This thesis describes the synthesis, application, and study of three types of molecular machines: nanocars, hemithioindigo switches and motors, and Feringa- type molecular motors. Each chapter involves a different type of molecular machine, designed for a specific purpose.
The first chapter, Nanocars with Permanent Dipoles: Preparing for the Second International Nanocar Race, is focused solely on the multi-step synthetic strategy involved to make the requite molecules. The cars are designed to be stimulated on a metal surface with an electric field gradient from a scanning probe microscopy tip. To optimize the ability to translate and rotate a car with extreme precision, a permanent dipole moment, generated by an N,N dimethylamine- moiety on one end of the car coupled with a nitro group on the other end, has been included in each structure. The nanocars all possess unexplored combinations of structural features. The second chapter, a collaboration with Dr. Ana L. Santos, Visible-Light Active Hemithioindigos Kill Gram-positive Bacteria by Oxidative Damage, focuses on the application of the molecules as new antimicrobial agents as well as the synthesis. We describe a set of new hemithioindigo (HTI)-based visible light-activated molecular switches and unidirectional molecular motors that kill Gram-positive, but not Gram-negative bacteria, within minutes of light activation (455 nm at 65 mW cm-2) without damaging mammalian cells. These molecules, with an oxidative mechanism of action, stand in contrast to previous work involving Feringa-type molecular motors, where the mechanism of action is mechanical. The final chapter, Probing the Rotary Cycle of Amine- Substituted Molecular Motors, is focused on studying the physical organic chemistry involved in the rotation of a new, diamine-substituted Feringa-type molecular motor. I describe the effects of the functionalization as well as a new method for determining the molar absorbance of the thermally fleeting metastable conformer. Here we use in situ NMR illumination and UV-vis spectroscopy to determine the kinetic and thermodynamic parameters of the rate limiting, thermal isomerization step of the molecular motor.