Table 4.

Overall complex-formation constants (logβ) of DFOB with divalent transition metal ions under different experimental conditions. The constants in parentheses correspond to the formation of the 1:1 complex of M(II) with DFOB protonated at its amino group and therefore refer to the equilibrium: M²⁺ + HL²⁻ = MHL.

	[MH3L]2+	[MH2L]+	[MHL]	[ML]−	[M2L]+	[M2HL]2+	I (mol·dm−3)	Background Electrolyte	T (°C)	Ref.
Mn(II)	-	25.9	17.8	7.5	-	-	0.10	NaCl	25.0	[11]
Fe(II)	33.53	27.90	-	-	-	-	0.10	NaNO3	20.0	[5]
Co(II)	33.91	28.06	21.31	(10.31)	-	-	0.10	NaNO3	20.0	[5]
	34.00	27.80	20.2	9.4	-	-	0.10	NaCl	25.0	[24]
Ni(II)	34.09	28.40	21.90	(10.90)	-	-	0.10	NaNO3	20.0	[5]
	33.20	27.66	19.71	8.89	-	-	0.20	KCl	25.0	[10]
Cu(II)	37.33	34.20	25.12	(14.12)	-	33.42	0.10	NaNO3	20.0	[5]
	37.18	33.55	24.63	(13.73)	-	32.20	0.10	NaClO4	20.0	[9]
	37.07	33.38	24.41	(13.54)		32.12	0.10	NaClO4	25.0	[9]
	36.99	33.10	23.98	13.73	-	32.09	0.20	KCl	25.0	[10]
Zn(II)	34.18	28.57	22.07	(11.07)	-	-	0.10	NaNO3	20.0	[5]
	33.71	28.32	20.44	(9.55)	-	-	0.10	KNO3	25.0	[9]
	33.40	28.17	20.40	10.36	-	-	0.20	KCl	25.0	[10]
Pb(II)	35.34	29.69	20.89	(10.00)	-	27.18	0.10	KNO3	25.0	[9]
Cd(II)	33.05	26.28	18.88	(7.88)	-	-	0.10	NaNO3	20.0	[5]
Sn(II)	43.46	40.76	32.01	21.90	37.72	42.05	0.10	KCl	25.0	[9]