An original method to study the local environment of vanadyl-containing components of heavy oils based on fine-tuning simulation of their electron spin resonance (ESR) spectra in situ is developed. The approach is backgrounded on precise computation of anisotropic ESR spectra of individual porphyrin complexes in specific solvents modeling a particular local environment of certain polarity using specific g and A tensor components, their dispersion, and linewidth determined by unresolved super-hyperfine interaction with the closest nitrogen. The high level of simulation accuracy allowed us to differentiate the values of the g and A tensor components related to individual vanadyl complexes in different solvents with certain polarity in reference systems and attribute the observed variation to the interaction of the vanadyl complex with surrounding molecules located in its axial direction. The method developed for the model systems is successfully applied to the real oil-based systems where different vanadyl complexes with different local environments are presented, forming the experimentally observed ESR spectrum. The Monte Carlo procedure was suggested to define the relative contribution (weight) of the individual spectra having tiny peculiarities related to vanadyl fragments in different local environments and finally mapping the g and A tensor components distribution which is characteristic for the particular oil-based sample. Extraordinary sensitivity to the localization and interaction with surrounding molecules of vanadyl-containing complexes which are present in heavy oil as a natural spin probe or can be specially introduced give us a unique opportunity to in situ study the local environment of asphaltenes and their intermolecular interactions with other oil components.

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ESR谱的微调模拟——现场识别沥青质局部环境的敏感工具

开发了一种基于原位电子自旋共振 (ESR) 光谱微调模拟研究重油含钒组分局部环境的原始方法。该方法的背景是精确计算特定溶剂中单个卟啉配合物的各向异性 ESR 光谱，使用特定g和A张量分量模拟具有特定极性的特定局部环境，它们的色散和线宽由与最近的氮的未解决的超超精细相互作用确定. 高水平的模拟精度使我们能够区分g和A的值与参考系统中具有一定极性的不同溶剂中的单个钒基配合物相关的张量分量，并将观察到的变化归因于钒基配合物与位于其轴向方向的周围分子的相互作用。为模型系统开发的方法成功地应用于实际油基系统，其中呈现了具有不同局部环境的不同钒基配合物，形成了实验观察到的 ESR 谱。建议使用蒙特卡罗程序来定义各个光谱的相对贡献（权重），这些光谱具有与不同局部环境中的钒基碎片相关的微小特性，并最终映射g和A张量分量分布，这是特定油基样品的特征。对作为天然自旋探针存在于重油中或可以特别引入的含氧钒配合物周围分子的定位和相互作用具有非凡的敏感性，这为我们提供了一个独特的机会来原位研究沥青质的局部环境及其分子间相互作用其他油成分。