Electron Spin Dynamics of the Photoexcited Triplet States of Bromoperylenebisimide Compounds: Computation and Analysis of the Electron Spin Polarization Evolution in TREPR Spectra

IF 1.1 4区 物理与天体物理 Q4 PHYSICS, ATOMIC, MOLECULAR & CHEMICAL
A. Mambetov, A. Sukhanov, Xue Zhang, Jianzhang Zhao, V. Voronkova
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引用次数: 0

Abstract

The dynamics of the photogenerated triplet electron spin polarization (ESP) of two perylenebisimide (PBI) derivatives, PBI-2Br and PBI-Br-NH, is studied by the time-resolved electron paramagnetic resonance (TREPR). The ESP inversion in the triplet TREPR spectra of two compounds is detected at delays after the laser pulse (DAF) of ~ 500–900 ns. A fairly efficient algorithm for the exact numerical solution of the equation of motion of the spin density matrix of an ensemble of photoexcited triplets taking into account the anisotropy of the decay rates of sublevels of the triplet state, spin–lattice and spin–spin relaxations is elaborated in order to analyze the ESP inversion of TREPR spectra. The calculated time evolution of the TREPR spectra and its fitting experimental ones shows that even a slight difference in decay rates for the triplet sublevels of PBI-2Br results in the ESP inversion in the TREPR spectra already at DAF of ~ 500 ns. At the same time, decay rates ( τX−1 = 4 µs−1; τY−1 = 4.4 µs−1; τZ−1 = 3.3 µs−1) are higher than those for the available examples of the ESP inversion of the triplet TREPR spectra. The replacement of a Br atom by NH leads to noticeable changes in the photoinduced properties of the triplet including decay rates (τX−1 = 1.25 µs−1; τY−1 = 0.125 µs−1; τZ−1 = 0.125 µs−1). PBI-Br-NH is characterized by an axial decay rate anisotropy with τx−1, which is ten times higher than τY−1 and τZ−1. The trend in the triplet lifetime change obtained from the TREPR spectra is consistent with the data of the nanosecond transient absorption spectra.

Abstract Image

溴过二亚胺化合物光激发三重态的电子自旋动力学:TREPR 光谱中电子自旋极化演变的计算与分析
通过时间分辨电子顺磁共振(TREPR)研究了两种过二亚胺(PBI)衍生物 PBI-2Br 和 PBI-Br-NH 光生三重电子自旋极化(ESP)的动态。在激光脉冲(DAF)后约 500-900 ns 的延迟时间内,检测到了两种化合物的三重 TREPR 光谱中的 ESP 反转。为了分析 TREPR 光谱中的 ESP 反转,详细阐述了一种相当有效的算法,用于精确数值求解光激发三重态集合的自旋密度矩阵运动方程,其中考虑到了三重态子级衰减速率的各向异性、自旋晶格和自旋-自旋弛豫。TREPR 光谱的计算时间演化及其拟合实验结果表明,即使 PBI-2Br 三重态子级的衰变率存在微小差异,也会导致 TREPR 光谱在 DAF 约为 500 ns 时出现 ESP 反转。同时,衰变率(τX-1 = 4 µs-1;τY-1 = 4.4 µs-1;τZ-1 = 3.3 µs-1)高于现有的三重 TREPR 光谱 ESP 反转实例。用 NH 取代 Br 原子会导致三重子的光诱导特性发生明显变化,包括衰减速率(τX-1 = 1.25 µs-1;τY-1 = 0.125 µs-1;τZ-1 = 0.125 µs-1)。PBI-Br-NH 的特征是轴向衰变速率各向异性,τx-1 比 τY-1 和 τZ-1 高十倍。从 TREPR 光谱得到的三重寿命变化趋势与纳秒瞬态吸收光谱的数据一致。
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来源期刊
Applied Magnetic Resonance
Applied Magnetic Resonance 物理-光谱学
CiteScore
1.90
自引率
10.00%
发文量
59
审稿时长
2.3 months
期刊介绍: Applied Magnetic Resonance provides an international forum for the application of magnetic resonance in physics, chemistry, biology, medicine, geochemistry, ecology, engineering, and related fields. The contents include articles with a strong emphasis on new applications, and on new experimental methods. Additional features include book reviews and Letters to the Editor.
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