The Structures, Properties And Nature Of Hydrogen, Halogen, Chalcogen And Tetrel Bonds Of F₂XY

(1) Complexes F2XO???HCN(X= C and Si) have been studied at the MP2/aug-cc-p VTZ level to investigate the competition between tetrel bond and hydrogen bond. F2 XO has a dual role of a Lewis acid and base with the p-hole on the X atom and the O atom to participate in tetrel bond and hydrogen bond with HCN, respectively. Both types of interactions become stronger for X = Si, and the tetrel bond is much stronger than the hydrogen bond, particularly, the tetrel bond in F2 Si O???NCH complex shows a binding energy of-119.8 k J/mol. The C-H???O hydrogen bond is dominated by the electrostatic interaction, and this conclusion is hold for the tetrel bond in F2CO???NCH complex, but the electrostatic and polarization contributions are similar in F2 Si O???NCH complex.(2) High-level quantum chemical calculations of the ternary systems F2CSe? ?NH3???HX(X = Be H, BH2, OH, CN, OCH3, Cl, and F) and the corresponding binary systems have been carried out in view of geometries, vibrational frequencies, interaction energies, orbital interactions, and electron densities. The molecular electrostatic potentials of F2 CSe demonstrate that the Se atom could play a dual role of Lewis acid and base to form a chalcogen bond with NH3 and a hydrogen bond or a covalent interaction with HX, respectively. The chalcogen bond can compete with the hydrogen bond for the complexes involving F2 CSe, but the covalent interaction is far stronger than the chalcogen bond. In the ternary complexes, both types of interactions are strengthened each other, characterized by a shorter binding distance, a larger electron density, and a stronger orbital interaction. The covalent interaction has a greater enhancing effect on the chalcogen bond than the hydrogen bond.(3) Ab initio calculations have been performed to identify local minima on the F2CSe?? HOX(X = F, Cl, Br, and I) potential surface and to evaluate their relative stabilization. Four types of structures are found for each complex except the HOF one. The Se???H hydrogen-bonded complexes(I) are accompanied with a secondary X???F interaction. The structure II is jointly connected with a tetrel bond and a X???Se interaction. The structures III and IV are stabilized by a chalcogen bond and a halogen bond, respectively. I has a little dependence in stabilization on the nature of X atom, while II, III, and IV become more stable with the increase of X atomic mass. The chalcogen-bondedcomplexes are least stable, the halogen-bonded complexes are more stable than the tetrel-bonded ones, and the hydrogen-bonded complex is weaker than the halogen-bonded one in the HOI complex but stronger in other complexes. The formation of these interactions has been understood by means of molecular electrostatic potentials and orbital interactions.(4) Selenium???gold interaction plays an important role in crystal materials, molecular self-assembly and pharmacochemistry involving gold. In this paper, we unveiled the mechanism and nature of selenium-gold interaction by studying complexes F2CSe???Au Y(Y=CN, F, Cl, Br, OH, and CH3). The results showed that the formation of selenium-gold interaction is mainly attributed to the charge transfer from the lone pair of Se atom to the Au-Y anbi-bonding orbital. Energy decomposition analysis indicated that the polarization energy is nearly equivalent to or exceeds the electrostatic term in the selenium-gold interaction. Interestingly, the chalcogen-gold interaction becomes stronger with the increase of chalcogen atomic mass in F2CX???Au CN(X = O, S, Se, and Te). The cyclic ternary complexes are formed with the introduction of NH3 into F2CSe???Au Y, in which selenium-gold interaction is weakened and selenium-nitrogen interaction is strengthened due to the synergistic effects.(5) F2CX(X = Se and Te) have two Lewis acid sites of ?-hole and ?-hole located respectively in the vicinity of X and C ends, participating in the chalcogen and tetrel bonds with HCN and NH3, respectively. F2 CSe forms a stronger tetrel bond, while F2 CTe forms a stronger chalcogen bond. F2 CX shows weaker tetrel and chalcogen bonds in the ternary system, exhibiting anticooperativity with some different features from positive one. The nature of two interactions and the origin of anticooperativity have been analyzed by means of energy decomposition, molecular electrostatic potential, and orbital interaction.