Sulfides and selenides

In the present text, the metallic sulfides, many of which are quite familiar, are described in chapters devoted to the respective metals. It is emphasized, however, that only very slightly soluble sulfides can survive in the presence of water. The HS ion is such a weak acid (K = 10 15) 

In addition to the familiar simple sulfide complexes, AsS 3, SbSi 3, SnSf2, and HgS 2, a number of complexes are known having the sulfur atom of an organic molecule acting as a coordinating atom, or ligand. Typical sulfur-containing complexes of this type are shown  

Selenium analogs of the mercury and palladium complexes are known, but no simple selenide complexes seem to have been reported. 

Zinc and Cadmium Sulfides and Sulfoselenides. The raw materials for the production of these sulfide phosphors are high-purity zinc and cadmium sulfides, which are precipitated from purified salt solutions by hydrogen sulfide or ammonium sulfide [5.291], [5.296], [5.307], [5.310], The concentration of contaminants such as Fe, Co, or Ni must be below 1 % of the activator concentration. The Zn, Cd S can be produced by mixing precipitated zinc sulfide and cadmium sulfide. However, coprecipitation from mixed zinc-cadmium salt solutions is preferred because of the better homogeneity. 

The most important activators for sulfide phosphors are copper and silver, followed by manganese, gold, rare earths, and zinc. The charge compensation of the host lattice is effected by coupled substitution with mono- or trivalent ions (e.g., Cl or Al3+). In addition, disorders, such as unoccupied sulfur positions, can also contribute to charge compensation. 

For the synthesis of phosphors, the sulfides are homogenized with readily decomposed compounds of the activators and coactivators in the presence of a flux and are fired in quartz crucibles at 800-1200 °C. 

The luminescent properties can be influenced by the nature of the activators and coactivators, their concentrations, the composition of the flux, and the firing conditions. In addition, specific substitution of zinc or sulfur in the host lattice by cadmium or selenium is possible, which also influences the luminescent properties. Zinc sulfide is dimorphic and crystallizes below 1020 °C in the cubic zinc-blende structure and above that temperature in the hexagonal wurtzite lattice. When the zinc is replaced by cadmium, the transition temperature is lowered so that the hexagonal modification predominates. Substitution of sulfur by selenium, on the other hand, stabilizes the zinc-blende lattice. 

Self-Activation. Although pure substances do not normally luminesce, zinc sulfide that has been fired in the presence of a halogen luminesces bright blue [5.311], [5.312], The luminescence center is assumed to be a cation vacancy. The charge compensation occurs through exchange of S2- by Cl-. 

Little is known about the properties and potential applications of the open-framework chalcogenides, though Jiang et al. [102,103] have recently described the adsorption and spectroscopic properties of some of the layered tin sulfides belonging to this family of materials. 

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A solid-liquid phase-transfer technique is used to synthesize aryl difluoro-methyl sulfides and selenides thiophenols dissolved in an aromatic solvent are treated with solid sodium hydroxide in the presence of a catalytic amount of tris(3,6-dioxaheptyl)amine (TDA1) [49] This condensation proceeds by a carbene mechanism (equation 44)... 

Chalcogenides of Cd are similar to those of Zn and display the same duality in their structures. The sulfide and selenide are more stable in the hexagonal form whereas the telluride is more stable in the cubic form. CdS is the most important compound of cadmium and, by addition of CdSe, ZnS, HgS, etc., it yields thermally stable pigments of brilliant colours from pale yellow to deep red, while colloidal dispersions are used to colour transparent glasses. 

The Transition to the Sphalerite Structure.—The oxide, sulfide and selenide of beryllium have neither the sodium chloride nor the cesium chloride structure, but instead the sphalerite or the wurzite structure. The Coulomb energy for the sphalerite arrangement is... 

In lithium chloride, bromide and iodide, magnesium sulfide and selenide and strontium chloride the inter-atomic distances depend on the anion radius alone, for the anions are in mutual contact the observed anion-anion distances agree satisfactorily with the calculated radii. In lithium fluoride, sodium chloride, bromide and iodide and magnesium oxide the observed anion-cation distances are larger than those calculated because of double repulsion the anions are approaching mutual contact, and the repulsive forces between them as well as those between anion and cation are operative. 

When exposed to daylight, the sulfide and selenide halides HgsY2X2 are blackened within a few minutes. This black color reversibly disappears when the sample is heated to 90 to 120°C, or stored in the dark for several days 204, 375-377). The nature of this phototropic behavior has now been widely investigated by analytical, spectroscopic, structural, magnetic, EPR, and radiotracer investigations 205, 233, 375-377, 379, 380, 382). During irradiation of the compounds, electrons belonging to or I ions are excited to upper states. The result-... 

The phase transiton from a paraelectric to a ferroelectric state, most characteristic for the SbSI type compounds, has been extensively studied for SbSI, because of its importance with respect to the physical properties of this compound (e.g., J53, 173-177, 184, 257). The first-order transition is accompanied by a small shift of the atomic parameters and loss of the center of symmetry, and is most probably of a displacement nature. The true structure of Sb4S5Cl2 106), Bi4S5Cl2 194), and SbTel 108,403) is still unknown. In contrast to the sulfides and selenides of bismuth, BiTeBr 108) and BiTel (JOS, 390) exhibit a layer structure similar to that of the Cdl2 structure, if the difference between Te, Br, and I (see Fig. 36) is ignored. 

In each of the composition diagrams in Fig. 14.2, the numbers represent a series of reactions run at a defined composition and temperature. These are isometric sulfur slices through three-dimensional K/P/RE/S quaternary phase diagrams. As just one example of what we have studied. Table 14.1 identifies the compositions at each point and the resulting phase(s). We have rigorously studied how phase formation is dependent upon the compositions of reactions for the rare-earth elements Y, Eu, and La and we have also discovered key structural relationships between the rare-earth elements, indicating a significant dependence on rare-earth and alkali-metal size for sulfides and selenides. 

Davies DA, Vecht A, Silver J, Marsh PJ, Rose JA (2000) A novel method for the preparation of inorganic sulfides and selenides 1. Binary materials and Group 11-Vl phosphors. J Electrochem Soc 147 765-771... 

Within the scope of applications in electronics, electrooptics, and photovoltaics, several metal sulfides and selenides, mostly binaries such as CdS, CdSe, Bi2S3, Bi2Sc3, PbS, PbSe, Ag2S, TlSe, M0S2, ZnSe, ZnS, and SnS2, but also the ternaries... 

Important results and a detailed insight into aqueous chemical deposition processes have been reported and discussed elsewhere for CdSe [248, 249] and ZnS [250, 251] target products. We should note also the work of Davies et al. [252] who described an alternative method for the chemical growth of metal sulfides and selenides on the basis of polysulfide or polyselenide solutions (containing hexa- and tetra-chalcogen anions) formed by the dissolution of sulfur or selenium in hydrazine monohydrate. ... 

Loglio F, Innocent M, Pezzatini G, Foresti ML (2004) Ternary cadmium and zinc sulfides and selenides electrodeposition by ECALE and electrochemical characterization. J Electroanal Chem 562 117-125... 

The interaction of dihalogens, particularly diiodine, with sulfur and selenium electron donors has been an area of increasing interest over the past decade because of potential biological, pharmaceutical, and electronic materials applications [35,179]. Devillanova and coworkers have recently reviewed the solution behavior of a large number of chalcogenides and I2, particularly thiones, selones, sulfides, and selenides [180]. Correlations between computational methods, thermodynamic parameters, and spectroscopic data (UV/Vis, 13C NMR, Raman, UPS) were discussed. 

An oxygen bound to a trifluoromethyl group has much less effect upon its chemical shift than a chlorine substituent. Thus, the fluorines of trifluoromethyl ethers (—58 ppm) are not as deshielded as those of CF3C1 (—28ppm). Those of CF3 sulfides and selenides are deshielded... 

In the late nineteenth century and early twentieth century, Lenard et al. in Germany carried out systematic research on phosphors. They prepared phosphors based on alkaline earth sulfides and selenides, and also on ZnS, and studied their luminescence. In these studies, they laid down the fundamentals of phosphor research.6 Other significant contributions included those of H. W. Leverenz and colleagues at the Radio Corporation of America (RCA)1 laboratories who investigated many phosphors for use in television tubes which led to detailed work being carried out on ZnS-type phosphors.7... 

The organic substrates in Chart 8 can be divided into two main categories in which (i) the oxidation of olefins, sulfides, and selenides involves oxygen atom transfer to yield epoxides, sulfoxides, and selenoxides, respectively, whereas (ii) the oxidation of hydroquinones and quinone dioximes formally involves loss of two electrons and two protons to yield quinones and dinitrosobenzenes, respectively. In order to provide a unifying mechanistic theme for the seemingly disparate transformations in Chart 8, we note that nitrogen dioxide exists in equilibrium with its dimeric forms, namely, the predominant N—N bonded dimer 02N—N02 and the minor N—O bonded isomer ONO—N02 (equation 88). 

Unlike 1,3,5-dioxaphosphorinanes the relative population of the con-former with the axial phenyl group at phosphorus decreases in 1,3,5-diazaphosphorinanes both for P(III) and for P(IV) compounds. Conformational analysis of 5-phenyl-1,3,5-diazaphosphorinanes and their oxides, sulfides, and selenides showed that the conformational equilibrium shifted toward the conformer with the axial phenyl group on changing from P(III) to P(1V) derivatives. The same conclusion made for 5-phenyl-l, 3,5-dioxaphosphorinanes, but it is contrary to that made for 1-phenyl-phosphorinane-4-ones and their derivatives (83MI1). 

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