Thermodynamics of the formation of nickel(II) complexes with L-histidine in aqueous solutions

The heat effects of the formation of Ni(II) complexes with L-histidine in an aqueous solution are determined via direct calorimetry at 298.15 K and ionic strengths of 0.2, 0.5, and 1.0 (KNO₃). The standard thermodynamic characteristics (Δ_r H ^○, Δ_r G ^○, Δ_r S ^○) of complex formation in the investigated system are calculated. It is concluded that the resulting values are consistent with the results from studying the structure of L-histidine complexes with Ni²⁺ ions by various spectral methods.