Isomerization of a second-generation molecular motor (e.g.7 , Figure 3A) leads to helix inversion of the overcrowded alkene moiety.21,27 The resulting metastable isomers are diastereomers of the stable isomers. The metastable isomer (R ,M )-7-ms is the pseudo-enantiomer of its corresponding stable isomer (R ,P )-7-st . These two isomers are called pseudo-enantiomers because they are near-mirror images, except for the methyl group at the stereogenic center. Metastable isomer (R ,M )-7-ms is pseudo-identical to the stable isomer (S ,M )-7-st . The term pseudo-identical, rather than identical, applies here because the point chirality at the motor stereogenic center differs between the