In- and out-of-cavity interactions by modulating the size of ruthenium metallarectangles

Cationic (arene)ruthenium-based tetranuclear complexes I [4, X = X1 = H; 5, X-X = CH:CHCH:CH, X1 = H; 6, X-X = X1-X1 = CH:CHCH:CH] and II [7-9, Z = bond, 7, X = X1 = H; 8, X-X = CH:CHCH:CH, X1 = H; 9, X-X = X1-X1 = CH:CHCH:CH; 10-12, Z = (E)-CH:CH, 10, X = X1 = H; 11, X-X = CH:CHCH:CH, X1 = H; 12, X-X = X1-X1 = CH:CHCH:CH] were obtained from the dinuclear (arene)ruthenium complexes [Ru2(?6-p-cymene)2(?-O2Q)Cl2] [1-3; (HO)2Q = 5,8-dihydroxy-1,4-naphthoquinone, 9,10,-dihydroxy-1,4-anthraquinone, 6,11-dihydroxy-5,12-naphthacenedione] by reaction with pyrazine or bipyridine linkers in the presence of silver triflate. All complexes 4-12 were isolated in good yield as triflate salts, and characterized by NMR and IR spectroscopy. The host-guest properties of the metallarectangles 7-12 were studied in soln. by means of 1D, ROESY, and DOSY NMR expts. The largest metallarectangles 10-12 incorporating 4,4'-[(1E)-ethene-1,2-diyl]bis[pyridine] linkers are able to host an anthracene, pyrene, perylene, or coronene mol. in their cavity, while the medium-size metallarectangles 7-9 incorporating 4,4'-bipyridine linkers are only able to encapsulate anthracene. However, out-of-cavity interactions are obsd. between these 4,4'-bipyridine-contg. rectangles and pyrene, perylene, or coronene. In contrast, the small pyrazine-contg. metallarectangles 4-6 show no interaction in soln. with this series of planar arom. mols. [on SciFinder(R)]