Integration of functional organic molecules on a surface is one of the most important challenges to develop the molecule-based devices with controlled nanoarchitect designs. Fabrication of controlled two-dimensional organizations via self-assembly would be achieved by the understanding of several intermolecular interactions such as molecule-molecule, molecule-substrate, and molecule-solvent interactions. In this contribution, we present our recent studies on the formation and transformation of two-dimensional structures in thermally-responsive isobutenyl compounds possessing long alkyl tails to achieve various nano-patterns. Effects of alkyl chain length, linkage, and thermal treatment on the two-dimensional structures were studied by using the scanning tunneling microscopy (STM) at the highly oriented pyrolytic graphite (HOPG)/liquid interface.
Modulations of two-dimensional structures in the isobutenyl ester compounds with C18-21 alkyl chains were found due to odd-even effect, whereas those with shorter alkyl tails (C14-17) displayed the unified structures. This is also the case for amide-linked isobutenyl compounds, namely the compounds with C18-21 alkyl chains displayed either wavy or tripod structures due to odd-even effect of alkyl chain units, whereas those with C14-17 formed the same zig-zag structure. These results suggest that there is a specific alkyl chain length range that shows odd-even alkyl chain length effect in the isobutenyl compounds. The ether function of the isobutenyl compounds could be transformed into hydroxyl group by a thermal reaction of tandem Claisen rearrangement (TCR). After the TCR, all the 2D structures were converged into the same linear structures, and odd-even effect was completely quenched for both compounds.
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