Fig. 1.

Structural formulas of the oligorotaxanes and schematic description of the AFM-based single-molecule force spectroscopy experiment. (A and B) Structure formulas and coconformations of the [4]rotaxane (A) and [7]rotaxane (B) of the [0.5(n − 1) + 2] family. The terms in square brackets denote the total number of interlocked components and n is the number of DNP units present in the backbone components. In this coconformation, half of the DNP units (in red) are encircled by CBPQT⁴⁺ rings (in blue). Noncovalent intramolecular interactions such as π-interactions linking DNP units and Blue Boxes, hydrogen bonds linking α-hydrogen atoms of the Blue Boxes with tetra(ethylene oxide) chains in the backbones, and Coulombic interactions between the molecular rings and PF₆⁻ counterions stabilize the folded conformation. PF₆⁻ counterions are not shown. (C) Mechanical unfolding of individual oligorotaxanes, leading to the breaking of the intramolecular interactions maintaining the folded conformation.