Reversible cargo shipping between orthogonal stations of a nanoscaffold upon redox input†
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 (= Cu1phen). In contrast, upon oxidative formation of Cu2+, ligand 4 was exclusively moved to the TerpyAr2 stations (Cu1terpy). Electrochemical oxidation–reduction prompted the cargo to be shipped reversibly on a subsecond time scale between the two different stations of 2.