Upright, symmetric cage molecules self-assembled on surfaces have simple domain and defect structures. Unlike linear molecules, such as alkanethiols on Au{111}, these cage molecules do not tilt and do not conformationally relax. The lattices of the cage molecules are determined by the projections of the cages on the surface. Thus, different isomers, such as carboranethiols on Au{111}, form identical lattice structures. These monolayers enable key tests of simple phenomena, such as the effects of dipole moment direction and amplitude. For example, molecules with dipoles parallel to the surface form nonpolar monolayers and outcompete molecules with dipoles normal the surface, which form polar monolayers. These properties can be measured both at the macroscopic and nanoscopic scales. We understand the enhanced stability of the nonpolar surfaces to aligned dipoles in the monolayers and set out to measure such effects. Using combinations of spectroscopic imaging and novel image analyses based on advances in compressive sensing and sparsity, we find that dipoles do align, even across strcutural domain boundaries and step edges. We use mixed self-assembled monolayers of carboranes to tune and to optimize the band alignment of organic electronic devices without changing the morphology of the active layer. We  assemble multifunctionalized cage molecules and show that we can protonate and deprotonate thiol(ate)s to change the valency of attachment to the surface through simple reactions. These experiments are closely coupled to theory and simulations to give us detailed understanding of the supramolecular systems.

Cage molecule self-assembly

254th National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.