Template-Directed Synthesis of Hexanuclear Arene Ruthenium Complexes with Trigonal- Prismatic Architecture Based on 2,4,6-Tris(3-pyridyl)triazine Ligands

Cationic arene ruthenium metalla-prisms of the general formula [Ru6(p-cymene)6(3-tpt)2-(OO∩OO)3] (3-tpt = 2,4,6tris(3-pyridyl)-1,3,5-triazine; OO∩OO = 5,8-dioxido-1,4-naphthoqui-nonato [1]6þ or 6,11-dioxido-5,12naphthacenedionato [2]6þ) have been obtained from the corresponding dinuclear arene ruthenium complexes [Ru2(pcymene)2(OO∩OO)Cl2] by reaction with 3-tpt, silver trifluoromethanesulfonate in the presence of an aromatic molecule (1,3,5-tribro-mobenzene, phenanthrene, pyrene, or triphenylene) that acts as a template. While the large template molecule triphenylene is permanently encapsulated in the metalla-prisms to give the complexes [triphenylene⊂1]6þ and [triphenylene⊂2]6þ, 1,3,5-tribromobenzene can be removed in toluene, thus leaving the empty cages [1]6þ and [2]6þ, which are isolated as their trifluoromethanesulfonate salts. In the case of the metalla-prism connected by the 5,8dioxido-1,4-naphthoquinonato bridging ligands, the NMR spectrum reveals two isomers, 1a and 1b, the formation of which can be rationalized by means of multiple NMR experiments (one-dimensional, two-dimensional, ROESY, and DOSY). The empty and filled metalla-prisms, [1]6þ, [2]6þ, [template⊂1]6þ, and [template⊂2]6þ, have been characterized by NMR, UV-vis, and IR spectroscopy. The slow exchange processes of a guest molecule moving in and out of the cavity of cages [1]6þ and [2]6þ have been studied in solution with phenanthrene and pyrene. One-dimensional exchange spectroscopic (1D EXSY) measurements show that [phenanthrene⊂1]6þ is in a faster exchange regime than [phenanthrene⊂2]6þ and that phenanthrene is more easily exchanged than pyrene in cages [1]6þ and [2]6þ, all observations being consistent with the portal size of the cages.