A Study On The Molecular Design, Synthesis, Characterization And Catalytic Performance Of A₃B Type Meso-substituted Unsymmetrical Porphyrin Compounds

This thesis systematically investigated the preparation of porphyrins process inmixed-solvents&mixed-aldehydes synthesis of A₃B type porphyrin based onliterature reviews of current research works at home and abroad. The structures of14targeted porphyrins and6metalloporphyrins have been characterized by means ofElemental Analysis, IR, UV-Vis, MS and1HNMR. Substituented porphyrins andmetalloporphyrins were calculated to explore the effects of different substituents atthe phenyls and kinds of ligand symmetry on the microscopic structure and frontierorbital energy, which put forward a class of low degree of asymmetry A₃B typemetalloporphyrins catalyst. Meanwhile, the pre-mixing means was added in themixed-aldehyde method to inherit the advantages of mixed-aldehyde anddipyrromethane method. The catalytic performance of these targeted products wasdetected in the oxidation of o-Cresol and2-nitro-4-methylsulfonyltoluene usingmolecular oxygen. These results are summarized as follows.1. The substitutions at the phenyls and ligand symmetry had little influence onthe configuration of the porphyrin ring, which mainly depended on the kinds ofmetal ions on the center. And it was found that EHOMOand ELUMOwere increased ordecreased simultaneously caused by different substations. The electron-withdrawinggroup lowered the energies of both frontier orbitals, while the electron-donating oneheightened them. What’s more, the low degree of asymmetry had almost no effect onsplitting degenerated orbits of metalloporphyrins with lower symmetry. To thecontrary, the low degree of asymmetry caused orbit splitting in porphyrins and zincporphyrin with relatively high symmetry. ΔEH-Lvalues of A₃B type porphyrin ligandand A₃B type zinc porphyrin were less than the corresponding A4type porphyrin andmetalloporphyrin. The axial chloride made the complex conducive to nucleophilesattack.2. The synthesis of A₃B type porphyrins, where pyrrole and two kinds ofaldehyde were used as raw materials while Bronsted acid as the catalyst andaromatic nitro compounds as the solvent and the oxygenant, was systematicallyinvestigated through considering the effects of reaction conditions including reactiontemperature, reflux time, dose and species of oxygenant and additive, variousmixed-solvents, mol ratio of two aldehyde, microwave assistance and pre-mixingprocess toward the yields of the targeted products. The optimized reaction conditionwas mixed-solvents consisted of acetic acid/propionic acid/nitrobenzene,20mL nitrobenzene,2:1mol ratio of two aldehyde, and under120¹40℃for1to1.5h.The yields of targeted products reached up to5.6%under this condition. When thetemperature and time of pre-mixing process was15℃and60min respectively, theyield was7.2%.3. Elemental Analysis, IR, UV-Vis, MS,1HNMR and melt point confirmed thestructures of targeted products. The UV-Vis spectrum indicated that the low degreeof asymmetry caused the orbital energy difference between a1uand a2u. The catalyticperformance of targeted products was detected in the oxidation of o-Cresol and2-nitro-4-methylsulfonyltoluene using molecular oxygen. Compared to A4typeferric metalloporphyrins, A₃B type ones behaved even higher activity, the selectivityof salicylic acid was increased by2.1⁴.5%and the selectivity of2-nitro-4-methylsulfonylbenzoic acid was increased by11.9%. What’s more, thecatalytic activity of A₃B type zinc metalloporphyrin was higher than that ofmetalloporphyrins with variable valence states metal ions, and the yield of salicylicacid increased by11.9%.