ARPN Journal of Science and Technology:: Spectrophotometric Analysis of Cobalt (II), Nickel (II), Copper (II) and Zinc (II) Complexes with Methylenedisalicylic Acid

Methylenedisalicylic acid was prepared as reported by the condensation reaction of salicylic acid with formaldehyde under acidic conditions. The complexes were prepared by refluxing ethanolic solutions of Methylenedisalicylic acid and some metal (II) salts. The ligand and its divalent metal complexes were characterized by solubility, melting point/decomposition temperature, molar conductance, and infrared. The ligand is white, has melting point of 238C and percentage yield of 83%. The Co (II), Ni (II), Cu (II) and Zn (II) complexes are pink, green, brown and white, respectively. They decompose above 246C and have percentage yield above75%. The ligand is soluble in most common organic solvent except xylene. The metal (II) complexes are insoluble in water and most common organic solvents, but slightly soluble in methanol and DMSO. The molar conductance of the complexes in 10M solution in DMSO determined is in the range 7.8 – 8.3 ohm cmmol. The metal analysis, water and ligand’s compositions determined for the complexes suggested the formulae [Co2(L-4H)(H2O)4].5H2O, [Ni2(L-4H)(H2O)8].7H2O, [Cu2(L-4H)(H2O)4].2H2O and [Zn2(L-4H)(H2O)8].2H2O. The infrared spectral analysis of the free ligand showed a strong sharp band at 3440cm and weak band at 1213 cm for v(O-H) and v(C-O) stretching vibrations respectively. The bands in the ranges 3370 – 3400 cm and 600 – 678 cm are attributable v(O-H) stretching frequencies for water of crystallization and coordinated water in the complexes, respectively. The bands observed in the range 453 – 481 cm are assigned to v(M-O) stretching frequencies, indicating coordination of the ligand to respective metal ions. The dissociation constant of the ligand is 4.534. The ratio of metal ion to the prepared ligand is 2:1 for all the complexes.