2D Structural Modulation by Odd-Even Effect of Alkyl Chains Revealed by Scanning Tunneling Microscopy at Solid/Liquid Interface

Abstract

This review paper presents our recent progress on the formation of self-assembled two-dimensional (2D) structures, and their modulation by the odd-even effect of alkyl chains on porphyrin derivatives, isobutenyl compounds and bipyridine derivatives. The 2D structures were directly visualized by scanning tunneling microscopy (STM) at the highly oriented pyrolytic graphite (HOPG)/solvent interface. The alkyl tails in the compounds work as molecule-molecule and molecule-substrate interaction sites, and the nature of the 2D structures depended on the alkyl chain length. These STM observations revealed that, for each compound, an odd-even effect exists for a specific range of alkyl chain lengths.