Unraveling the Decomposition Process of Lead(II) Acetate: Anhydrous Polymorphs, Hydrates, and Byproducts and Room Temperature Phosphorescence

Lead­(II) acetate [Pb­(Ac)2, where Ac = acetate group (CH3–COO–)2] is a very common salt with many and varied uses throughout history. However, only lead­(II) acetate trihydrate [Pb­(Ac)2·3H2O] has been characterized to date. In this paper, two enantiotropic polymorphs of the anhydrous salt, a novel hydrate [lead­(II) acetate hemihydrate: Pb­(Ac)2·1/2H2O], and two decomposition products [corresponding to two different basic lead­(II) acetates: Pb4O­(Ac)6 and Pb2O­(Ac)2] are reported, with their structures being solved for the first time. The compounds present a variety of molecular arrangements, being 2D or 1D coordination polymers. A thorough thermal analysis, by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), was also carried out to study the behavior and thermal data of the salt and its decomposition process, in inert and oxygenated atmospheres, identifying the phases and byproducts that appear. The complex thermal behavior of lead­(II) acetate is now solved, finding the existence of another hydrate, two anhydrous enantiotropic polymorphs, and some byproducts. Moreover, some of them are phosphorescent at room temperature. The compounds were studied by TGA, DSC, X-ray diffraction, and UV–vis spectroscopy.乙酸铅(II) [Lead(II) acetate，其中Ac代表乙酸根基团(CH3–COO–)] 是一类历史悠久、用途广泛的常见盐类。然而迄今为止，仅三水合乙酸铅(II) [Pb(Ac)2·3H2O] 的结构得到了表征。 本文首次报道了无水乙酸铅(II)的两种互变多晶型物、一种新型水合物——半水合乙酸铅(II) [Pb(Ac)2·1/2H2O]，以及两种分解产物——两种不同的碱式乙酸铅(II)：Pb4O(Ac)6与Pb2O(Ac)2，并首次解析了它们的晶体结构。 上述化合物呈现多样化的分子排布形式，属于二维或一维配位聚合物（coordination polymers）。研究人员通过差示扫描量热法（differential scanning calorimetry, DSC）与热重分析法（thermogravimetric analysis, TGA）开展了全面的热分析研究，考察了该盐及其分解过程在惰性气氛与含氧气氛中的热行为与热学数据，鉴定了反应过程中生成的物相与副产物。 本研究首次阐明了乙酸铅(II)复杂的热行为，发现了另一种水合物、两种无水互变多晶型物及相关副产物。此外，其中部分化合物在室温下具有磷光特性。 本研究通过热重分析、差示扫描量热法、X射线衍射以及紫外-可见光谱法对上述化合物进行了系统表征。