Quantum-chemical Studies Of Solvent Effect

Quantum-chemical descriptors have been widely applied to structure-activity relationship studies in biochemistry or pharmaceutical chemistry. These descriptors are usually acquired by quantum chemical calculations in vacuum, however, all biochemical process refer to liquid media. Such contradiction intrigues us to investigate the solvent effects of molecular systems by quantum chemical methods. This dissertation falls into five parts and can be summarized as follows.Part one briefly describes the signification, the progress and several physical methods used to study the solvent effects.Part two detailedly introduces the definition of the solvation process, some key parameter to describe the solvent effects and several solvation models. Furthermore, two main quantum mechanical treat of the solvent effects are recommended. The first is strict quantum chemical methods, i.e. self-consistent reaction field methods. The second is simulation methods (Molecular Dynamics; Monte Carlo) employing classical force field. However each method has merits, defects and traits.In part three, 40 organic molecules are studied by DFT (B3LYP, B3P86), MP4 with different basis sets using the PCM/UAHF model within the self-consistent reaction field method to assess solvent effects. For these molecules, the solvation free energies (â–³G_sol) in water and the dipole moments in vacuo as well as in water are obtained. By comparing the calculated values of â–³G_sol with experimental values and molecular simulation results, it is found that â–³G_sol values generated by DFT method are in better agreement with experimental values. Moreover, especially for B3LYP/6-31+G* level, the results of both â–³G_sol and dipole moments are more accurate considering the lower computational cost. It can be noted that the dipole...