Nitroxide radicals, encapsulated into the cavities of metal–organic frameworks (MOFs), have recently drawn attention as multifunctional spin probes. In this work, we investigate the mobility of TEMPO nitroxide in ZIF-8 framework in the presence of various solvent molecules located in the same cavity. We employ simulations of continuous wave (CW) EPR spectra to reveal anisotropic rotation of radical. It is shown that the largest anisotropy of rotation occurs for ZIF-8 impregnated with alcohols: it is most pronounced at low temperatures, but also manifested at room temperatures. Linear alkanes do not indicate any significant effect onto the rotation anisotropy of TEMPO, while various benzene derivatives show more complicated trends caused by their bulkier shapes. With a number of examples, we demonstrate the ability of CW EPR analysis to disclose effects of solvent ordering in MOFs via anisotropic rotation of encapsulated spin probe.

封装在金属有机框架 (MOF) 的空腔中的氮氧自由基最近作为多功能自旋探针引起了人们的关注。在这项工作中，我们研究了在存在位于同一腔中的各种溶剂分子的情况下，TEMPO nitrooxide 在 ZIF-8 框架中的迁移率。我们采用连续波 (CW) EPR 光谱的模拟来揭示自由基的各向异性旋转。结果表明，用醇浸渍的 ZIF-8 发生最大的旋转各向异性：它在低温下最明显，但在室温下也表现出来。直链烷烃对TEMPO的旋转各向异性没有任何显着影响，而各种苯衍生物由于其较大的形状而表现出更复杂的趋势。举几个例子，