Mutual influence of tetrel and halogen bonds between XCN (X=Cl, Br) and 4-TF-pyridine (T=C, Si, Ge).

Interplay between tetrel and halogen bonds in the XCN⋯4-TF-pyridine⋯XCN (X=Cl, Br; T=C, Si, Ge) and 4-TF-pyridine⋯XCN⋯4-TF-pyridine complexes was studied by using quantum chemical methods. The respective binary complexes XCN⋯4-TF-pyridine and 4-TF-pyridine⋯XCN have also been investigated. Mutual influence of both interactions has been analyzed in terms of the molecular electrostatic potential, binding distance, binding energy, electron density shift, and energy decomposition. Both the tetrel and halogen bonds have been strengthened in the ternary complexes. The cooperativity of the XCN⋯4-TF-pyridine⋯XCN complex is more prominent than that of the 4-TF-pyridine⋯XCN⋯4-TF-pyridine complex. The variation of molecular electrostatic potentials in the binary complexes and the electron density shift of the complexes well explains this cooperative effect. Energy decomposition analysis revealed that the interactions are mainly dominated by electrostatic contribution; meanwhile, electrostatic contribution, induction, and dispersion enlarged in the ternary complexes.