2019 Fiscal Year Research-status Report
Reactions of Super Reductants and Oxidants Explored by Ultrafast Spectroscopy
| Project/Area Number |
19K21127
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| Allocation Type | Multi-year Fund |
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| Research Institution | Nagoya University |
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Principal Investigator |
LU CHAO 名古屋大学, 工学研究科, 研究員 (90828112)
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| Project Period (FY) |
2019-04-01 – 2021-03-31
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| Keywords | Excited Ions / Electron Transfer / Laser Flash Photolysis / Physical Chemistry / Photochemistry |
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| Outline of Annual Research Achievements |
In the current research, the unprecedented properties and various electron transfer/hole transfer processes caused by excited radical ions/excited divalent ions as the super reductants and super oxidants are explored. The purposes of this research plan are the clarification of excited-state dynamics and reaction mechanisms of excited radical ions/excited divalent ions and the exploration of their application for various redox systems to establish a new science field of super reductants and super oxidants.
Aromatic diimides, especially naphthalenediimide (NDI) and perylenediimide (PDI), are among the most widely explored components for n-type semiconductor materials. Considering the roles of the compactly located chromophores in homo- and heterogeneous organic semiconductors, excited dimer radical anions should be regarded as the important species. Nevertheless, no research work has been yet reported for understanding the related processes in polymeric and crystalline structures. Thus, in this study, by using 2,7-di-tert-butyl-9,9-dimethyl-xanthene (X) as a linker, NDI-X-NDI, PDI-X-PDI, and NDI-X-PDI have been perpared. X holds NDIs or (and) PDIs at van der Waals distances to realize strong π-π interaction between them. By applying femtosecond laser flash photolysis after chemical reduction, the excited-state dynamics and electron transfer properties of (NDI-X-NDI)－*, (PDI-X-PDI)－*, and (NDI-X-PDI)－* have been directly observed.
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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
In this research project, the unprecedented properties and various electron transfer/hole transfer processes caused by excited radical ions/excited divalent ions as the super reductants and super oxidants are explored. The purposes of this research project are the clarification of excited-state dynamics and reaction mechanisms of excited radical ions/excited divalent ions and the exploration of their application for various redox systems to establish a new science field of super reductants and super oxidants.
In the current study, by using 2,7-di-tert-butyl-9,9-dimethyl-xanthene (X) as a linker, NDI-X-NDI, PDI-X-PDI, and NDI-X-PDI have been synthesized. X holds NDIs or (and) PDIs at van der Waals distances to realize strong π-π interaction between them. By applying femtosecond laser flash photolysis after chemical reduction, the excited-state dynamics and electron transfer properties of (NDI-X-NDI)－*, (PDI-X-PDI)－*, and (NDI-X-PDI)－* have been directly observed. For the first time, a systematic investigation was conducted to exhibit the unprecedented characteristics of the excited radical anions in intensely interacting molecular systems.
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| Strategy for Future Research Activity |
1) Characteristics of excited states of closed shell systems (excited divalent ions) will be clarified for the first time compared with the corresponding excited mono radical anions or cations. Based on the detected dynamics and redox potentials, molecular systems for studying the charge transfer from excited dianions or dications as the newly developed super reductants or oxidants will also be designed.
2) Femtosecond stimulated Raman spectroscopy (FSRS) provides a fundamental advance in the quest for real-time vibrational information of chemical changes. Thus, in this study, FSRS will be applied to dianions or dications compared with the corresponding excited mono radical ions. For the first time, a structural dynamic study with atomic spatial and femtosecond resolution will be realized for the excited divalent ions.
3) Considering the roles of the densely populated charges in organic semiconductors, the generation of bipolarons via the super oxidants i.e. excited radical cations should be regarded as an important process.In this study, a series of the mesitylene (M)-linked nT derivatives will be prepared as the target molecules. By applying femtosecond laser flash photolysis after chemical oxidation, for the first time, a systematic investigation will be performed to illustrate the bipolaron-generating nature of excited bis(radical cation)s.
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| Causes of Carryover |
I need to prolong the period of my research project because I have recently moved my position with the research place. I need more time to adapt to the new environment and carry out my research.
Usage plan is shown as follows:1) Characteristics of excited states of closed shell systems (excited divalent ions) will be clarified for the first time compared with the corresponding excited mono radical anions or cations. 2) Femtosecond stimulated Raman spectroscopy (FSRS) will be applied to dianions or dications compared with the corresponding excited mono radical ions. For the first time, a structural dynamic study with atomic spatial and femtosecond resolution will be realized for the excited divalent ions. 3) By applying femtosecond laser flash photolysis after chemical oxidation, for the first time, a systematic investigation will be performed to illustrate the bipolaron-generating nature of excited bis(radical cation)s.
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