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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]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.
Designing the host-guest properties of tetranuclear arene ruthenium metalla-rectangles to accommodate a pyrene molecule
Cationic tetranuclear rectangular macrocyclic arene ruthenium complexes [Ru4(p-cymene)4(?-N-N)2(?-dhnq)2](CF3SO3)4 [1-3, dhnq = 5,8-dihydroxy-1,4-naphthoquinonato(2-); N-N = pyrazine, 4,4'-bipyridine, 1,2-bis(4-pyridyl)ethene], featuring Ru-dhnq-Ru-N-N-Ru-dhnq-Ru rectangle structures with adjustable Ru-Ru distances (7.0 Ã…, 11.2 Ã…, 13.6 Ã…, resp.), are obtained in methanol from the reaction of the dinuclear arene ruthenium precursor [Ru2(p-cymene)2(dhnq)2Cl2] with pyrazine or bipyridine linkers in the presence of AgCF3SO3. All complexes 1-3, isolated in good yield as triflate salts, have been characterized by NMR and IR spectroscopy. The interaction of these rectangular complexes with pyrene as a guest mol. has been studied in soln. by various NMR techniques (1D, DOSY, ROESY). In CD3CN, the pyrazine-contg. metalla-rectangle 1 shows no meaningful interactions with pyrene. On the other hand, the 4,4'-bipyridine- and 1,2-bis(4-pyridyl)ethylene-contg. metalla-rectangles 2 and 3 clearly interact with pyrene. DOSY measurements suggest that, in the case of the 4,4'-bipyridine complex 2, the interactions occur on the outside of the rectangular assembly, while in the case of dipyridylethylene complex 3 the pyrene mol. is found inside the hydrophobic cavity of the metalla-rectangle, thus giving rise to a host-guest system. [on SciFinder(R)]
Designing the Host-Guest Properties of Tetranuclear Arene Ruthenium Metalla-Rectangles to Accommodate a Pyrene Molecule
Cationic tetranuclear arene ruthenium complexes of the general formula [Ru4(p-cymene)4(N∩N)2(dhnq)2]4+ comprising rectangular structures are obtained in methanol from the reaction of the dinuclear arene ruthenium precursor [Ru2(p-cymene)2(dhnq)2Cl2] (dhnq = 5,8-dihydroxy-1,4-naphthoquinonato) with pyrazine or bipyridine linkers [N∩N = pyrazine, 1; 4,4-bipyridine, 2; 1,2-bis(4-pyridyl)ethylene, 3] in the presence of AgCF3SO3. All complexes 1-3, isolated in good yield as triflate salts, have been characterised by NMR and IR spectroscopy. The interaction of these rectangular complexes with pyrene as a guest molecule has been studied in solution by various NMR techniques (1D, DOSY, ROESY). In [D3]acetonitrile, the pyrazine-containing metalla-rectangle 1 shows no meaningful interactions with pyrene. On the other hand, the 4,4-bipyridine- and 1,2-bis(4-pyridyl)ethylene-containing metalla-rectangles 2 and 3 clearly interact with pyrene in [D3]acetonitrile. DOSY measurements suggest that, in the case of [Ru4p-cymene)4(4,4-bipyridine)2(dhnq)2]4+ (2), the interactions occur on the outside of the rectangular assembly, while in the case of [Ru4(p-cymene)4{1,2-bis(4-pyridyl)ethylene}2 (dhnq)2]4+ (3), the pyrene molecule is found inside the hydrophobic cavity of the metalla-rectangle, thus giving rise to a host-guest system.