Department of Organic Chemistry, Bioorganic Chemistry and Biotechnology, Faculty of Chemistry, Silesian University of Technology, B. Krzywoustego 4, 44-100 Gliwice, Poland.
Department of Physics of Crystals, Institute of Physics, University of Silesia, 75 Pułku Piechoty 1, 41-500 Chorzów, Poland.
Molecules. 2020 Mar 10;25(5):1257. doi: 10.3390/molecules25051257.
Salens, as chelating, double Schiff base ligands, are an important group utilized in transition metal catalysis. They have been used to build interesting functional metal-organic frameworks (MOFs). However, salens interacting with amino acids have also found applications in receptors. Here, we intended to form a "green" glycine-derived salen fragment, but the available literature data were contradictory. Therefore, we optimized the synthetic conditions and obtained the desired product as two different crystallographic polymorphs (orthorhombic Pcca and monoclinic P/c space groups). Their structures differ in conformation at the glycine moiety, and the monoclinic form contains additional, disordered water molecules. Despite the high stability of Schiff bases, these newly obtained compounds hydrolyze in aqueous media, the process being accelerated by metal cations. These studies, accompanied by mechanistic considerations and solid-state moisture and thermal analysis, clarify the structure and behavior of this amino acid Schiff base and shed new light on the role of water in its stability.
萨伦作为螯合双席夫碱配体，是过渡金属催化中应用广泛的重要配体之一。它们已被用于构建有趣的功能金属有机框架（MOFs）。然而，与氨基酸相互作用的萨伦也在受体中找到了应用。在这里，我们打算形成一个“绿色”的甘氨酸衍生的萨伦片段，但现有文献数据存在矛盾。因此，我们优化了合成条件，得到了所需产物的两种不同晶体多晶型物（正交 Pcca 和单斜 P/c 空间群）。它们的结构在甘氨酸部分的构象上有所不同，而单斜形式含有额外的无序水分子。尽管席夫碱具有很高的稳定性，但这些新获得的化合物在水介质中会水解，金属阳离子会加速这一过程。这些研究，伴随着对机制的考虑以及固态水分和热分析，阐明了这种氨基酸席夫碱的结构和行为，并揭示了水在其稳定性中的作用。
