2022 Fiscal Year Research-status Report
Photoinduced macroscopic polarization change with long-lived metastable state
| Project/Area Number |
21K05085
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| Research Institution | Kyushu University |
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Principal Investigator |
SU SHENGQUN 九州大学, 先導物質化学研究所, 助教 (90817496)
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| Project Period (FY) |
2021-04-01 – 2024-03-31
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| Keywords | polarization change / spin transition / photoexcitation / ion displacement |
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| Outline of Annual Research Achievements |
The purpose of this research project is to realize the photoinduced persistent polarization change in spin crossover crystals attained by Light-Induced Excited Spin-State Trapping (LIESST) effect. After we obtained a Fe(II) spin transition complex with photoinduced polarization change in the first year, we mainly focused on exploring the factors induced the polarization change. Considering the structure of the excited state is difficult to analysis due to the low structural conversion ratio after irradiation, we confirmed that 24% of Fe(II) changes from the low spin state of the ground state to the high spin state of the excited state through variable temperature Mossbauer spectra before and after irradiation. In addition, the variable temperature IR spectra have also afforded the evidence for this result. The structure data during the spin transition from 273 K to 393 K were determined by the variable temperature single structure analysis. Combined the point charge calculation and the theoretic calculation, the calculated result indicates that the large polarization change originates from the off-centering ion displacement because of the shrinkage or expansion of cations due to the spin transition. It also shows that light-induced ion movement in a polar crystal is realized. To improve this work, the other spin crossover complex that exhibited photoinduced polarization change and complete spin transition was developed. It is a better model to study the mechanism of photoinduced polarization change and then to improve the polarization change.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The following factors allowed this research project to progress smoothly. Our work mainly focused on developing molecular magnetic switches in response to external stimuli, such as temperature and light. Some spin transition complexes with LIESST effect have been developed and well-studied. We can make full use of such experience and knowledge to develop our target complexes. In addition, we have measurement conditions of the photoinduced magnetic property and polarization change and are familiar with them. Moreover, we have established well collaborations with other research laboratories for other analysis, such as photoinduced variable temperature Mossbauer spectroscopy and infrared spectroscopy.
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| Strategy for Future Research Activity |
I will complete other measurements of the second target spin crossover complex already obtained, such as the variable temperature structure before and after light exposure, and then propose a mechanism for the generation of polarization changes through combining point charge calculations and theoretical calculations in the near future. I will continue to design and synthesize such spin-crossover compounds where the excited state will be stable in the higher temperature; and grasp the mechanism of polarization change to improve the value of the polarization change.
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Research Products
(4 results)
