2020 Fiscal Year Annual Research Report
強発光と高性能単イオン磁性を示す多機能性シアノ架橋型錯体の研究
| Project/Area Number |
19J22088
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| Research Institution | The University of Tokyo |
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Principal Investigator |
WANG JUNHAO 東京大学, 理学系研究科, 特別研究員(DC1)
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| Project Period (FY) |
2019-04-25 – 2022-03-31
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| Keywords | molecular nanomagnet / luminescent thermometer / re-absorption effect / single molecule magnet |
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| Outline of Annual Research Achievements |
In the second year of research, I focused on a family of Ho(III)-M(III) dinuclear molecules (M = Co, Rh, Ir). The slow relaxation of magnetization behavior was observed in the Ho(III) center under zero dc field, which is ascribed to the suitable ligand field of the Ho(III) coordination sphere. Additionally, under UV excitation, the magnetically diluted samples of these three analogues show blue emission due to the fluorescence of the 4-pyridone ligand. Moreover, a series of negative lines were found denting into the broad blue emission band, due to the f-f re-absorption transitions of Ho(III) ion. The re-absorption lines are strongly temperature dependent due to the involvement of hot-band transitions, thus, re-absorption intensity ratios between non-hot-band peak at 446 nm and hot-band peaks at 456/459 nm were used to construct highly sensitive ratiometric thermometric calibration curve.
In summary, the research progress in this year not only present a rare example of Ho(III)-based molecular nanomagnets, but also proposed an innovative approach in constructing high-performance optical thermometer, i.e., using re-absorption effect. This approach is of great importance for the temperature monitoring of the non-emissive lanthanide ions, especially when their functional molecules are manufactured in advanced nanodevices. Thus, I believe this result will be appealing to wide research communities of molecular magnets, luminescence ratiometric thermometry and nanodevice fabrication.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
In this year, I have achieved an functionality conjunction of Single-Molecule Magnet (SMM) behavior and luminescence ratiometric thermometry. The SMM behavior in this work resulting from the non-Kramer Ho(III) ion contributes a valuable example to the rare group of Ho(III)-based molecular nanomagnets. Given that the number of reported Ho-SMMs is up-to-date less than 15, much more unpopular to the commonly investigated Dy-SMMs (over 600 examples). Besides, the work in this year suggests an totally new approach in constructing high-performance luminescent thermometer using temperature dependent re-absorption peaks. Furthermore, we even tried to correlated the SMMs behavior and the re-absorption effect. Although the effective energy barrier is hard to predict from re-absorption spectra, but the whole energy splitting of the ground f multiplet were successfully estimated.
Therefore, judging from this year's research achievement as described above, I believe the progress is more than the expected.
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| Strategy for Future Research Activity |
For the next year, I plan to investigate luminescence thermometry using Er(III) analogue, which are also know to be optically absorptive in the visible region, and I would like to find out if there are anything even more interesting behavior concerning the optical thermometric functionality.
Also I plan to keep investigating several newly synthesized coordination polymers containing lanthanide(III) ions. The humidity dependences of the magnetic and luminescent functionalities are of particular interest as some of the new compounds contain many water molecules in the porous supramolecular frameworks. Therefore, I would like to investigate deeply the correlation between proton-conductivity, slow relaxation of magnetization, and emission properties under the external humidity stimuli.
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