Self-assembly of PcOC8 and its sandwich lanthanide complex Pr(PcOC8)2 with oligo(phenylene-ethynylene) molecules

Self-assemblies of octakis(octyloxy) phthalocyanine (PcOC8) and its sandwich lanthanide complex, substituted praseodymium bis(phthalocyanine) (Pr(PcOC8)(2)), with oligo(phenylene-ethynylene) (OPE) have been investigated by scanning tunneling microscopy (STM) on a highly oriented pyrolytic graphite (HOPG) surface. The assemblies were prepared by dissolving the molecules in phenyloctane solution. It was found that both PcOC8 and Pr(PcOC8)2 can form 4-fold or 6-fold symmetrical adlayers on HOPG. The intramolecular structure of Pr(PcOC8)2 molecule was revealed by a high-resolution STM image. When OPE molecules are added into phenyloctane solvent, Pr(PcOC8)2 molecules prefer to form an ordered adlayer at the top of the OPE adlayer, while PcOC8 molecules adsorb on HOPG surface directly and form separated domains with OPE. These results may be helpful to construct surface assemblies and develop molecular electronic devices in the future.