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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Low Magnetic Field Dependence of the ~(31)P Chemically Induced Dynamic Nuclear Polarization in the Photolysis of a Benzoyl Phosphonate. Role of S-T- Mechanism
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Low Magnetic Field Dependence of the ~(31)P Chemically Induced Dynamic Nuclear Polarization in the Photolysis of a Benzoyl Phosphonate. Role of S-T- Mechanism

机译:苯甲酰膦酸酯光解中〜(31)P化学诱导的动态核极化的低磁场依赖性。科技机构的作用

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摘要

The chemically induced dynamic nuclear polarization (CIDNP) upon the photolysis of 2,4,6-trimethylben-zoylphosphonic acid dimethyl ester in solvents of different viscosities has been studied in high and low magnetic fields. The reaction was carried out in the presence of an effective radical scavenger, bromotrichloromethane, which allows the study of only the geminate contribution to the CIDNP. The theory proposed earlier, considering S-T_ transitions in the level crossing region in the balance approximation, has been modified by taking into account the reaction with scavengers, anisotropy of the exchange interaction, and the reactivity of radicals and has been used for the description of the CIDNP field dependencies obtained. Good agreement of theoretical and experimental results is achieved with the following set of parameters: J_0 =-450+- 100 mT, #lambda# =0.7 +- 0.1 A, f(steric factor)=0.08 +- 0.02, #tau#_r (correlation time of modulation of the exchange interaction and reactivity anisotropy) =7 +- 2 ps (in CH_3CN), 25 +- 3 ps (in dioxane).
机译:在高和低磁场中研究了2,4,6-三甲基苯甲酰膦酸二甲酯在不同粘度的溶剂中光解后的化学诱导动态核极化(CIDNP)。该反应是在有效的自由基清除剂溴三氯甲烷的存在下进行的,该研究仅研究了双胺对CIDNP的贡献。先前提出的理论,考虑了与清除剂的反应,交换相互作用的各向异性和自由基的反应性,考虑了平衡近似中水平交叉区域中的S-T_跃迁,已被描述。获得的CIDNP字段依赖性。使用以下参数集可实现理论和实验结果的良好一致性:J_0 = -450 +-100 mT,#lambda#= 0.7 +-0.1 A,f(空间系数)= 0.08 +-0.02,#tau#_r (交换相互作用和反应性各向异性的调制的相关时间)= 7±2ps(在CH_3CN中),25±3ps(在二恶烷中)。

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