Douglas C. Friedman

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The tendency for viologen radical cations to dimerize has been harnessed to establish a recognition motif based on their ability to form extremely strong inclusion complexes with cyclobis(paraquat-p-phenylene) in its diradical dicationic redox state. This previously unreported complex involving three bipyridinium cation radicals increases the versatility of(More)
The preparation, characterization, and switching mechanism of a unique single-station mechanically switchable hetero[2]catenane are reported. The facile synthesis utilizing a "threading-followed-by-clipping" protocol features Cu(2+)-catalyzed Eglinton coupling as a mild and efficient route to the tetrathiafulvalene-based catenane in high yield. The(More)
Five donor-acceptor oligorotaxanes made up of dumbbells composed of tetraethylene glycol chains, interspersed with three and five 1,5-dioxynaphthalene units, and terminated by 2,6-diisopropylphenoxy stoppers, have been prepared by the threading of discrete numbers of cyclobis(paraquat-p-phenylene) rings, followed by a kinetically controlled stoppering(More)
Two series of oligorotaxanes R and R' that contain -CH(2)NH(2)(+)CH(2)- recognition sites in their dumbbell components have been synthesized employing template-directed protocols. [24]Crown-8 rings self-assemble by a clipping strategy around each and every recognition site using equimolar amounts of 2,6-pyridinedicarboxaldehyde and tetraethyleneglycol(More)
Degenerate [2]rotaxanes, with their two identical binding sites, generally exhibit equilibrium dynamics with free energies of activation (DeltaG(double dagger)) for the shuttling process starting as low as 10 kcal x mol(-1). This DeltaG(double dagger) value can be raised quite dramatically by inserting "speed bumps" in the form of steric and/or(More)
Two [3]catenane 'molecular flasks' have been designed to create stabilized, redox-controlled tetrathiafulvalene (TTF) dimers, enabling their spectrophotometric and structural properties to be probed in detail. The mechanically interlocked framework of the [3]catenanes creates the ideal arrangement and ultrahigh local concentration for the encircled TTF(More)
Two donor-acceptor [3]catenanes-composed of a tetracationic molecular square, cyclobis(paraquat-4,4'-biphenylene), as the π-electron deficient ring and either two tetrathiafulvalene (TTF) and 1,5-dioxynaphthalene (DNP) containing macrocycles or two TTF-butadiyne-containing macrocycles as the π-electron rich components-have been investigated in order to(More)
A [2]pseudorotaxane-based mechanised nanoparticle system, which operates within an aqueous acidic environment, has been prepared and characterised; this integrated system affords both water-soluble stalk and ring components in an effort to improve the biocompatibility of these promising new drug delivery vehicles.
Two [2]rotaxane initiators for single-electron-transfer living-radical-polymerization were synthesized and used for the controlled polymerization of methyl acrylate. The mechanically interlocked polymers exhibited distinct responses to mechanical activation by ultrasound. Monitoring the fate of the rotaxanes' charge transfer absorption bands provides(More)
A strategic modification to the corner ligands in Pd(II)-containing, electron-poor cyclophanes has profound repercussions for their assemblies with electron-rich aromatic crown ethers in both the solid and solution states; the formation of ring-in-ring complexes can override competing [3]catenane production on masking the hydrogen bond donor capabilities of(More)