Abstract
The single-molecule conductance of saturated molecules can potentially be fully
suppressed by destructive quantum interference in their σ-system. However, only few molecules
with σ-interference have been identified and the structure-property relationship remains to be
elucidated. Here, we explore the role of substituents in modulating the electronic transmission of
saturated molecules. In functionalized bicyclo[2.2.2]octanes, the transmission is suppressed by σ-
interference when fluorine substituents are applied. For bicyclo[2.2.2]octasilane and -
octagermanes the transmission is suppressed when carbon-based substituents are used, and such
molecules are likely to be highly insulating. For the carbon-based substituents we find a strong
correlation between the appropriate Hammett constants and the transmission. The substituent
effect enables systematic optimization of the insulating properties of saturated molecular cores.
Content

Supplementary material

Supporting Information
SI for submission
optimized structures
DFT optimized structures in xyz format
Supplementary weblinks
Code
Code to generate structures