. 2023 Apr 28;62(50):20621–20633. doi: 10.1021/acs.inorgchem.3c00621

Table 1. Acidity Constants (pK_a) of NO3S, TACN, TACN-Me, and TACN-n-Bu at T = 25 °C and I = 0.15 M NaNO₃ (unless otherwise stated).

	pK_a
Equilibrium reaction^a	NO3S	TACN^b	TACN-Me^b	TACN-n-Bu
H₃L³⁺ ⇌ H⁺ + H₂L²⁺	-	2.1	–0.4	-
H₂L²⁺ ⇌ H⁺ + HL⁺	2.70 ± 0.02^c	6.86	5.1	5.04 ± 0.05^c
H₂L²⁺ ⇌ H⁺ + HL⁺	2.33 ± 0.04^d	6.86	5.1	5.0 ± 0.05^e
HL⁺ ⇌ H⁺ + L	12.72 ± 0.08^c	10.68	11.7	-^f
HL⁺ ⇌ H⁺ + L	11.52 ± 0.01^d	10.68	11.7	-^f

L represents the completely deprotonated form of the ligand as shown in Figure 1C. The reported uncertainty was obtained by the fitting procedure and represents one standard deviation unit.

From Bianchi et al. (I = 0.1 M KNO₃, T = 25 °C).³⁰

Obtained via ¹H NMR.

Obtained via pH potentiometry in 1:1 water/methanol.

Obtained via pH potentiometry.

Not determined due to precipitation of the sparingly soluble, completely deprotonated L.

Table 1. Acidity Constants (pKa) of NO3S, TACN, TACN-Me, and TACN-n-Bu at T = 25 °C and I = 0.15 M NaNO3 (unless otherwise stated).

Table 1. Acidity Constants (pK_a) of NO3S, TACN, TACN-Me, and TACN-n-Bu at T = 25 °C and I = 0.15 M NaNO₃ (unless otherwise stated).