Controlled Hydrogen-Bond Breaking in a Rotaxane by Discrete Solvation

摘要

Mechanically interlocked molecules are appealing nanoscale structures for the development of artificial molecular machinery components, such as switches, actuators, ratchets, and motors. Well-known examples are [2]rotax-anes, which are composite molecular systems consisting of a macrocycle mechanically trapped onto a linear thread by bulky end groups ("stoppers"). The ability to reversibly control the relative orientation and position of the macrocycle with respect to the thread is the key to their function. The way to induce large-amplitude internal motions is by influencing the non-covalent binding interactions between macro-cycle and thread. However, understanding how such processes occur is very difficult to probe experimentally because bulk solvation involves many solvent molecules that can adopt numerous different arrangements of similar energies. Herein we demonstrate that these interactions can be addressed controllably and that a macrocycle can be unlocked from a thread by adding solvent molecules to a single [2]rotaxane one at a time.