Hybrd QM/MM Studies on Energetics of malonaldehyde in Condensed Phase.

摘要

Energetics of eight enol isomers of a malonaldehyde(MA) at the ground state in CCL_4 solvent environment have been ivnestigated using a hybrid quantum mechanical (QM)/molecular mechanics(MM) method.It is found that relative energies of the isomers slightly change due to interactiosn between MA and surroundign atoms.In an isolated environement all eight isomers have stable planar structure.On the other hand,most of the isomers have nonplanar structure in CCl_4 whose interactions with the solute molecules are,however,weak.Mainly,structural changes are found in the H-O-C=C dihedral angle phi_H-O-C=C,i.e.,a hydrogen and other atoms remain almost planar.Vertical excitation energies of low-lying excited states at the resultant optimized structure of each isomer are evaluated.the vertical excitation energies in CCl_4 are almost the same as those in the isolated environment,but some changes were found in the triplet excitation states.