Scanning tunneling microscopy study of Pd bis(β-diketonate) on graphite

Using bis[1-3′,4′,-trioctyloxyphenyl-3-(4′-octyloxphenyl) propane-1,3-dionate] palladium (II) and bis[1-3′,4′,-trihexadecyloxyphenyl-3-(4′-hexadecyloxphenyl) propane-1,3-dionate] palladium (II) discotic metallomesogens as examples, we have demonstrated the possibility to prepare an ordered 2D array of molecular films with tunable intermolecular spacing. It was observed by scanning tunnelling microscopy (STM) with near molecular resolution that these molecules form regular and cognate surface structures upon adsorption on the basal plane of HOPG. Change in the length of side chain alkyl groups (from octyl to hexadecyl) resulted in the change of molecular periodicity in the films. It is hoped that this method could provide a complementary approach to create ordered 2D nanostructure with controllable metal density.