Mineralisator-Konzept für Polyphosphide: Cu2P20und Cu5InP16

Crystal Structure and Properties of Layered Pnictides BaCuSi2Pn3 (Pn = P, As)

Two novel layered compounds BaCuSi₂Pn₃ (Pn = P, As) adopting new structure types are reported. As revealed by single-crystal X-ray diffraction, both compounds are composed of unique Cu-Si-Pn layers featuring CuPn₃ and Si₂Pn₆ structural motifs found in other archetypal pnictide materials. The stacking of the isostructural Cu-Si-Pn layers is different for phosphide and arsenide compounds. Synthesis from elements aided by in situ synchrotron powder X-ray diffraction resulted in the obtainment of bulk powders with a minimized amount of admixtures. Experimentally measured physical properties of BaCuSi₂As₃ unexpectedly showed metal-like behavior at temperatures above 15 K, despite the fact that density functional theory calculations predict a small band gap of 0.4 eV. BaCuSi₂As₃ exhibits ultralow thermal conductivity, which can be explained by the combination of a layered crystal structure with alternating covalent and ionic bonding, which feature rattling of Cu atoms similar to that in tetrahedrites.

Mechanistic exploration of the copper(i) phosphide synthesis in phosphonium-based and phosphorus-free ionic liquids

The mechanism of the synthesis of copper(i) phosphide (Cu_3-xP) in the ionic liquid (IL) trihexyl(tetradecyl)phosphonium chloride ([P₆₆₆₁₄][Cl]) was investigated. The phosphide formation is promoted by a transformation of red phosphorus (P_red) into mobile P₄ molecules and a surface activation of copper caused by the IL including the Brønsted acidic impurity. The surface activation is important to obtain a quantitative product yield. Moreover, we demonstrate that single-phase Cu_3-xP can also be synthesized in the nitrogen-based IL tetrabutylammonium chloride ([N₄₄₄₄][Cl]). Further substitution of the anion of the IL using tetrabutylammonium bromide ([N₄₄₄₄][Br]) or the complete replacement of the IL by a deep eutectic solvent consisting of adipic acid and betaine do not lead to single-phase Cu_3-xP. Therefore, the nature of the anions present in the IL also seems to be relevant for the convenient phosphidization reaction.

An Elemental Phosphorus Photocatalyst with a Record High Hydrogen Evolution Efficiency

Semiconductive property of elementary substance is an interesting and attractive phenomenon. We obtain a breakthrough that fibrous phase red phosphorus, a recent discovered modification of red phosphorus by Ruck et al., can work as a semiconductor photocatalyst for visible-light-driven hydrogen (H2 ) evolution. Small sized fibrous phosphorus is obtained by 1) loading it on photoinactive SiO2 fibers or by 2) smashing it ultrasonically. They display the steady hydrogen evolution rates of 633 μmol h(-1)  g(-1) and 684 μmol h(-1)  g(-1) , respectively. These values are much higher than previous amorphous P (0.6 μmol h(-1)  g(-1) ) and Hittorf P (1.6 μmol h(-1)  g(-1) ). Moreover, they are the highest records in the family of elemental photocatalysts to date. This discovery is helpful for further understanding the semiconductive property of elementary substance. It is also favorable for the development of elemental photocatalysts.

mP-BaP₃: a new phase from an old binary system

A polyphosphide, mP-BaP3, with a unique two-dimensional phosphorus layer has been discovered and characterized. It crystallizes in the monoclinic space group P2₁/c with unit-cell parameters a=6.486(1), b=7.710(1), c=8.172(2) Å; β=104.72(3)°; Z=4. Its phosphorus polyanion can be derived from the strong elongation of 2/3 of the P-P bonds present in the layers of black phosphorus. The unit-cell volume of the mP-BaP3 phase is 1.4% larger than the volume of another polymorph, mS-BaP3, reported more than 40 years ago. The latter phase features the presence of one-dimensional phosphorus chains separated by Ba atoms. The differences in the structures of the phosphorus fragments in both polymorphs of barium triphosphide result in large differences in both the thermal stability of these materials as well as in their properties as evidenced by DSC, (31)P solid-state MAS NMR, UV/Vis, and surface photovoltage spectroscopies, alongside quantum-chemical calculations.

Temperature initiated P-polymerization in solid [Cd3Cu]CuP10

[Cd3Cu]CuP10, a polyphosphide containing adamantine-analogue [P10] unit undergoes a solid-state polymerization to form [P6] rings and tubular [P26] polymer units at elevated temperatures. This reaction represents the rare case of a polyphosphide polymerization in the solid state. The formation of such a polymeric unit starting from a molecular precursor is the first evidence of the general possibility to perform a bottom-up route to the well-known tubular polyphosphide units of elemental phosphorus in a solid material. Temperature-dependent X-ray powder diffraction experiments substantiate the solid phase transformation of [Cd3Cu]CuP10 starting at 550 °C to the polymerized form via an additional intermediate step. A single crystal structure determination of the quenched product at room temperature was performed to evaluate the structural properties and the resulting polyphosphide units. The full polymerization and decomposition mechanism has been analyzed by thermogravimetric experiments and subsequent X-ray powder phase analyses. The present [P26] polymer unit represents a former unseen one-dimensional cut-out of the two-dimensional polyphosphide substructure of Ag3P11 and can be directly related to the tubular polyphosphide substructures of violet or fibrous phosphorus.