Simple molecular-level machines. Interchange between different threads in pseudorotaxanes
In suitably designed supramolecular systems, composed of a macrocycle and two different thread-like compounds, it is possible to choose, by means of chemical inputs, which thread enters the macrocycle's cavity, and it is also possible to cause reversible interchange between the two threads. Two such systems are described. In one of them, the macrocyclic component is 1,5-dinaphtho-38-crown-10, the potential threads are 1,1′-dibenzyl-4,4′-bipyridinium and 2,7-dibenzyldiazapyrenium dications, and the chemical input used is amine/acid. In the other system, the macrocyclic component is the tetracationic cyclophane, cyclobis(paraquat-p-phenylene), the potential threads are tetrathiafulvalene and a 1,5-dioxynaphthalene derivative, and the input is reduction/oxidation. These systems are examples of chemically driven molecular-level mechanical machines.