K2TiSi3O9·H2O

Single crystals of dipotassium titanium trisilicate hydrate were synthesized and the crystal structure was refined using data from single‐crystal X‐ray diffraction. The structure is a three‐dimensional mixed framework and contains channels formed by six‐ and eight‐membered rings. K⁺ ions and water mol­ecules are located in the channels.     

Structural and Raman Spectroscopic Investigations of K4BaSi3O9 and K4CaSi3O9

The crystal structures of K₄BaSi₃O₉ and K₄CaSi₃O₉ have been characterized by X‐ray diffraction techniques as well as Raman spectroscopy. The structure of K₄CaSi₃O₉ has been refined from powder diffraction data via the Rietveld method using polycrystalline material prepared from solid state reactions. The compound is isostructural with form I of K₄SrSi₃O₉. It crystallizes with 16 formula units in a cubic primitive cell (a = 15.94014(3) Å, V = 4050.20(1) ų) and adopts space group . K₄CaSi₃O₉ belongs to the group of cyclosilicates and contains highly puckered twelve‐membered [Si₁₂O₃₆]‐rings centered on the . Five of the seven crystallographically independent alkaline and alkaline earth cations are surrounded by six oxygen ligands in the form of distorted octahedra, which share opposite triangular faces and form non‐intersecting columns parallel to the body diagonals of the cubic unit cell. This arrangement corresponds to one of the cubic cylinder or rod packings. The two remaining sites have more irregular coordination environments with eight next oxygen neighbors. High temperature X‐ray powder diffraction data have been collected to determine the thermal expansion of this material: between room temperature and 700 °C the coefficient of thermal expansion has a value of α = 12.9(2) × 10^?6 [°C^?1]. Single crystals of K₄BaSi₃O₉ have been obtained from the devitrification of a glass with the same composition. The structure was determined from a single crystal diffraction data set collected at ?100 °C and refined to a final R index of 0.0298 for 1288 observed reflections (I > 2σ(>I)). The compound is isostructural with modification II of K₄SrSi₃O₉. Basic crystallographic data are as follows: space group Ama2, a = 11.0695(15) Å, b = 8.0708(10) Å, c = 11.905(2) Å, V = 1063.6(3) ų, Z = 4. With respect to the silicate anions the material can be classified as a sechser single chain silicate. The crankshaft‐like chains run parallel to [100] and are linked by K and Ba cations, which are distributed among five crystallographically independent sites. The coordination polyhedra of two of the non‐tetrahedral cations can be described by distorted octahedra sharing opposite triangular faces. They build non‐intersecting columns parallel to [011] and [0‐11], respectively. The other sites exhibit more irregular coordination spheres with 7‐9 neighbours.     

K4H2[PMo9V3O40]·10H2O的合成及其晶体结构

采用低温技术,用X射线单晶衍射法测定了标题化合物的结构。晶体属P4/mnc空间群,=12.515(3),c=17.636(7)A,Z=2.用788个独立可观测反射精修所有结构参数得R=0.061.钼钒磷杂多酸阴离子中,PO4四面体是无序的,P-O键长1.54A.M(Mo,V)是6配位,M-O键长1.62-2.48A,K是7配位,K-O键长2.84-3.10A。     

Ein neues Periodat Zum Aufbau von K9Li3I2O13 = K9Li3O[IO6]2

A Novel Periodate: On the Structure of K₉Li₃I₂O₁₃ = K₉Li₃O[IO₆]₂ New obtained are weakly dichroitic (pale yellow/bluish) single crystals of K₉Li₃I₂O₁₃ by reaction of KIO₄, K₂O, and Li₂O (KIO₄:K₂O:Li₂O = 1:1:1.5; 800°C, 42 d). Space group P62c, Z = 2, a = 954.9 pm, c = 1172.2 pm, R = 6.2%, Rw = 5.6%, 957 symmetry independend I₀(hkl), MoKα . Characteristic for this structure are ?isolated”? O^2? and octahedral groups [IO₆]. The crystal structure has been determind. The Madelung Part of Lattice Energy, MAPLE, is calculated and discussed.     

Structure, stability, and spectra of C9H3, C11H3, and C13H3 radicals

Density functional theory has been used to investigate the geometries, vibrational frequencies, rotational constants, and dipole moments of the C(9)H(3), C(11)H(3), and C(13)H(3) radicals. Vertical electronic transition energies of C(9)H(3), C(11)H(3), and C(13)H(3) are calculated by the time-dependent density functional theory. Present results show that the most stable arrangements of C(9)H(3), C(11)H(3), and C(13)H(3) are H(2)C(9)H, H(2)C(11)H, and H(2)C(13)H with a C(2v) symmetry, respectively. Such lowest-energy isomers have an obvious single and triple bond alternation carbon chain. Their isomers HC(4)(HC)C(4)H, HC(4)[C(C(2)H)]C(4)H, and C(C(4)H)(3) are predicted to have vibrational frequencies and vertical excitation energies in good agreement with experimental observations. HC(4)(HC)C(4)H, HC(4)[C(C(2)H)]C(4)H, and C(C(4)H)(3) have similar trigonal structure, which gives rise to the remarkably similar spectroscopic features as obtained experimentally. On the basis of present calculations, the isomers HC(4)(HC)C(4)H, HC(4)[C(C(2)H)]C(4)H, and C(C(4)H)(3) of C(9)H(3), C(11)H(3), and C(13)H(3) radicals are most likely the carriers of the observed spectra.     

Theoretical exploration of hydrogen loss from Al3H9

The Al(3)H(9) and Al(3)H(7) potential energy surfaces were explored using quantum chemistry calculations to investigate the H(2) loss mechanism from Al(3)H(9), which provide new insights into hydrogen production from bulk alane, [AlH(3)](x), a possible energy storage material. We present results of B3LYP/6-311++G(d,p) calculations for the various Al(3)H(9) and Al(3)H(7) optimized local minima and transition state structures along with some reaction pathways for their interconversion. We find the energy for Al(3)H(9) decomposition into Al(2)H(6) and AlH(3) is slightly lower than that for H(2) loss and Al(3)H(7) formation, but the calculations show that H(2) loss from Al(3)H(9) is a lower energy process than for losing hydrogen from either Al(2)H(6) or AlH(3). We found four transition state structures and reaction pathways for Al(3)H(9) → Al(3)H(7) + H(2), where the lowest energy activation barrier is around 25-73 kJ/mol greater than the experimental value for H(2) loss from bulk alane. Intrinsic reaction coordinate calculations show that the H(2) loss pathway involves considerable rearrangement of the H atom positions around a single Al center. Three of the pathways start with the formation of an AlH(3) moiety, which then enables a terminal H on the AlH(3) to get within 1.1 to 1.2 ? of a nearby bridging H atom. The bridging and terminal H atoms eventually combine to form H(2) and leave Al(3)H(9). One implication of these H(2) loss reaction pathways is that, since the H atoms in bulk alanes are all at bridging positions, if a similar H(2) loss mechanism were to apply to bulk alane, then H(2) loss would most likely occur on the bulk alane surface or at a defect site where there should be more terminal H atoms available for reaction with nearby bridging H atoms.