Formation of Tellurido Mercurates with Tunable Optical Band Gaps in Ionic Liquids at Room Temperature

Chalcogenido metalate compounds of heavy elements represent an important class of materials, as they offer the opportunity to develop future narrow-band gap semiconductors. Nonclassical syntheses in ionic liquids at moderate temperatures enable access to chalcogenido metalates with unprecedented structural motifs that are not accessible through traditional high-temperature routes. Inspired by the successful ionothermal transformations of Na2[HgTe2] and Na2[Hg3Te4] that recently afforded numerous compounds, we investigated the treatment of K2[Hg2Te3] (A) in various imidazolium-based ionic liquids (ILs) with different cations at room temperature, which yielded a series of compounds. (CmC1Im)6[Hg7Te10] (with m denoting the number of carbon atoms of the alkyl chains attached to the imidazolium ring in 1-position; C1 = Me attached in 3-position; m = 1, 1a; m = 2, 1b), (CmC1Im)4[Hg5Te7] (m = 3, 2a; m = 4, 2b), (C4ImC3ImC4)2[Hg5Te7] (3; C3 = n-Pr attached in 3-position), and (CBnC1Im)2[Hg2Te3] (4; Bn = benzyl) were obtained in (mostly) high crystalline yields and characterized by powder X-ray and single-crystal X-ray diffraction as well as ultraviolet−visible (UV−vis) spectroscopy. ... mehrIn addition, compound 1b, which was formed with the highest selectivity, was subjected to successful upscaling and processing tests, and its thermochromic behavior as well as its thermal properties were investigated by means of temperature-dependent UV−vis spectroscopy and TGA-DSC studies, respectively.