Cavity Constriction and Chiralization of Polyaromatic Subnanotubes via Post-assembly Ligand/Metal Modification

High Resolution Image Download MS PowerPoint Slide Late-stage modification of coordination-driven tubular and cage-like structures is a promising method to tune and alter their cavity functions yet remains difficult owing to the intrinsic instability of metal–ligand bonds against the modification conditions. Here we report polyaromatic tubes with a subnanometer-sized cavity, composed of three metal hinges and three polyaromatic ligands, both of which are modifiable in a post-assembly fashion. The new subnanotube, prepared from PtCl 2 salts and the anthracene-embedded bispyridine ligands, is reversibly converted into a constricted subnanotube by the symmetrical modification of the ligands with O 2 . Using an analogous aqueous tube, one molecule of rod-like coumarin dyes is bound by the subnanocavity in water, and their emission properties are largely enhanced (up to 4-fold) through the ligand modification. On the other hand, the asymmetrical modification of the metal hinges with chiral ammonium groups generates a cryptochiral subnanotube while retaining the polyaromatic cavity. The resultant tube also binds the coumarin dye in water to induce its chiroptical properties as strong CD and CPL activities (up to | g abs | = 2 × 10 –3 and | g lum | = 3 × 10 –3 ). Two-directional post-assembly multi-modifications are demonstrated unprecedentedly, using polyaromatic subnanotubes, for the development of multi-functional host–guest systems.