Thermochemical energy storage is considered as an auspicious method for the recycling of medium-temperature waste heat. The reaction couple Mg(OH)₂–MgO is intensely investigated for this purpose, suffering so far from limited cycle stability. To overcome this issue, Mg(OH)₂, MgCO₃, and MgC₂O₄·2H₂O were compared as precursor materials for MgO production. Depending on the precursor, the particle morphology of the resulting MgO changes, resulting in different hydration behavior and cycle stability. Agglomeration of the material during cyclization was identified as main reason for the decreased reactivity. Immersion of the spent material in liquid H₂O decomposes the agglomerates restoring the initial reactivity of the material, thus serving as a regeneration step.

A modified phase‐transfer‐catalyst‐assisted synthetic pathway was developed that widens the pool of accessible 1‐substituted tetrazoles, which are possible ligands for iron(II) spin‐crossover compounds. Within the family of α,ω‐bis(tetrazol‐1‐yl)alkanes, a series of ligands and their respective iron(II) spin‐crossover compounds were synthesized and structurally and spectroscopically characterized in the past. The classical route to prepare these ligands is based on the respective amino‐precursors. Hence the pool of accessible compounds is limited by the commercial or synthetical availability of α,ω‐diaminoalkanes. Furthermore, the concomitant transformation to the tetrazole moieties turns out to be easier for diamino‐alkanes with an even number of carbon atoms than for those with an odd number. In line with this observation, the shortest odd‐numbered homologues such as 1,1‐bis(tetrazol‐1‐yl)methane (1ditz) and 1,3‐bis(tetrazol‐1‐yl)propane (3ditz) were inaccessible so far. In this paper, we report the successful preparation and characterisation of the classically inaccessible 1,3‐bis(tetrazol‐1‐yl)propane (3ditz) and of its spin‐crossover complex [Fe(3ditz)₃](BF₄)₂, which features an abrupt and almost complete spin transition at T${1 \over 2}$ = 159 K. The single‐crystal X‐ray structure of the low‐spin and the high‐spin species is presented. The magnetic data are supported by variable‐temperature IR, UV/Vis/NIR, and ⁵⁷Fe Mössbauer spectra.