No abstract

A new antimonide K8–x Zn18+3x Sb16 was synthesized using reactive potassium hydride KH as a precursor. Owing to intimate mixing of starting materials, the hydride route allows rapid phase “screening” of ternary systems and is particularly suitable for the search of new antimonides. The crystal structure of K8–x Zn18+3x Sb16 (x = 1.12(8); P42/nmc (no. 137), a = 12.3042(5) Å, c = 7.3031(3) Å, V = 1105.6(1) Å3, R 1 = 0.029) has a [Zn18Sb16] framework with large channels alternately filled by K cations and Zn3 triangular units. The Zn3 triangles break the channels into finite cages by forming covalent bonds to the framework, preventing K migration along the channel. This structural feature is responsible for its stability in air, uncommon for this class of compounds, as well as for its low thermal conductivity. Transport property measurement and computational analysis of the electronic structure indicate that the title compound is a semimetal with properties highly dependent on the precise composition, i.e., the K/Zn3 ratio in the channels. The hydride preparative route provides accurate control over the composition of the target phase, thereby facilitating transport properties tuning. This synthetic method will allow for the synthesis of novel alkali metal antimonides as well as for the development of functional materials via precise compositional control.

Herein, we describe the synthesis of a toroidal Au 10 cluster stabilized by N -heterocyclic carbene and halide ligands via reduction of the corresponding NHC–Au–X complexes (X = Cl, Br, I). The significant effect of the halide ligands on the formation, stability, and further conversions of these clusters is presented. While solutions of the chloride derivatives of Au 10 show no change even upon heating, the bromide derivative readily undergoes conversion to form a biicosahedral Au 25 cluster at room temperature. For the iodide derivative, the formation of a significant amount of Au 25 was observed even upon the reduction of NHC–Au–I. The isolated bromide derivative of the Au 25 cluster displays a relatively high ( ca . 15%) photoluminescence quantum yield, attributed to the high rigidity of the cluster, which is enforced by multiple CH−π interactions within the molecular structure. Density functional theory computations are used to characterize the electronic structure and optical absorption of the Au 10 cluster. 13 C-Labeling is employed to assist with characterization of the products and to observe their conversions by NMR spectroscopy.