Global Advanced Research Journals::::::GARJM>Aliyu and Mohammad:Studies on Potentially Therapeutic Cis- and Trans- Bis(3 – phenyl – o carboxyphenyl – 3

A ligand was prepared by rapidly mixing a diazotized product of 2 – aminobenzoic acid with a solution of 50% aqueous/ethanol mixture (50%) of phenylhydroxylamine at 5^oC. The cis and trans- nickel(II) complexes were synthesized as reported. Their solubility, melting point/decomposition temperature, molar conductance, IR and potentiometric studies of the ligand and its nickel(II) complexes were carried out. The melting point of the ligand and the decomposition temperature of the complexes determined are high. The ligand is soluble in most organic solvents except acetone. The nickel (II) complexes are insoluble in water and most common organic solvents, except acetone. The molar conductance of the complexes determined is 49.8 and 49.6ohm^-1cm²mol^-1, respectively. The metal analysis and water composition determined for each complex suggested the formula [NiL₂].2H₂O. The infrared spectra of the ligand showed band at 1397 cm^-1 which is assigned to v(N=N) stretching vibrations. Similar bands were observed in the Ni(II) complexes, confirming the coordination of the ligand to the respective metal ions. The band at 3463 cm^-1 in the free ligand is attributable to v(O-H) stretching vibrations, which is absent on deprotonation and subsequent coordination of the ligand to the Ni(II) ion. The spectral bands at 3318 cm^-1 observed in the Ni(II) complexes are attributable to v(O-H) stretching frequencies for water of crystallization. The dissociation constant of the ligand determined is 10.38. The stability constants of the cis and trans Ni(II) complexes determined are the same, 2.48x10⁹, and the corresponding Gibbs free energy also are the same -52.47 KJmol^-1.

Keywords: Ligand, complexes, 2-aminobenzoic acid, phenylhydroxylamine, potentiometry, stability constant and dissociation constant.