Molecular machines (either synthetic or biological) are defined as molecules or groups of molecules that perform mechanical-like movements in response to certain stimuli (light, electricity, or chemical energy). Because a braking system is important for any moving object, researchers at National Taiwan University and Academia Sinica (both in Taipei, Taiwan) have developed the first light-driven, room-temperature molecular brake.
Based on nuclear magnetic resonance (NMR) studies, spectral simulations, and molecular modeling, it is possible to calculate the rotation rate of the rigid pentiptycene group, a four-bladed wheel structure that can exhibit two different motion states (trans-1 and cis-1). In dichloromethane solution at 298 K, the pentiptycene wheel freely rotates in a trans-1 state but slows by nine orders of magnitude in the cis-1 state. The two states can be switched by using different wavelengths of light (306 and 254 nm) due to the wavelength-sensitive dinitrostyryl group within the pentiptycene. This molecular “brake” could be attached to other molecular machines in solution to effectively control or stop their motion as a function of illumination wavelength. Contact Jye-Shane Yang at [email protected].