RESUMO
Two novel selenite oxychlorides Pb2MCu(SeO3)4Cl(H2O) (M = Fe, Ga) were hydrothermally synthesized and structurally characterized. They are isostructural and crystallize in the two-dimensional [MCu(SeO3)4Cl(H2O)]4- anionic layer structure mediated with hydrogen bonds and aligned between neighboring layers which assist in building the three-dimensional framework with a polar space group. Optical properties measurements revealed that the optical band gaps are 2.61 and 3.22 eV for Pb2FeCu(SeO3)4Cl(H2O) (1) and Pb2GaCu(SeO3)4Cl(H2O) (2) and the SHG responses are about 0.12 and 0.18 times that of KDP, respectively. Furthermore, 1 exhibits an interesting metamagnetic phenomenon under varied applied fields from around 1 to 4 T at 2 K, and 2 behaves with potential ferromagnetic ordering at low temperature.
RESUMO
A new polar material Ag3I[(MoO3)2(IO3)2], which contains the extended 2D [(MoO3)2(IO3)2]∞2n+ molybdenyl iodate framework found in the known noncentrosymmetric material K2[(MoO3)2(IO3)2], has been synthesized through the conventional hydrothermal method at 200 °C. It crystallizes in the orthorhombic system space group Pna21 with a = 8.0072(2) Å, b = 21.2678(6) Å, c = 7.3241(2) Å, and V = 1247.26(6) Å3. Its structure features 2D corrugated [(MoO3)2(IO3)2]∞2n+ anionic layers with neighboring anionic layers stitched through 1D [IAg3]∞2n+ cationic chains to form a 3D structure. The 1D [IAg3]∞2n+ cationic chain acts as the template for parallel alignments of the polar iodate anions along the c axis in 2D [(MoO3)2(IO3)2]∞2n+ anionic layers, which leads to the polar structure of the material. Second-harmonic generation (SHG) measurements on Ag3I[(MoO3)2(IO3)2] show a moderate SHG efficiency of about 0.7 times that of the KDP reference under 1064 nm laser radiation. In addition, the thermogravimetric analyses (TGA) and optical measurements of the compound were also carried out.
RESUMO
A formal thio [3+2] cyclization catalyzed by Takemoto's organocatalyst has been reported for the construction of optically active spiroannulated dihydrothiophenes in high yields with excellent regio-, chemo-, diastereo-, and enantioselectivities.
RESUMO
A new series of quaternary CsRE2Ag3Te5 (RE = Pr, Nd, Sm, Gd-Er) and RbRE2Ag3Te5 (RE = Sm, Gd-Dy), which have been synthesized from the elemental mixtures in ACl flux (A = Rb, Cs) and crystallized in the orthorhombic space group Cmcm, with a = 4.620(2)-4.504(2) Å, b = 16.232(8)-16.027(8) Å, c = 18.84(1)-18.32(2) and Z = 4, are isostructural to RbSm2Ag3Se5. These isostructural ARE2Ag3Te5 feature a three-dimensional tunnel framework constructed by ionically bound RETe6 octahedron and covalently bound AgTe4 tetrahedron in which tunnels are filled by A. Typical semiconducting behavior is revealed by the electrical conductivity, Seebeck coefficient, optical band gap measurement, and the theoretical calculations. The undoped sintered polycrystalline pellets of CsRE2Ag3Te5 (containing 1.1-1.7% CsCl impurity) show very low electrical conductivity (σr.t. = 0.5-2.4 S/cm), very low thermal conductivity (kr,t = 0.66-0.53 W/(m·K)), and moderate Seebeck coefficient (160-200 µV/K at 700 K).
RESUMO
Two novel lanthanoid thioantimonates [Sm(4)(tepa)(4)(µ-η(2),η(3)-Sb(3)S(7))(2)(µ-Sb(2)S(4))] (1, tepa = tetraethylenepentamine) and [Eu(2)(tepa)(2)(µ-SbS(3))(µ-OH)](2)(SbS(4))(OH)·H(2)O (2) were solvothermally synthesized. Compound 1 represents the only example of different types of [Sb(3)S(7)](5-) and [Sb(2)S(4)](2-) anions coexisting in the same lanthanoid thioantimonate framework, while 2 displays rare mixed-valent Sb(3+)/Sb(5+) character with the Sb(3+) in a noncondensed pyramid [Sb(III)S(3)](3-). The theoretical band structure and luminescence properties have also been investigated.
