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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >The Lowest Photoexcited Triplet State of Subphthalocyanine in Solid and Fluid Environments. Time-Resolved Electron Paramagnetic Resonance Studies
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The Lowest Photoexcited Triplet State of Subphthalocyanine in Solid and Fluid Environments. Time-Resolved Electron Paramagnetic Resonance Studies

机译：固体和流体环境中亚酞菁的最低光激发三重态。时间分辨电子顺磁共振研究

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摘要

Time-resolved EPR spectra of the lowest excited triplet state of boron subphthalocyanine chloride have been measured in toluene at various temperatures (5-360 K). On the basis of the observed and simulated spectra, electronic structure and molecular motion of the triplet state (~1T) were analyzed, both in solid and fluid solution. The simulations were carried out using a model, which considers a temperature-dependent exchange between sites having different zero-field splitting (ZFS) parameters and molecular orientations. The ZFS parameter, D, was nearly the same at all temperatures examined. At very low temperatures, below 20 K, the spectrum was analyzed by a static model. At 40-120 K, two conformers with different ZFS parameter, E, have been found. The population ratio between the two conformers showed strong temperature dependence. These conformers were attributed to Jahn-Teller states and were identified by their different ZFS parameters. The exchange rate and activation energy of the conformers were compared with similar experiments performed in solid solution. Further increase in temperature (130-160 K) resulted in noticeable change in the spectra. However, at this temperature range the spectra could not be analyzed quantitatively because of the unstable crystal structure of toluene (soft glass). Above 163 K, the solvent turns slowly into fluid and the spectra were strongly dependent upon temperature. In this range of temperatures, molecular rotations occur, initially around the out-of-plane z-axis, and, as temperature rises, also around the in-plane x- and y-axes. Anisotropic exchange rates were obtained from the spectral simulation and were analyzed by a population exchange between the Jahn-Teller states combined with anisotropic rotations. Anisotropic spin-lattice (T_1) and spin-spin (T_2) relaxation times were also obtained and discussed. The rotations become isotropic above 263 K, where the spectrum exhibits a single sharp Lorentzian line and is analyzed in terms of the dipolar spin interaction.
机译：在各种温度（5-360 K）下，已在甲苯中测量了氯化亚酞菁硼的最低激发三重态的时间分辨EPR光谱。根据观察和模拟的光谱，分析了固溶和流体溶液中三重态（〜1T）的电子结构和分子运动。使用模型进行模拟，该模型考虑了具有不同零场分裂（ZFS）参数和分子方向的位点之间的温度依赖性交换。在所有检查的温度下，ZFS参数D几乎相同。在非常低的温度（低于20 K）下，通过静态模型分析光谱。在40-120 K处，发现了两个ZFS参数E不同的构象体。两个构象体之间的人口比例显示出强烈的温度依赖性。这些构象异构体归因于Jahn-Teller状态，并通过其不同的ZFS参数进行识别。将构象异构体的交换速率和活化能与在固溶体中进行的类似实验进行了比较。温度的进一步升高（130-160 K）导致光谱发生明显变化。但是，在此温度范围内，由于甲苯（软玻璃）的晶体结构不稳定，无法对光谱进行定量分析。高于163 K时，溶剂会慢慢变成液体，并且光谱强烈依赖于温度。在此温度范围内，首先围绕平面外z轴发生分子旋转，并且随着温度升高，还围绕平面内x轴和y轴发生分子旋转。各向异性交换率是从光谱模拟中获得的，并通过Jahn-Teller态与各向异性旋转之间的总体交换来进行分析。还获得并讨论了各向异性自旋晶格（T_1）和自旋自旋（T_2）弛豫时间。旋转在263 K以上变为各向同性，在该处光谱显示一条单一的洛伦兹直线，并根据偶极自旋相互作用进行分析。

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