Theoretical studies on the interaction between HArF molecules involved in
|Course||Physical and chemical|
|Keywords||HArF intermolecular interactionn frequency shift cooperativity substitution effect|
HArF is a stable compound containing a noble-gas atom, and this molecule displays a linear structure, in which the H-Ar bond is mainly covalent in nature and the Ar-F bond has an ionic character. In recent years, the intermolecular interactions involving noble-gas elements have been extensively characterized with experimental and theoretical methods. In this thesis, we study the intermolecular interactions involved with HArF using quantum chemical calculations to investigate the influence of the intermolecular interactions on the frequency shift of HArF and to expand the types ofthe intermolecular interactions involved with HArF.The main results are as follows:1:Ab initio calculations have beenperformed for the complexesof benzene with HArF,HKrF, and HXeF.The computed results indicate that the complexes of benzene-HArF exist in different conformations and among them those with π-hydrogen bonds are the more stable than those with C-H…F hydrogen bonds. Interestingly, the Ar-H stretching frequency is redshifted in the more stable isomer and blueshifted in the less stable form. The Ng (Ng=Ar, Kr, and Xe) atomic number dependence of the Ng-H…π and C-H…F hydrogen bonds has been explored. The result indicates that the strength of Ng-H…π and C-H…F hydrogen bonds is weakened with the increase of Ng atomic number. Natural bond orbital analysis has been performed to understand the interaction nature, frequency shift of H-Ng stretch, and dependenceof Ng-H…π and C-H…F hydrogen bonds on the Ng atomic number.2:A novel interaction mechanism between HArF and BeH2has been validated and characterized with quantum chemical calculations at the MP2/aug-cc-pVQZ level They can interact through beryllium bonding formed between the positively charged Be atom in BeH2and the negatively charged F atom in HArF, besides through dihydrogen bonding. The former (61.3kcal/mol) is much stronger than the latter (5.9kcal/mol). The red shift is found for the associated H-Ar stretch in the dihydrogen bonding, whereas the big blue shift is observed for the distant H-Ar stretch in the beryllium bonding. The blue shift of the distant H-Ar stretch is affected greatly by computational methods. It is calculated to be712cm-1at the CCSD(T)/6-311++G(3df,2p) level, which appears to be the largest blue shift validated for any weakly bound complex yet. The substitution effect on the beryllium bond is similar to that on hydrogen bonds. The Kr atom makes the beryllium bond weaken and the distant blue shift decrease. The nature and properties of beryllium bond have been analyzed with natural bond orbital (NBO), atoms in molecules (AIM), and energy decomposition.3:A theoretical study of the complexes formed between HArF and XH2P (X=F, Cl, and Br) has been carried out using ab initio methods (MP2/aug-cc-pVDZ, MP2/aug-cc-pVTZ, and CCSD(T)/aug-cc-pVTZ). Three minima were found, which correspond to a hydrogen-bonded complex (Ⅰ), a pnicogen-bonded complex (Ⅱ), and a halogen-bonded complex (Ⅲ). The pnicogen-bondedcomplex is the most stable, followed by the hydrogen-bonded complex, and the halogen-bonded complex is the least stable. The Ar-H bond is enhanced in FH2P-HArF-I complex and exhibits a blue shift, while it is weakened in ClH2P-HArF-I and BrH2P-HArF-I complexes and shows a red shift. A blue shift is also found for the distant Ar-H bond in the halogen-bonded and pnicogen-bonded complexes. These complexes have been understood with the electrostatic potentials and symmetry adapted perturbation theory (SAPT) method.4:CH3Li-FArH-X (X=H2, OC,N2,P2, CO2, CO, BeH2)trimers have been investigated using quantum chemical calculations at the QCISD/6-311++G(2d,2p) level. The results show that the lithium bonding has a prominent effect on the strength and properties ofthe hydrogen bonding. The hydrogen-bonding interaction energy is increased by160-340%, due to the presence of lithium bonding. The Ar-H stretch vibration shows a blue shift in the FArH-X (X=H2, OC, N2, CO2, CO) dimer, but a red shift in the FArH-X (X=P2, BeH2) dimer. The red shift is increased in the corresponding trimer, while the blue shift shows a dfferentchange.The blue shift is also increased in CH3Li-FArH-X (X=H2, OC, N2, CO2) trimers, but it changes to a red shift in the CH3Li-FArH-CO trimer. The shift change is consistent with the explanation given by Joseph and Jemmis.