Encapsulation of aromatic molecules in hexanuclear arene ruthenium cages: A strategy to build up organometallic carceplex prisms with a dangling arm standing out

Self-assembly of 2,4,6-tris(pyridin-4-yl)-1,3,5-triazine (tpt) subunits with p-cymene (p-(PrC6H4Me)-C-i) or hexamethylbenzene (C6Me6) ruthenium building blocks and 2,5-dihydroxy-1,4-benzoquinonato (dhbq) or 2,5-dihchloro-3,6-dihydroxy-1,4-benzoquinonato (dchq) bridges affords the triangular prismatic organometallic cations [Ru-6(p-(PrC6H4Me)-C-i)(6)(tpt)(2)(dhbq)(3)](6+) ([1](6+)), [Ru-6(p-(PrC6H4Me)-C-i)(6)(tPt)(2)(dchq)(3)](6+) ([2](6+)), [Ru-6(C6Me6)(6)(tpt)(2)(dhbq)(3)](6+) ([3](6+)), and [Ru-6(C6Me6)(6)(tpt)(2)(dchq)(3)](6+) ([4](6+)). These hexanuclear cationic cages are isolated in good yield as their triflate salts. The assembly of 1-4 can also be achieved in the presence of large aromatic molecules such as pyrene, fluoranthene, benzo[e]pyrene, triphenylene, or coronene to give the corresponding inclusion systems [aromatic subset of 1](6+), [aromatic subset of 2](6+), [aromatic subset of 3](6+), and [aromatic subset of 4](6+). The closed proximity of the encapsulated molecule with the different components of the cage and the carceplex nature of these systems are confirmed by one-dimensional ROESY H-1 NMR experiments, mass spectrometry, and the single-crystal structure analysis of [pyrene subset of 1][O3SCF3](6) and [benzo[e]pyrene subset of 1] [O3SCF3](6). Pyrene can be encapsulated even if it contains a functionalized aliphatic substituent; in this case the aromatic moiety is included in the cage, while the functionalized side arm stands out. Thus, methyl 4-(pyren-l-yl)butanoate (pyrene-R) is encapsulated in I to give the carceplex [pyrene-R subset of 1](6+), in which the methyl butyrate arm dangles outside the cage while the pyrene moiety is firmly trapped by the metallo-prismatic cation, as demonstrated by H-1 NMR experiments and ESI-MS.