Cobalt (II) and copper (II) chelates of 2-picolylamine have been studied spectrophotometrically in aqueous solution. Formation of 2-picolylamine chelates was pH dependent, and the optimum pH range of the cobalt (II) chelate was at pH 8.8-9.6, and copper(II) chelate at 4.7-6.8, respectively. The mole ratio of 2-picolylamine to both of metal(II) ions was found to be 2 to 1 stoichiometry. The spectrophotometric sensitivities are 0.23γ of Co/Cm2 and 8.9γ of Cu/Cm3, at 373 mμ, pH 9.0 for Co(II) chelate and 588 mμ, pH 6.0 for Cu (II) chelate. The stability constants (logK) of the chelates CoL22+ and CuL22+ have been evaluated at a constant ionic strength of 0.10 at 20, 25, 30, 35 and 40°C. Enthalpy and entropy changes characterizing the formation of the chelates have been calculated at 25°C The results are collected as follows:
