This manuscript describes skeletal isomerization strategies to install one to four quaternary germanium atoms in the sila-adamantane core, in a cluster analogy to precision germanium doping in silicon-germanium alloys. The first strategy embodies an inorganic variant of single-atom skeletal editing, where we use a sila-Wagner-Meerwein bond shift cascade to exchange a peripheral Ge atom with a core Si atom. We can install up to four Ge atoms at the quaternary diamondoid centers based on controlling the SixGey stoichiometry of our precursor. We find that bridgehead Ge centers can be selectively functionalized over bridgehead Si centers in SiGe adamantanes; we use this chemistry in conjunction with scanning tunneling microscopy break-junction (STM-BJ) measurements to show that Si8Ge2 adamantane wires give a 60% increase in single-molecule conductance compared to Si10 adamantanes. These are the first quantum transport measurements in sila-diamondoid structures, and highlight how main-chain Ge doping can be used to increase electronic transmission in sila-diamondoid-based molecular wires.
Additional figures, synthetic details, structural characterization, density functional theory details, and crystallography details (PDF). The supporting crystallography data for 1a (CCDC 2267502), 2a (CCDC 2267500), 3a (CCDC 2267503), and 4a (CCDC 2267501) can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/structures.