The thermodynamic characteristics of complex formation between Ni2+ ions and dl-leucine

The heat effects of the interaction of nickel(II) ions with dl-leucine in a queous solutions at ionic strengths of 0.5, 1.0, and 1.5 with sodium nitrat e as a background electrolyte and the necessary heats of dilution were dete rmined by direct calorimetric measurements at 288, 298, and 308 K. The heat s of formation of NiL+ and NiL2 were calculated by the RRSU universal progr am taking into account protolytic equilibria. Temperature and background el ectrolyte concentration effects on the heat of complex formation between th e amino acid and nickel ions were considered. Solution ionic strength growt h increased exothermic complex formation effects, whereas an increase in te mperature had the opposite action. The standard enthalpies of complex forma tion were found by extrapolation to a zero ionic strength. The Gurney schem e was used to calculate the temperature-dependent and temperature-independe nt components of the standard thermodynamic characteristics of complex form ation.