Synthesis of Extended Conjugation Porphyrin Based Bimetallic Complexes and Their Electronic Effect on Catalytic Reactions

Abstract

The major work of this thesis involves the synthesis of a series of extended conjugation bimetallic porphyrin complexes and the study of electronic effect on catalytic activities. The target ligand (H2TPP-Phen) was prepared by extension of conjugation through coupling with 1,10-phenatroline moiety. First, H2TPP was metallated with copper ion, followed by the nitration at β-pyrrole position to give β-NO2-CuTPP in good yields. De-metallation of β-NO2-CuTPP and subsequent reduction of nitro group into amino group β-NH2-H2TPP in the presence of tin(II) chloride and HCl proceeded smoothly. Under oxygen and photo conditions, the desired diketo-porphyrin H2TPPO2 was formed by oxidation. Finally, H2TPP-Phen was established by the condensation of H2TPPO2 and diamino-1,10-phenatroline in presence of trifluoroacetic acid. The metal complexes were prepared via the complexation with the desired metal ions. Catalytic oxidations of alkene and sulfide by a series of cobalt complexes such as CoTPP-PhenCoCl2, ZnTPP-PhenCoCl2 and CoTPP-Phen were investigated. In the epoxidation, all of the three cobalt complexes showed good catalytic activities, indicating that the cobalt ions in the coordination mode either in a porphyrin moiety or in a phenatroline site remained the same activity. Surprisingly, only the ZnTPP-PhenCoCl2 could catalyze the oxidation of a sulfide to form sulfoxide. In a detailed finding, the oxidation was through the singlet oxygen, which was produced by the irradiation of visible light of ZnTPP-PhenCoCl2 in the air. In other words, the zinc porphyrin complex can act as a photosensitizer to help the generation of singlet oxygen. Furthermore, a series of palladium complexes (MgTPP-PhenPdCl2, CoTPP-PhenPdCl2, NiTPP-PhenPdCl2, CuTPP-PhenPdCl2 and ZnTPP-PhenPdCl2) were prepared by a similar manner. The catalytic behaviors of these complexes toward Heck and Suzuki-Miyaura reactions were also investigated. In the Heck reaction, these palladium complexes showed different activities. In fact, ZnTPP-PhenPdCl2 appeared to be the most active, whereas CoTPP-PhenPdCl2 illustrated to be the least active. In Suzuki-Miyaura coupling reaction, the ZnTPP-PhenPdCl2 still remained to be the most active one.