Anion Encapsulation Drives the Formation of Dimeric GdIII[15-metallacrown-5]3+ Complexes in Aqueous Solution.

Metallacrown complexes capable of sequestering dianions, as shown in the solid state, also exist in aqueous solution at neutral pH, as demonstrated by calorimetric and mass spectrometric data. The driving forces for the formation of these dimeric complexes in solution strongly depend on the chain length of the guest rather than its degree of unsaturation.