Rigid rod oligo(phenylene-ethynylene-butadiynylene)s (oPEBs), "half-rings'' of two rigid rods connected via a molecular clamp unit, and shape-persistent macrocycles (cyclic "half-ring dimers'') are synthesized and their self-assembled monolayers (SAMs) are investigated by scanning tunneling microscopy (STM) at the interface of 1,2,4-trichlorobenzene (TCB)/highly oriented pyrolytic graphite (HOPG). The results are important for the design of molecular building blocks for two-dimensional nanoscale architectures on solid surfaces.