MS4 Tetrahedra Research Articles

Rare-Earth/d10 Dual-Metal Oxychalcogenides as Infrared Nonlinear-Optical Materials.

Oxychalcogenides are receiving increasing interest as nonlinear-optical (NLO) materials because of the possible combination of advantages from oxides and chalcogenides. Here, two new pentanary oxythiogermanates Eu2MGe2OS6 [M = Zn (1), Cd (2)] were obtained by the facile metal oxide-boron-sulfur solid-state route. They crystallize with a melilite-type structure and feature {[MGe2OS6]4-}∞ layers built by Ge2OS6 dimers and MS4 tetrahedra. Their optical band gaps are 2.37 and 2.38 eV. As the first NLO rare-earth (RE)/d10 dual-metal oxychalcogenides, they exhibit phase-matchable NLO responses and enhanced laser-induced damage thresholds. Theoretical calculations show that the NLO responses are predominantly contributed by the EuOS7 motifs. This work provides the potential of RE/d10 dual-metal-based NLO materials.

Solvothermal Syntheses and Characterizations of Four Quaternary Copper Sulfides BaCu3MS4 (M = In, Ga) and BaCu2MS4 (M = Sn, Ge).

Hydro(solvo)thermal syntheses of quaternary copper sulfides containing alkaline earth metal ions remain a great challenge because of the low solubility of Cu-S compounds. Herein, a new facile solvothermal method was developed, and four quaternary copper sulfides, i.e., BaCu3InS4 (1), BaCu3GaS4 (2), BaCu2SnS4 (3), and BaCu2GeS4 (4), were prepared using excess sulfur as a mineralizer. Compound 1 possesses a novel three-dimensional (3D) anionic [Cu3InS4]2- framework constructed by an 8-membered ring of [Cu4S4] and [Cu2In2S4] alternatively. Compound 2 features a unique 3D anionic [Cu3GaS4]2- framework composed of [Cu3GaS10]n14n- anionic chains and 8-membered rings, in which [Cu4S4] and [Cu2Ga2S4] reside alternatively. Compounds 3 and 4 feature 3D anionic [Cu2MS4]2- (M = Sn, Ge) frameworks composed of CuS4 and MS4 tetrahedra with Ba2+ located in the channels. It is worth noting that different 3D Cu-S frameworks exist in the title crystal structures, in which main group ions are incorporated. This paper provides a new synthetic strategy for new quaternary sulfides.

Ge2 S5 (S2 )]4- , A NLO-Active Unit Leading to an Asymmetric Structure Discovered in Li2 Cs4 Ge2 S5 (S2 )Cl2 : An Experimental and Theoretical study.

Metal-centered MS4 tetrahedra are fundamentally important building blocks for the structural construction of infrared (IR) nonlinear optical (NLO) mateirals, because they have a large effect on properties like second-harmonic generation, birefringence, band gap, etc. Therefore, rational design and selection of these tetrahedra could effectively help synthesize new materials and give satisfactory properties. In this work, we reported a new NLO-active [Ge2 S5 (S2 )]4- unit composed of two corner-shared GeS4 tetrahedra with a nonpolar covalent S-S bond, discovered in a new compound of Li2 Cs4 Ge2 S5 (S2 )Cl2 . To the best of our knowledge, this [Ge2 S5 (S2 )]4- unit has never been discovered. [Ge2 S5 (S2 )]4- units have intrinsic asymmetric features and lead to the whole structure being noncentrosymmetric (NCS). Further, real-space atom-cutting methods reveal that they make almost all the contribution to the second-harmonic generation response (SHG) for Li2 Cs4 Ge2 S5 (S2 )Cl2 . All of the above indicate that the [Ge2 S5 (S2 )]4- unit is a new functional unit and a good choice for designing new IR NLO materials.

Minerals and synthetic Pb(II) compounds with oxocentered tetrahedra: review and classification

The crystal structures of minerals and inorganic compounds with OPb4 oxocentered tetrahedra are reviewed. It is shown that the OPb4 tetrahedral units may link by sharing common Pb atoms to form structural units of various shape and dimensionality. These units determine basic topology of the structures and influence their stability and properties. The high strength of the OPb4 te trahedral units involves interplay between high basicity of additional O2– anions and stereochemical activity of the 6s 2 lone electron pairs on Pb2+ cations. The structural chemistry of polycations based upon OPb4 tetrahedra, in general, follows major trends previously observed for cation-centered tetrahedral units (silicates, phosphates, metal sulphides with MS4 tetrahedra, etc.). One may conclude that the basic structural correlations depend upon size and charge parameters of the ions only, irrespective of their positive or negative sign.