Molecular Power Spring: Circular Dichroism Inversion of Polythiophene Aggregates from the Right-Handed Helix to Left-Handed Helix.

In molecular rotors, a type of molecular machine, spontaneous rotors without the need for an external stimulus are promising because conventional molecular rotors require a continuous energy supply. In this study, we demonstrate spontaneous transformation from kinetically favored metastable right-handed helical aggregates to thermodynamically stable left-handed helical aggregates after an evaporation procedure. In addition, we propose the conditions for preparation of metastable right-handed helical aggregates, whose chirality can be spontaneously inverted, based on kinetic analysis. This molecular power spring will be useful for designing new types of molecular machines.