Quantum Chemistry Study And Topological Analysis Of Electron Density On Hydrogen Bond And Halogen Bond Between Cycloalkene, Cyclic Ether And XY(X, Y=H, F, Cl, Br)

Weak interaction between molecules plays a very important role in supermolecular chemistry, molecular biology, and material science. Hydrogen bond and halogen bond are two common kinds of weak interaction between molecules. They are also of importance in physics, chemistry and life sciences. The purpose of this paper is to study the geometry configurations, bonding nature by Quantum Chemistry and topological analysis of the electronic density methods in order to help the further research in this field.In this thesis, we studied the hydrogen bond and halogen bond. The perturbation theory, density function theory and the theory of electron density topological analysis were used in discussing the bonding nature of hydrogen bond and halogen bond. All calculations are carried out using the Gaussian 03 program package. The molecular graphs were plotted by AIM 2000 program.The topological properties at the bond critical points, contour maps of Laplacian of electron density and contour maps of Laplacian ofÏ€electron density were finished by our modified program GTA-2010.The main contents are the following aspects:1. Geometries and interaction energies of the hydrogen-bonded complexes B…HY and the halogen-bonded complexes B…BrY (B=C₄H₄, C₆H₆, Y=F, Cl, Br) have been investigated using MP2/aug-cc-pVDZ methods. The geometries of B…HY and B…BrY (Y = F, Cl, Br) are very similar. In comparison, binding energies of the halogen-bonded complexes B…BrY are stronger than the corresponding hydrogen-bonded complexes B…HY. The topological properties of electron density indicate that the interactions of C₄H₄(S)…BrY and C₄H₄(T)…BrF are between covalent and ionic. The other hydrogen-bonded and halogen-bonded interactions belong to"closed-shell"interactions. The formation of hydrogen bonds and halogen bonds results in the changes of the integration over the atom basin. The energies of hydrogen atom increase, while the energies of halogen atom decrease upon complex formation.2. Theoretical Studies on the hydrogen-bonding interactions of C₄H₆O, C₄H₆S and HX (X=F, Cl, Br) were investigated at the MP2/aug-cc-pVDZ level. Results show that both n-type andÏ€-type hydrogen-bonded complexes can be formed between C₄H₆O, C₄H₆S and HX. The interaction energies, electron densities at the hydrogen bond critical point, and the charge transfer amount indicate that the n-type hydrogen bonds are stronger than theÏ€-type hydrogen bond, which are consistent with the experimental results. The interactions of C₄H₆O…HX(n), C₄H₆S…HX(n) (X=Cl, Br) are between covalent and ionic, the other hydrogen-bonded interactions belong to"closed-shell"interactions. The formation of hydrogen bonds results in the changes of the integration over the atom basin. The energies of hydrogen atom increase, the dipole moments, and the volumes of hydrogen atom decrease upon complex formation.3. Theoretical Studies on the halogen-bonding interactions of 2,5-dihydrofuran, 2,5-dihydrothiophene and XF (X=F, Cl, Br) were investigated at the MP2/aug-cc-pVDZ level. Results show that both n-type andÏ€-type halogen-bonded complexes can be formed between C₄H₆O, C₄H₆S and XF. For C₄H₆O…XF(n), C₄H₆O…XF(Ï€) and C₄H₆S…XF(n), the interaction energies, electron densities at the halogen bond critical point, and the charge transfer amount from donor to acceptor are all in sequence of B…F24H₆O…BrF(n), C₄H₆O…BrF(Ï€), C₄H₆S…F2(n), C₄H₆S…ClF(n), C₄H₆S…BrF(n), C₄H₆S…BrF(Ï€) are stronger, with bond character between covalent and ionic, the other halogen-bonded interactions are weaker, which belong to"closed-shell"interactions.4. The interactions of the dihydrogen-bonded complexes have been investigated using MP2/6-311++G(d,p) methods. In comparison, binding energies of imidazole…HLi and imidazole…HNa are stronger than other complexes. Excellent linear relationships btween the interaction energies and dihydrogen bond lengths, the bond length changes of N-H bond and the frequency changes of the N-H bond were found. The topological properties of electon density indicate that the interactions of imidazole…HBeX(X=F, Cl, Br, H) and imidazole…HMgH belong to closed-shell interactions, the imidazole…HLi, imidazole…HNa are between covalent and ionic interactions. The formation of dihydrogen bonds results in the changes of the integration over the atom basin. The electron denstiy at the dihydrogen bond crtical point, and atomic net charges ?q(H), atomic energies ?E(H), dipolar polarization ?M(H) and atomic volume ?V(H) of electron acceptor could be well applied as the measures of the strength of dihydrogen bond.The innovations in this thesis:1. The GTA-2010 program package, which was compiled by our research group, was used to deal with theÏ€-electron separating fromÏ€-type hydrogen bond complexes, it could describe contour maps of Laplacian ofÏ€electron and contour maps of ?2ρand make GTA-2010 link to program of AIM2000 calculate theÏ€-electron integral. All of the results proved clearly the nature ofÏ€-type hydrogen bond.2. Detailed studies on the hydrogen bond, halogen bond, and dihydrogen bond have been carried out. The formation of hydrogen bonds and halogen bonds results in the changes of the integration over the atom basin. The energies of hydrogen atom increase, the dipole moments, and the volumes of hydrogen atom decrease upon hydrogen complex formation. The dipole moments, the volumes and the energies of halogen atom all decrease upon halogen complex formation..3. The interactions of the dihydrogen-bonded complexes on imidazole as electronic acceptor have been investigated firstly. The electron denstiy at the dihydrogen bond crtical point, and atomic net chargesâ–³q(H), atomic energiesâ–³E(H), dipolar polarizationâ–³M(H) and atomic volumeâ–³V(H) of electron acceptor could be well applied as the measures of the strength of dihydrogen bond.