Crystal structure of chalcogenides R'xR''yR'''zPbSi2S8 (R' – La, R'' – Tb, R''' – Er)

The chalcogenides LaxTbyErzPbSi2S8 were obtained by synthesizing the elementary components in vacuum quartz containers at 1320 K. The synthesized alloys were homogenized by annealing at 770 K during 500 hours. The cell parameters of synthesized sulfides are: a = 0,89576(3) nm, c = 2,65646(8) nm – La1,2Tb0,4Er0,4PbSi2S8; a = 0,89209(1) nm, c = 2,63466(5) nm – La0,9Tb0,2Er0,9PbSi2S8; a = 0,89002(3) nm, c = 2,62714(7) nm – La0,67Tb0,67Er0,67PbSi2S8; a = 0,88993(1) nm, c = 2,62973(4) nm – La0,6Tb1,2Er0,2PbSi2S8; a = 0,885161(7) nm, c = 2,60445(3) nm – La0,2Tb0,9Er0,9PbSi2S8 respectively. The atoms of statistical mixture (La,Tb,Er,Pb) occupy the site 18e (x y 1/4), and the atoms of Si occupy the site 12c (1/3 2/3 z) in the structure of the obtained chalcogenides. Coordinating polyhedra of atoms of the statistical mixture (La, Tb, Er, Pb) are trigonal prism with two additional atoms (CN = 8), and the atoms of Si occupying the crystallographic point system 12c describes with the tetrahedron. According to the results of the experiment, the synthesized chalcogenides crystallize in the structure type of La2PbSi2S8 (hR26,167). The structure of La2PbSi2S8 is described by using the theory of second anion coordination (SAC).

Crystal-to-Crystal Transformation from K2[Co(C2O4)2(H2O)2]·4H2O to K2[Co(μ-C2O4)(C2O4)]

Crystal-to-crystal transformation is a path to obtain crystals with different crystal structures and physical properties. K2[Co(C2O4)2(H2O)2]·4H2O (1) is obtained from K2C2O4·2H2O, CoCl2·6H2O in H2O with a yield of 60%. It is crystallized in the triclinic with space group P1 and cell parameters: a = 7.684(1) Å, b = 9.011(1) Å, c = 10.874(1) Å, α = 72.151(2)°, β = 70.278(2)°, γ = 80.430(2)°, V = 670.0(1) Å3, Z = 2 at 100 K. 1 is composed of K+, mononuclear anion [Co(C2O4)2(H2O)22−] and H2O. Co2+ is coordinated by two bidentated oxalate anion and two H2O in an octahedron environment. There is a hydrogen bond between mononuclear anion [Co(C2O4)2(H2O)22−] and H2O. K2[Co(μ-C2O4)(C2O4)] (2) is obtained from 1 by dehydration. The cell parameters of 2 are a = 8.460(5) Å, b = 6.906 (4) Å, c = 14.657(8) Å, β = 93.11(1)°, V = 855.0(8) Å3 at 100 K, with space group in P2/c. It is composed of K+ and zigzag [Co(μ-C2O4)(C2O42−]n chain. Co2+ is coordinated by two bisbendentate oxalate and one bidentated oxalate anion in trigonal-prism. 1 is an antiferromagnetic molecular crystal. The antiferromagnetic ordering at 8.2 K is observed in 2.

Interconversion between Pd3L2 trigonal prism and Pd6L8 cube via anion exchange: binding affinity of monoatomic vs. polyatomic anions

Systematic interconversion between trigonal prisms [Pd3X6L2] (X- = Cl-, Br-, and I-) and cubic cages [Pd6L8]12+(X-)12 (X- = BF4- with CF3SO3-) via anion exchange was established. Self-assembly of K2PdX4 (X-...

Investigations on the g factors and local structure for the trigonal Ce3+ center in YAl3(BO3)4 crystal

The perturbation formulae of the EPR gyromagnetic factors g// and g⊥ for the lowest Kramers doublet of a 4f1 ion in trigonal symmetry are established. By using the above perturbation formulae, the anisotropic g factors and the local structure for the trigonal Ce3+ center in YAl3(BO3)4 crystal are theoretically studied. From the studies, this center is attributed to the impurity Ce3+ occupying the trigonal prism Y3+ site in YAl3(BO3)4. The Ce3+–O2− bond is found to undergo an angular variation Δθ(≈ 1.72°) related to the C3 axis. The calculated g factors based on the above impurity angular distortion display consistence with the measured results. The anisotropic g factors and the trigonal distortion of the Ce3+ center are analyzed with respect to the host Y3+ site in YAl3(BO3)4.

The first amino acid bound manganese–calcium clusters: a {[MnIII3Ca]2} methylalanine complex, and a [MnIII6Ca] trigonal prism

The use of methylalanine in manganese/calcium chemistry has led to the synthesis and characterization of the first manganese/calcium amino acid containing polynuclear clusters.

Na+[Me3NB12Cl11]−·SO2: a rare example of a sodium–SO2 complex

In the title compound, Na+[Me3NB12Cl11]−·SO2 [systematic name: sodium 1-(trimethylammonio)undecachloro-closo-dodecaborate sulfur dioxide], the SO2 molecule is η 1-O-coordinated to the Na+ cation. Surprisingly, the SO2 molecule is more weakly bound to sodium than is found in other sodium–SO2 complexes and the SO2 molecule is essentially undistorted compared to the structure of free SO2. The Na+ cation has a coordination number of eight in a distorted twofold-capped trigonal prism and makes contacts to three individual boron cluster anions, resulting in an overall three-dimensional network. Although the number of known η 1-O-coordinated SO2 complexes is growing, sodium-SO2 complexes are still rare.