This study addresses azobenzene's structural compression and reactivity under hydrostatic high-pressure conditions. Synchrotron X-ray diffraction data of single crystals compressed with neon as the pressure-transmitting medium allowed the refinement of the crystal structure up to 28 GPa, at which the onset of the reaction was observed. Analysis of the pressure-dependent lattice parameters reveals a first-order isostructural phase transition at 13 GPa. We have solved the crystal structure of the high-pressure phase of azobenzene offering a key insight into the strong contribution of stress on the structural compression mechanism and crystal's reaction chemistry at elevated pressures. While the collapse of the b cell parameter, previously observed under non-hydrostatic conditions, was identified as the crucial step toward the formation of azobenzene-derived double-core nanothreads, under quasi-hydrostatic conditions the compression of the cell parameters up to 33 GPa followed a different route. The evolution of the cell parameters and the refinement of the crystal structure close to the onset of the reaction identified a topochemical polymerization path, corroborated by reaction kinetics data by infrared spectroscopy and by computed polymer structures, suggesting a complex growth process, resulting in a distinctly different material compared to that formed upon non-hydrostatic compression. These findings underscore the pivotal role of compression conditions in determining the reaction pathways of azobenzene, providing novel insights for its application in nanomaterial synthesis.

中文翻译：

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通过单晶 X 射线衍射深入了解偶氮苯的拓扑化学与应力诱导的高压反应性


本研究解决了偶氮苯在静水压高压条件下的结构压缩和反应性。以氖作为传压介质压缩的单晶的同步加速器 X 射线衍射数据允许将晶体结构细化至 28 GPa，此时观察到反应的开始。对压力相关晶格参数的分析揭示了 13 GPa 处的一阶等构相变。我们已经解决了偶氮苯高压相的晶体结构，为了解应力在高压下对结构压缩机制和晶体反应化学的强烈贡献提供了关键见解。虽然以前在非静水压条件下观察到的 b 细胞参数的崩溃被确定为形成偶氮苯衍生的双核纳米线的关键步骤，但在准静水压条件下，细胞参数的压缩高达 33 GPa 遵循不同的路线。细胞参数的演变和接近反应开始时晶体结构的细化确定了拓扑化学聚合路径，红外光谱和计算聚合物结构的反应动力学数据证实了这一点，表明存在复杂的生长过程，导致材料与非静压压缩时形成的材料明显不同。这些发现强调了压缩条件在确定偶氮苯反应途径中的关键作用，为其在纳米材料合成中的应用提供了新的见解。