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

• Published in: European Journal of Inorganic Chemistry 2010-06, Vol.2010 (16), p.2400-2405
• Main Authors: Freudenreich, Julien, Barry, Nicolas P. E., Süss-Fink, Georg, Therrien, Bruno
• Format: Article
• Language: English
• Subjects: Arene ligands; Host-guest sys­tems; Ruthenium; Supramolecular chemistry
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.201000191

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 × 104 M–1 for these host–guest systems ([D3]acetonitrile, 21 °C). Two cationic arene ruthenium metallaprisms possessing different portal sizes are presented. In solution, they are both able to allow small aromatic molecules to enter and leave their hydrophobic cavity (host–guest behavior). However, for larger aromatic molecules permanent encapsulation (carceplex formation) is observed during the assembly of the cages in the presence of the guest molecule.