Quantum Chemistry Calculation And Spectroscopic Investigations Of Metallocorroles

Corroles, which belong to the ring shrinkage analogues of porphyrins, have similar skeleton structure as the porphyrins and Corrins in vitamin B12. Free base corroles are normally used as trivalent anions to stable high valence metal ions (such as Fe, Mn and Cr etc.), and have potential applications on many aspects, such as fine chemical catalysis, anti-tumor treatments, catalysis of fuel cell electrode, electrochemical sensors, nanomaterials and nonlinear optical materials. Studies on the structures and spectra of corroles are helpful to understand the relationship between their structures and properties and to provide theoretical and experimental basis for their applications in various fields. In this dissertation, we used the density functional theory (DFT) calculations and spectroscopic experiments to investigate the ground state structures and electronic spectra of protonated corroles, and the ground state structures, the effects of core size, vibrational and electronic spectra of metallocorroles. The dissertation includes five chapters.The first chapter described the basic theories of quantum chemistry calculation, ordinary Raman and resonance Raman scattering. The current researches on the structures and molecular spectra of metallocorroles are reviewed and the research background and the main contents of the dissertation are outlined.In the second chapter, the calculations on the structures, electronic spectra and structural inter-conversion of N-protonated products of unsubstituted free base corrole and its three meso-substituted derivatives were performed by using the density functional theory (DFT) at the B3LYP/6-31G*level. The calculated results show that the protonation corroles have two stable configurations. The conversion between two chiral enantiomers of the ground state for each protanated corrole is a multistep process. The electronic absorption spectra of the four protonated corroles were calculated with the time-dependent density functional theory (TDDFT), the results were compared with the experimental results. TDDFT was also used to calculate the electronic circular dichroism spectra. The results show that the electronic circular dichroism spectra can serve as an effective tool to study the electronic properties of N-protonaled corroles.In the third chapter, the infrared absorption and Raman scattering spectra were measured for the metallotriphenylcorroles (MTPCs, M=Cu, Co, Ni, Mn). The ground-state structures and vibrational spectra of MTPCs have been calculated with DFT method. The observed Raman and IR bands have been assigned based on the calculated results. Due to the symmetry lowering, the vibrational spectra of MTPCs are much more complex in comparison with metalloporphyrins, and several skeletal modes are found strongly coupled to the phenyl vibrations. The relationship between the Raman/IR frequencies and the structures of TPC ring is investigated. It is found that the vibrations involving the CαⅠ-CαⅠ stretch and Cα-Cm stretch are sensitive to the size of corrole core. In particular, the frequency of v5, which is assigned to CαⅠ-CαⅠ stretch in coupling with the Ca-Cm symmetric stretch, increases linearly with the decrease of the corrole core-sizes and may be used as a mark band to evaluate the structural change of the metallocorroles.In Chapter four, density functional theory calculations are carried out to study the structures and molecular vibrations of the first series transition metal complexes of peripherally unsubstituted corrole (MCors). Relationships of their geometries, frequencies, the distributions of total energy on bond-lengths/bond-angles with the core sizes of MCors (half of the distances between two opposite nitrogens) were analyzed. According to their atomic Cartesian displacements, the normal vibrations of MCors are systematically assigned to the local coordinates. Among the in-plane vibration modes, the modes that are mostly sensitive to the core-size change are those involving the stretching vibrations of CαⅠ-CαⅠ, Cα-Cm and Ca-Cp bonds. For out-of-plane modes, the vibrations corresponding to the saddeling deformation and umbrella deformation of corrole macrocycle are mostly sensitive to the change of core size.In the five chapter, the ground-state geometries of one-electron reduced/oxidized species ([VOP]-/[VOP]*) of vanadyl porphyrin (VOP) have been calculated with the DFT-PBE1PB1method. The results show that for both [VOP]’and [VOP]+the ground states are triplet. In contract to the C4V symmetry of neutral VOP molecule,[VOP]-anion has a "rectangular" distorted C2V structure due to the Jahn-Teller effect. The linear vibronic coupling constants for the Jahn-Teller active modes of [TOP]-were evaluated with DFT calculations. The nodal patterns of the frontier KS orbitals were used to explain the reason why Jahn-Teller distortion of [TOP]-occurs along specific modest. The ground state [VOP]+has a porphyrin ring with pronounced bond length alternation due to the pseudo-Jahn-Teller (pJT) effect, which causes its symmetry declined to C4from C4V.