Spectrophotometric Determination of the Stoichiometry of Cobalt (II) and Copper (II) Salicylhydroxamate Complexes

Abstract

Salicylhydroxamic acid was prepared by coupling reaction of methyl salicylate and free hydroxylamine, precipitated by acidification and recrystallized by hot water/ acetic acid it was characterizedby melting point, iron and vanadiumcolor test and FT-IR absorption bands at 3260cm-1 (OH), 1663 cm-1 (C=O), and 900 cm-1 (N-O) and 1H-NMR characteristic peak of the proton of the hydroxyl group attached to the nitrogen atom in the region 9.566 – 9.762 ppm. The shifting of the resonance signal of hydroxyl proton to lower field supports intermolecular hydrogen bonding. The peak proton of aromatic ring appears in the region 7.699 – 7.714 ppm. The peakprotons of – NH appears in the region 3.772 – 3.783 ppm.The 13C NMR spectra exhibit absorption signal due to carbonyl (C=O) group at nearly 166.118 ppm. The chemical shifts of aromatic carbons appear in the region of 133.329 – 127.148 ppm. The complexation ofsalicylhydroxamic acideither withCo2+ orCu2+cation wasboth determined by continuous variationmethod. Spectrophotometric analysis for determination of Co2+ and Cu2+salicylhydroxamate complexes was based on formation of colored complexes in weak acidic media. The produced colored complexes of Co2+ andCu2+showed maximum absorption at λmax510 nmand 385nm respectively. The mole ratio of complexes were determined in different chemical environments,and found to be in ratio of 1:3 and 1:1( M:L), respectively.