Loprete Fabio, Pandolfi Lorenzo, Giunchi Andrea, Pandolfi Sara, d'Agostino Simone, Tarroni Riccardo, Graziosi Patrizio, Della Valle Raffaele G, Salzillo Tommaso, Venuti Elisabetta
Dipartimento di Chimica Industriale "Toso Montanari", Università di Bologna, Via Piero Gobetti 85, 40129 Bologna, Italy.
Dipartimento di Chimica "Giacomo Ciamician", Università di Bologna, Via F. Selmi 2, 40126 Bologna, Italy.
J Am Chem Soc. 2025 Jun 18;147(24):21109-21120. doi: 10.1021/jacs.5c06303. Epub 2025 Jun 4.
The solid-state [2 + 2] cycloaddition of vitamin K (VK3) polymorphs has been systematically reexamined, overcoming the limitations of powder-based studies by focusing on single-crystal behavior. Using THz micro-Raman and FTIR-ATR vibrational spectroscopies combined with X-ray diffraction and solid-state density functional theory (DFT) calculations, we unveil distinct photoreactivity and stereoselectivity in both polymorphs. Monochromatic irradiation at the absorption tail preserved the crystal integrity, enabling a detailed investigation of the reaction outcomes. While both polymorphs undergo photoreaction, their transformations proceed via distinct crystal-to-crystal processes, yielding and dimers selectively. The photochemical pathway to the formation of the -isomers is analyzed by quantum mechanical calculations. These findings highlight the critical role of polymorphism in solid-state photochemistry while questioning the conventional dichotomy between defect-driven and purely topochemical mechanisms.
维生素K（VK3）多晶型物的固态[2 + 2]环加成反应已被系统地重新研究，通过关注单晶行为克服了基于粉末研究的局限性。结合太赫兹显微拉曼光谱和傅里叶变换红外衰减全反射（FTIR-ATR）振动光谱以及X射线衍射和固态密度泛函理论（DFT）计算，我们揭示了两种多晶型物中不同的光反应性和立体选择性。在吸收尾部的单色辐射保持了晶体完整性，从而能够对反应结果进行详细研究。虽然两种多晶型物都发生光反应，但其转变通过不同的晶体到晶体过程进行，选择性地产生 和 二聚体。通过量子力学计算分析了形成 -异构体的光化学途径。这些发现突出了多晶型在固态光化学中的关键作用，同时对缺陷驱动机制和纯拓扑化学机制之间的传统二分法提出了质疑。
