Tl2CuAsO4 – ein Zwischenprodukt bei der Oxidation von Tl/Cu/As-Legierungen im Sauerstoffstrom

Tl₂CuAsO₄ – an Intermediate Phase in the Oxidation of Tl/Cu/As Alloys with Oxygen Waxy, honey-jellow single crystals of the new compound Tl₂CuAsO₄ (monoclinic, P2₁/c, a = 860.1(1) pm, b = 533.94(7) pm, c = 1200.1(2) pm, β = 98.10(1)°, Z = 4) were prepared as an intermediate product of the oxidation process in the reaction of Tl/Cu/As-alloys with oxygen. Their structure was determined from IPDS data (w2R = 0.071 for 1271 F² values and 74 parameters). The structure contains an isolated [Cu₂As₂O₈]^4– group consisting of two AsO₄-tetrahedra connected by two Cu⁺ ions with an approximately linear O–Cu–O coordination. The [Cu₂As₂O₈]^4– groups are linked to a threedimensional framework by thallium(I) ions which show an hemispheric coordination sphere of oxygen ions indicating the stereochemical activity of the Tl⁺ lone pair.     

Zn11Rh18B8 and Zn10MRh18B8 with M = Sc,Ti, V,Cr, Mn,Fe, Co,Ni, Cu,Al, Si,Ge, Sn – New Ternary and Quaternary Zinc Rhodium Borides

Zn₁₁Rh₁₈B₈ and Zn₁₀MRh₁₈B₈ with M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Al, Si, Ge and Sn are obtained by reaction of the elemental components in sealed tantalum tubes at 1500 K. They crystallize tetragonally with Z = 2 in the spacegroup P4/mbm with lattice constants a = 1771.2(2) pm, c = 286.40(4) pm for Zn₁₁Rh₁₈B₈ and in the range a = 1767.65(9) pm, c = 285.96(3) pm (Zn₁₀NiRh₁₈B₈) to a = 1774.04(9) pm, c = 286.79(2) pm (Zn₁₀SnRh₁₈B₈) for the quaternary compounds. According to powder photographs all compounds are isotypic. Struture determinations based on single crystal X-ray data were performed with Zn₁₁Rh₁₈B₈, Zn₁₀FeRh₁₈B₈ and Zn₁₀NiRh₁₈B₈. The structure of Zn₁₁Rh₁₈B₈ is related to the Ti₃Co₅B₂ type. Along the short axis planar nets of rhodium atoms composed of triangles, squares, pentagons and elongated hexagons alternate with layers containing the boron and zinc atoms. The rhodium atoms form trigonal prisms centered by boron atoms, two kinds of tetragonal and pentagonal prisms centered by zinc atoms and elongated hexagonal prisms containing pairs of zinc atoms. In the quaternary compounds Zn₁₀MRh₁₈B₈ the zinc atoms in one sort of tetragonal prisms are replaced by M atoms.     

Modelling of θ-conditions for bisphenol—A polycarbonate single chains

Assessing conformational dimensions of macromolecules is a topic of long-standing interest. Because of its simplicity, it is attractive to investigate the chain properties in θ-conditions. Under these special conditions, the effects of excluded volume of the segments of the polymer chain vanish. The molecular chain is only subject to local constraints resulting from the bond structure and the hindrance to rotations about bonds. To model θ-conditions a contour length dependent cutoff is introduced ensuring that only nonbonded interactions of atoms of neighbouring monomeric units are taken into account for energy calculations. Using this energy model we will show that it is possible to model θ-conditions of a single bisphenol-A polycarbonate (BPA-PC) chain in vacuum by two different methods: (i) (Pseudo-) Langevin dynamics simulations and (ii) regular reassignment of randomly generated atom velocities during a molecular dynamics simulation. Both methods can be used to avoid oscillative dynamic behaviour of the chain. Calculations of the end-to-end vector and the radius of gyration of the equilibrium ensembles derived from simulations at different temperatures show good agreement with experimental data. Thus our model techniques are well suited to simulate θ-conditions with small computational expense.     

Impact of symmetry-breaking of non-fullerene acceptors for efficient and stable organic solar cells

The concurrent enhancement of short-circuit current (J_SC) and open-circuit voltage (V_OC) is a key problem in the preparation of efficient organic solar cells (OSCs). In this paper, we report efficient and stable OSCs based on an asymmetric non-fullerene acceptor (NFA) IPC-BEH-IC2F. The NFA consists of a weak electron-donor core dithienothiophen[3,2-b]-pyrrolobenzothiadiazole (BEH) and two kinds of strong electron-acceptor (A) units [9H-indeno[1,2-b]pyrazine-2,3-dicarbonitrile (IPC) with a tricyclic fused system and 2-(5,6-difluoro-3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (IC2F)]. For comparison, the symmetric NFAs IPC-BEH-IPC and IC2F-BEH-IC2F were characterised. The kind of flanking A unit significantly affects the light absorption features and electronic structures of the NFAs. The asymmetric IPC-BEH-IC2F has the highest extinction coefficient among the three NFAs owing to its strong dipole moment and highly crystalline feature. Its highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels lie between those of the IPC-BEH-IPC and IC2F-BEH-IC2F molecules. The IPC group also promotes molecular packing through the tricyclic π-conjugated system and achieves increased crystallinity compared to that of the IC2F group. Inverted-type photovoltaic devices based on p-type polymer:NFA blends with PBDB-T and PM6 polymers as p-type polymers were fabricated. Among all these devices, the PBDB-T:IPC-BEH-IC2F blend device displayed the best photovoltaic properties because the IPC unit provides balanced electronic and morphological characteristics. More importantly, the PBDB-T:IPC-BEH-IC2F-based device exhibited the best long-term stability owing to the strongly interacting IPC moiety and the densely packed PBDB-T:IPC-BEH-IC2F film. These results demonstrate that asymmetric structural modifications of NFAs are an effective way for simultaneously improving the photovoltaic performance and stability of OSCs.

A 9H-indeno[1,2-b]pyrazine-2,3-dicarbonitrile (IPC) moiety in asymmetric non-fullerene acceptors promotes the formation of a densely packed crystalline structure, enabling efficient and long-term stable organic solar cells.