Chain‐length‐adjusted assembly of substituted porphyrins on graphite

A series of alkyloxyphenyl‐substituted porphyrins were synthesized, and their adsorption and assembling behaviour on a highly oriented pyrolytic graphite (HOPG) surface were studied by scanning tunneling microscope (STM) in ambient conditions. A characteristic stripe‐like structure was observed from these samples. In high‐resolution images, we found that within the stripe structure porphyrin cores are arranged side by side with each other and the alkyl chains interdigitate to form a uniform alkane lamella. This high stability and close‐packed assembly is attributed to van der Waals interactions between the alkyl chains and the graphite substrate, which substantially increases the desorption barrier of the combined molecules. This observation illustrates that molecular alkylation is an effective method to obtain stable low‐dimensional molecular assemblies.