Spin–Spin interactions between unpaired electrons in organic radicals are of utter importance from the viewpoint of molecular magnetism and the development of smart materials. The diamagnetic to paramagnetic phase transition observed in some radicals often leads to “magnetic bistability,” sometimes associated with a thermally accessible structural phase transition. The noncovalent interactions determining the solid-state packing arrangement are highly susceptible to external stimuli (temperature, pressure, light, electric field, etc.) and allow the radicals to respond reversibly. Thus, a qualitative understanding of the communication pathway of the spin centers and factors determining the solid-state packing arrangement for the radicals is most important. In this perspective, we mainly discuss the effect of noncovalent interactions rearranging the radicals’ position with temperature determining the mechanistic pathway of such phase transitions. We focus on the importance of electronic parameters stabilizing different polymorphic phases of the radicals, secondary dynamic effects arising from the π-stacking in solid-state, and their role in a magnetic phase transition, along with the consequences of different external stimuli in fine-tuning the magnetic bistable states.

中文翻译：

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有机自由基中的磁跃迁：晶体工程方面

从分子磁性和智能材料的发展的角度来看，有机自由基中未成对电子之间的自旋-自旋相互作用非常重要。在一些自由基中观察到的抗磁性到顺磁性相变通常导致“磁双稳，”有时与热可及的结构相变有关。决定固态堆积排列的非共价相互作用非常容易受到外部刺激（温度、压力、光、电场等）的影响，并允许自由基做出可逆反应。因此，对自旋中心的通信路径和决定自由基固态堆积排列的因素的定性理解是最重要的。从这个角度来看，我们主要讨论非共价相互作用重新排列自由基位置与温度的影响，这决定了这种相变的机制途径。我们关注稳定自由基不同多晶相的电子参数的重要性，固态 π 堆积产生的二次动力学效应，