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

Table 1

Compositions, overall stability formation constants (log 𝛽), and acidity constants (pK𝑎) for the species formed in 𝐻₄cacp and Cu(II)-𝐻₄cacp system, over the pH range 2.00–10.0 thus obtained from the potentiometric study (25^∘C, 𝐼=0.10𝑚𝑜𝑙𝑑𝑚⁻³𝐾𝐶𝑙, pK_𝑤=13.78, and 𝛾=0.78).

(p, q, r)	Species	log 𝛽	pK𝑎
(0, 1, 1)	[H2cacp]^2−	8.40±0.01	8.47^a
(0, 1, 2)	[H3cacp]^−	13.18±0.04	4.84^b
(0, 1, 3)	[H4cacp]	15.56±0.02	2.42^c
(1, 1, −1)	[Cu(Hcacp)(OH)]^2−	8.17±0.01
(2, 2, 0)	[Cu2(Hcacp)2]^2−	11.26±0.02
(1, 1, 0)	[Cu(Hcacp)(H2O)]^−	14.58±0.02
(1, 2, 2)	[Cu(H2cacp)2]^2−	17.62±0.02
(1, 1, 1)	[Cu(H2cacp)(H2O)]	22.94±0.01

^aPhenolate or aromatic carboxylate oxygen group, ^bcarboxylate oxygen group, ^camine nitrogen group.