Conductometric Studies of Thermodynamics of Complexation of Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ Cations with Aza-18-crown-6 in Binary Acetonitrile-Methanol Mixtures

Table 2

Thermodynamic parameters for different M²⁺-A18C6 complexes in various AN-MeOH mixtures.

Cation	wt% AN	ΔH^∘ (kJ mol^−1)	ΔS^∘ (J mol^−1 K^−1)	ΔG^∘ (kJ mol^−1)
Co^2+	100	−27.9±3.3	9.8±11.1	−30.8±4.7
	80^a	1.6±0.6	79.8±2.0	−21.8±0.8
	60^b	13.1±0.3	100.4±1.1	−16.3±0.5
	40^c	1.6±0.8	59.6±2.7	−15.9±1.1
Ni^2+	100	−24.6±7.5	19.2±25.3	−30.2±10.7
	80	14.6±3.7	123.5±12.4	−21.6±5.2
	60	14.2±2.0	105.3±6.7	−16.7±2.8
	40	5.4±0.8	75.7±2.5	−16.8±1.1
Cu^2+	100	—^d	—^d	—^d
	80	13.2±1.0	111.5±3.2	−19.5±1.4
	60	5.1±0.1	77.5±0.3	−17.6±0.1
	40	−3.6±0.4	46.3±1.5	−17.2±0.6
Zn^2+	100^e	−46.5±0.5	120.8±1.6	−81.9±0.7
	80	12.9±2.4	107.9±8.1	−18.7±3.4
	60	12.7±0.9	101.7±3.1	−17.1±1.3
	40	80.5±3.3	311.7±11.0	−10.8±4.6

^aWithout considering Log 𝐾_𝑓 at 30°C.
^bWithout considering Log 𝐾_𝑓 at 40°C.
^cWithout considering Log 𝐾_𝑓 at 20°C.
^dHigh uncertainty.
^eWithout considering Log 𝐾_𝑓 at 10°C.