Application of Calixarenes as Macrocyclic Ligands for Uranium(VI): A Review

Table 2

Stability constants (𝐾^a_uranyl) for the complexes of UO₂²⁺ and calixarene derivatives at 25°C.

Entry	Extraction agent	log𝐾uranyl	Medium	pH	Reference
1	1 ^b	17.7	carbonate buffer	10.4	[49]
2	2	18.9	10^−2 M carbonate	10.4	[50]
3	3	19.2	10^−2 M carbonate	10.4	[50]
4	4	3.2	10^−2 M carbonate	6.5	[50]
5	5	18.4	10^−2 M carbonate	10.4	[50]
6	6	18.7	10^−2 M carbonate	10.4	[50]
7	7	3.1	10^−2 M carbonate	6.5	[50]
8	8	18.7 (log𝐾1)^c	carbonate buffer	10.4	[49]
		18.1 (log𝐾2)^c
9	9	3.2	10^−2 M carbonate	6.5	[50]
10	10	16.3	10^−2 M carbonate	10.4	[51]
11	10	17.5	10^−2 M carbonate	11.5	[51]
12	11	2.7	methanol	—	[52]
13	11	3.72	acetonitrile	—	[52]
14	12	3.26	methanol	—	[52]
15	12	3.6	acetonitrile	—	[52]
16	13	9.93	methanol	—	[53]
17	14	14.2	methanol	—	[54]

^a𝐾_uranyl=[UO₂²⁺⋅𝐄𝐱𝐭𝐫𝐚𝐜𝐭𝐢𝐨𝐧𝐚𝐠𝐞𝐧𝐭complex]/[UO₂²⁺][𝐄𝐱𝐭𝐫𝐚𝐜𝐭𝐢𝐨𝐧𝐚𝐠𝐞𝐧𝐭].
^bnon-cyclic extractant 1.
^c𝐾₁=[UO₂²⁺⋅𝟖complex]/[UO₂²⁺][𝟖],𝐾₂=[(UO₂²⁺)₂⋅𝟖complex]/[UO₂²⁺][UO₂²⁺⋅𝟖complex].