| Intermolecular interactions play a crucial role in fields of chemistry, physics, and biologyincluding stabilizing biomolecular structures, modulating specificity of enzymatic reactions, andconstructing supramolecular structures. Intermolecular interactions involved with metals are widelyused in fields of material designing, biological systems and catalytic systems. In this thesis, westudied the cation-π interaction and halogen bonds with metals directly or indirectly to discuss howto enhance their strength. The main results are as follows:1：Quantum chemical calculations have been performed for the MCCBr-NCM’（M and M’=H, Li, Na, F, NH2, and CH3） halogen-bonded complexes at the MP2/aug-cc-pVTZ level. Thebinding energy is in a range of1.34-23.42kJ/mol. The results show that the alkali metal has aprominent effect on the strength of halogen bond and this effect is different for the alkali metal inthe halogen and electron donors. The alkali atom in the halogen donor makes it weaken greatly,whereas that in the electron donor causes it enhance greatly. Natural bond orbital （NBO） analysisshows that the alkali atom is electron-withdrawing in the halogen donor and electron-donating inthe electron donor. In formation of halogen bond, the former is a negative contribution, whereas thelatter is a positive one. A similar charge transfer is also found for the H atom in the halogen andelectron donors. These complexes have also been analyzed with the atoms in molecules （AIM）theory.2：We designed the title complexes to enhance the halogen-hydride halogen bonding with thecation-π interaction. The interaction strength has been estimated mainly in terms of the bindingdistance and the interaction energy. The results show that the halogen-hydride halogen bonding isstrengthened greatly by the cation-π interaction. The interaction energy in the triads is1.98-5.55times as much as that in the dyads. The largest interaction energy is-8.31kcal/mol for the halogenbond in Li+···C6H5Br···HNa complex. The enhancement of the halogen bond has a relation with thenature of the cation, the halogen donor, and the metal hydride. The enhancement effect of Li+onthe halogen bond is larger than that from the corresponding Na+one. The halogen bond in the Cldonor suffers a greater enhancement than that in the Br one. The metal hydride imposes its effect inthe order: HBeH <HMgH <HLi <HNa. This indicates that there is a strong interplay between the halogen-hydride halogen bonding and the cation-π interaction. The natural bond orbital and energydecomposition analyses indicate that the electrostatic interaction plays a dominate role in enhancingthe halogen bonding by the cation-π interaction.3：Quantum chemical calculations have been performed to study the cation-π interaction inLi+···C6H6-nLin（n=0-6） complex. The results show that the cation-π interaction is enhanced by thelithium substitution in the aromatic ring. With the increase of lithium substitution number in thearomatic ring, the total interaction energy becomes more negative. However, the averagecontribution from one Li atom to the interaction energy becomes smaller. The substituted Li atomin the aromatic ring displays a negative nonadditivity in enhancing the cation-π interaction. Thesubstitution position of Li atom in the aromatic ring has a prominent effect on the strength of thecation-π interaction. The largest interaction energy （-97.7kcal/mol） is found in Li+···1,3,5-C6H3Li3complex. The enhancing effect of Li atom has been understood with natural population analysis（NPA） charge on the carbon atom in the aromatic ring and the most negative electrostatic potentialat the center of aromatic ring.4：Quantum chemical calculations have been performed to study the all-metal π halogenbonding in Al42-···halohydrocarbon complexes. The result shows the existence of the all-metal πhalogen bond in the complexes. There are three interaction modes （top, corner, and side） betweenAl42-and halohydrocarbon. The interaction energy of this interaction varies from a positive value to-90.54kJ/mol in Al42-···I-ethyne-s complex. The interaction strength is affected greatly by thehybridizaition of C atom and follows the order of C（sp3）<C（sp2）<C（sp） in most complexes. Themethyl group in the halogen donor plays a negative contribution to the formation of halogen bond.The halogen bonding becomes stronger for the heavier halogen atom. The effect of binding site onthe strength of halogen bond is related with the nature of halogen atom. The complexes have beenanalyzed with NICS, ELF, NBO, and AIM. |
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