Azulene Based Nanocars

The precise design of Nanocars and single-molecule machines requires understanding the mechanisms of inducing and controlling molecular motion and hence allowing the conversion of electric power into controlled movement. We present a series of azulene-based Nanocars specifically designed to uncover the influence of several chemical groups on the movement performance. While the azulene core is characterized by a high dipole moment, the rational choice of lateral groups can further enhance the dipole moment and influence the interaction of the molecules with the Au(111) surface and with each other. First, we investigated the high electric dipole moment molecule di-tert-butyl 2-isocyanoazulene-1,3-dicarboxylate (BCA). While single molecules were immobile, a complex structure consisting of cleaved molecules and gold adatoms moved under STM voltage pulses. This structure could be driven along an arbitrarily chosen path. To investigate the influence of the different functional chemical groups and the impact of the manifold physical effects taking place, two modified molecules were investigated. The results of these experiments demonstrate the efficiency of the functional chemical groups attached to the azulene core and shed new light on design strategies for fast and controllably moving Nanocars in general.