Density Functional Theory Study Of Meso-tetrasubstitued Porphyrin And á-tetrahalogen Substitued Phthalocyanine

Porphyrins,and phthalocyanines,have been expected to have widely potential application in material science as novel functional materials,such as molecular electronics,molecular information storage,and nonlinear optics,etc.due to the unique optical,electrical,and properties,associated with the intriguing intramolecularÏ€-Ï€interactions.To further deepen the understanding of the experimental results and provide guidance for further experimental research,we decided to introduce quantum chemistry studies into our research.In the past few years,we have studied the geometry,electronic structure,IR,Raman,XPS,and UV-vis spectroscopy of many porphyrins, phthalocyanines,and their derivatives,using quantum chemistry calculations,and found some interesting results.In this thesis,the geometry,electronic structure,and vibrational spectroscopy of some substituted porphyrin and phthalocyanine compounds are studied on the basis of density functional theory calculation.Firstly,a theoretical investigation of the fully optimized geometries and electronic structure of meso-tetraphenyl porphyrin compounds H₂TPP,MgTPP and ZnTPP as well as meso-tetra(3-pyridyl)porphyrins H₂T3PyP,MgT3PyP and ZnT3PyP is conducted on the basis of density functional theory(DFT)method.The geometry, molecular orbital and atomic charge of the meso-tetra(3-pyridyl)substituted porphyrins H₂T3PyP,MgT3PyP,and ZnT3PyP are compared with those of H₂TPP,MgTPP,and ZnTPP,respectively.According to our calculation results,the molecular structrue of H₂TPP,MgTPP,and ZnTPP has D₂,D₄,and D₄ symmetry,respectively,while that of H₂T3PyP,MgT3PyP,and ZnT3PyP has C₂,C₄,and C₄ symmetry.The calculation results reavel that,the substitution of phenyl groups in meso-tetraphenyl porphrins with 3-pyridyl groups induces the reduction of molecular radius and the enlargement of the sizes of the central hole.The orbital energy level of the molecular from HOMO-4 to LUMO+4 of meso-tetra(3-phridyl)porphyrin show some decreace in comparison with corresponding orbitals of meso-tetraphenyl derivatives.However,almost no change is found for the HOMO-LUMO gaps.The vibrational bands in the IR spectra of all the six porphyrin compounds are assigned in detail with the assistance of the animated picture.Secondly,The geometries and electronic structures of the meso=substituted porphyrin Compounds with the nitrogen atom of pyridyl group at different position MT2PyP and MT4PyP(M=2H,Mg,Zn)are investigated using DFT calculation.A comparison between the geometry,molecular orbital,and atomic charge of MT2PyP and MT4PyP and those of MTPP and MT3PyP is carried out.R is found that the position of nitrogen atom in pyridyl groups has many influence to the structrue properties of porphyrins.According to our calculation results,the substitution of phenyl groups in Meso-tetraphenyl porphyrin compounds with pyridyl groups cause the reduction of molecular structrue.The farther the distance between N atom of pyridyl group and the central 16-membered ring is,the smaller the reduction degree of the molecular.On the contrary,the farther the N atom from the molecular center is,the smaller the size of the central hole.The vibrational bands in IR spectra of these porphyrins are comparatively assigned in detail.Finally,we studied the geometries and electronic structures of four isomers ofα-tetrahalogen substituted magnesium phthalocyanines on the basis of DFT calculations.The molecular symmetry of the four isomersα-MgPcF₄ andα-MgPcCl₄ is C_4h,C_s,D_2hand C_2v.respectively,according to the relative position of the halogen substituents in each isoindole segment.The calculation results show that when two C-F or two C-Cl bond between two isoindole link,the band length of C-F or C-Cl is the shortest.The homologous central angle /NMgN is the smallest.When two C-F or two C-Cl bond is neighboring,the molecular orbital energy level trend to increase.But the neighbor of two group of C-Cl bond cause the HOMO-LUMO gap to reduce.Detailed assignments of the vibrational band in IR spectra of the four isomers has been tried on basis of the assistance of the animated picture.