H. Azehara¹, Y. Suzuki¹, T. Ishida^{2, 3}, W. Mizutani⁴, K. Hiratani⁵, H. Tokumoto⁴

1) Joint Research Center for Atom Technology (JRCAT) - Japan Science and Technology Corporation (JST) - National Institute of Advanced Industrial Science and Technology (AIST)
2) Institute for Mechanical System Engineering, AIST
3) Precursory Research for Embryonic Science and Technology (PREST) - JST
4) JRCAT - AIST, Nanotechnology Research Institute
5) Nanoarchtectonics Research Center, AIST

Rotaxanes are molecular complexes composed of rotational ring and axis-rod molecules. It was also found that the ring could shuttle along the rods in some cases. Collier et al. [Science, 285, 391 (1999)] showed a monolayer of such a rotaxane could be utilized for logic gates. They confirmed an electric conductance change depending on the molecular states of the rotaxane, measuring a large number of molecules macroscopically. The relationship between the molecular states and their properties is not well understood. In order to investigate it using scanning probe microscopes, the rotaxane molecules should be sparsely immobilized on well-defined surfaces, e.g., self-assembled monolayers (SAMs).
We succeeded in immobilizing rotaxane molecules sparsely in n-hexanethiol-based SAMs, where the orientation and concentration of the molecules are well controlled, via co-adsorption onto Au(111) surfaces. We could observe the isolated rotaxane molecules using the tapping-mode AFM with carbon nanotube tips as well as commercial silicon tips.