The solid-state phase transition of a multicomponent active pharmaceutical ingredient (M-APIs), composed of (1:1) agomelatine and phosphoric acid (AGL-P), is characterized using a set of complementary techniques: in situ variable temperature powder X-ray diffraction (VT-PXRD), thermal analysis, spectroscopic techniques, and hot stage microscopy (HSM). It is observed that these dimorphic forms (AGL-P RT-form and HT-form) are enantiotropic and reversible in nature. The salt–cocrystal continuum of this system is demonstrated using ab initio powder XRD structure determination (SDPD) and dispersion corrected density functional theory (DFT-D2) analysis. Furthermore, this solid-state phase transition can be inferred as a martensitic-like transformation, where simultaneous proton migration and small conformational switching trigger the concerted molecular displacements of entire layers, leading to microscopic crystal contraction.

中文翻译：

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沿盐-共晶连续体的Agomelatine-磷酸分子复合物的固态相变：从头算粉末X射线衍射结构测定和DFT-D2分析

由（1：1）阿戈美拉汀和磷酸（AGL-P）组成的多组分活性药物成分（M-API）的固态相变使用一组互补技术进行表征：原位变温粉末X射线衍射（VT-PXRD），热分析，光谱技术和热台显微镜（HSM）。可以观察到，这些双晶形式（AGL-P RT形式和HT形式）本质上是对映体且可逆。从头开始演示该系统的盐-共晶连续体粉末XRD结构测定（SDPD）和色散校正密度泛函理论（DFT-D2）分析。此外，可以将这种固态相变推断为马氏体样转变，其中同时质子迁移和小的构象转换触发整个层的一致分子位移，从而导致微观晶体收缩。