Structure-wise, the key difference between the S and M isomers is the extent of the out-of-plane displacement of the rotor with respect to the stator, measured with dihedral angle φ, defined in Figure . In the absence of steric hindrance, this angle should be close to 0 • /180 • which would correspond to a flat arrangement, energetically preferred in the C=C bonded sp 2 systems. At the same time, due to the steric repulsion between the rotor and the switching unit, this angle becomes distorted from planarity. Depending on which side of the switch the rotor moiety is interacting with, the repulsion strength varies, giving rise to different energies and different φ values of the S and M forms. Importantly, this varying repulsion does not induce pronounced changes in the orientation of the switching unit, measured with dihedral angle θ, also defined in Figure .