Studies on rare earth coordination compounds with crown ether: Part 9

A pNa method used for determining the stability constants is reported and applied to the study on coordination reaction of benzo-15-crown-5 (L1) and 4'-nitrobenzo-15-crown-5 (L2) with 10 rare earth ions in methanol solution, and their stability constants are calculated according to the formation of 1:1 coordination compounds. It is found that the coordination capability of L2 to rare earth ions is stronger than that of L1, especially with heavy rare earth. The coordination behavior of L1 and L2 towards yttrium (III) is studied under the same conditions. It is observed that log KY3+ of L2 is larger than that of L1, which is similar to the regularity that the coordination capability of L2 with Ln3+ is stronger than that of L1. This shows that L1 and L2 are also similar as to the property of solution coordination compounds of yttrium and lanthanum with the two ligands. Comparing the log K of the coordination compounds formed by coordinating of the 3 kinds of ions whose radii are similar but their electric charges are different with the ligand L1, the following result is obtained: logKNa+ > logKCa2+ > logKLa3+, but with L2, the result is logKCa2+ > logKLa3+ > logKNa+