Figure 16.
Design and pH-dependent operation of mechanized nanoparticles. (A) When pH is lowered such that the anilinium nitrogen atom is protonated, the CB[6] ring shuttles to the distal hexamethylenediammonium station, and PI is released. (B) At neutral pH, the CB[6] ring sits on the tetramethylenediammonium recognition unit, blocking the nanopores. (C) When the pH is raised, all of the nitrogen atoms on the stalk are deprotonated resulting in dethreading of the CB[6] ring. The system is designed such that the pH-response can be fine-tuned by changing the functional group R to modulate the pKa of the anilinium nitrogen atom. Reprinted with permission from 56, copyright (2009) J. Am. Chem. Soc.