Interplay between tetrel bonding and hydrogen bonding interactions in complexes involving F2XO (X = C and Si) and HCN

The complexes F2XO⋯NCH⋯NCH and F2XO⋯HCN⋯HCN (X = C and Si) have been studied by quantum chemical calculations at the MP2/aug-cc-pVTZ level. These four trimers show similar stability except F2SiO⋯HCN⋯HCN. The C–H⋯N hydrogen bond is enhanced by the presence of tetrel bond in F2XO⋯NCH⋯NCH. Interestingly, the stronger tetrel bond in F2SiO⋯NCH⋯NCH exhibits a greater enhancement than the weaker one in F2CO⋯NCH⋯NCH. The positive cooperativity is mainly attributed to the polarization and dispersion energies in the former but to the polarization energy in the latter. The tetrel bond and CH⋯O hydrogen bond are also strengthened each other in HCN⋯F2XO⋯HCN. The tetrel bonds are weakened in HCN⋯F2XO⋯NCH, where the weakening is caused mainly by electrostatic energy for HCN⋯F2CO⋯NCH and by electrostatic and polarization energies for HCN⋯F2SiO⋯NCH. The CH⋯N and CH⋯O hydrogen bonds show a positive cooperative effect in F2XO⋯HCN⋯HCN due to the polarization interaction.