Dynamic Control of Intramolecular Rotation by Tuning the Surrounding Two-Dimensional Matrix Field.

The intramolecular rotation of 4-farnesyloxyphenyl-4,4-difluoro-4-bora-3a,4a-diaza- s-indacene (BODIPY-ISO) was controlled by tuning its local physical environment within a mixed self-assembled monolayer at an air-water interface. Intramolecular rotation was investigated by considering the twisted intramolecular charge transfer (TICT) fluorescence of BODIPY-ISO, which increases in intensity with increasing viscosity of the medium. In situ fluorescence spectroscopy was performed on mixed monolayers of BODIPY-ISO with several different lipids at the air-water interface during in-plane compression of the monolayers. Depending on the identity of the lipid used, the fluorescence of the mixed monolayers could be enhanced by mechanical compression, indicating that the rotation of BODIPY-ISO can be controlled dynamically in mixtures with lipids dispersed at the air-water interface. Taken together, our findings provide insight into strategies for controlling the dynamic behavior of molecular machines involving mechanical stimuli at interfaces.