Thermodynamics of complex formation in aqueous solution. Reactions of copper(II) with ethylenediamine, N,N'-dimethylethylenediamine, and N,N-dimethylethylenediamine. Log K, ΔH, and ΔS values

Equil. in 0.5M KNO3 at 25° between Cu(II) and the ligands (L) H2N(CH2)2NH2, MeNH(CH2)2NHMe, and Me2N(CH2)2NH2 were studied by emf., calorimetric, and spectrophotometric detns. Equil. consts. for Cu2+ + nL .dblharw. [CuLn]2+ (n = 1, 2) and nCu2+ + nL + 2OH- ↹ [Cun(OH)2Ln](2n-2)+ (n = 1, hydrolysis: n = 2, olation) were detd. from potentiometric data using a computer. The enthalpies of reaction were detd. by calorimetry. Spectra of individual complexes were calcd. N-Me substitution reduces the heat of reaction and increases the pos. entropy changes.