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A uranium(iii) silylate complex [K(DME)₄]-[UI₂{(Si(SiMe₃)₂SiMe₂)₂O}] (1) was stabilized by the addition of 18-crown-6 to form [K(18-crown-6)][UI₂{(Si(SiMe₃)₂SiMe₂)₂O}]. This species was fully characterized using multinuclear NMR spectroscopy, electronic absorption spectroscopy and X-ray crystallography. 

Recently, chalcogenide perovskites, of the form ABX3, where typically A = alkaline earth metals Ca, Sr, or Ba; B = group IV transition metals Zr or Hf; and X = chalcogens S or Se, have become of interest for their potential optoelectronic properties. In this work, we build upon recent studies and show a general synthesis protocol, involving the use of carbon disulfide insertion chemistry, to generate highly reactive precursors that can be used towards the colloidal synthesis of numerous ABS3 nanomaterials, including BaTiS3, BaZrS3, BaHfS3, α-SrZrS3 and α-SrHfS3. We overcome the shortcomings in the current literature where BaZrS3 nanoparticles are synthesized in separate phases via colloidal methods and lack a reproducible protocol for orthorhombic perovskite nanoparticles. We present a high-temperature, hot-injection method that reliably controls the formation of the colloidal BaZrS3 nanoparticles with the Pnma orthorhombic distorted perovskite structure. We show that the alternate phase, most notably denoted by its extra peaks in the pXRD pattern, is distinct from the distorted perovskite phase as it has a different bandgap value obtained via UV-vis measurements. We also show that the reaction byproducts, resulting from the use of oleylamine and CS2, have their own photoluminescence (PL), and their residual presence on the surface of the nanoparticles complicates the interpretation of PL from the nanoparticles. The utility of these nanomaterials is also assessed via the measurement of their absorption properties and in the form of highly stable colloidal inks for the fabrication of homogeneous, crack-free thin films of BaZrS3 nanoparticles. 

Synthesis of homoleptic zirconium and hafnium dithiocarbamate via carbon disulfide insertion into zirconium and hafnium amides were investigated for their utility as soluble molecular precursors for chalcogenide perovskites and binary metal sulfides. Treating M(NEtR)4 (M= Zr, Hf and R= Me, Et) with CS2 resulted in quantitative yields of homoleptic Group IV dithiocarbamates. Zr(2-S2CNMeEt) (1), Zr(2-S2CNEt2)4 (2), and Hf(2-S2CNEt2)4 (4), a rare example of a crystal of a homoleptic hafnium CS2 inserted amide species, were characterized. A computational analysis confirmed assignments for IR spectroscopy. To exemplify the utility of the Group IV dithiocarbamates, a solution-phase nanoparticle synthesis was performed to obtain ZrS3 via the thermal decomposition of Zr(S2CNMeEt)4. 

Chalcogenide perovskites have recently attracted significant attention for renewable energy applications due to their predicted combination of air, moisture, and thermal stability, which has been experimentally validated, along with their excellent optoelectronic properties, which are still under experimental investigation. While historically requiring high synthesis temperatures, some solution-processed routes have recently emerged for synthesizing chalcogenide perovskites, such as BaZrS3 and BaHfS3, at temperatures below 600 °C. This study discusses several experimental challenges associated with the moderate-temperature synthesis of solution-deposited chalcogenide perovskites. Firstly, we identify Ruddlesden–Popper (RP) phases as thermodynamically stable competing secondary phases in perovskite synthesis. High sulfur pressures favor the formation of BaZrS3 or BaHfS3, whereas lower sulfur pressures result in a mixture of perovskite and RP phases. Additionally, we briefly discuss the mechanism of moderate-temperature synthesis of chalcogenide perovskites, including some of the morphological and optoelectronic challenges it presents, such as grain overgrowth, secondary phase contamination entrapment, and the presence of mid-band gap emissions. Finally, we address the importance of substrate selection and the potential presence of Ca- and Na-based impurities originating from cation out-diffusion from glass substrates. Addressing these challenges will be crucial as these unique materials continue to be investigated for applications in optoelectronic devices.