Abstract: | An M2L4 quadruple helicate, formed by wrapping four molecules of 1,4‐bis(3‐pyridyloxy)benzene ( L1 ) about two palladium(II) centers, is shown to bind anions within its internal cavity. 1H NMR exchange experiments provide a quantitative measure of anion selectivity and reveal a preference for ClO4? over the other tetrahedral anions BF4? and ReO4? and the octahedral anion PF6?. X‐ray crystal structures of Pd2( L1 )4]4+ helicates containing ClO4, BF4? and I? reveal that the cavity size can dynamically change in response to the size of the guest. |