Guanidinium and Mixed Cesium-Guanidinium Tin(II) Bromides: Effects of Quantum Confinement and Out-of-Plane Octahedral Tilting.

Hybrid organic-inorganic main-group metal halide compounds are the subject of intense research owing to their unique optoelectronic characteristics. In this work, we report the synthesis, structure, and electronic and optical properties of a family of hybrid tin (II) bromide compounds comprising guanidinium [G, C(NH) ] and mixed cesium-guanidinium cations: GSnBr, CsGSnBr, and CsGSnBr. GSnBr has a one-dimensional structure that consists of chains of corner-sharing [SnBr] square pyramids and G cations situated in between the chains.

Guanidinium-Formamidinium Lead Iodide: A Layered Perovskite-Related Compound with Red Luminescence at Room Temperature.

Two-dimensional hybrid organic-inorganic lead halides perovskite-type compounds have attracted immense scientific interest due to their remarkable optoelectronic properties and tailorable crystal structures. In this work, we present a new layered hybrid lead halide, namely [CH(NH)][C(NH)]PbI, wherein puckered lead-iodide layers are separated by two small and stable organic cations: formamidinium, CH(NH), and guanidinium, C(NH). This perovskite is thermally stable up to 255 °C, exhibits room-temperature photoluminescence in the red region with a quantum yield of 3.

Luminescent and Photoconductive Layered Lead Halide Perovskite Compounds Comprising Mixtures of Cesium and Guanidinium Cations.

Interest in hybrid organic-inorganic lead halide compounds with perovskite-like two-dimensional crystal structures is growing due to the unique electronic and optoelectronic properties of these compounds. Herein, we demonstrate the synthesis, thermal and optical properties, and calculations of the electronic band structures for one- and two-layer compounds comprising both cesium and guanidinium cations: Cs[C(NH)]PbI (I), Cs[C(NH)]PbBr (II), and Cs[C(NH)]PbBr (III). Compounds I and II exhibit intense photoluminescence at low temperatures, whereas compound III is emissive at room temperature.

YAlC: A Bonding Chameleon with Heteropolyacetylene Features.

YAlC was prepared by a flux method. It crystallizes as a partially filled-up TlI structure, showing remarkable structural aspects at the border between Zintl phases and intermetallics. This novel ternary aluminide-carbide exhibits a unique one-dimensional multi-center bond and a polyacetylene-related aluminum carbide substructure.

Crystal structure and electronic properties of Y3AlC3.

A novel ternary aluminum carbide, Y(3)AlC(3), has been synthesized under application of a lithium metal flux at high temperature (1523 K). Single-crystal structure determination of this compound revealed a new structure type with the Wyckoff sequence 2j3e and remarkable structural features at the border between Zintl and intermetallic phases. The puzzling bonding structure of Y(3)AlC(3) is analyzed with the aid of electronic structure calculations (energy bands and the electron localization function).