Theoretical study on the working mechanism of a reversible light-driven rotary molecular motor

Recent progress in the experimental design and synthesis of artificial light-driven molecular motors has made it possible to reverse the light-powered rotation of a molecular motor during the rotary process with multilevel control of rotary motion. With the interconversion between the photochemically generated less-stable isomers in one unidirectional rotary cycle with the stable isomers in the other cycle, the clockwise and anticlockwise rotations can be regulated with configuration inversion at the stereogenic centre. In this work, we report theoretical calculations by using density functional theory and time-dependent density functional theory, revealing the working mechanism of the clockwise and anticlockwise rotations. Specifically, by locating the relevant stationary points along the excited-state and ground-state reaction paths, the clockwise and anticlockwise rotary cycles are explored in great detail, which is of complementary importance in understanding the overall rotary process of the reversible rotation.