The mechanism and the effect of Lewis bases in gold-catalyzed CO2 hydrogenation to formic acid were investigated using first principle calculations. The calculations indicate that different types of gold surfaces are all capable of heterolytically splitting H2 by coupling with Lewis bases (e.g., NH3). The generated hydride and proton (in NH4) on gold surfaces can be concertedly transferred to CO2 with high reactivity. Furthermore, instead of the disfavored hydride transfer to the formate (HCOO) intermediate, the effective proton transfer from NH4 to HCOO provides an alternative pathway for the formation of formic acid. (Chemical Equation Presented). © 2017 American Chemical Society.

Quaternary metal thiophosphates containing second-order Jahn-Teller distorted d(10) Ag+ and lone-pair cations, Ag3Bi(PS4)(2) (1), Ag7Sn(PS4)(3) (2), and Ag7Pb(PS4)(3) (3), were obtained by solid-state synthesis. The structural frameworks of 2 and 3 feature an infinite 1-D interchiral double helix(infinity)(1)Ag(3)P(2)S(11)), which is rare in inorganic compounds. Compound 3 undergoes a significant first-order structural phase transition from monoclinic to hexagonal at similar to 204 degrees C. This can be ascribed to the significant mismatch in the expansion coefficients between Pb-S (Ag-S) and P-S bonds evaluated by bond valence theory. The three compounds are Ag+ ionic conductors, and Ag+ ion migration pathways are proposed by calculating maps of low bond valence mismatch. Moreover, the optical properties of the three compounds were studied, and electronic structure calculations were performed. The combination of second-order Jahn-Teller distorted d(10) cation and lone -pair cation provides a new strategy to explore new metal thiophosphates with interesting structures and promising properties.

Two new phases in the Ag-Cd-P-S system containing two second-order Jahn-Teller (SOJT) distorted d(10) cations (Cd2+ and Ag+), namely, Ag2Cd(P2S6) (1) and AgCd3(PS4)S-2 (2), are obtained via medium temperature solid-state synthesis. Compound I exhibits a two-dimensional layered structure and undergoes a first-order structural phase transition at approximately 280 degrees C. This outcome can be ascribed to the significant mismatch in the expansion coefficients between Cd-S (Ag-S) and P-P (PS) bonds evaluated through bond valence theory. The three-dimensional noncentrosymmetric (NCS) framework of 2 is constructed by two types of tetrahedral layers consisting of corner-shared CdS4, AgS4, and PS4 tetrahedra. Compound 2 exhibits second harmonic generation (SHG) intensity of 0.45 times that of commercial AgGaS2 (AGS) at a laser irradiation of 1.85 mu m and an optical band gap of 2.56 eV, and no intrinsic vibrational absorption of chemical bonds is observed in the range of 2.5-18.2 mu m. Both phase transition in 1 and SHG properties in 2 are closely related to the SOJT distorted d(10) cations and diverse phosphorus-sulfur polyanions (PaSb)(n-), which together can easily result in NCS distorted structures and interesting properties.

Three new ternary rare-earth zirconium chalcogenides, Ce2ZrSe5 (1), Pr2ZrSe5 (2) and Nd2ZrSe5 (3), have been synthesized by a facile solid-state route with boron as the reducing reagent. They crystallize in the space group Pnma of the orthorhombic system, belonging to the U3Se5 structure type. Their 3-D structures are constructed by parallel polyanionic {[ZrSe5](6-)}(n) chains and LnSe(8) bicapped trigonal prisms. The magnetic susceptibilities' data indicate their antiferromagnetic-like behavior without magnetic order down to 2 K. The structural relationships among several similar structures are discussed, together with the lanthanide contraction in the Ln(2)ZrSe(5) system. (C) 2016 Elsevier B.V. All rights reserved.

Three new ternary rare-earth zirconium chalcogenides, Ce2ZrSe5 (1), Pr2ZrSe5 (2) and Nd2ZrSe5 (3), have been synthesized by a facile solid-state route with boron as the reducing reagent. They crystallize in the space group Pnma of the orthorhombic system, belonging to the U3Se5 structure type. Their 3-D structures are constructed by parallel polyanionic {[ZrSe5]6-}n chains and LnSe8 bicapped trigonal prisms. The magnetic susceptibilities' data indicate their antiferromagnetic-like behavior without magnetic order down to 2 K. The structural relationships among several similar structures are discussed, together with the lanthanide contraction in the Ln2ZrSe5 system. © 2016 Elsevier B.V. All rights reserved.

The electronic structure of s-cis-1,3-butadiene (CH2=CH-CH=CH2) encouraged us to explore a transition metal (TM) free strategy for homolytic H-2 activation by replacing both terminal CH2 groups of CH2=CH-CH=CH2 with X = NH, O, SiH2, PH, S, GeH2, AsH, and Se. The study predicts that the six molecules with X = SiH2, PH, S, GeH2, AsH, and Se may activate H-2 with barriers lower than 21.7 kcal mol(-1), but the three with X = CH2, NH, and O have barriers higher than 38.9 kcal mol(-1). Unlike homolytic H-2 activation by TM complexes, which occurs on an active site with only one reactive center, the present activations are enabled through an active site with two reactive centers. The greatly increased reactivity of these heavier analogs originates from the significantly reduced EOFMO-EUFMO gaps (EOFMO/EUFMO represents the occupied/unoccupied frontier molecular orbital that has the correct symmetry to interact with the H-2 sigma*/sigma orbital). Interestingly, H-2 activations by experimentally reported derivatives with X = PH, S, and Se were predicted to have experimentally accessible barriers and to be exergonic, which is an exciting observation. The electronic structure of 1,3-dipoles is also suitable for designing geminal active sites for homolytic H-2 activation.

The first indiumsilicate oxysulfide Ba2In2Si3O10S (1) was obtained by an alkali polychalcogenide flux method through a high-temperature solid-state reaction. It crystallizes in the non-centrosymmetric space group Pca2(1) (No. 29), with a = 23.060(6), b = 5.2954(6), c = 8.779(2) angstrom, and Z = 4. Its three-dimensional (3D) framework is constructed from one-dimensional (1D) infinite infinity(1)[In2O7S2/2] double octahedral chains bridged by corner-sharing Si tetrahedral trimers [Si3O10](8-), yielding a 3D framework with the channels filled with Ba2+ cations along the b direction. It is unprecedented in that the two distorted indium octahedra in 1 face-share to form a [In2O7S2] dimer in indium oxides and oxide chalcogenides.

A novel pentanary selenide (K3I)[InB12(InSe4)3] was obtained via a high-temperature solid-state method. It crystallizes in the hexagonal space group P6322 which features an InSe4 tetrahedron consolidated B12 icosahedron and 1-D chain constructed by InSe6 octahedron and B12Se12 cluster alternatively connected along the c-axis. Second-order nonlinear optical property measurement shows that it is second harmonic generation-active. Theory calculation indicates that it is an indirect semiconductor with the energy gap of 1.15 eV. © The Royal Society of Chemistry 2016.

A novel pentanary selenide (K3I)[InB12(InSe4)(3)] was obtained via a high-temperature solid-state method. It crystallizes in the hexagonal space group P6(3)22 which features an InSe4 tetrahedron consolidated B-12 icosahedron and 1-D chain constructed by InSe6 octahedron and B12Se12 cluster alternatively connected along the c-axis. Second-order nonlinear optical property measurement shows that it is second harmonic generation-active. Theory calculation indicates that it is an indirect semiconductor with the energy gap of 1.15 eV.

Mid-far infrared (IR) non-linear optical (NLO) materials are of great importance in military and civil fields. However, commercial IR-NLO crystals (such as AgGaS2, AgGaSe2 and ZnGeP2) do not currently satisfy the requirements of large second-harmonic generation (SHG) and high laser induced damage thresholds (LIDTs), which seriously limits their practical applications. Herein, we have developed a new series of salt-inclusion chalcogenides, [A(3)X][Ga3PS8] (A = K, Rb; X = Cl, Br), which are constructed from alternate stacking of adamantane-like [Ga3PS10](6-) cluster layers and cationic [A(3)X](2+) salt layers. Importantly, they display both large SHG responses of several-fold and high LIDTs for dozens of times that of commercial AgGaS2, which exhibit the highest LIDTs among the reported IR-NLO materials with a larger SHG conversion efficiency than that of AgGaS2. These properties together with wide transparent region, type I phase-matching features and congruent-melting behaviors indicate they are promising IR-NLO materials.