Synthesis, Structure, and Dynamic Properties of Hybrid Organic−Inorganic Rotaxanes

The synthesis and characterization of a series of hybrid organic−inorganic [2]rotaxanes is described. The ring components are heterometallic octa- ([Cr7MF8(O2CtBu)16]; M = Co, Ni, Fe, Mn, Cu, Zn, and Cd) nuclear cages in which the metal centers are bridged by fluoride and pivalate (tBuCO2−) anions; the thread components feature dialkylammonium units that template the formation of the heterometallic rings about the axle to form the interlocked structures in up to 92% yield in conventional macrocyclization or one-pot ‘stoppering-plus-macrocyclization’ strategies. The presence in the reaction mixture of additives (secondary or tertiary amines or quaternary ammonium salts), and the nature of the stoppering groups (3,5-tBu2C6H3CO2− or tBuCONH−), can have a significant effect on the rotaxane yield. The X-ray crystal structures of 11 different [2]rotaxanes, a pseudorotaxane, and a two-station molecular shuttle show two distinct types of intercomponent hydrogen bond motifs between the ammonium groups of the organ...