CuI–Br Oligomers and Polymers Involving Cu–S(cystamine) Bonds

The syntheses, crystal structures, and thermal properties of five cuprous bromides derived from cystamine, [NH3(CH2)2SS(CH2)2NH3]2+, here denoted by (SS), are reported. Whereas (SS)2Cu4Br8 (1) is a polar tetramer and (SS)2Cu2Br6 (2) consists of [(SS)Cu2Br6]2– dimers, α1-(SS)Cu2Br4 (3), (SS)Cu3Br5 (4), and α2-(SS)Cu2Br4 (5) are polymers; 3 and 5 are one-dimensional and 4 has a corrugated 2D network. All the compounds contain corner-shared tetrahedra with Cu–Br–Cu connections, and in some cases, edge-shared with double bromine bridges. The copper coordination is tetrahedral, either CuBr4 or CuBr3S, except in one case, in which trigonal geometry was encountered. Compounds 1, 2, and 4, which are synthesized at 50 °C, display Cu–S bonds with the cystamine through either one or both sulfur atoms. On the other hand, 3 and 5, which are synthesized at 80 °C, do not have any. There is a high tendency to form hydrogen bonds between the polar ammonium heads of the cystamine with the bromine atoms. The range of phases experienced in this system is related to the bifunctional nature of cystamine, which is characterized by its primary ammonium ends and its disulfide bridge, and to the subtle competition between Br– and S–S ligands towards the CuI ions, which appears to be controllable by temperature. The presence of both chiral M- and P-helicoidal conformers of cystamine in 1–5 results in racemic compounds adopting centrosymmetric structures for 1, 3, 4, and 5 but 2 adopts a noncentrosymmetric structure (P212121) resulting from the coordination of copper ions to one conformer; the other conformer is noncoordinated and acts as the counterion

Structural diversity and retro-crystal engineering analysis of iodometalate hybrids

With guidance from retro-crystal engineering, iodometalate structures based on MI6 octahedra of group 14 (M = Sn(II), Pb(II)) and group 15 (M = Sb(III) and Bi(III)) are analysed. The criterion of I/M ratio, with the function of indicating the degree of condensation of octahedra in inorganic networks and the average charge density at the organic–inorganic interface, is introduced to classify all of the iodometalate networks, resulting in an easy and clear way to identify isomers with different dimensionalities. Of all iodometalates, the 2D M(II)I4 anion derived from the perovskite network is special since it can be easily stabilized by a range of common organic cations. We provide here the up-to-date progress in this extensively studied field, focusing on crystal engineering of hybrids in the aim of getting materials with a reduced band gap. Relationships between the molecular layouts of cationic entities and the structures of several non-perovskite anionic networks, focusing on the organic–inorganic interface, are highlighted. Distinct dependences between different types of cations and different types of anions are revealed, although it is still unfeasible to apply them in the actual control, design, or prediction of specific hybrid structures

Example of Disulfide Conformational Change in the Solid State: Preparation, Optical Properties, and X-ray Studies of a Cystamine-Based Iodoplombate Hybrid

A novel cystamine-based hybrid, namely, α-[NH3(CH2)2SS(CH2)2NH3PbI6]·2H3O (1a), was prepared under solvothermal conditions. Interestingly, 1a, which is built up from isolated PbI6 octahedra, can be easily changed into its polymorph, namely, β-[NH3(CH2)2S–S(CH2)2NH3PbI6]·2H3O (1b) only by heating it up to 45 °C. According to the results of X-ray diffraction analyses, the polymorphic phenomenon of 1a and 1b results from a conformational change in the helical diprotonated cystamine cation in the solid state. Both 1a and 1b crystallized in the orthorhombic Pna21 space group. The reversibility of this transformation is proved by single-crystal X-ray diffraction and second harmonic generation measurements

A 3D metal halide framework in the organic–inorganic compound (H3N(CH2)2SS(CH2)2NH3)3Pb5I16

A novel organic–inorganic hybrid compound, namely (H3N(CH2)2SS(CH2)2NH3)3Pb5I16, was synthesized from the reaction of lead iodide, cystamine chloride, and concentrated hydriodic acid in ethanol under solvothermal condition. According to the results of X-ray single crystal structural analysis, its 3D inorganic framework was constructed from lead iodide octahedra in corner-, edge- or face-sharing mode, which can be considered as connected staircase-like sheets. Disordered cystamine molecules are located both in the cages defined between two consecutive steps of the staircase-like network and in the channels formed by 10 adjacent bridged PbI6 octahedra. The formation and high stability of such a unique 3D metal halide network can be partly attributed to the unusual weak interactions between disulfides and iodides (d(S⋯I) ≈ 3.55 Å) in the structure.Monoclinic, space group: C2/c, a = 35.396(2) Å, b = 8.984(1) Å, c = 22.623(2) Å, β = 120.66(2)°, V = 6188.1(9) Å3, Z = 4

A Switchable NLO Organic-Inorganic Compound Based on Conformationally Chiral Disulfide Molecules and Bi(III)I5 Iodobismuthate Networks

A novel organic-inorganic hybrid based on cystamine and BiI5chains is prepared. Due to the flexibility of the disulfide molecules in the structure, single crystals or crystalline thin films of this hybrid undergo a reversible acentric-to-centric structural transition at moderate conditions (T = 36.8 °C). This makes the title compound an excellent candidate for temperature controlled SHG or THG switches

Comparative Study of Various Algorithms for the Merging of Parton Showers and Matrix Elements in Hadronic Collisions

We compare different procedures for combining fixed-order tree-level matrix-element generators with parton showers. We use the case of W-production at the Tevatron and the LHC to compare different implementations of the so-called CKKW and MLM schemes using different matrix-element generators and different parton cascades. We find that although similar results are obtained in all cases, there are important differences

A Standard format for Les Houches event files

A standard file format is proposed to store process and event information, primarily output from parton-level event generators for further use by general-purpose ones. The information content is identical with what was already defined by the Les Houches Accord five years ago, but then in terms of Fortran commonblocks. This information is embedded in a minimal XML-style structure, for clarity and to simplify parsing