We describe a new concept for rotaxane synthesis through intramolecular slippage using π-conjugated molecules as rigid axles linked with organic soluble and flexible permethylated α-cyclodextrins (PM α-CDs) as macrocycles. Through hydrophilic–hydrophobic interactions and flipping of PM α-CDs, successful quantitative conversion into rotaxanes was achieved without covalent bond formation. The rotaxanes had high activation barrier for their de-threading, so that they were kinetically isolated and derivatized even under conditions unfavorable for maintaining the rotaxane structures. ¹H NMR spectroscopy experiments clearly revealed that the restricted motion of the linked macrocycle with the rigid axle made it possible to control the kinetic stability by adjusting the length of the rigid axle in the precursor structure rather than the steric bulkiness of the stopper unit.

Insulated π-conjugated molecules, in which the π-conjugated compounds are covered by a cyclic protective sheath, have attracted considerable attention because of their potential applicability in next-generation mono-molecular electronic devices. We have developed new methods of synthesizing insulated π-conjugated molecules involving the self-inclusion of rotaxane precursors linking π-conjugated units as a guest and permethylated cyclodextrin (PMCD) as a macrocyclic host. The insulated π-conjugated molecules thus formed are highly soluble in organic solvents and display photoluminescence efficiency. This paper also highlights a new method for synthesizing insulated molecular wire (IMW) through the polymerization of insulated π-conjugated molecules as monomers. The IMWs thus formed have a high covering ratio, rigidity, and showed high charge mobility in the solid state; further, they are readily soluble in a variety of organic solvents. In this account, the synthetic methodologies and characteristic of insulated π-conjugated molecules and IMWs are discussed. DOI 10.1002/tcr.201100009

Summary: We developed a new method for synthesizing an organic-soluble permethylated cyclodextrin-based insulated molecular wire (IMW); this method involves the polymerization of a symmetrical linked inclusion complex as a monomer. This monomer was synthesized by dimerization of linked inclusion complexes at the terminal alkynyl groups by Glaser coupling. The polyrotaxane thus obtained is highly soluble in a variety of organic solvents and has a high covering ratio, regioregularity, and photoluminescence efficiency.