Theoretical Study Of Several Compounds About 4-acyl Pyrazolone

With the fast-growing performance of computer hardware and more perfectly enrichment of computing technique, quantum chemistry calculation has become powerful tool for exploring and analyzing problems of chemistry by the chemists. It has been playing very important role in revealing and predicting the behavior of abroad range of chemical phenomenon.In this paper, in order to gain a deeper insight into the compounds about 4-acyl pyrazolone, Gaussian03 program package has been performed to investigate various properties of two compounds (PMCP-TSC and PMCP-MTSC) in different solvents on the basis of previously experimental and theoretical work. With the view of identifying the mechanism of photochromism of PMCP-TSC, the properties of PMCP-TSC in the gas phase and in methanol solution have also been investigated. Furthermore, the coordinated property of PPePP-SAH has been calculated and discussed as well.Part 1 provides theoretically studies on the molecular structure and the stability and reactivity of PMCP-TSC and PMCP-MTSC in different solvents. The experimental and computational results indicate that the angles between pyrazolone-ring and benzene-ring have a close relationship with the photochromic property. AIM and NBO theories are applied to investigate the nature of intramolecular hydrogen bonds of two compounds in different solvents, and the correlation between E(2) and AIM parameters have been established. In addition, the free energy of solvation, the electronic energies and the dipole moments have been used to discuss the stability of compounds, DFT-based reactivity descriptor—the atom-condensed Fukui function has also been used to describe the site reactivity.Part 2 is devoted to the photochromic mechanism of PMCP-TSC. The results from analyzing the structure, charge distribution and stability of enol form, transiton state and keto form in the gas phase and in methanol solution indicate that methanol can reduce the electronic energies and the barrier height of the reaction. Furthermore, the absorption spectrum of keto form and enol form obtained from TDDFT theory prove that the hypothesis of photoisomerization from enol form to keto form is reasonable.Part 3 focuses on the coordinated property of PPePP-SAH. The calculated results, merging from the molecular energies, the dipole moments, molecular electrostatic potential of the three isomers, gain a deeper insight into the relationship between the electronic structure and the coordinated properties. It is found that the O1, O2, N5 and N6 atoms is the possible site for coordination. In addition, the molecular energy shows that form I of PPePP-SAH is more stable than other forms. These findings are in good agreement with experimental results.