Self-assembly of thiophene compounds at interfaces can influence the properties of devices with components containing these ubiquitous functional groups, yet this process is poorly understood. Here the influence of substitution on self-assembly of alkylthiophenes is studied to uncover the affects of substitution on the patterns formed by molecules at the liquid/solid interface. Monofunctionalized thiophene derivatives including N-octadecyl-2-thiophenecarboxamide, N-octadecyl-3-thiophenecarboxamide, N-octadecyl-N'-2-thiophene-urea, and N-octadecyl-N'-3-thiophene-urea were generated and the self-assembled monolayers were studied using scanning tunneling microscopy (STM). It is apparent that different moieties and ring-substitution positions influence packing pattern. Attaching amide functional groups at the 2- versus the 3-position affected the orientation of molecules within the monolayer in a manner consistent with a drive toward centrosymmetricity. Introduction of urea functionality induced dramatic changes in the molecular conformation and hydrogen-bonding pattern. The monolayers were modeled using molecular mechanics and analyzed using DFT calculations to explore why changes in molecular structure influenced the packing patterns.

Synthesis and self-assembly of monofunctionalized thiophenes

245th National Meeting (2013)

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