml of 50 % hydrazine hydrate were added and the bulk was reduced to half by heating. It was then allowed to stand overnight. The product was crystallized from DMF and water, yield 75 %, M.P. 169ºC. The thiosemicarbazone ligand was prepared from the equimolecular quantity of aldehyde and thiosemicarbazide dissolved in 50 mL of ethanol. The mixture was heated at reflux temperature for 2 hr.25and allowed to stand for overnight and will get corresponding thiosemicarbazone. The product was crystallized from DMF-water, light yellow color crystals were obtained [M.P. 198ºC]. The reagent p-CBCST is insoluble in common organic solvent but soluble in DMF, DMSO, and NMP. The structure of Cu- p-CBCST is presented below. p- Chlorobenzaldehyde -4-(2’-carboxy-5’-sulphophenyl)-3-thiosemicarbazone [p-CBCST]: Light yellow crystals; m.p. 198ºC; yield 80 %; IR (KBr, cm-1): 1578 (C-N ), 1089 (C=S), 1275 (N-N), 1622 (C=O) , NMR (400.1 MHz, CHCl): 9.97 (s, -OH or -NH), 2.35 (s, 3H, -H), 7.4-7.8 (m, 7H,Ar-H), 9.45 (s, 1H, -NH); Anal. Calcd for: C1512Cl (413.5); Found (C, 43.45; H, 2.79; O, 19.44; N, 10.06; S, 15.26; Cl, 8.32 %); requires (C, 43.53; H, 2.90; O, 19.34; N, 10.15; S, 15.47, Cl, 8.58 %). Synthesis of Cu (II) Complex:A solution of copper sulphate (0.005 mol) of CuSO4. 5HO in ethanol (40 mL) was added to a solution of p-CBCST (0.01 mol) in ethanol (40 mL). The Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 4(2), 1-6, February (2014) Res. J. Chem. Sci. International Science Congress Association 2 mixture was refluxed on water bath for about two hrs. The precipitated solid was filtered, washed with ethanol and dried under vacuum. Cu (II) complex of p- Chlorobenzaldehyde -4-(2’-carboxy-5’-sulphophenyl)-3-thiosemicarbazone [Cu (p-CBCST)]: Pale yellow color; yield 82 %; IR (KBr, cm-1): 1436 (C-N), 1089 (C=S), 1275 (N-N), 1606 (C=O), Anal. Calcd for: 302210ClCu (888.546); Found (C, 40.33; H, 2.45; O, 17.98; N, 9.51; S, 13.97; Cl, 7.93%); requires (C, 40.51; H, 2.47; O, 18.006; N, 9.45; S, 14.40; Cl, 7.99 %). Results and Discussion p- Chlorobenzaldehyde -4-(2’-carboxy-5’-sulphophenyl)-3-thiosemicarbazone with copper gave pale yellow color in acidic pH. The pH studies showed that the absorbance was maximum in a solution of pH 4.0. The studies relating to the effect of Cu (II) showed linear relationship between metal ion concentration and absorbance in the range 24.88 - 34.21 ppm. Table 2 describes spectrophotometric data of Cu (II) p-CBCST. The stoichiometry of the Cu (II) - p-CBCST complex was determined by two methods namely, Job`s method26 continuous variation and molar ratio method27. The ratio of 1:2 (metal: ligand) complex with p- Chlorobenzaldehyde -4-(2’-carboxy-5’-sulphophenyl)-3-thiosemicarbazone formed a stable pale yellow Cu (II) complex. The stability constant of the complex was found to be 1.184 × 1012 as described in table 3. A Shimadzu UV-visible spectrophotometer (Model UV-160A) equipped with 1-cm matched quartz cells was used for absorbance measurements. A EUTECH Li-127 digital pH meter was used for pH measurements. Melting points of the synthesized compounds were determined in open-glass capillary on Stuart SMP10 melting point apparatus and are uncorrected. The purity of the compounds was checked by thin layer chromatography (TLC). Silica gel plates (Kieselgel 0.25 mm, 60G F254), were used for TLC and the spots were visualized by iodine vapors / ultraviolet light as visualizing agents. IR spectra of the ligand and complex were recorded using KBr pellets on Shimadzu – Japan 8400 FTIR. IR bands28,29for the ligand and complex are presented in table 4. NMR spectra were recorded on “Varian 400” using DMSO. Table 5 describes results for Cu (II) p-CBCST having ratio of Metal: Ligand, 1:2. Analytical Application: Determination of Copper in Brass: Brass alloy sample was brought into solution as described in the standard procedure by using Conc. HNO and Conc. HClSolutions were analyzed for Cu (II) as described in the general procedure. To an aliquot of alloy solution (1.0 ml) in 50 ml beaker, pH was adjusted to 4.0 and 2.0 ml of 0.001M reagent solution was added and solution was diluted to 10 ml with distilled water. Absorbance was measured at 325 nm. Brass solution: 0.2347gm brass in 250 ml stock solution. 1 ml aliquot contains 0.09388 mg brass. Absorbance was found to be 0.205 (figure 3), it corresponds to 0.0635 mg of copper in 1 ml diluted solution. Determination of Copper in German-Silver: German silver alloy sample was brought into solution as described in the standard procedure by using Conc. HNO and Conc. HClSolutions were analyzed for Cu (II) as described in the general procedure. To an aliquot of alloy solution (1.0 ml) in 50 ml beaker, Ph was adjusted to 4.0 and 2.0 ml of 0.001M DMF solution of reagent was added and diluted to 10 ml with DMF. Absorbance was measured at 325 nm. German-silver solution: 0.250 gm in 250 ml stock solution. Absorbance was found to be 0.191 nm, (figure 3), it corresponds to 0.04953 mg of copper in 1 ml sample solution. Thermogravimetric Analysis: TG curve of Cu (II) complex of p-CBCST shows that there is no weight loss up to 200ºC indicating the absence of lattice as well as co-ordinate water molecules in complexes. A gradual increase in temperature above 200ºC has been accompanied by loss in weight up to 300ºC. it indicate part decomposition of ligand moiety (% wt. loss obs./cal.17.00/16.67). The remaining part of the ligangd break at 350-400ºC. A horizontal curve has been observed after 600ºC. The total weight loss up to 550ºC is nearly 82 % and equal to two moles of ligand indicating 1:2 compositions of the complex30. This constant weight region corresponds to metal oxides, the final pyrolysis produce. Antibacterial Activity: Cu (II) ligand complexes have been screened for their inhibitory effects against four organismsviz, Staphylococcus aureus,Escherichia coli,Bacillus subtilis and Pseudomonas aeruginosa. Table 4 showed the results obtained for zone of inhibition of the growth of bacteria of the tested compounds and under similar condition using Ciprofloxacin as a standard for comparison, control experiment was carried out by Kirby-Bauer method31. Cu-complex showed less activity towards the Staphyloccucus aureus than other organism32. The zones of inhibition have been measured and the activity results regarding the ligands and their complexes have been recorded. Table-1 Determination of Copper in Various Samples Using the Spectrophotometric Method Sr No. Composition Copper content Relative Error (%) Reported (%) Found (%) 1 Brass 63.5 64 -0.78 2 German – silver 50.00 49.53 - 0.94 *Average value of three determinations Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 4(2), 1-6, February (2014) Res. J. Chem. Sci. International Science Congress Association 3 Table-2 Spectrophotometric data of Cu (II) – p-CBCST Characteristics Results Molar absorptivity (L mole-1cm-1) 5.137×103 Stability constant(k) 1.184 × 1012 Table-3 Stability of Cu (II) p-CBCST at 30ºC Method Employed Em Es aa K s = (1- aa)/4c 2 aa 3 Mole ratio method 0.483 0.467 0.0331 1.184 × 1012 Table-4 Antibacterial activity of p-CBCST ligands and its metal chelates Sample Antibacterial activity (20 mm) Staphylococcus aureus Escheriachia coli Bacillus subtilis Pseudomonas aeruginosa p-CBCST 13 12 14 12 Cu (II)-pCBCST 9 14 10 11 Ciprafloxacin 20 20 21 19 Figure-1 Job’s Method 0.00.20.40.60.81.00.100.150.200.250.300.350.40 ABSORBANCEcm/cm+cr Research Journal of Chemical Sciences ___________________________________________________________ ISSN 2231-606XVol. 4(2), 1-6, February (2014) Res. J. Chem. Sci. International Science Congress Association 4 0.00.20.40.60.81.01.21.41.61.82.02.20.10.20.30.40.5 Es=0.467Em=0.483 ABSORBANCEcm/cr Figure-2 Mole ratio Method 0.20.40.60.81.01.21.41.61.82.02.20.150.160.170.180.190.200.21 B=German silverA=BrassCu (II) ion in ml ABSORBANCE Figure-3 Cu (II) ion in ml×0.03175 Conclusion The proposed procedure was simple, sensitive and rapid. The stability constant and the molar absorptivity of the proposed method were reported to be 1.184 × 1012 and 5.137×103 lit molecm-1. Cu (II) forms a 1:2 stable pale yellow colored complex with p- Chlorobenzaldehyde -4-(2’-carboxy-5’-sulphophenyl)-3-thiosemicarbazone. This complex is used for the determination of copper in microgram quantities. The method has been applied for the analysis of copper in synthesized mixtures and also in alloys. The proposed structure of Cu (II) complexes with p-chlorobenzaldehyde-4-(2’-carboxy-5’-sulphophenyl)-3-thiosemicarbazone where M = Cu (II) has been shown in figure-4. 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