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Solid state reactions are notoriously slow, because the rate‐limiting step is diffusion of atoms or ions through reactant, intermediate, and product crystalline phases. This requires days or even weeks of high temperature treatment, consuming large amounts of energy. Metal oxides are particularly difficult to react, because they have high melting points. The study reports a high‐speed solid state fluorination of WO₃ with Teflon to the oxyfluorides WO₃₋ₓFx on a minute (<10 min) scale by spark plasma sintering, a technique that is used typically for a high‐speed consolidation of powders. Automated electron diffraction analysis reveals an orthorhombic ReO₃‐type structure of WO₃₋ₓFx with F atom disorder as demonstrated by ¹⁹F magic angle spinning nuclear magnetic resonance spectroscopy. The potential of this new approach is demonstrated by the following results. i) Mixed‐ valent tungsten oxide fluorides WO₃₋ₓFx with high F content (0 < x < 0.65) are obtained as metastable products in copious amounts within minutes. ii) The spark plasma sintering technique yields WO₃₋ₓFx nanoparticles with high photocatalytic activity, whereas the corresponding bulk phases obtained by conventional solid‐state (ampoule) reactions have no photocatalytic activity. iii) The catalytic activity is caused by the microstructure originating from the processing by spark plasma sintering.

Chemical composition is leading among the numerous factors that determine the spin transition properties of coordination compounds. Classic dicyanometallic bridges {M(CN)2}− are commonly used to build Hofmann-like spin-crossover frameworks, but some extended bridges are also synthetically available. In this paper, we describe a successful synthesis of two very similar spin-crossover frameworks that differ in the cyanometallic bridges involved, namely [Fe(etpz)2{Ag(CN)2}2] (1) and {Fe(etpz)2[Ag2(CN)3][Ag(CN)2]} (2) (where etpz = 2-ethylpyrazine). Magnetic and Mössbauer studies demonstrated the occurrence of abrupt one-step high-spin (HS) ↔ low-spin (LS) transitions for both complexes. The spin transition temperatures are T1/2 ↓ = 233 K and T1/2 ↑ = 243 K for 1 and T1/2 ↓ = 188 K and T1/2 ↑ = 191 K for 2 with thermal hysteresis loops of 10 K for 1 and 3 K for 2. The bridging mononuclear [Ag(CN)2]− units and FeII cations assemble to form infinite 2D layers in the structure of 1. Interestingly, compound 2 forms 2D layers of FeII cations bridged by both binuclear [Ag2(CN)3]− and mononuclear [Ag(CN)2]− units. The structures of 1 and 2 comprise different types of intermolecular interactions including Ag⋯Ag and Ag⋯Netpz, which induce the creation of supramolecular 3D frameworks. The synergy between metallophilic interactions and the spin transition is also confirmed by the variation of Ag⋯Ag distances during spin crossover. The characterization of such analogues allowed us to analyze in detail the effect of the cyanometallic bridge on the structure of new frameworks and on the bistability in Hofmann-like complexes.

A new guest-free Hofmann clathrate analogue Fe(2-ethoxypyrazine)2{Ag(CN)2}2 which undergoes a four-step spin crossover during the transition from the low-spin to the high-spin state is reported. At the first step 1/3 of centers become high spin, at the second step another 1/3 of centres become high spin, at the third step spin mixed crystallographic centres are observed, and after the fourth step all centers are high spin.

We report on a molecular cationic iron(II) complex with a 4-amino-1,2,4-triazole ligand and a tetraiodomercurate anion exhibiting an incomplete spin crossover (SCO). The complex exhibits an unusual disordered structure with a linear arrangement of ligand and water molecules that can potentially accommodate up to four iron atoms, but both terminal metal positions have half chemical occupancies, while occupancies of all ligands are full. This corresponds to the crystallisation of disordered trinuclear complexes arranged into 1D supramolecular chains. Iron cations have different N6 or N3O3 coordination environments, leading to the thermally induced SCO in two thirds of the metal centres. This SCO behaviour was characterised by magnetic susceptibility measurements and Mössbauer spectroscopy.

Calcium sulfate is an important construction material. More than 1600 million square meters of interior surfaces are covered with plasterboards in Europe each year. Plasterboard is manufactured by transforming mined or recycled gypsum (CaSO4 × 2 H2O) to bassanite (CaSO4 × ½H2O) in a time- and energy-consuming heating process. A fast and sustainable way to produce bassanite by solvent-assisted milling, thereby eliminating the need for energy-intensive dehydration, is described. The milling reaction is complete after ≈200 min. Kinetic studies revealed that gypsum crystals transform to bassanite by shear forces during milling. 1H nuclear magnetic resonance (NMR) spectroscopic techniques and Fourier-transform infrared spectroscopy (FT-IR) show that the resulting bassanite nanocrystals are stabilized by surface functionalization with the auxiliary solvent methanol. Bassanite particles produced over extended milling times of 990 min form long-term stable dispersions without stabilizers and no signs of precipitation. Addition of water to bassanite leads to instant agglomeration, followed by a phase change to gypsum. The dispersibility in volatile methanol and the elucidation of the crystallization mechanism allow also for applications of the bassanite nanocrystals in hybrid materials. © 2022 The Authors. Advanced Functional Materials published by Wiley-VCH GmbH.