Reversible cargo shipping between orthogonal stations of a nanoscaffold upon redox input

Abstract

The sterically shielded terpyridine 5 was prepared, both as a new ligand and as part of the four-station nanoscaffold 2. Mixing of terpyridine 5, the parent phenanthroline 4 and the shielded phenanthroline 3 in the presence of Zn²⁺ (1 : 1 : 1 : 1) furnished quantitatively the inverse HETTAP complex [Zn(4)(5)]²⁺ by self-sorting, while in the presence of Cu⁺ the HETPHEN complex [Cu(3)(4)]⁺ was preferred (89%). Due to the akin coordination preferences of Cu²⁺ and Zn²⁺, the above self-sorting was implemented for Cu⁺/Cu²⁺ on nanoscaffold 2, the latter equipped with the binding motifs of 3 (PhenAr₂) and 5 (TerpyAr₂). When 2 was reacted with Cu⁺ and phenanthroline (4) in a 1 : 2 : 2 ratio, only the PhenAr₂ stations became involved in complex formation (= ^Cu1_phen). In contrast, upon oxidative formation of Cu²⁺, ligand 4 was exclusively moved to the TerpyAr₂ stations (^Cu1_terpy). Electrochemical oxidation–reduction prompted the cargo to be shipped reversibly on a subsecond time scale between the two different stations of 2.