Substituent effect on the self-assembled structures of two carboxyl-functionalised phthalocyanine derivatives on highly oriented pyrolytic graphite.

: The self-assembling behaviour of two kinds of 4-carboxyphenoxy phthalocyanines (Pc1 and Pc2) has been investigated by scanning tunneling microscope (STM). Pc1 and Pc2 are isomers with the same substituent at alpha- andbeta-position of the phthalocyanine core, respectively. Our STM results have shown that the Pc1 molecule fabricates into stable networks with nanoscale cavities, while Pc2 forms an unstable linear-like structure at the 1-heptanoic acid/graphite interface. The different supramolecular assembling structures may result from the different substituent position of the carboxyl groups which influence the formation of intermolecular hydrogen bonds.