Quantum Chemistry Study Of The Molecular Structures, Atomic Charges, And IR Spectra Of Metalfree Phthalocyanine And Zinc Phthalocyanine

The preparative chemistry and characterization of phthalocyanines and metallo-phthalocyanines have been extensively studied over the past six decades. This class of compounds has attracted a great deal of interest of research because of their intense coloration and diverse redox chemistry associated with both 18Ï€-electron system of the phthalocyanine ring and the central metal atom. In recent years, phthalocyanine compounds have attracted more and more interest of research because of the unique photic, electric, thermal and magnetic properties as well as the great application potential as functional materials such as molecular conductor, molecular magnets, molecular electronic devices, etc.To deepen the understanding of experimental results and provide theoretical guidance for further experimental research, many researchers decided to introduce quantum chemistry studies into their research. My researches concentrate on the molecular structures, atomic charges and fundamental vibration modes in the infrared spectra of metal-free phthalocyanine and zinc phthalocyanine complexes.Systematic calculation and research of phthalocyanine and zinc phthalocyanine complex ZnPc are performed at the level of density functional B3LYP using the 6-31G (d) basis sets with Gaussian98 program. By comparing the calculated results of two types of phthalocyanine, one of which is restricted to planar and the other without such restriction, we get the conclusion that the one without planar restriction is steadier than the other. Our calculated molecular structure of metal-free phthalocranine corresponds well with the X-ray crystal data, indicating that the B3LYP method and the 6-31G(d) basis sets are appropriate for calculating phthalocyanine complexes. We have also studied the IR spectrum and charge distribution. The calculated IR vibrational modes for phthalocyanine are investigated in detail and compared with the experimental ones, and we have found that their correlations are very good. Detailed assignments of the IR spectrum of phthalocyanine have also been made based on the assistance of the animated pictures and the shifts of atoms. Some new assignments about the disputed peaks are given here. A theoretical investigation of the fully optimized geometries of the zinc phthalo-cyanine complex ZnPc based on density functional B3LYP level using the 6-31G (d) basis sets has been conducted. The good consistency between our calculated structural parameters and the X-ray crystal analysis data clearly indicates that the method and basis sets chosen here are suitable for ZnPc. We have also calculated the IR spectra and atomic charges. Detailed assignments of ZnPc in the IR spectrum have been made based on the assistance of animated pictures. Good consistencies between the calculated and experimental IR spectra verify the good performance of the B3LYP method and the 6-31G (d) basis sets used for ZnPc again.The infrared frequencies and intensities of H₂PC and ZnPc have been compared. Our present work has given valuable information to the traditional empirical assignment and will be helpful for further investigation of the vibration spectra of phthalocyanine analogues and their metal complexes.