The influence of silicon tetrachloride as a coupling agent for the surface assembly of 2,3,7,8,12,13,17,18-octaethylporphyrin (OEP) on Si(111) was investigated using atomic force microscopy (AFM). Nanopatterned films of porphyrins were prepared using particle lithography to evaluate the morphology, thickness and molecular orientation of Si-OEP films. Porphyrins have a macrocyclic tetrapyrrole structure which may be functionalized with various substituents. Modifications of the macrocycle, peripheral groups or bound metal ions can generate a range of electrical and photoelectrical properties. When preparing surface films, the planar macrocycles of porphyrins spontaneously self-associate to form stacked structures. This natural capability of self-stacking poses a challenge for developing processes for molecular patterning. When preparing films, porphyrins associate by electrostatic interactions between macrocycles as well as physisorption to the substrate to form coplanar arrangements of stacks of molecules, analogous to a stack of coins. The orientation of porphyrins on surfaces is also affected by the nature of the peripheral substituents and their position on the macrocycle. We introduced silicon tetrachloride to the porphyrin reaction vessel to mediate coupling between the surface and porphyrins through covalent interactions. Protocols of particle lithography were used as a nanoscale patterning tool to prepare well-defined surface structures and films of OEP. Our goals are to correlate nanoscale properties (conductance, photocurrent generation) with designed surface structures of porphyrins in which the coupling between the surface and porphyrins is mediated by covalent interactions. Conceptually, by arranging and orienting the macrocycles of porphyrins with defined orientation, local surface measurements can be address questions about how structure influences properties.<br/><br/>

Porphyrin macrocycles linked to surfaces by centrally coordinated Si-O bridges

2019 Spring National Meeting

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