| dc.description.abstract | In this study, we utilized tetraphenyl-N-confused porphyrin (HCTPPH2) as a ligand to react with VO(acac)2, resulting in the formation of VO(HCTPP). Subsequently, through further reactions conducted under various conditions, we successfully synthesized three derivatives of oxovanadium N-confused porphyrin: VO(HCTPPO), VO(CTPPOMe), and VO(CTPPOEt). The structures of these complexes were confirmed through spectroscopic and mass spectrometry analyses, including paramagnetic 1H NMR, UV-Vis, and ESI-Mass. Our study also aimed to investigate the interconversion among these oxovanadium N-confused porphyrin derivatives and explore the potential reaction mechanism involving oxygen activation and carbon-vanadium bond insertion.
For the catalytic reaction investigations, cyclohexene was chosen as the substrate, and the catalysts employed were VO(HCTPP), VO(HCTPPO), and VO(HCTPPOMe). Oxygen atom transfer reactions were carried out using either 30% H2O2 or mCPBA as the oxygen atom donors. The primary products, namely cyclohexene epoxide, 2- cyclohexen-1-ol, 2-cyclohexen-1-one, and cyclohexane-1,2-diol, were identified by comparing their retention times with those of standard samples. The conversion percentage to each product was calculated based on the obtained product amounts using individual calibration curves. The total conversion yields were determined from the sum of the yields of the primary products. In the control experiments conducted without any oxidants or catalysts, no product formation was observed. Additionally, in the control groups with only oxidants but no catalysts, no product formation occurred when 30% H2O2 was used as the oxygen source. However, cyclohexene epoxide was identified as the main product when mCPBA was employed. Upon introducing the synthesized vanadium porphyrin metal catalysts, significant changes in product selectivity were observed. In catalytic experiments using 30% H2O2 as the oxidant, 2- cyclohexen-1-one became the predominant product. On the other hand, when mCPBA was used as the oxidant, the products were distributed between cyclohexene epoxide and cyclohexane-1,2-diol, indicating a substantial alteration in product selectivity. Based on these results and supported by information from the literature, we explored possible catalytic reaction pathways and mechanisms. | en_US |