The field of molecular logic gates originated 25 years ago, when A. P. de Silva published a seminal article in Nature. Stimulated by this ground breaking research, scientists were inspired to join the race to simulate the workings of the fundamental components of integrated circuits using molecules. The rules of this game of mimicry were flexible, and have evolved and morphed over the years. This tutorial review takes a look back on and provides an overview of the birth and growth of the field of molecular logics. Spinning-off from chemosensor research, molecular logic gates quickly proved themselves to be more than intellectual exercises and are now poised for many potential practical applications. The ultimate goal of this vein of research became clearer only recently – to “boldly go where no silicon-based logic gate has gone before” and seek out a new deeper understanding of life inside tissues and cells.

Acid fuels the motion of a threaded ring: A central goal in the construction of molecular-scale machines is the efficient achievement of one-way motion. Erbas-Cakmak et al. developed a class of machines that transmit pH changes into the two-stage guided motion of molecular rings threaded on a linear or cyclic axle. The design relies on temporary blocking groups and landing sites along the axle that toggle between active and passive states in response to acid or base. Trichloroacetic acid initiates the first stage of motion until it is decomposed by base in the solution, spurring the second phase. Science , this issue p. 340

Mechanical point-chirality in a [2]rotaxane is utilized for asymmetric catalysis. Stable enantiomers of the rotaxane result from a bulky group in the middle of the thread preventing a benzylic amide macrocycle shuttling between different sides of a prochiral center, creating point chirality in the vicinity of a secondary amine group. The resulting mechanochirogenesis delivers enantioselective organocatalysis via both enamine (up to 71:29 er) and iminium (up to 68:32 er) activation modes.