Understanding the electron-proton decoupling effect in the hydrogen/proton transfer reaction by electron-nucleus conjugated measurements

2018 Fiscal Year Final Research Report

• Project/Area Number: 15H02157
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Physical chemistry
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Fujii Masaaki 東京工業大学, 科学技術創成研究院, 教授 (60181319)
• Co-Investigator(Kenkyū-buntansha): 宮崎 充彦 東京工業大学, 科学技術創成研究院, 助教 (00378598)
• Project Period (FY): 2015-04-01 – 2019-03-31
• Keywords: 励起状態ダイナミクス / 励起状態水素移動反応 / 溶媒和クラスター

Outline of Final Research Achievements

In this project, a femtosecond time-resolved near infrared-ultraviolet spectroscopy on gas phase solvated clusters was developed, and this method was applied to the phenol-(ammonia)5 cluster to investigate the mechanism of the excited-state hydrogen transfer reaction.
The reaction dynamics was composed of an electron transfer with ca. 350 fs and a proton transfer with ca. 20 ps. This result means that the electron and the proton transfer processes proceeds in totally different time-scales, i.e. there is decoupling between the electron and the proton though this reaction is a hydrogen transfer reaction.
The decoupling mechanism stems from a strong coupling of the pi-sigma* state with a charge-separated state. Solvation strongly affects the stability of the charge separated state and also changes the degree of the decoupling.

Free Research Field

物理化学

Academic Significance and Societal Importance of the Research Achievements

最も単純な原子である水素原子あるいはその原子核であるプロトンの移動メカニズムは、細胞活動から燃料電池の作用メカニズムまで幅広い分野で重要である。
本研究では、電子励起状態での水素移動反応において、水素原子の移動が原子核と電子に分かれて進行する場合があることを示した。またその原因には、溶媒和の程度や複数の電子状態の関与があることを明らかにした。
これらの結果は、様々な反応における反応機構を考える上で重要な基礎となる。