Synergistic and antagonistic interplay between tetrel bond and pnicogen bond in complexes involving ring compounds.

The binary and ternary complexes composed of GeHF, AsHF and ring compounds (benzene, borazine and cyclopentadienyl anion) have been studied by theoretical calculations to understand the interplay between the tetrel bond and pnicogen bond interactions. The bonding strength of intermolecular interactions in these complexes is analyzed by means of atoms in molecules (AIM), natural bond orbital (NBO) and noncovalent interaction (NCI) index methods. The binary tetrel-bonded and pnicogen-bonded complexes can be classified as an n-type or π-type complex according to the orbital interactions involved in the complexes. Three binding modes can be distinguished according to the interplay between interactions for the ternary complexes. The binding mode A is characterized by the interplay between π-type tetrel bond and n-type pnicogen bond; binding mode B is characterized by the interplay between π-type pnicogen bond and n-type tetrel bond, and binding mode C is characterized by the interplay between π-type tetrel bond and π-type pnicogen bond. The binding modes A and B exhibit the synergistic interplay effect, while the antagonistic effect is reflected in mode C. The synergistic effect in binding modes A and B is stronger than antagonistic effect in mode C, and the synergistic effect in binding mode B is stronger than that in mode A.