Fig. 5: 1H NMR spectrum of the tetrahedron-to-helicate transformation.

a Tetrahedron-to-helicate transformation from [Eu4L16] to [Eu2L13] (4.53 × 10−4 M in CD3CN). [Eu4L16] slowly rearranged back to [Eu2L13] after dilution in CD3CN for 11 days. b Tetrahedron-to-helicate transformation from [Sm4L16] to [Sm2L13] (4.12 × 10−4 M in CD3CN) (bottom) upon dissolution in CD3CN. [Sm4L16] slowly rearranged back to [Sm2L13] after dilution in CD3CN for 14 days.