2018 Fiscal Year Annual Research Report
Reactions of Super Reductants and Oxidants Explored by Ultrafast Spectroscopy
| Project/Area Number |
18H05976
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| Allocation Type | Single-year Grants |
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| Research Institution | Osaka University |
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Principal Investigator |
LU CHAO 大阪大学, 産業科学研究所, 特任研究員 (90828112)
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| Project Period (FY) |
2018-08-24 – 2020-03-31
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| Keywords | Excited Ions / Laser Flash Photolysis / Physical Chemistry |
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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.
ADIs, especially naphthalenediimide (NDI) and perylenediimide (PDI), are among the most widely explored components for n-type semiconductor materials. Nevertheless, no research work has been yet reported for understanding the related processes in polymeric and crystalline structures. 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. 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 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 of (NDI-X-NDI)－*, (PDI-X-PDI)－*, and (NDI-X-PDI)－* can be directly observed. For the first time, a systematic investigation is conducted to exhibit the unprecedented characteristics of excited dimer radical anions as the super reductants.
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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 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.
ADIs, especially naphthalenediimide (NDI) and perylenediimide (PDI), are among the most widely explored components for n-type semiconductor materials. Nevertheless, no research work has been yet reported for understanding the related processes in polymeric and crystalline structures. 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. 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 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 of (NDI-X-NDI)－*, (PDI-X-PDI)－*, and (NDI-X-PDI)－* can be directly observed. For the first time, a systematic investigation is conducted to exhibit the unprecedented characteristics of excited dimer radical anions as the super reductants.
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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 radical anions or cations. Thus, I am going to study the excited dianions of aromatic diimides (ADI2－*) and excited dications of oligothiophenes (nT2+*), because their excited states of radical ions have been examined in my previous studies. Based on the detected dynamics and redox potentials, molecular systems for studying intramolecular 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 ADI2－ and nT2+ compared with the corresponding excited 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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