Synthesis and Characterization of complexes of ... - Ultrascientist.org

402 Prem. Mohan Mishrafrom alcohol as colourless needles (M.P. = 492K). The pure and dried compound was chemicallyanalyzed. The compound is slightly soluble inmethanol and ethanol, highly soluble in DMFbut insoluble in water and acetone.Preparation of complexes :Aqueous solution of chromium (III)chloride, Iron (III) chloride, cobalt (III) chlorideand Manganese(II) chloride was mixed withthe solution of ligand – hydroxy naphthylmethanal thiosemicarbazide in DMF. Sodiumacetate is mixed and the whole solution wasrefluxed for two hours and left to stand forone hour. The coloured crystal separated. Thesewere filtered, washed with cold water, driedin air. The pure complexes were chemicallyanalysed.Chromium, Iron & Cobalt complexesare insoluble in water, methanol and ethanolbut soluble in DMF whereas Manganese (II)complex is insoluble in water, slightly solublein ethanol but fairly soluble in DMF.PROPERTIES OF COMPLEXES(i) Thermal stability :Cr (III) and Iron (III) complexdecompose below 480K , Co(III) complex at508 K where as Mn(II) complex decomposeswhen heated above 573 K.(ii) Electrical Conductivity :The molar conductance values of thecomplexes in 10 -3 M solution in DMF werefound to be 89.3, 90.2, and 98.6 ohm -1 cm 2mol -1 for Cr(III), Fe(III) and Co(III) complexesrespectively indicating 1:1 electrolytic nature.Whereas lower value (20.70 Ohm -1 cm 2 mol -1 )for Mn(II) complex show its non electrolyticnature. Magnetic susceptibility value of Cr(III)(3.82 BM), Fe(III) (5.96 BM), Co(III) (0BM)& Mn(II) (1.10 BM) indicates presence of 3,5, 0 and one unpaired electron respectively.Result and Discussion(a) Probable structure of ligand :The interpretation of I.R. spectra isquite complicated due to the presence of varioussimilar groups and hence many absorptionbands. However, comparision of the spectralbands of the ligand (HN-TS), with those of itscomplexes gives some important informationsregarding the nature of the ligand as well asthe co – ordination sites through which metalion is co - ordinated with the ligand.The band at 3210 cm -1 in the ligandassignable to phenolic O - H (hydrogen bonded)stretching frequency disappears in the Co (III),Cr (III) and Fe (III) complexes, showingdeprotonation of phenolic proton. The ligandalso shows strong band at 1270 cm -1 whichmay be attributed to the phenolic C – Ovibration. A shift of this band to higher frequency(~1310 cm -1 ) in the complexes indicatechelation of the ligand to metal ion throughphenolic oxygen. The presence of a band near3250 cm -1 in Mn (II) complex may be due toO - H of co – ordinated water molecule 9 . Thisis further justified by the presence of a bandaround 1610 cm -1 as deformation band of watermolecule.