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Electronic states and their molecular dynamics in fluid solution by multi-frequency EPR

通过多频 EPR 研究流体溶液中的电子态及其分子动力学

基本信息

批准号：
12440157
负责人：
YAMAUCHI Seigo
金额：
$ 9.28万
依托单位：
TOHOKU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12440157/
关键词：
Excited Multiplet Excited Triplet State Excited High spin State High Frequency EPR Two Dimensional EPR Multi-Frequency EPR Metalloporphyrin Time-Resolved EPR 溶液ダイナミクスラジカル軸配位金属フタロシアニン WバンドESR 軸配位フラーレンアダクト

项目摘要

The following results were obtained in this research project.1. We succeeded in observations and simulations of the EPR spectra of the excited triplet (T_1) states in fluid solution. The molecules include metalloporphyrins (MTPP : M = Zn, Mg, H_2), phthalocyanines and subphthalocyanine. The processes concerning the Jahn-Teller split state and/or the second excited triplet (T_2) state and in-plane and out-of-plane rotations were separated at various temperatures and the activation energies were obtained in each process.2. The spin-relaxation times of metalloporohyrins were obtained in the T_1 states by multi frequency, X, Q, and W band, EPR techniques. The results that the spin-spin relaxation time remained the same and that the spin-lattice relaxation time varied depending on the band, ex. two orders of magnitude longer in the W band, indicate that theses relaxations are dominated by the spin dipolar mechanism The shorter spin-lattice relaxation time in ZnTPP and MgTPP indicate the proximity of the T_2 state.3. The g values of the excited quartet states were obtained by X band EPR in the T_1-radical systems. The values were different depending on the system and gave rise to the intersystem crossing rate between the excited doublet and quartet states. On the basis of the transient absorption experiments, it turned out that the larger are the J value between T_1 and the radical, the slower the intersystem crossing rates are.4. The EPR spectra of the excited doublet and quartet states and the doublet ground state were separated and assigned for the first time in solution. The time profiles of these states show that the two excited states, the doublet and the quartet, (toy different indicating independent decay processes involving in the excited states.

在本研究项目中取得了以下研究成果。我们成功地观测和模拟了流体溶液中激发三重态(T_1)的EPR谱。这些分子包括金属卟啉(MTPP：M=锌、镁、氢)、酞菁和亚酞菁。在不同温度下分离了Jahn-Teller分裂态和/或第二激发三重态(T_2)以及面内和面外转动的过程，得到了每个过程的活化能。用多频、X、Q和W谱、EPR技术得到了金属卟啉在T_1态的自旋弛豫时间。结果表明，自旋-自旋驰豫时间保持不变，而自旋-晶格驰豫时间随能带不同而不同。在W带长两个数量级，表明这些弛豫是由自旋偶极机制主导的，而较短的自旋晶格驰豫时间表明它们接近T2态。用X带电子顺磁共振测定了T_1-自由基体系激发四重态的g值。这些值随系统的不同而不同，并导致激发的二重态和四重态之间的系间交叉率。在瞬时吸收实验的基础上，发现T_1与自由基间的J值越大，体系间的交叉速率越慢。首次在溶液中分离和归属了激发态双重态和四重态以及双重态基态的EPR谱。这些态的时间分布表明，二重态和四重态是两个不同的激发态，表明激发态之间存在相互独立的衰变过程。