| AVS 55th International Symposium & Exhibition | |
| Nanometer-scale Science and Technology | Thursday Sessions |
| Session NS+NC-ThM |
| Session: | Nanoscale Assembly |
| Presenter: | C.J. Baddeley, University of St Andrews, UK |
| Authors: | S.N. Patole, University of St Andrews, UK C.J. Baddeley, University of St Andrews, UK M. Schuler, University of St Andrews, UK D. O'Hagan, University of St Andrews, UK N.V. Richardson, University of St Andrews, UK |
| Correspondent: | Click to Email |
Long chain hydrocarbons were designed and synthesized with carboxylic acid functionalities at each end and two amide linkages in the central region of the molecule. The amide linkages are separated by two –CHF- units. These units are each chiral centres and the molecules were synthesized as a racemic mixture of (R,R) and (S,S) species. We report an STM investigation of the adsorption of these molecules onto highly oriented pyrolytic graphite (HOPG) from phenyloctane solution. There are a number of motivations for this study. Firstly, we are interested in establishing control over 2-D assembly via intermolecular H-bonding interactions. Secondly, we assess the use of fluorine atoms as contrast agents in STM to aid the elucidation of structural aspects of complex molecule adsorption at surfaces. Thirdly, we are interested in the influence of chirality on the ordered adlayers produced on HOPG. The molecules adopt a flat lying geometry on graphite. The conformation of the central (fluorinated) section of the adsorbed molecular species differs significantly from the preferred geometry in the crystal structure. We demonstrate that the ordered molecular assemblies produced are dictated by a combination of effects including the preference of carbon backbones to align along high symmetry directions of HOPG; steric constraints imposed by the C-F bonds at the chiral centres and intermolecular H-bonding. We outline a heirarchy of effects which determine the lateral stacking and head-to-head interactions and explain the influence of stereochemistry on the molecular ordering. We conclude that enantiomerically pure 1-D domains are produced and examine the behaviour at the boundaries between domains of each enantiomer.