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A template containing two secondary dialkylammonium ion recognition sites for encirclement by olefin-bearing dibenzo[24]crown-8 derivatives has been used to promote olefin cross metatheses with ruthenium−alkylidene catalysts. For monoolefin monomers, the rates of metatheses and yields of the dimers are both amplified in the presence of the template. Likewise, for a diolefin monomer, the yield of the dimer is enhanced in the presence of the template under conditions where higher oligomers are not formed.

Olefin metathesis has been employed in the efficient syntheses of a [2]catenane with the templation being provided by the recognition between a secondary ammonium ion and a crown ether. In one approach, a crown ether precursor has been clipped around an NH2⁺ center situated in a macrocyclic ring, yielding the mechanically interlocked compound. In the other approach, the reversible nature of olefin metathesis allows for a magic ring synthesis to occur wherein two free macrocycles can be employed as the stationary materials, leading to the formation of the same [2]catenane.

A rotaxane-like complex, based on a dumbbell-shaped component containing an NH2⁺ recognition site for a [25]crown-8 ring component and a slippage stopper in the form of a p-(tert-butyl)phenyl group, has been synthesized by a “threading-followed-by-stoppering” approach. The half-life for dissociation of this complex, which is very sensitive to its environment, can be varied from minutes to months by changing the temperature and the polarity of the solvent.

Dipyrido[24]crown-8 (DP24C8) has been synthesized and shown to form [2]pseudorotaxanes spontaneously with dibenzylammonium ions. These complexes, which have been demonstrated by ¹H NMR spectroscopy to form faster in solution than when the macrocyclic polyether is dibenzo[24]crown-8 (DB24C8), are also stronger than their DB24C8 counterparts. One of the [2]pseudorotaxanes has been used to construct a [2]rotaxane (see above) comprising a dumbbell-shaped component based on a dibenzylammonium ion which is encircled by a DP24C8 macrocycle and terminated by (triphenylphosphonium)methyl stoppers.

A linear bis secondary dialkylammonium ion-containing scaffold&sbd;based upon an anthracenyl core&sbd;has been synthesized. It has been demonstrated that it is possible to dock either one or two dibenzo[24]crown-8 (DB24C8) macrocycles onto this scaffold to afford either a [2]- or [3]pseudorotaxane, respectively. In solution, the association constants for the formation of each of these species has been quantified by employing ¹H NMR spectroscopy, and both species survive in the “gas phase” as evidenced by FAB mass spectrometry. Additionally, the X-ray crystal superstructure of the [3]pseudorotaxane has been determined.

Two ammonium ion/crown ether-based [2]rotaxane monomers&sbd;each incorporating (i) a dumbbell-shaped component, possessing an exchangeable benzylic triphenylphosphonium stopper, and (ii) a ring component, bearing an aldehyde function&sbd;undergo a sequence of Wittig reactions in which the surrogate triphenylphosphonium stopper is exchanged for a ring component either (i) in the same rotaxane molecule to give cyclic daisy chains by an intramolecular, chain-terminating reaction or (ii) in another rotaxane molecule to give acyclic daisy chains by an intermolecular chain-propagating reaction.

Dibenzylammonium (DBA⁺) ions thread through the cavity of tribenzo[27]crown-9 (TB27C9) to generate [2]pseudorotaxanes that are stabilized principally by hydrogen-bonding interactions. The stabilities and complexation kinetics associated with these pseudorotaxanes depend markedly on the nature of the substituents situated on the phenyl rings of the DBA⁺ ions. For example, the complex formed between TB27C9 and the DBA⁺ ion bearing electron-withdrawing p-CO2Me substituents is stronger than that obtained from TB27C9 and the “parent”, unsubstituted DBA⁺ ion itself. Furthermore, the “parent” complex equilibrates much more rapidly with its uncomplexed components than do the complexes generated from TB27C9 and substituted DBA⁺ ions.

Thermodynamic control operates in the synthesis of a [2]rotaxane based upon the dibenzylammonium ion/crown ether recognition motif. When dibenzo[24]crown-8 is added to an acetonitrile solution containing a diimine dumbbell-like component, the dynamic nature of the system (i.e., imine hydrolysis/reformation) offers the ring component access to the NH2⁺ center, allowing the self-assembly of the corresponding “dynamic” [2]rotaxane to occur. The “fixing” of this [2]rotaxane can be achieved upon reduction of the imine bonds, affording a kinetically inert [2]rotaxane.

The template-directed syntheses of two [2]rotaxanes, one carrying one and the other two triphenylphosphonium stoppers, have been achieved using a threading-followed-by-stoppering approach. Either one or two benzylic bromide functions&sbd;located at the para-positions of dibenzylammonium-based ions, which become encircled by dibenzo[24]crown-8 macrocycles during the initial thermodynamically controlled phases that mark the recognition events&sbd;serve as sites for nucleophilic attack by triphenylphosphine during the subsequent kinetic stages that lead to the formation of the two [2]rotaxanes.

In contrast with dibenzo[24]crown-8 (DB24C8), when tetrabenzo[24]crown-8 (TB24C8) is mixed with dibenzylammonium hexafluorophosphate (DBA·PF6) in noncompetitive solvents, the thermodynamically driven noncovalent synthesis of the threaded 1:1 complex&sbd;a [2]pseudorotaxane&sbd;does not occur. However, on crystallization from solution&sbd;in a process which is presumably kinetically controlled&sbd;TB24C8 molecules and DBA⁺ cations form an array of [2]pseudorotaxanes stabilized by a plethora of [C−H···F] hydrogen bonds to highly ordered, interstitially located PF6^- anions.