Catalytic Self-Threading:  A New Route for the Synthesis of Polyrotaxanes

Abstract

Main chain and branched polyrotaxanes have been synthesized in which polymerization and rotaxane formation occur simultaneously, due to the presence of the catalytically active self-threading macrocycle cucurbit[6]uril. Using monomers that contain stopper groups to prevent the catalytic macrocycle from noncatalytic threading, it was possible to prepare polyrotaxanes in high yields with molecular weights up to 39000. These polyrotaxanes are structurally perfect in the sense that exactly two macrocycles are threaded onto each structural repeat unit. Investigations into the polymerization mechanism have demonstrated that the catalyst cucurbit[6]uril is highly sensitive toward the structure of the monomers employed and a poorly designed monomer may result in complete inactivity. Features of the mechanism are discussed in some detail.

[5]Rotaxane and [5]Pseudorotaxane Based on Cucurbit[6]uril and Anchored to a Meso-tetraphenyl Porphyrin

“…For this purpose, (pseudo)rotaxanes have been designed and synthesized; these are compounds which respond to external stimuli, be it chemical, electrochemical or photochemical, by changing their shape or by switching processes or movements [2]. Cyclodextrin, crown ethers, cyclophanes, and calixarenes are the most widely used macrocyles [2,3], but recently cucurbit [6]uril [4] and its homologues [4c] have joined this list as macrocycles in the synthesis of (pseudo)rotaxanes, and (pseudo)polyrotaxanes [4,5].…”

“…This multi functional hexameric macrocycle, cucurbit [6]uril, comprises a hydrophobic interior with two identical hydrophilic portals, and is synthesized from an acid-catalyzed condensation reaction of glycoluril and formaldehyde [4,5]. Its ability to encapsulate protonated diaminoalkanes along with its pH-dependent binding interactions have been used to design molecular switches and pseudopolyrotaxanes [4a,b, 5, 6].…”

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AbstractWater soluble [5]rotaxane and [5]pseudorotaxane based on cucurbit [6]uril and anchored to a meso-tetraphenyl porphyrin have been synthesized and characterized by spectroscopic methods ( 1 H-NMR, 13 C-NMR and UV), and by elemental analysis, and mass spectrometry. The preliminary results of the pH-driven switching properties of [5]rotaxane investigated through 1 H-NMR spectroscopy are reported.

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Encapsulation of alkyl and aryl derivatives of quaternary ammonium cations within cucurbit[n]uril (n = 6,7) and their inverted diastereomers: density functional investigations

“…A family of cucurbit[n]uril, CB [n], hosts comprising of methylene-bridged glycouril units have attracted considerable attention owing to their potential applications in organic synthesis [1][2][3][4], molecular recognition [5,6], nanoscience [7,8], catalysis [9][10][11], drug delivery vehicles [12] and separation technology [13,14]. The number of glycouril units in cucucrbituril homologues renders varying size to their hydrophobic cavity while portal carbonyl groups on portals provide hydrophilic exterior to these macrocycles.…”

Clicking cyclophane to boron doped diamond surfaces

“…Recently, this "click" methodology has been extended to feature interlocked structures (e.g. rotaxanes and catenanes) [9][10][11][12][13][14][15][16]. This methodology offers higher yields and better resulting structure compared to traditional methods.…”