Study of excited state chiral dynamics of transition metal complexes by time-resolved circular polarization spectroscopy

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K05526
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 34010:Inorganic/coordination chemistry-related
• Research Institution: University of Toyama
• Principal Investigator: Iwamura Munetaka 富山大学, 学術研究部理学系, 講師 (60372942)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 金属錯体 / 希土類 / 円偏光発光 / 時間分解発光 / キラル / 光学選択的反応 / アロステリック効果 / 遭遇イオン対

Outline of Final Research Achievements

Time-resolved emission measurements, including time-resolved circularly polarized luminescence (CPL) spectroscopy, have been carried out for photo-excited transition metal complexes. A copper(I) complex exhibiting Jahn-Teller structural change in the excited state was excited by circularly polarized light, and the temporal profiles of the femto-second time-resolved CPL was measured in the femto - pico second time regions. However, no detectable CPL signal was obtained. On the other hand, when we measured the nano - milli second time-resolved CPL of aqueous solutions containing Eu complex and chiral cobalt complexes, we found intense CPL signals in the microsecond time region on the temporal profiles. This is an evidence of that the encounter complex formation between the Eu and Co complexes causes the quenching reaction due to energy transfer and the chiral structural change of the Eu complex by the interactions between the Eu and the Co complexes.

Free Research Field

錯体化学　分子科学

Academic Significance and Societal Importance of the Research Achievements

アキラルな[Eu(pda)2]-がキラルな[Co(en)3]3+により円偏光発光を示すことが明らかとなった。アミノ酸以外のキラル分子で円偏光を[Eu(pda)2]-に誘起するはじめての例である。時間分解CPLを計測することにより、短寿命種がCPLを示すことが分かった。これは時間分解CPLの有効性を示した珍しい例のひとつである。一方、フェムト秒時間分解CPLでは課題を残すことになった。直励起で励起縮重状態を生成する系にて再検討する必要がある。