pH-Potentiometric Investigation towards Chelating Tendencies of 𝑝-Hydroquinone and Phenol Iminodiacetate Copper(II) Complexes

Table 2

Compositions, overall stability formation constants (log 𝛽), and acidity constants (pK𝑎) for the species formed in 𝐻₆bicah and Cu(II)-𝐻₆bicah system, over the pH range 2.00–10.0 thus obtained from the potentiometric study (25^∘C, I = 0.10 mol 𝑑𝑚⁻³ KCl, p𝐾_𝑤=13.78, and 𝛾=0.78).

(p, q, r)	Species	log 𝛽	pK𝑎
(0, 1, 0)	[H2bicah]^4−	8.41±0.02	8.47^a
(0, 1, 2)	[H4bicah]^2−	13.40±0.01	7.26^b
(2, 1, −2)	[Cu2(bicah)(OH)2]^4−	11.57±0.15
(2, 1, −1)	[Cu2(bicah)(H2O)(OH)]^3−	15.72±0.11
(2, 1, 0)	[Cu2(bicah)(H2O)2]^2−	32.90±0.16
(2, 1, 1)	[Cu2(Hbicah)(H2O)2]^−	39.33±0.16
(2, 1, 2)	[Cu2(H2bicah)(H2O)2]	45.52±0.12

a Phenolate oxygen group, b carboxylate oxygen group.