Cage molecules for self-assembly

Self-assembled monolayers using functionalized cage molecules offer distinct advantages because of their symmetry, lack of conformational flexibility, and well-defined chemistries. While these systems have not yet been studied to the extent that linear alkanethiols on Au{1 1 1} have been, early explorations indicate great promise and important differences. For simple cage molecules that bind upright on the substrate, tilt domain boundaries found in linear chain systems are completely eliminated. Cage molecules can be designed to have a great range of intermolecular interactions, which thereby define the stabilities of the assemblies. Weakly interacting monolayers, such as those of 1-adamantanethiol on Au{1 1 1} are labile relative to exchange reactions from solution, vapor, or contact, and thus can be used as sacrificial placeholders and diffusion barriers in soft lithography. Such molecules can be further functionalized to serve as molecular resists for chemical patterning. Cage molecules can also be designed with directional interactions, as for carboranethiols, where molecules with identical lattices have dramatically different chemical and physical properties, and film stabilities. Multifunctional cage molecules enable further directed surface reactions, higher order supramolecular assembly, and ultimately, precise three-dimensional assembly off the surface. (C) 2010 Elsevier B.V. All rights reserved.