Reaction of Silyl radicals within a Porphyrin π-Cloud

• Project/Area Number: 11650883
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Synthetic chemistry
• Research Institution: The University of Tokyo
• Principal Investigator: KONISHI Katsuaki The University of Tokyo, Department of chemistry and Biotechnology Research Associate, 大学院・工学系研究科, 講師 (80234798)
• Project Period (FY): 1999 – 2000
• Project Status: Completed (Fiscal Year 2000)
• Budget Amount: ¥2,900,000 (Direct Cost: ¥2,900,000); Fiscal Year 2000: ¥1,400,000 (Direct Cost: ¥1,400,000); Fiscal Year 1999: ¥1,500,000 (Direct Cost: ¥1,500,000)
• Keywords: Porphyrin / Silicon Porphyrin / Silyl radical / Visible Light / Radical Reaction / Photoreaction

Research Abstract

A series of organosilicon porphyrins) with alkyl (sp^3), alkenyl, aryl (sp^2), and alkynyl (sp), groups at the axial positions were synthesized. Upon irradiation with visible light, dialkylsilicon porphyrins reacted with nitroxy compounds, such as TEMPO to give dinitroxysilicon porphyrins. In the absence of nitroxy compounds, photolysis resulted in the formation of a long-lived (>50 days at 25℃) EPR-active silicon diradical with a g-value of 2.0026, which did not react with nitroxy compounds in the dark but was smoothly trapped by TEMPO to give dinitroxysilicon complex upon excitation with visible light. Irradiation of the dinitroxysilicon with visible light in the presence of free nitroxy compoundss resulted in reversible axial ligand exchange, which proceeded in response to the switching-on and-off of the light, to reach an equilibrium.