Solid-State Dilution of Dihydroxybenzophenones with 4,13-Diaza-18-crown-6 for Photocrystallographic Studies

This work forms part of the ongoing drive toward identifying and developing suitable light sensitive substances for photocrystallographic studies. In order to investigate the solid-state dilution of the photoactive dihydroxybenzophenone, X-ray crystal structures of three dihydroxybenzophenone·4,13-diaza-18-crown-6 co-crystals are reported and analyzed. The dihydroxybenzophenone molecules within the co-crystal are compared to those observed in homomolecular dihydroxybenzophenone crystals in terms of their intermolecular contacts, bond geometry and conformation. Molecular volumes and void spaces were calculated using Voronoi–Dirichlet polyhedra and Hirshfeld surface-based space partitioning, demonstrating new ways to represent potential reaction cavities around a photoactive molecule and calculate their packing efficiency. In each case the conditions of solid-state dilution were met. The molecular conformations of the homomolecular environments are retained to varying degrees in the analogous co-crystals. Results show that the co-crystals studied are potentially suitable for photocrystallography. In particular, 2,4-dihydroxybenzophenone molecules in 4,13-diaza-18-crown-6·2­(2,4-dihydroxybenzophenone) co-crystals exhibit high structural similarity to their homomolecular analogues suggesting its photochemical properties could be common to both environments.

本研究属于持续探索与开发适用于光晶体学（photocrystallographic）研究的光敏物质工作的一部分。为探究光活性二羟基二苯甲酮的固态稀释效应，本文报道并分析了三种二羟基二苯甲酮·4,13-二氮杂-18-冠-6共晶的X射线晶体结构。将共晶中的二羟基二苯甲酮分子与同分子二羟基二苯甲酮晶体中的分子，从分子间相互作用、键几何构型与构象等维度进行对比。研究采用沃罗诺伊-狄利克雷多面体（Voronoi–Dirichlet polyhedra）与基于赫希菲尔德表面（Hirshfeld surface）的空间划分方法，计算了分子体积与空隙空间，展示了表征光活性分子周围潜在反应空腔并计算其堆积效率的新途径。所有体系均满足固态稀释的条件。同分子环境中的分子构象在对应共晶中以不同程度得以保留。研究结果表明，本次研究的共晶均具备用于光晶体学研究的潜在适用性。其中，4,13-二氮杂-18-冠-6·2(2,4-二羟基二苯甲酮)共晶中的2,4-二羟基二苯甲酮分子，与其同分子对应物展现出高度的结构相似性，提示二者在两种环境下的光化学性质可能具有一致性。