Permanent Encapsulation or Host–Guest Behavior of Aromatic Molecules in Hexanuclear Arene Ruthenium Prisms

Cationic arene ruthenium metallaprisms of the general formula [Ru6(p-cymene)6(tpt)2(OO∩OO)3]6+ {tpt = 2,4,6-tris(4-pyridyl)-1,3,5-triazine; OO∩OO = 9,10-dioxo-9,10-dihydroanthracene-1,4-diolato [1]6+, 6,11-dioxo-6,11-dihydronaphthacene-5,12-diolato [2]6+} have been obtained from the corresponding dinuclear arene ruthenium complexes [Ru2(p-cymene)2(OO∩OO)Cl2] by reaction with tpt and silver trifluoromethanesulfonate. Aromatic molecules (phenanthrene, pyrene, triphenylene, coronene) present during the synthesis of these metallaprisms are permanently encapsulated to give carceplex systems. All empty cages ([1]6+ and [2]6+) and carceplex systems ([guest⊂1]6+ and [guest⊂2]6+) were isolated in good yield as trifluoromethanesulfonate salts and characterized by NMR, UV, and IR spectroscopy. The host–guest properties of [1]6+ and [2]6+ were studied in solution in the presence of small aromatic molecules (phenanthrene andpyrene). The stability constant of association (Ka) wasestimated by NMR spectroscopy for the following host–guest systems: [phenanthrene⊂1]6+, [pyrene⊂1]6+ and [phenanthrene⊂2]6+, [pyrene⊂2]6+. All Ka values were found to be larger than 2.0 × 104M–1 for these host–guest systems ([D3]acetonitrile, 21 °C).