Observation of chirality in the photo-excited triplet state of pi-conjugated molecules

2018 Fiscal Year Final Research Report

• Project/Area Number: 16H04127
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Functional solid state chemistry
• Research Institution: Tohoku University
• Principal Investigator: ARAKI YASUYUKI 東北大学, 多元物質科学研究所, 准教授 (80361179)
• Research Collaborator: Hasobe Taku ; Sakai Hayato
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: キラリティ / 励起三重項 / 円二色性

Outline of Final Research Achievements

Recently, circular polarized luminescence (CPL) has been focused on to develop the newer light-emitting devices. Moreover, the importance of the chirality understanding in the photo-excited triplet states comes to be considered from the viewpoint of multi-wavelength EL devices including phosphorescence with circular polarization. From the academic viewpoint, the detection of the chirality in the excited triplet state of organic molecules in room temperature in solution is still a nascent and almost unexplored field. For chirality detection in the excited triplet state, the circular dichroism measurement is the promising methodology because phosphorescence is basically hopeless in room temperature.
Therefore, in this work, we plan to develop a methodology for measuring the chirality of the photo-excited triplet state based on our sensitive circular dichroism spectrum measurement system, which is particularly important for the development of phosphorescent CPL materials.

Free Research Field

光化学

Academic Significance and Societal Importance of the Research Achievements

本研究では、励起三重項状態のキラリティを観測するために、ベンゼン環がらせん状に縮環したヘリセン分子に着目し、その励起三重項状態のキラリティを観測するために過渡円二色性測定を行った。現有設備を本申請により発展させ、検出効率を大幅に向上させることに成功し、ベンゼン環が6つらせん状に縮環した[6]ヘリセンの励起三重項の室温、溶液中での円二色性測定にも成功した。
この実験結果は、時間依存密度汎関数法による円二色スペクトル予測とも定性的に一致し、りん光CPL材料開発に重要とされる励起三重項のキラリティの理解には、実験、および計算化学的手法が有効であることが実証された。