Realization of ultra-fast (fs) intersystem crossing of purely organic systems utilizing pai-radical substituent and elucidation of the mechanism

2021 Fiscal Year Final Research Report

• Project/Area Number: 18K19062
• Research Category: Grant-in-Aid for Challenging Research (Exploratory)
• Allocation Type: Multi-year Fund
• Review Section: Medium-sized Section 32:Physical chemistry, functional solid state chemistry, and related fields
• Research Institution: Osaka City University
• Principal Investigator: TEKI YOSHIO 大阪市立大学, 大学院理学研究科, 教授 (00180068)
• Project Period (FY): 2018-06-29 – 2022-03-31
• Keywords: πラジカル / 超高速系間交差 / ペンタセン / π共役 / 増強系間交差 / 光耐久性 / 有機半導体

Outline of Final Research Achievements

To establish the method to stabilize the unstable materials for the visible light without major modification of the electronic structures, we synthesized novel pentacene derivatives with both π-radical- and TIPS-substituents and their excited-state dynamics were evaluated. The pentacene-radical-linked systems showed a remarkable improvement in photochemical stability, which was more one-hundred times higher than that of 6,13-bis(triisopropylsilylethynyl)pentacene, which is a famous commercially available photostable pentacene derivative. Transient absorption spectroscopy showed that this remarkable photostability is due to the ultrafast intersystem crossing induced by effective π-conjugation between the radical substituent and pentacene moiety. The realization of the ultrafast intersystem crossing occurred within sub-pico second in the purely organic systems is the result with a potential to change the common sense of the excited-state dynamics of the organic materials.

Free Research Field

スピン科学、物理化学

Academic Significance and Societal Importance of the Research Achievements

ペンタセンは有機半導体の代表的な物質である。ペンタセン骨格とπラジカル部位とを強くπ共役させることにより、光耐久性の著しく高いペンタセン誘導体の代表格として知られているTIPS-ペンタセンを遥かに凌駕する光耐久性が実現できた点は、この種の手法を用いて光に不安定な物質を著しく安定化できる手法を示したことになり、その社会的意義は高い。また、重原子を含まない純有機化合物で、サブピコ秒程度（フェムト秒領域）で起こる系間交差を実現できることを示した点は、学術的意義が高いと判断される。