[reaction: see text] A highly efficient stereoselective synthesis of unusual alpha-silylamines via a direct silyl anion addition reaction is reported. This approach is convergent and avoids any problematic aza-Brook shifts of the anionic intermediates. The use of enantiopure tert-butanesulfinyl imines as the electrophiles affords exceedingly high levels of diastereocontrol for the newly formed stereogenic carbon.

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The influence of nanoparticle surface facets on electrochromic properties remains largely unexplored in nanostructured "smart" materials. Here, we explore how surface facets influence the coloration efficiency (CE) and long-term optical density (OD) stability of hexagonal WO 3 nanorod (h-WO 3 NR) thin films. We synthesized two h-WO 3 NR samples with distinct surface facet orientations and studied how the electrochemical, electrochromic, electrical, and surface chemistry properties change after long-term cycling. The sample with unique {120} facets exhibited reversible optical switching after 500 cycles and negligible variation in interfacial charge transfer resistance. The (120) surface features an open network of square window channels that may enable reversible ion transport and reduced ion trapping, enhancing the optical switching stability. However, the {120}-dominant sample exhibited lower CE than the {100}-dominant sample. The reduced optical density changes in the {120}-dominant sample could be due to a greater fraction of optically inactive trigonal cavity sites on the {001} end-caps. The results indicate surface facet and particle morphology engineering are viable strategies to enhance the CE and long-term stability/lifetime in electrochromic thin films for smart window applications.

Olivine Fe2GeS4 has been identified as a promising photovoltaic absorber material introduced as an alternate candidate to iron pyrite, FeS2. The compounds share similar benefits in terms of elemental abundance and relative nontoxicity, but Fe2GeS4 was predicted to have higher stability with respect to decomposition to alternate phases and, therefore, more optimal device performance. Our initial report of the nanoparticle (NP) synthesis for Fe2GeS4 was not well understood and required an inefficient 24 h growth to dissolve an iron sulfide impurity. Here, we report an amide-assisted Fe2GeS4 NP synthesis that directly forms the phase-pure product in minutes. This significant advance was achieved by the replacement of the poorly understood hexamethyldisilazane (HMDS) additive and TMS2S by the conjugate base, lithium bis­(trimethylsilyl)­amide (LiN­(SiMe3)2), and elemental S, respectively. We hypothesized that fragments of both TMS2S and HMDS had carried out the roles that Brønsted bases play in amide-assisted NP syntheses and were necessary for Ge incorporation. Convolution of this role with the supply of S in TMS2S caused the iron sulfide impurities. Separating these effects in the use of LiN­(SiMe3)2 and elemental S resulted in synthetic control over the ternary phase. Herein we explore the Fe–Ge–S reaction landscape and the role of the base. Its concentration was found to increase the reactivities of the Fe, Ge, and S precursors, and we discuss possible metal-amide intermediates. This affords tunability in two areas: favorability of NP nucleation versus growth and phase formation. The phase-purity of Fe2GeS4 depends on the molar ratios of the cations, base, and amine as well as the Fe:Ge:S molar ratios. The resultant Fe2GeS4 NPs exhibit an interesting star anise-like morphology with stacks of nanoplates that intersect along a 6-fold rotation axis. The optical properties of the Fe2GeS4 NPs are consistent with previously published measurements showing a measured band gap of 1.48 eV.

In many synthetic pyrite single crystals of high quality and purity we could detect Cr3 + and Ni2 + by EPR at 78 K as unwanted impurities. The assignment was possible by means of the isotopes Cr53 and Ni61, occurring in natural abundance. The paramagnetic centers exhibit unusual g-values. In case of Ni2 + a ligand hyperfine interaction could be observed beside the normal hyperfine interaction with the Ni61 nucleus. For some crystals the Cr 3 + signal intensity could be increased up to ten times by temperature increasement from 78 K to about 100 K. At 78 K the Cr3 + intensity was quenched by IR irradiation.