Nifedipine-pyrazine (2/1).

In the title compound, 2C(17)H(18)N(2)O(6)·C(4)H(4)N(2) [systematic name: 3,5-dimethyl 2,6-dimethyl-4-(2-nitro-phen-yl)-1,4-di-hydro-pyridine-3,5-dicarboxyl-ate-pyrazine (2/1)], the complete pyrazine molecule is generated by crystallographic inversion symmetry. The center of the pyrazine ring lies on an inversion center. The nifedipine mol-ecules are linked into chains along the c axis through N-H⋯O hydrogen bonds, while the pyrazine mol-ecules are organized in the structure through van der Waals inter-actions.

Three isostructural solvates of finasteride and their solid-state characterization.

Three crystalline hemi-hydrate, channel solvates (classified as solvates from here on) of finasteride (N-(1,1-di-methylethyl)-3-oxo-4-aza-5 alpha-androst-1-ene-17beta-carboxamide) have been obtained and fully characterized. The acetone, methyl ethyl ketone (MEK), and toluene solvates of finasteride, described herein, were found to be isostructural and belong as additional members to a family of previously reported finasteride solvates. Vacuum drying at 85 degrees C for 1 day produced the metastable, anhydrous Form II of finasteride from all three solvated materials.

Structure and magnetic properties of Pb2Cu3B4O11: a new copper borate featuring [Cu3O8]10- units.

Pb2Cu3B4O11 crystallizes in the monoclinic space group P2/n (No. 13) with a = 6.8016(15) A, b = 4.7123(10) A, c = 14.614(3) A, beta = 97.089(3) degrees, and Z = 2. The crystal structure consists of infinite [Cu3O8]10- zigzag chains of alternating dimers and monomers. The magnetic susceptibility and specific heat capacity show spin-gap and Curie-Weiss behaviors that can be explained by a model of Cu(2)-Cu(2) dimers and isolated or weakly coupled Cu(1) monomers.

A spectroscopic and computational investigation of the vanadomolybdate local structure in the lyonsite phase Mg(2.5)VMoO(8).

The vibrational spectrum of Mg2.5VMoO8 obtained by quantum mechanical simulation is compared with the experimentally observed Raman spectrum. This simulation suggests that the observed band at 1016 cm(-1) is attributed to the Mo=O-Mg stretching from two-coordinate oxygen atoms that are adjacent to Mg2+ cation vacancies. Extended X-ray absorption fine structure spectroscopy supports the structural model used to simulate the vibrational modes in Mg2.5VMoO8 that match the observed Raman data.

The adaptable lyonsite structure.

Crystal frameworks that can accommodate a wide range of elements, oxidation states, and stoichiometries are an important component of solid-state chemistry. These frameworks allow for unique comparisons of different metal-cation compositions with identical atomic arrangements. The mineral Lyonsite, alpha-Cu(3)Fe(4)(VO(4))(6), is emerging as the archetypal framework structure for a large class of materials, similar to known frameworks such as perovskite, garnet, apatite, and spinel. The new lyonsite-type oxides Li(2.82)Hf(0.795)Mo(3)O(12) and Li(3.35)Ta(0.53)Mo(3)O(12), in which hafnium and tantalum retain their highest oxidation states, are presented to advance the concept of the lyonsite structure as an adaptable framework.

Synthesis, crystal structure, and nonlinear optical properties of Li6CuB4O10: a congruently melting compound with isolated [CuB4O10]6- units.

Single crystals of Li(6)CuB(4)O(10) have been synthesized, and its crystal structure has been determined. Li(6)CuB(4)O(10) crystallizes in the non-centrosymmetric triclinic space group P1 (No. 1). The structure consists of isolated [CuB(4)O(10)](6)(-) polyanions that are bridged by six LiO(4) tetrahedra. Li(6)CuB(4)O(10) is a congruently melting compound. It produces SHG intensity similar to that produced by KH(2)PO(4) and is phase-matchable.

Probing the vanadyl and molybdenyl bonds in complex vanadomolybdate structures.

A solid solution was found to exist in the quaternary Li(2)O-MgO-V(2)O(5)-MoO(3) system between the two phases Mg(2.5)VMoO(8) and Li(2)Mg(2)(MoO(4))(3). Both Mg(2.5)VMoO(8) and Li(2)Mg(2)(MoO(4))(3) are isostructural with the mineral lyonsite, and substitution according to the formula square(1/4-x/6)Li(4x/3)Mg(15/4-7x/6)V(3/2-x)Mo(3/2+x)O(12) (0 < or = x < or = 1.5, where square denotes a cation vacancy) demonstrates that a complete solid solution exits coupling the addition of molybdenum and lithium with the subtraction of cation vacancies, magnesium, and vanadium and vice versa. Vibrational Raman spectroscopy indicates that molybdenum-oxo double bonds preferentially associate with the cation vacancies.

Structure of Mg2.56V1.12W0.88O8 and vibrational raman spectra of Mg2.5VWO8 and Mg2.5VMoO8.

Mg(2.56)V(1.12)W(0.88)O(8) crystals were grown from a MgO/V(2)O(5)/WO(3) melt. X-ray single-crystal diffraction studies revealed that it is orthorhombic with space group Pnma, a = 5.0658(5) A, b = 10.333(1) A, c = 17.421(2) A, Z = 6, and is isostructural with Mg(2.5)VMoO(8). Raman spectra are reported, and the assignment of the Raman bands is made by comparing the metal-oxygen vibrations of VO(4)/WO(4) tetrahedra in Mg(2.5)VWO(8) with the metal-oxygen vibrations of VO(4)/MoO(4) tetrahedra in Mg(2.5)VMoO(8). The stretching vibrations appearing at 1016 and 1035 cm(-)(1) are assigned to Mo=O and W=O double bonds, respectively, associated with the Mg(2+) cation vacancies.