Red and Blue-Black Tin Monoxide, SnO: Pitfalls, Challenges, and Helpful Tools in Crystal Structure Determination of Low-Intensity Datasets from Microcrystals

Abstract

The crystal structures of red and blue-black tin(II) oxide, SnO, have been determined for the first time by single-crystal X-ray diffraction. Blue-black SnO crystallizes in the tetragonal space group P4/nmm, representing a layer structure consisting of the square–pyramidally coordinated tin and slightly distorted tetrahedrally coordinated oxygen atoms, in accordance with previous results. In contrast, red SnO crystallizes in the orthorhombic centrosymmetric space group Pbca rather than in the non-centrosymmetric space group Cmc21, as assumed for a long time. Its layer structure consists of very regular, trigonal–pyramidally coordinated tin atoms as well as trigonal–planar coordinated oxygen atoms. Special care was taken on space group determination, including lattice centering. C-centering could be excluded because of systematic absence violations detected when collecting and processing a primitive triclinic dataset and by generating precession images. In the absence of meaningful extinction conditions resulting from the very small crystal under examination, the structure was initially solved and refined in the triclinic space group P1. Subsequently, the observed atom coordinates were used to reconstruct the actual symmetry skeleton. The various possibilities to identify the correct space group starting from the triclinic solution are demonstrated, and the unique structural features of the crystal structure are visualized.

One Precursor, Two Different Outcomes: SnO-Graphite Composite and Anion-Doped SnO2 with Ester Surface Functionality

“…Chemical of 62.11 and 63.09 ppm confirm the presence of C−O. 50,52 Combining FTIR and 13 C NMR spectral results, we confirmed the surface functionalization of SnO 2 nanocrystallites with ester functionality. Yellow SnO 2 's UV−vis diffuse reflectance spectrum is shown in Figure 5b, from which an optical bandgap value of 2.9 eV is estimated.…”

“…In the FTIR spectrum, bands at 529 and 647 cm 4f). 50,51 To determine the nature of surface functionality, a yellow SnO 2 's solid-state 13 C NMR spectrum was recorded. Two signals at δ (ppm) 176.95 and 171.57 corresponding to ester and carboxylic acid functional groups, respectively, are located in the 13 C NMR spectrum (Figure 5a).…”

“…50,51 To determine the nature of surface functionality, a yellow SnO 2 's solid-state 13 C NMR spectrum was recorded. Two signals at δ (ppm) 176.95 and 171.57 corresponding to ester and carboxylic acid functional groups, respectively, are located in the 13 C NMR spectrum (Figure 5a). 52 Additional signals in the 50−60 ppm range denote different types of aliphatic C atoms in the organic moiety.…”

“…It has structural similarities with litharge mineral (α-PbO). − Each Sn atom is surrounded by four oxygen atoms, forming a square pyramid base with the lone pair of Sn atoms occupying the top vertex. Four Sn atoms tetrahedrally surround each oxygen atom, and the asymmetric environment created by lone pairs results in the layered structure. − Few reports have dealt with the red modification of SnO crystallizing in a novel structural arrangement and found it to be an insulator. − Among many application aspects of tetragonal SnO, its use as an anode material in lithium-ion batteries stands out as it has a higher reversible theoretical capacity (876 mAhg –1 ) than that of graphite (372 mAhg –1 ) . Sn as a dopant and surface coating in lithium-rich manganese oxide-based cathode materials is highly beneficial for structural stabilization, cyclic stability, and decreased voltage fade. − Susceptibility of Sn 2+ to disproportionation or oxidation to Sn 4+ poses a greater challenge to adopting a synthetic solution route to make SnO.…”