PHYS 420 |
| To understand the role solvent plays in molecular self-assembly, a series of benzene carboxylic acid derivatives have been studied at the liquid-graphite interface using scanning tunneling microscopy (STM). The 2D hydrogen-bonded networks formed by three molecules – trimesic acid (1,3,5-benzenetricarboxylic acid), trimellitic acid (1,2,4-benzenetricarboxylic acid), and pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid) – have been individually investigated in alkanoic acids and alcohols of varying chain length, and mixtures of these solvents. Lackinger et al. reported solvent induced polymorphism in the assembly of trimesic acid on graphite (Langmuir 2005 21, 4984-4988). In addition to the open structures observed previously, the present work shows a dominant high density structure of trimesic acid for the same series of solvents. For trimellitic acid, only a high density packing structure is observed under all experimental conditions. For pyromellitic acid, both open and high density assembly structures are observed depending on the solvent utilized. Details of the molecular packing on graphite will be discussed in light of both the STM results and Density Functional Theory geometry optimizations and relaxed potential energy surface scans of isolated carboxylic acid derivatives. |
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PHYS Poster Session - Nanostructured Materials and Nanophotonics
7:30 PM-10:00 PM, Wednesday, April 9, 2008 Morial Convention Center -- Hall A, Poster
Sci-Mix
Division of Physical Chemistry |