Distinguishing Trimethylsilyl’s Spatial Configurations of Molecules on Metal Surfaces

Trimethylsilyl (TMS) is one of the most frequently employed protecting groups in organosilicon chemistry, which has also been introduced in on-surface chemistry. However, it remains a challenge to visibly identify the TMS’s spatial configuration, due to its rotational C–Si(CH3)3 bond. Here, we report the adsorbed configurations of 1,4-bis(trimethylsilyl)-2,3,5,6-tetrabromobenzene and trimethyl(2,3,5,6-tetrabromo-4-methylphenyl) silane on various metal surfaces with distinguished TMS’s spatial configurations by a combined study of scanning tunneling microscopy (STM) and density functional theory (DFT) simulations. It is found that the TMS group shows different adsorption configurations with either one or two methyl groups pointing down to the surface, which can be finely tuned by the choice of metal substrates. This study provides fundamental insights into the spatial TMS group of molecules on metal surfaces.