Group 14 Central Atoms and Halogen Bonding in Different Dielectric Environments: How Germanium Outperforms Silicon

The nature of halogen bonding under different dielectric conditions remains underexplored, especially for inorganic systems. The structural and energetic properties of model halogen bonded complexes (R₃ M-I-NH₃ for R=H and F, and M=C, Si, and Ge) are examined computationally for relative permittivities between 1 and 109 using an implicit solvent model. We confirm and assess the exceptionally high maximum potentials at the sigma hole on I (V_s,max ) in F₃ Ge-I relative to cases where M=C or Si. In particular, Ge far outperforms Si in mediating inductive effects. Linear relationships, typically with R² >0.97, are identified between V_s,max , the full point charge on I in R₃ M-I, and the interaction energy, and optimized I-N distance in the complexes. An anomalous trend is identified in which, for each M, F₃ M-I-NH₃ becomes less stable as the optimized I-N distance gets shorter in different dielectric environments; it is explained using the F-I-NH₃ complex as a reference.