Tomohide Takami

Changing Stations in Single Bistable Rotaxane Molecules under Electrochemical Control

We have directly observed electrochemically driven single-molecule station changes within bistable rotaxane molecules anchored laterally on gold surfaces. These observations were achieved by employing molecular designs that significantly reduced the mobility and enhanced the assembly of molecules in orientations conducive to direct measurement using scanning tunneling microscopy. The results reveal molecular-level details of the station changes of surface-bound bistable rotaxane molecules, correlated with their different redox states. The mechanical motions within these mechanically interlocked molecules are influenced by their interactions with the surface and with neighboring molecules, as well as by the conformations of the dumbbell component.

Building Self-Assembled Molecular Layers with Axially Substituted Titanium Phthalocyanines

Adsorption on graphite (HOPG) by titanium phthalocyanine axially bonded to a catechol ligand (TiPcat), titanylphthalocyanine (TiOPc), and 1:1 mixtures of these are studied at the HOPG-octylbenzene interface. The surface structures of a two-component bilayer, and of the individual monolayers of TiOPc and TiPcat, were determined by scanning tunneling microscopy (STM). TiPcat self-segregates onto a monolayer of TiOPc when an equal molar mixture is used. The preferential formation of a TiOPc monolayer from a solution containing both molecules is attributed to the difference in adsorption energies between TiPcat and TiOPc on graphite. The transformation of the hexagonal lattice of the pure TiOPc monolayer into a pseudo-square lattice was induced by the adsorption of TiPcat molecules. DFT calculations of the catechol orientation are presented.