Preprogrammed 2D folding of conformationally flexible oligoamides: foldamers with multiple turn elements.

Abstract

Controlling the molecular conformation of oligomers on surfaces through noncovalent interactions symbolizes an important approach in the bottom-up patterning of surfaces with nanoscale precision. Here we report on the design, synthesis, and scanning tunneling microscopy (STM) investigation of linear oligoamides adsorbed at the liquid-solid interface. A new class of extended foldamers comprising as many as four turn elements based on a structural design "rule" adapted from a mimic foldamer was successfully synthesized. The self-assembly of these progressively complex oligomeric structures was scrutinized at the liquid-solid interface by employing STM. Submolecularly resolved STM images of foldamers reveal characteristic in-plane folding and self-assembly behavior of these conformationally flexible molecules. The complexity of the supramolecular architectures increases with increasing number of turn elements. The dissimilarity in the adsorption behavior of different foldamers is discussed qualitatively in light of enthalpic and entropic factors. The modular construction of these oligomeric foldamers with integrated functionalities provides a simple, efficient, and versatile approach to surface patterning with molecular precision.