Temperature‐induced change in reactivity of the frequently used ionic liquid 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([C4C1im]BF4) is presented as a prerequisite for the rational screening of reaction courses in material synthesis. [C4C1im]BF4 becomes active with oxidic precursor compounds in reduction reaction at ϑ≥200 °C, even without the addition of an external reducing agent. The reaction mechanism of forming red amorphous selenium from SeO2 is investigated as a model system and can be described similarly to the Riley oxidation. The reactive species but‐1‐ene, which is formed during the decomposition of [C4C1im]BF4, reacts with SeO2 and form but‐3‐en‐2‐one, water, and selenium. Elucidation of the mechanism was achieved by thermoanalytical investigations. The monotropic phase transition of selenium was analyzed by the differential scanning calorimetry. Beyond, the suitability of the single source oxide precursor Bi2Se3O9 for the synthesis of Bi2Se3 particles was confirmed. Identification, characterization of formed solids succeeded by using light microscopy, XRD, SEM, and EDX.
The Cover Feature shows the correlation between the stability and reactivity of ionic liquids (ILs). Undercutting the maximum operating temperature (MOT) the IL initially is protected. Reaching the MOT, reactive species can be formed by thermal decomposition and functionality of the IL changes. Thus IL, actually used as a solvent, can become reactants. A current case study shows, that, exceeding the calculated MOT, reactive decomposition products of [C4C1im]BF4 lead to the reduction of the oxide precursor SeO2 and the formation of red amorphous selenium. Analyzing the gaseous species formed during the reaction, the reaction mechanism can be deduced similar to Riley oxidation. Thereby, but‐1‐ene, reacts with SeO2 to Se, H2O, and but‐3‐en‐2‐one. Concluding, the suitability of the single‐source oxide precursor Bi2Se3O9 for the synthesis of Bi2Se3 is proven. More information can be found in the Full Paper by Monika Knorr et al.
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