Description
Flyer: Prof. Timothy Su Flyer
Title: Sila-Diamondoids: Atomically Precise Clusters of Crystalline Silicon
Abstract: This talk will describe the synthesis, derivatization, and quantum transport properties of silicon diamondoids—atomically precise clusters of crystalline silicon. First, we describe strategies for the functionalization of the fundamental silicon diamondoid cluster, sila-adamantane. Mechanistic insights support that an aluminate-stabilized silylium at the 2-position of sila-adamantane is the terminal intermediate in its isomerization synthesis; we can intercept this intermediate to install halides at the 2-position. In addition, we can tetra-substitute sila-adamantane at its bridgehead positions with the same or different functional group, or precisely edit the skeletal structure of the adamantyl core by installing up to four Ge atom dopants at the bridgehead positions. We can extend this strategy to access, for the first time, the all-germanium adamantane. We have also developed radical-mediated approaches to catenate these clusters together to make supermolecules out of sila-diamondoid superatoms. As sila-adamantane represents the ultimate limit of miniaturization for nanocrystalline silicon, these regioselective approaches allow us to probe structure-property relationships in cluster models of silicon semiconductors at an atomically exact level. To showcase this, we show how the symmetry and dimensionality of sila-adamantane gives rise to unusual quantum interference effects in conductive single-molecule junctions studied with the scanning tunneling microscopy break-junction (STM-BJ) technique that may be controlled by chemical substitution. Finally, we exploit this phenomenon to create single-molecule conductance switches where we can mechanically toggle between different conductive pathways through the diamondoid cluster.
