Direct visualization of metal ions in supramolecules.

We performed high resolution scanning-tunneling microscopy with simultaneous current-voltage characteristics (STS) measurements on single molecules deposited on graphite surfaces. We present our recent results on Co [2$\times $2], Mn [3$\times $3] grid-type molecules, Cu$_{20}$ wheel-shaped polyoxoanions, as well as on Cu coordination polymers. In our STS measurements we found a rather large signal at the positions of the metal centers in the molecules i.e. the location of the individual metal ions in their organic matrix is directly addressable by STS even if these ions are covered by the organic ligands.