Flexibility and anion exchange of [(X)@Pd2L4] cages for recognition of size and charge of polyatomic anions

Abstract

The self-assembly of Pd(NO₃)₂ with L (L = 1,2-bis(dimethyl(pyridin-3-yl)silyl)ethane) gives rise to [PdL₂](NO₃)₂ in high yields. Anion exchange of [PdL₂](NO₃)₂ with X⁻ (X⁻ = BF₄⁻, ClO₄⁻, and PF₆⁻) changes the skeleton into a cage of [(X)@Pd₂L₄](X)₃. Successive anion exchange of [(X)@Pd₂L₄](X)₃ (X⁻ = BF₄⁻, ClO₄⁻, and PF₆⁻) with X⁻ (X⁻ = ReO₄⁻ and SiF₆²⁻) produces [(ReO₄)@Pd₂L₄](ReO₄)₃ and [(SiF₆)@Pd₂L₄](SiF₆), respectively, irrespective of anion charge. The flexible nature and conformation of cages are significantly dependent on the nestled polyatomic anions. Thus, this system can be used as a molecular recognizer of the size and charge of ubiquitous polyatomic anions.