Concentration-dependent patterns at the liquid/solid interface.

We report STM investigations on a linear oligophenyleneethylene (OPE)-based self-assembling Pd(ii) complex that forms highly-ordered concentration dependent patterns on HOPG. At high concentration, 2D lamellar structures are observed whereas the dilution of the system below a critical concentration leads to the formation of visually attractive rhombitrihexagonal arrangements featuring three different kinds of polygons: triangles, hexagons and rhombi. The key participation of the Cl ligands attached to the Pd(ii) centre in multiple C-H···Cl interactions was demonstrated by comparing the patterns of with those of an analogous non-metallic system .