Density Functional Theory Study On The Structure And Properties Of Porphyrin Compounds

Porphyrins are highly conjugated macrocyclic compounds formed by four pyrrole rings connected at the position α of the ring by unsaturated methine bridges. Porphyrins, metalloporphyrins, and their derivatives are expected to play key roles in biology, for instance, an iron and copper complex in blood, a magnesium complex in chlorophyll, and a cobalt complex in vitamin B12. They are all derivatives of metalloporphyrins. Porphyrins’ excellent electromagnetic and unique electronic properties, admirable stability render them to be applied in many fields, such as enzyme catalysis, molecular recognition, light-emitting devices, sensor, solar energy conversion, photo-dynamics therapy and nonlinearoptics. They also can be used as anticancer drugs, biological chromogenic reagents, and other functional materials.Density functional theory is a new theory to study the ground state properties of multi-particle systems used electron density distribution as the basic variables, and one of the important methods to study chemical problems theoretically in quantum chemistry calculation. After decades of correction and improvement, DFT and its numerical implementation method has been widely used in chemistry, physics, material and biological discipline. The molecular characters including configuration, atomic natural and Mulliken charge, molecular orbital, charge density and other parameters can be obtained by the theory. From these informations we can realize the chemical properties of molecule and their change rules. Thus offering theoretical basis or explaining experiment phenomena, and the experiment results can also be verify. Hence, using DFT to study porphyrin compounds, exploring the relationship between the substituent or central metal ion and chemical property of porphyrins, is very significant to varify and predict the experimental results.In this thesis, porphyrins, which are substituted by β-enaminones and polycyclic aromatic hydrocarbons in meso-position, and different metalloporphyrins, are studied using density functional theory(DFT). There are four parts in this thesis, and the main contents are as follows:Chapter one: Introduction. This chapter details the existence, application and research methods of porphyrin compounds; discusses the emergence and development of quantum chemistry, and evolution of the Schr?dinger equation; describes the origin, development and application of density functional theory, especially in the study of porphyrin compounds.Chapter two: Theoretical study of 5,10,15,20-Tetrakis(4-aminophenyl) porphyrin substituted by different number of β-enaminones and different metal ions. Using density functional theory, optimizing six different numbers of β-enaminone substituted porphyrin and six metalloporphyrins, study their structure parameters, energy of frontier orbitals and charge density distribution, etc. Natural bond orbital(NBO) analysis is used to analysis the natural charges and the second order perturbation stabilization energy, obtaining a series of change rules.Chapter three: Theoretical study of porphyrins substituted by polycyclic aromatic hydrocarbons. This chapter study porphine substituted in meso-position by different kinds of polycyclic aromatic hydrocarbons to form four Zinc-porphyrin molecules. On the basis of DFT/B3LYP/6-31G(d) Zinc-porphyrin structures with different valence states are optimized, discussing their structure and orbital parameters, comparing chemical propertis of porphyrin in different molecules and the same molecule with different valence state. Excellent results are achieved.Chapter four: The influence of different basis set on calculation results of Zinc-porphyrin. Optimizing Zn NPP with three different basis sets to study how basis set affect the results, and discussing the importance of basis set in quantum chemical calculation.