Only in apolar media is the calix[6]arene wheel threaded from its upper rim by asymmetric bipyridinium axles. This leads to the formation of oriented pseudorotaxanes. Their stoppering with a different stopper yields rotaxanes characterized by the unequivocal orientation of the wheel rims with respect to the two different stoppers (see picture, R1=CHPh2/CHCy2, R2=CHCy2/CHPh2, Cy=cyclohexyl, Ts=toluene‐4‐sulfonyl).
Nur in apolaren Medien werden in das Calix[6]aren‐Rad vom oberen Rand asymmetrische Bipyridinium‐Achsen eingefädelt. Das führt zur Bildung orientierter Pseudorotaxane. Das Anbringen eines zweiten, sich vom ersten unterscheidenden Stoppers liefert Rotaxane mit einer eindeutigen Orientierung der Radränder relativ zu den beiden Stoppern (siehe Bild, R1=CHPh2/CHCy2, R2=CHCy2/CHPh2, Cy=Cyclohexyl, Ts=Toluol‐4‐sulfonyl).
Gold nanoparticles protected with thiolate Calix[4]arenes hosts were synthesized through an exchange reaction in toluene, starting from tetraoctyl ammonium bromide stabilized gold nanoparticles having a mean core size of ∼6 nm. In low polar solvents, these new Calix[4]arene-coated nanoparticles are able to self-assemble through supramolecular interactions with dialkyl dipyridinium-based guests (2−3). The guest-induced self-assembly process between nanoparticles has been studied using UV−vis spectroscopy, dynamic light scattering, and TEM measurements. The size and the solubility of the aggregates strongly depend on the length and rigidity of the bifunctional guest used as “supramolecular linker” between the nanoparticles. In particular, the long and flexible guest 2 gives rise to superaggregates of nanoparticles that remain soluble in common low polar solvents.
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