Polymeric molecular shuttles: Polypseudorotaxanes & polyrotaxanes based on viologen (paraquat) urethane backbones & bis(p-phenylene)-34-crown-10

A [2]pseudorotaxane based on a pillar[6]arene and its application in the construction of a metallosupramolecular polymer

A novel metallosupramolecular polypseudorotaxane was constructed by pillar[6]arene-based host–guest recognition and metal coordination.

Desymmetrization of disubstituted aromatic crown ethersviaintramolecular Cannizzaro reactions

Ba⁺⁺templated Cannizzaro reactions convert symmetrical aromatic crown ether dialdehydes of various types [dibenzo and bis(meta-phenylene)] and sizes (20–32 atom rings) to acid–alcohol functionalized crown ethers in 70–98% yields.

Viologen-Based Rotaxanes from Dibenzo-30-crown-10

Three [2]rotaxanes (4, 7, and 12) and one [3]rotaxane (8) were synthesized based on the dibenzo-30-crown-10/viologen binding motif. To the best of our knowledge, these are the first rotaxanes formed from dibenzo-30-crown-10 and viologens. The rotaxanes were all characterized by ¹H NMR, ¹³C NMR, and HRMS. An X-ray crystal structure of one of the [2]rotaxanes (7) was obtained. This work demonstrates for the first time that dibenzo-30-crown-10 does form pseudorotaxane complexes with viologens in solution.

One-pot synthesis of block-copolyrotaxanes through controlled rotaxa-polymerization

The aqueous reversible addition fragmentation chain-transfer (RAFT) copolymerization of isoprene and bulky comonomers, an acrylate and an acrylamide in the presence of methylated β-cyclodextrin was employed for the first time to synthesize block-copolyrotaxanes. RAFT polymerizations started from a symmetrical bifunctional trithiocarbonate and gave rise to triblock-copolymers where the outer polyacrylate/polyacrylamide blocks act as stoppers for the cyclodextrin rings threaded onto the inner polyisoprene block. Statistical copolyrotaxanes were synthesized by RAFT polymerization as well. RAFT polymerization conditions allow control of the composition as well as the sequence of the constituents of the polymer backbone which further effects the CD content and the aqueous solubility of the polyrotaxane.

Insights into the Difference Between Rotaxane and Pseudorotaxane

Rotaxane and pseudorotaxane are two types of mechanically interlocked molecular architectures, and there is a clear topological difference and boundary between them. In this work, a "suggested [2]rotaxane 1⊂α-CD" was constructed based on axle molecule 1 bearing two terminal ferrocene groups and a wheel component α-cyclodextrin (α-CD), but the result obtained indicated that the ferrocene group cannot prevent α-CD dethreading under UV irradiation. That is, 1⊂α-CD is just a pseudo[2]rotaxane. Furthermore, the two ferrocene groups in 1⊂α-CD were encapsulated by two cucurbit[7]uril (CB[7]) units to obtain a heteropseudo[4]rotaxane 1⊂α-CD⋅2CB[7]. This heteropseudo[4]rotaxane displayed high stability towards harsh temperatures and the isomerization of azobenzene in 1, so it can be regarded as a [2]rotaxane. In this [2]rotaxane, the stoppers are not the bulky groups covalently bonded to the axle, but the cyclic CB[7] units connected through noncovalent interactions.

Femtosecond excited state dynamics of a stilbene–viologen charge transfer complex assembled via host–guest interaction

The ultrafast photoinduced electron transfer in a supramolecular charge transfer complex was studied.

Discrete 1 : 1 complexes and higher order assemblies formed from aminobenzene sulphonate anions and a tetraimidazolium “molecular box”

Aminobenzene sulphonate species having different isomeric patterns act as substrates for a tetracationic molecular box.

Cu(II) Ion-Responsive Self-Assembly Based on a Water-Soluble Pillar[5]arene and a Rhodamine B-Containing Amphiphile in Aqueous Media

Cu(II) ion-responsive self-assembly in aqueous media was achieved based on a water-soluble pillar[5]arene host and a rhodamine B-containing amphiphile guest. The host-guest complex acted as a supra-amphiphile and self-assembled into vesicles. After addition of Cu(II), vesicles turned into solid nanoparticles, accompanied by the color change of the solution from colorless to red and a fluorescence "on" phenomenon.

Iterative Synthesis of Oligo[n]rotaxanes in Excellent Yield

We present an operationally simple iterative coupling strategy for the synthesis of oligomeric homo- and hetero[n]rotaxanes with precise control over the position of each macrocycle. The exceptional yield of the AT-CuAAC reaction, combined with optimized conditions that allow the rapid synthesis of the target oligomers, opens the door to the study of precision-engineered oligomeric interlocked molecules.

Aromatic sulfonate anion-induced pseudorotaxanes: environmentally benign synthesis, selectivity, and structural characterization

Aromatic sulfonates allow the effective construction of anion-containing pseudorotaxanes from a tetracationic macrocycle known as the “Texas box” in organic media and under organic-free aqueous conditions.