Template-free coordination-driven self-assembly of discrete hexanuclear prismatic cages employing half-sandwich octahedral RuII2 acceptors and triimidazole donors

Abstract

Coordination-driven self-assembly of dinuclear half-sandwich p-cymene ruthenium(II) complexes [Ru2(μ-η4-C2O4)(CH3OH)2(η6-p-cymene)2](O3SCF3)2 (1a) and [Ru2(μ-η4-C6H2O4)(CH3OH)2(η6-p-cymene)2](O3SCF3)2 (1b) separately with imidazole-based tritopic donors (L1–L2) in methanol yielded a series of hexanuclear [3+2] trigonal prismatic cages (2–5), respectively [L1 = 1,3,5-tris(imidazole-1-yl)benzene; L2 = 4,4′,4″-tris(imidazole-1-yl)triphenylamine]. All the self-assembled cages 2–5 were characterized by various spectroscopic techniques (multinuclear NMR, Infra-red and ESI-MS) and their sizes, shapes were obtained through geometry optimization using molecular mechanics universal force field (MMUFF) computation. Despite the possibility due to the free rotation of donor sites of imidazole ligands, of two different atropoisomeric prismatic cages (C3h or Cs) and polymeric product, the self-selection of single (C3h) conformational isomeric cages as the only product is a noteworthy observation.