Observation of face-to-face host-guest associated states prior to threading of dialkylammonium ions into the DB24C8-like openings of a molecular cage.

The threading of bis(dialkylammonium) ions through the DB24C8-like openings of a molecular cage proceeds through a stepwise mechanism: formation of a face-to-face complex between the NH2(+) centers and the crown ether, significant dissociation of this complex, and passage of the terminus of the cation through the macrocycle.

A two-stage molecular retractable cable featuring push-button and rotary two-way switching modes.

A molecular cage based [2]rotaxane is reported in which the linear thread component can be elongated and contracted in a stepwise manner, mimicking a two-stage retractable cable that can be operated in both push-button (free-selection) and rotary (continuous-change) modes, depending on the choice of reagents.

Weakly associated TFPB anions are superior to PF6 anions when preparing (pseudo)rotaxanes from crown ethers and secondary dialkylammonium ions.

Making the right choice: Tetrakis(3,5-trifluoromethylphenyl)borate (TFPB) counter anions can facilitate the threading of dibenzylammonium (DBA(+)) ions through macrocycles in cases where the corresponding PF(6)(-) salts fail to exhibit complexation.

A molecular cage-based [2]rotaxane that behaves as a molecular muscle.

We report a molecular cage-based [2]rotaxane that functions as an artificial molecular muscle through the control of the addition and removal of fluoride anions. The percentage change in molecular length of the [2]rotaxane is about 36% between the stretched and contracted states, which is larger than the percentage change (approximately 27%) in human muscle.