Theoretical Studies On New Types Of Halogen Bonds-σ-hole And π-hole Interactions

Noncovalent interactions always popular be researched because of their extensive potential utilization in diverse fields such as molecular recognition, drug design, crystal engineering, and versatile materials. Recently, σ-hole and π-hole interactions as new types of interaction have attracted a lot of attention. In this work, we discussed the property of σ-hole, π-hole, halogen/hydrogen-bonded interactions and the effect from each other.1 The second order M?ller-Plesset perturbation theory(MP2) calculations have been performed to investigate the cooperativity between the σ-hole and π-hole interactions in Cl O···XONO2/XONO···NH3(X = Cl, Br, I) complexes. The σ-holes and π-holes have been found on the outer surfaces of XONO2/XONO: the σ-hole is outside the halogen atoms approximately along the extensions of X–O bond, and the π-hole is above and below the nitrogen atom and the terminal oxygen atom. Both the σ-hole and π-hole interaction energies are consistent with the most positive electrostatic potentials(VS, max) of the σ-holes and π-holes, indicating that electrostatic interactions play an important role in the σ-hole and π-hole interactions. From a two to a three body interaction, the interaction energies, binding distances, and infrared vibrational frequencies prove that there is negative cooperativity between the σ-hole and π-hole interactions.2 The region of positive electrostatic potentials(σ-hole) has been found along the extension of the C―I bond in the iodine-ylide CH2 IH under the MP2 calculations,and then we constructed the CH2IH···NCX(X = H, F, Cl, Br, I) bimolecular complexes to study the I···N σ-hole interaction in these bimolecular complexes. The NCCl···CH2IH···NCX(X = H, F, Cl, Br, I) termolecular complexes were constructed to investigate the weakly-bonded σ-hole interactions to be strengthened by Cl···C halogen bond. And then, the NCY···CH2IH···NCCl(Y = H, F, Cl, Br, I) termolecular complexes were designed to investigate the enhancing effects of the I···N σ-hole interaction on the Y···C halogen/hydrogen-bonded interactions. Accompany with the mutual enhancing processes of the σ-hole interactions and halogen/hydrogen-bonded interactions in the iodine-ylide containing termolecular complexes, both the I···N σ-hole interactions and Y···C halogen/hydrogen-bonded interactions become more polarizable.3 In this work,we studied the π type interactions in the group of IIIA,IVA,VA by the second order M?ller-Plesset perturbation theory, ELF and QTAIM theory.From the ESP, in the electron density isosurfaces of M2H2(M= B, Al, Ga, In) exist two π-hole at the above and below the M atom.While in the electron density isosurfaces of the X2H2(X = C, Si, Ge, Sn),there is a negative region exist aroud the middle of X-X bond. And there also has a negative region exist aroud the middle of Y-Y bond in Y2H2(Y = N, P, As, Sb) molecule.The M2H2···NCI(M= B, Al, Ga, In), X2H2···ICN(X=C,Si,Ge,Sn) and Y2H2···ICN(Y = N, P, As, Sb) bimolecular complexes were constructed to disscuss the π type interactions in the group of IIIA, IVA, VA.Because of forming the M2H2···NCI(M= B, Al, Ga, In) complexe,the electronic density of M(M = B, Al, Ga, In)get decrease. While the electronic density of X(X = C, Si, Ge, Sn) and Y(Y = N, P, As, Sb)get increase for forming the X2H2···ICN(X = C, Si, Ge, Sn) and Y2H2(Y = N, P, As, Sb) bimolecular complexes.The innovations in this thesis:1 From the ESP anlysis, the positive electrostatic potential regions(σ-hole and π-hole) was found in the IONO2、IONO molecules which play an important role in the atmosphere.This paper use the σ-hole and π-hole region interact with NH3 and Cl O which are most relevant molecules in atmosphere to investigate the cooperativity between the σ-hole and π-hole interactions.2 The region of positive electrostatic potentials(σ-hole) has been found along the extension of the C―I bond in the iodine-ylide CH2 IH and then we studied the σ-hole interaction which is formed by iodine-ylide.The topological parameters of the Lacplacian of electron density and the molecular formation density difference(MFDD) analysis was used to study the enhancing effects of the σ-hole interactions and halogen/hydrogen-bonded interactions in the iodine-ylide.