Парамагнитные центры в легированном хромом монокристалле Na-=SUB=-5-=/SUB=-AlF-=SUB=-2-=/SUB=-(PO-=SUB=-4-=/SUB=-)-=SUB=-2-=/SUB=-

The paramagnetic resonance of Na5AlF2(PO4)2 single crystals with chromium impurity was studied. The Cr3+ centers have been found to replace the triclinic Al3+ positions. In the local coordinate system, the spectra of these centers were described by the spin Hamiltonian of rhombic symmetry. In addition, vanadium centers and unidentified triclinic symmetry centers have been observed.

Парамагнитные центры Mn-=SUP=-2+-=/SUP=-, Gd-=SUP=-3+-=/SUP=- и Cu-=SUP=-2+-=/SUP=- в легированном хромом монокристалле Li-=SUB=-2-=/SUB=-CaSiO-=SUB=-4-=/SUB=-

In the Li2CaSiO4 crystal, in addition to intense axial centers of Cr4+, the EPR spectra of impurity ions Mn2+ (S = 5/2), Gd3+ (S = 7/2), and Cu2+ (S = 1/2) have been discovered and studied. Manganese and gadolinium ions exhibit spectra of tetragonal symmetry, copper ions are represented by spectra of both axial and triclinic symmetry. The parameters of the spin Hamiltonians of tetragonal centers are determined. It was shown that Mn2+ and Gd3+ ions substitute for calcium ions with an eightfold oxygen environment, copper ions are localized in lithium positions with a tetrahedral environment. The reasons for the appearance of Cu2+ triclinic centers are discussed.

Crystal structures of [Li7(i-PrO)3(C4H10NO)3]2O and [Na(i-PrOH)2(C8H18NO2)]2

The title compounds, hexakis[μ3-2-(dimethylamino)ethanolato]hexa-μ2-isopropanolato-μ4-oxido-tetradecalithium(I), [Li7(i-PrO)3(C4H10NO)3]2O (1), and {3-[(2-methoxyethyl)(methyl)amino]-1,1-dimethylpropanolato}diisopropanolsodium(I), [Na(i-PrOH)2(C8H18NO2)] (2), were crystallized in the presence of 2-propanol (i-PrOH, C3H7OH). The structure 1 has monoclinic symmetry (C2/c) and the asymmetric unit contains half of the compound. Title compound 2 has triclinic symmetry (P\overline{1}) and the asymmetric unit is half of an inversion-symmetric aggregate. Both compounds consist of an alkali metal, an aminoalkoxide and a 2-propanol compound. Furthermore, the dimeric sodium aggregate 2 is build up by hydrogen bonding through the 2-propanol and the alkoxides. Compound 1 does not exhibit hydrogen bonding, due to the fact that the 2-propanol is deprotonated. In compound 1, benzene appeared as co-crystallate, but was suppressed by solvent masking because of strong disorder. The formula mass and density do not take account of the solvent.

Hierarchical structure of the triclinic α-phase crystal in nylon 6,12 mediated by two-dimensional confinement

It has been recognized that macromolecular chains can self-assemble into a hierarchical structure from lamellae to spherulites in bulk crystallization. However, little account has been taken of crystal symmetry effects on the hierarchical nanostructure in polymers under cylindrical confinement. In this research, a model polymer, nylon 6,12, most commonly occurring in the triclinic α phase, was chosen in order to demonstrate the effect of triclinic symmetry on the 2D-constrained polymer nanostructure. The self-arranging unit of nylon 6,12 takes various forms, including stems, unit cells, hydrogen-bonded sheets, lamellae and complex spherulites, which is an essential structural feature for investigating hierarchical nanostructure. The rod nanostructure in confinement was examined by cross-checking electron and X-ray diffraction techniques. It is found that the a* axis of the α-phase cell is inclined at about ±6–11° to the rod long axis within the a*b* plane around the c axis (c axis ⊥ rod long axis). The rotation of the a*b* plane most likely results from the impact of the triclinic symmetry on the molecular chain packing under 2D confinement. A mechanism for this a*b* plane tilting is proposed.

Phase transition in the extreme: a cubic-to-triclinic symmetry change in dielectrically switchable cyanide perovskites

Two novel three-dimensional metal–organic compounds of formula FA2KM(CN)6, where M = Co, Fe and FA = formamidinium (CH(NH2)2+), have been found to crystallize in a perovskite-like architecture.

A triclinic polymorph of dicadmium divanadate(V)

The title compound, Cd2V2O7, was obtained under hydrothermal conditions. Different from the known monoclinic form, the new polymorph of Cd2V2O7has triclinic symmetry and is isotypic with Ca2V2O7. The building units of the crystal structure are two Cd2+cations, with coordination numbers of six and seven, and two V atoms with a tetrahedral and a significantly distorted trigonal–pyramidal coordination environment, respectively. Two VO5pyramids share an edge and each pyramid is connected to one VO4tetrahedronviaa corner atom, forming an isolated V4O148−anion. These anions are arranged in sheets parallel to (-211) and are linked through the Cd2+cations into a three-dimensional framework structure.

A third polymorph of (2-thiazolidinethionato)(triphenylphosphine)gold(I)

The title compound, [Au(C3H4NS2)(C18H15P)], is a third polymorphic form of a compound previously reported by Grant, Forward & Fackler Jr [Z. Kristallogr. (1996). 211, 483–484]. At 100 K, the present polymorph shows triclinic symmetry, as do the other two polymorphs.