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

Abstract

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.

Polymeric Lead(II) Iodoacetate: Pb···I and I···I Non‐Covalent Interactions in the Solid State

“…All iodoacetate ligands are bridging, connecting either four (Pb–O = 2.562–2.711 Å) or two Pb atoms; in the latter case, one of the oxygen atoms remains terminal (Pb–O tetm = 2.370 Å, Pb–µ 2 ‐O = 2.715–2.732 Å), to produce 2D layers (Figure ). Similar connectivity patterns are found in other lead(II) monocarboxylates, although 1D chain polymers are more common . The I ··· I distances between the iodine atoms of the neighboring IOAc – units are slightly shorter (3.944 Å) than the sum of Bondi's van der Waals radii (3.96 Å), so it can be considered as a weak supramolecular contact (Figure ) of type I according to the classification proposed earlier,, since the C–I–I angles are 128.73 and 136.12,° which is very far from both 90 and 180° usual for XB.…”

Upgrading of methylammonium lead halide perovskite layers by thermal imprint

“…Accordingly, we chose a temperature window based on the properties of the precursor lead acetate-MABr is not critical ( Table 1). At the minimum temperature of 75 °C the Pb(AcO) 2 3H 2 O melts and dehydration is not yet complete [35]; at the highest temperature of 200 °C the Pb(AcO) 2 itself begins to decompose [34]. Furthermore, as our precursor contains water, a soft-bake temperature of 100 °C represents a threshold when preparing layers with or without water.…”

“…Important thermodynamic data (melting point, boiling point and vapour pressure) of all components of interest are summarized in Table 1 indicating, in addition, the physical phase at the temperatures and pressures characteristic of our investigation, at the soft-bake temperatures T SB (referring to preparation of the pristine layers) and the imprint temperature T i (referring to the upgrade), as well as under exposition to vacuum (VAC, referring to the status/consistence testing). Table 1 Thermodynamic properties of precursors, products, side-products and common solvents involved in the preparation of MAPbBr 3 from MABr and Pb(AcO) 2 as well as their physical phase at characteristic temperatures and pressures Nomenclature: T M = melting point, T B = boiling point, T SB1 and T SB2 = soft-bake temperatures, T i = imprint temperature, p v = vapor pressure, VAC = vacuum, Dec = decomposition, -= not applicable/no specification possible *Dehydration at already about 50 °C and a beginning decomposition at 200 °C are also reported [34,35] **Dehydration (abstraction of water) at 130 °C and decomposition at 145 °C are also reported [36] References: with the exception of the given references all values are taken from the CRC Handbook [37] Compounds Phase transitions Phase at Table 1 was used to design the experiments and to discuss the respective results. Table 1 is of central importance for our approach.…”

On metal and ‘spoiled’ wine: analysing psimythion (synthetic cerussite) pellets (5th–3rd centuries BCE) and hypothesising gas-metal reactions over a fermenting liquid within a Greek pot

“…Both systems had access to atmospheric CO 2 and O 2 , the main difference being that Katsaros et al heated their sample container (27–55 °C) by placing it outside ‘in the sun’, followed by washing and drying the sample outside in sunlight. Washing removes soluble acetates which do not convert on heating to carbonates (Martínez-Casado et al 2016 ) but whether heating/sunlight converts plumbonacrite to cerussite is unknown. Finally, Gonzáles et al ( 2019b )) addressed the question of hydrocerussite stability in air and reported no evidence at all of cerrusite formation after hydrocerrusite was exposed to laboratory air for 26 months; it is therefore unlikely that the cerussite analysed here was formed during burial.…”