SnIP is the first atomic-scale double helical semiconductor featuring a 1.86 eV bandgap, high structural and mechanical flexibility, and reasonable thermal stability up to 600 K. It is accessible on a gram scale and consists of a racemic mixture of right- and left-handed double helices composed by [SnI] and [P] helices. SnIP nanorods <20 nm in diameter can be accessed mechanically and chemically within minutes.

Stabilization of the central atom in an oxidation state of zero through coordination of neutral ligands is a common bonding motif in transition-metal chemistry. However, the stabilization of main-group elements in an oxidation state of zero by neutral ligands is rare. Herein, we report that the transamination reaction of the DAMPY ligand system (DAMPY=2,6-[ArNH-CH2 ]2 (NC5 H3 ) (Ar=C6 H3 -2,6-iPr2 )) with Sn[N(SiMe3 )2 ]2 produces the DIMPYSn complex (DIMPY=(2,6-[ArNCH]2 (NC5 H3 )) with the Sn atom in a formal oxidation state of zero. This is the first example of a tin compound stabilized in a formal oxidation state of zero by only one donor molecule. Furthermore, three related low-valent Sn(II) complexes, including a [DIMPYSn(II) Cl](+) [SnCl3 ](-) ion pair, a bisstannylene DAMPY{Sn(II) [N(SiMe3 )2 ]2 }2 , and the enamine complex MeDIMPYSn(II) , were isolated. Experimental results and the conclusions drawn are also supported by theoretical studies at the density functional level of theory and (119) Sn Mössbauer spectroscopy.

A new ternary compound, Li(1-x)Sn(2+x)As2, 0.2 < x < 0.4, was synthesized via solid-state reaction of elements. The compound crystallizes in a layered structure in the R3̅m space group (No. 166) with Sn-As layers separated by layers of jointly occupied Li/Sn atoms. The Sn-As layers are comprised of Sn3As3 puckered hexagons in a chair conformation that share all edges. Li/Sn atoms in the interlayer space are surrounded by a regular As6 octahedron. Thorough investigation by synchrotron X-ray and neutron powder diffraction indicate no long-range Li/Sn ordering. In contrast, the local Li/Sn ordering was revealed by synergistic investigations via solid-state (6,7)Li NMR spectroscopy, HRTEM, STEM, and neutron and X-ray pair distribution function analyses. Due to their different chemical natures, Li and Sn atoms tend to segregate into Li-rich and Sn-rich regions, creating substantial inhomogeneity on the nanoscale. The inhomogeneous local structure has a high impact on the physical properties of the synthesized compounds: the local Li/Sn ordering and multiple nanoscale interfaces result in unexpectedly low thermal conductivity and highly anisotropic resistivity in Li(1-x)Sn(2+x)As2.

The lithium-ion battery electrode material TiSnSb shows excellent electrochemical performance related to its high capacity (550 mA h g −1 ) and rate capability over 210 cycles. To discriminate between the role of active material and the role of the electrode formulation in the good electrochemical features of the TiSnSb electrodes, a full study comparing the electrochemical mechanisms of TiSnSb and a Ti/ Sn/Sb composite vs Li is undertaken by combining X-ray diffraction (XRD), 121 Sb, 119 Sn Mossbauer and 7 Li NMR spectroscopic in situ measurements. During the first discharge, TiSnSb undergoes a direct conversion reaction while Ti/Sn/Sb composites proceed by a stepwise alloying process, both leading to a mixture of lithium antimonide, lithium stannides, and titanium. More surprisingly the charge occurs differently with a reformation of the "TiSnSb" phase in the first case and the formation of Sn and Sb in the second case. The key role of the interfaces in conversion type reactions is discussed. The nature of the interfaces is linked to the long-range order of elements in the starting material. Furthermore, the length scales of the interfaces between Li 3 Sb, Li x Sn and Ti appear to control the reactions that occur on charge.

International audienceNew YbMo2Al4-type cadmium compounds CaAu4Cd2, SrAu4Cd2, and EuAu4Cd2 were synthesized from the elements in sealed tantalum tubes. The structures of CaAu4Cd2 (I4/mmm, a = 710.7(1), c = 550.2(3) pm, wR2 = 0.026, 168 F 2 values, 10 variables) and EuAu4.80Cd1.20 (a = 716.6(1), c = 545.9(1) pm, wR2 = 0.024, 167 F 2 values, 11 variables) were refined from X-ray single-crystal diffractometry data. The gold and cadmium atoms show different substructures: Au4 squares (279 pm Au-Au in CaAu4Cd2) and cadmium chains (275 pm Cd-Cd in CaAu4Cd2). EuAu4Cd2 forms a solid solution EuAu4+x Cd2−x up to x ≈ 1, where almost every other cadmium atom within the chains is substituted by gold. Chemical bonding analyses on CaAu4Cd2 shows almost complete charge transfer from calcium to the [Au4Cd2] network. Bader charge analysis classifies CaAu4Cd2 as an auride. EuAu4Cd2 shows Curie-Weiss behavior above 25 K with an experimental magnetic moment of 7.86 μB/Eu atom, near to the free ion value of 7.94 μB for Eu2+ and orders ferromagnetically at T C = 16.3(5) K. 151Eu Mössbauer spectra show a single signal at an isomer shift of about −10 mm/s, compatible with divalent europium. At 5 K, and therefore clearly below T C, magnetic hyperfine splitting is observed