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

Abstract

Cationic arene ruthenium metalla-prisms of the general formula [Ru6(p-cymene)6(3-tpt)2(OO∩OO)3]6+ (3-tpt = 2,4,6-tris(3-pyridyl)-1,3,5-triazine; OO∩OO = 5,8-dioxido-1,4-naphthoquinonato [1]6+ or 6,11-dioxido-5,12-naphthacenedionato [2]6+) have been obtained from the corresponding dinuclear arene ruthenium complexes [Ru2(p-cymene)2(OO∩OO)Cl2] by reaction with 3-tpt, silver trifluoromethanesulfonate in the presence of an aromatic molecule (1,3,5-tribromobenzene, 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]6+ and [triphenylene⊂2]6+, 1,3,5-tribromobenzene can be removed in toluene, thus leaving the empty cages [1]6+ and [2]6+, which are isolated as their trifluoromethanesulfonate salts. In the case of the metalla-prism connected by the 5,8-dioxido-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]6+, [2]6+, [template⊂1]6+, and [template⊂2]6+, 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]6+ and [2]6+ have been studied in solution with phenanthrene and pyrene. One-dimensional exchange spectroscopic (1D EXSY) measurements show that [phenanthrene⊂1]6+ is in a faster exchange regime than [phenanthrene⊂2]6+ and that phenanthrene is more easily exchanged than pyrene in cages [1]6+ and [2]6+, all observations being consistent with the portal size of the cages.