Table 2.

Proton dissociation constants (pK_a) of the studied proligands; overall stability constants (logβ), pK_a and derived constants (logK_derived) of their copper(II) complexes, pCu (=−log[Cu(II)]) values calculated (I = 0.1 M (KCl); t = 25 °C), distribution coefficients (logD_7.4) of the proligands and copper(II) complexes at pH 7.4, as well as the observed rate constants (k_obs) for the redox reaction of the complexes with GSH (pH = 7.4; c_complex = 25 μM; c_GSH = 1.25 mM).

	[H2LH]Cl	[H2LMe]Cl	[H2LEt]Cl	[H2LPh]Cl
pKa (H2L+)	7.46 ± 0.01	7.54 ± 0.01	7.31 ± 0.01	7.03 ± 0.01
% HL at pH 7.4	47%	42%	55%	70%
logD7.4 (proligand)	−0.84 ± 0.03	−0.39 ± 0.01	0.06 ± 0.04	0.68 ± 0.04
logβ [Cu(HL)]2+ [a]	12.00 ± 0.01	11.73 ± 0.02	11.66 ± 0.03	11.26 ± 0.02
logβ [CuL]+ [b]	8.14 ± 0.01	7.76 ± 0.02	7.67 ± 0.03	8.55 ± 0.02
logβ [CuLH−1] [c]	−1.66 ± 0.02	−1.48 ± 0.08	−1.65 ± 0.09	−1.31 ± 0.05
pKa [Cu(HL)]2+	3.86	3.97	3.99	2.71
pKa [CuL]+	9.80	9.24	9.32	9.86
logKderived [CuLH−1]+ [d]	0.68	0.22	0.36	1.52
pCu [e]	12.21	11.79	11.82	12.80
logD7.4 (complex)	−1.00 ± 0.01	−0.79 ± 0.01	−0.40 ± 0.01	−0.17 ± 0.01
kobs (min−1)	0.080 ± 0.008	0.073 ± 0.002	0.058 ± 0.001	0.025 ± 0.005

^[a]β [Cu(HL)]²⁺ = [Cu(HL)]²⁺/[Cu²⁺] × [HL]. ^[b] β [CuL]⁺ = [CuL]⁺ × [H]⁺/[Cu²⁺] × [HL]. ^[c] β [CuLH₋₁] = [CuLH₋₁] × [H]⁺ × [H]⁺/[Cu²⁺] × [HL]. [CuLH₋₁] = [CuL(OH)]. ^[d] logK_derived = logβ [CuL]⁺ − pKa (H₂L⁺) for the equilibrium: Cu²⁺ + H₂L⁺ [CuL]⁺ + 2H⁺. ^[e] pCu = −log[Cu(II)] at pH = 7.4; c_Cu(II) = 10 μM; c_L = 10 μM.