Self-repairing complex helical columns generated via kinetically controlled self-assembly of dendronized perylene bisimides

The dendronized perylene 3,4:9,10-tetracarboxylic acid bisimide (PBI), (3,4,5)12G1-3-PBI, was recently reported to self-assemble in complex helical columns containing tetramers of PBI as basic repeat unit. These tetramers contain a pair of two molecules arranged side-by-side and another pair in the next stratum of the column turned upside-down and rotated around the column axis. Intra- and intertetramer rotation angles and stacking distances are different. At high temperature, (3,4,5)12G1-3-PBI self-assembles via a thermodynamically controlled process in a 2D hexagonal columnar phase while at low temperature in a 3D orthorhombic columnar array via a kinetically controlled process. Here, we report the synthesis and structural analysis, by a combination of differential scanning calorimetry, X-ray and electron diffraction, and solid-state NMR performed at different temperatures, on the supramolecular structures generated by a library of (3,4,5)nG1-3-PBI with n = 14-4. For n = 11-8, the kinetically controlled self-assembly from low temperature changes in a thermodynamically controlled process, while the orthorhombic columnar array for n = 9 and 8 transforms from the thermodynamic product into the kinetic product. The new thermodynamic product at low temperature for n = 9, 8 is a self-repaired helical column with an intra- and intertetramer distance of 3.5 ? forming a 3D monoclinic periodic array via a kinetically controlled self-assembly process. The complex dynamic process leading to this reorganization was elucidated by solid-state NMR and X-ray diffraction. This discovery is important for the field of self-assembly and for the molecular design of supramolecular electronics and solar cell.     

Synthesis,structural, and retrostructural analysis of helical dendronized poly(1‐naphthylacetylene)s

Structural and retrostructural analysis of chiral, nonracemic ( poly [(3,4,5)dm8G1‐1EN] ), and achiral ( poly[(3,4,5)12G1‐1EN] ) poly(1‐naphthylacetylene)s demonstrates new design principles for helical dendronized polyarylacetylenes. The oblate cylindrical dendronized polymers self‐organize in a c2mm centered rectangular columnar (Φ_r‐c) lattice. An all cis‐polyene backbone microstructure with very high cisoid character is introduced to rationalize features from small‐ and wide‐angle X‐ray diffraction experiments. More compact helical conformations are ideal for efficient communication or amplification of chirality over long distances. Peripheral chiral tails select a preferred helical screw sense of the polyene backbone. In solution, the preferred helical conformation persists over a wide temperature range. In bulk, the naphthyl moiety facilitates a longer correlation length for helical order compared to an analogous minidendritic poly(phenylacetylene). These attributes suggest that the naphthyl moiety may be better suited for expressing helical chirality in monolayer domains. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4974–4987, 2007     

Steric communication of chiral information observed in dendronized polyacetylenes

Structural and retrostructural analysis of helical dendronized polyacetylenes (i.e., self-organizable polyacetylenes containing first generation dendrons or minidendrons as side groups) synthesized by the polymerization of minidendritic acetylenes with [Rh(nbd)Cl]2 (nbd = 2,5-norbornadiene) reveals an approximately 10% change in the average column stratum thickness (l) of the cylindrical macromolecules with a chiral periphery, through which a strong preference for a single-handed screw-sense is communicated. The cylindrical macromolecules reversibly interconvert between a three-dimensional (3D) centered rectangular lattice (Phi r-c,k) exhibiting long-range intracolumnar helical order at lower temperatures and a two-dimensional (2D) hexagonal columnar lattice (Phi h) with short-range helical order at higher temperatures. A polymer containing chiral, nonracemic peripheral alkyl tails is found to have a larger l as compared to the achiral polymers. In methyl cyclohexane solution, the same polymer exhibits an intense signal in circular dichroism (CD) spectra, whose intensity decreases upon heating. The observed change in l indicates that the chiral tails alter the polymer conformation from that of the corresponding polymer with achiral side chains. This change in conformation results in a relatively large free energy difference (DeltaGh) favoring one helix-sense over the other (per monomer residue). The capacity to distort the polymer conformation and corresponding free energy is related to the population of branches in the chiral tails and their distance from the polymer backbone by comparison to recently reported first and second generation dendronized polyphenylacetylenes.     

[Co(2,3-tri)(men)Cl][ZnCl4] 体系中三个经式异构体的晶体结构

在[Co(2,3-tri)(men)Cl][ZnCl₄](2,3-tri = N-(2-氨乙基)-1,3-丙二胺;men=N-甲基乙二胺)体系中可能的几何异构体的数目多达二十个,其中经式异构体八个,面式异构体十二个。用单晶 X-射线衍射分析方法解析了三个获得单晶的经式异构体,它们的晶体学参数:(1)m3-[ZnCl₄](monoclinic P2₁/c,a=8.0874(18),b=1     

Self-assembling phenylpropyl ether dendronized helical polyphenylacetylenes

The first example of a self-assembling phenylpropyl ether based dendronized polymer has been reported and its preferred helical handedness has been determined. Dendronized polymer poly(10) and its nondendritic analogue poly(8) are high-cis-content polyphenylacetylenes (PPAs) prepared by using [Rh(nbd)Cl]2/NEt3 (nbd: 2,5-norbornadiene). Both polymers possess a stereocenter in their side chain, which selects a preferred helical handedness. Based on negative exciton chirality observed in the CD spectra of poly(10), we have designated this molecule as a right-handed helical polymer, which persists over a wide temperature range. Poly(10) self-organizes into both Phiioh and Phih lattices in bulk. The Phiioh-to-Phih transition is associated with thermoreversible cis-cisoidal to cis-transoidal isomerization of the helical PPA, accompanied by a dramatic decrease in the column diameter and a decrease in the pi-stacking correlation length along the column. A model for the right-handed helical dendronized PPA has been proposed wherein dendrons from adjacent column strata interdigitate to effectively fill space.     

One-dimensional polymers containing strictly collinear metal ions: synthesis and XRPD characterization of homoleptic binary metal pyrazolates

The synthesis of a number of 3d transition metal binary pyrazolates in microcrystalline form, thus suitable for a full XRPD characterization, has been pursued. The crystal and molecular structures of the Fe(pz)3, Co(pz)2, Co(pz)3, and Ni(pz)2 polymers, together with the few congeners reported in the recent literature, show that these species tend to afford highly crystalline materials where strictly collinear chains of metal atoms are present. Depending on the synthetic strategy used, Ni(pz)2 has been found to crystallize as two different alpha (orthorhombic) and beta (monoclinic) phases, possessing nearly identical intramolecular features. Data for each compound follow. Fe(pz)3: C9H9FeN6, hexagonal, P63/m, a = 9.1745(3) A, c = 7.2191(4) A, Z = 2. Co(pz)2: C6H6CoN4, orthorhombic, Ibam, a = 7.5239(5) A, b = 14.3461(9) A, c = 7.4331(5) A, Z = 4. Co(pz)3: C9H9CoN6, hexagonal, P63/m, a = 9.1966(3) A, c = 7.1051(3) A, Z = 2. Alpha-Ni(pz)2: C6H6N4Ni, orthorhombic, Cmcm, a = 16.6758(11) A, b = 6.4872(4) A, c = 6.9423(6) A, Z = 4. Beta-Ni(pz)2: C6H6N4Ni, monoclinic, P21/m, a = 9.967(2) A, b = 6.975(1) A, c = 6.016(1), A, beta = 98.50(1)degrees, Z = 2. The thermal stability and the detailed structural properties of these model compounds have been evaluated, in the light of the technologically relevant crystal phases (the well-known metal-diazolates showing reversible spin-crossover or spin-transition behavior) obtainable upon doping, magnetic dilution, and ring substitution (in the 4-position).     

Thermoreversible cis-cisoidal to cis-transoidal isomerization of helical dendronized polyphenylacetylenes

High cis content (81-99%) cis-transoidal polyphenylacetylene (PPA) jacketed with amphiphilic self-assembling dendrons, poly[(3,4-3,5)mG2-4EBn] with m = 8, 10, 12, 14, 16, and (S)-3,7-dimethyloctyl, were synthesized by Rh(C triple bond CPh)(nbd)(PPh(3))(2) (nbd = 2,5-norbornadiene)/N,N-(dimethylamino)pyridine (DMAP) catalyzed polymerization of macromonomers. The resulting cylindrical PPAs self-organize into hexagonal columnar lattices with intracolumnar order (Phi(h)(io)) and without (Phi(h)). The polymers with m = 12, 14, and 16 exhibit also a hexagonal columnar crystal phase (Phi(h,k)). The reversible Phi(h,k)-to-Phi(h)(io)-to- Phi(h) phase transition in these dendronized PPAs was analyzed by a combination of differential scanning calorimetry and small and wide-angle X-ray diffraction experiments performed on powder and oriented fibers. In the Phi(h,k) and Phi(h)(io) phases, the dendronized PPAs form helical porous columns. The helical pore disappears in the Phi(h) phase. This change is accompanied by a decrease of the external column diameter that is induced by stretching of the polymer backbone along the axis of the cylinder. The helix sense of the porous PPA is selected by homochiral alkyl dendritic tails. This transition is generated by an unprecedented conversion of the PPA backbone from the cis-cisoidal conformation in the Phi(h,k) and Phi(h)(io) phases to the cis-transoidal conformation in the Phi(h) phase. Under the same conditions, the pristine cis-PPA undergoes cis-trans isomerization and irreversible intramolecular 6pi electrocyclization of 1,3-cis,5-hexatriene sequences followed by chain cleavage. These processes are eliminated in the dendronized cis-PPA below its decomposition temperature.     

Synthesis and molecular structures of two [1,4-bis(3-pyridyl)-2,3-diazo-1,3-butadiene]-dichloro-Zn(II) coordination polymers

Two novel coordination polymers with 3D metal-organic frameworks (MOFs) have been synthesized by reacting 1,4-bis(3-pyridyl)-2,3-diazo-1,3-butadiene (L) with zinc dichloride. Both compounds have the same repeating unit consisting of a distorted tetrahedral Zn(II) center coordinated by two chlorides and two pyridyl nitrogen atoms of two bridging bismonodentate L ligands, however, different structural conformations have been found, one forming a helical chain and the other producing a square-wave chain. The intermolecular C-H...Cl hydrogen bonds in 1 and 2 play important roles in the formation of three-dimensional coordination polymers. Compound 1 crystallized in an orthorhombic space group Pna21 with a = 7.9652(3), b = 21.4716(7), c = 8.2491(3)A, V = 1410.81(9) A 3 and Z = 4. Compound 2 crystallized in a monoclinic space group P21/n with a = 9.1752(3), b = 14.5976(4), c = 10.3666(3) A , beta = 98.231(2) degrees , V = 1374.16(7) A 3 and Z = 4.     

Polar compounds constructed with the [Cr2O7]2- anion

Crystalline KTiOPO4 (KTP), an inorganic nonlinear optical material with a waveguide figure-of-merit that is twice that of other mixed-metal oxides, contains helical chains of TiO(4/2)O(2/2) octahedra in which a long, short Ti-O bond motif results in a net c-directed polarization. The alternating long and short Ti-O bonds that occur along these chains are the major contributors to the large nonlinear optic and electrooptic coefficients. Analogous chains have been constructed using dichromate [Cr2O7]2- anions and [M(py)4]2+ (M = Cu, Zn) cations; these new transition metal oxides crystallize in the same space group as KTP. Crystal data for Cu(py)4Cr2O7: orthorhombic, space group Pna2(1) (No. 33), with a = 15.941(7) A, b = 16.324(3) A, c = 8.857(2) A, and Z = 4; for Zn(py)4Cr2O7, orthorhombic, space group Pna2(1) (No. 33), with a = 16.503(1) A, b = 16.005(1) A, c = 8.8130(5) A, and Z = 4; for Cd(py)4Cr2O7, monoclinic, space group C2/c (No. 15), with a = 14.8034(9) A, b = 11.1847(7) A, c = 15.788(1) A, beta = 110.023(1) degrees, and Z = 4.     

Phase transformation and negative thermal expansion in TaVO5

Two phase transformations of TaVO(5) were observed by DSC and/or dilatometry measurements in the studied temperature range. X-ray diffraction and neutron powder diffraction structure refinements indicated a phase transformation at -14 °C from a monoclinic symmetry with space group P2(1)/c to an orthorhombic symmetry with space group Pnma above this temperature. The rigid TaO(6) octahedron in orthorhombic phase becomes nonregular at -14 °C, which results in the transition from Pnma to P2(1)/c. TaVO(5) was found to be a negative thermal expansion material above room temperature. The calculated volumetric thermal expansion coefficients (TECs) are -8.92 × 10(-6) °C(-1) in the range of 20-600 °C, and -2.19 × 10(-5) °C(-1) above 600 °C, respectively. The negative thermal expansion behavior is accounted for by the tilt of the TaO(6) and VO(4) polyhedra, where the shrinkage of the VO(4) tetrahedra result in the increase of Ta-O-V angles on heating, while the angle of Ta-O1-Ta maintains at 180° in the framework.     

Crystal structures of a family of silver cyanide complexes of thiourea and substituted thioureas

The syntheses and crystal structures of a family of silver cyanide complexes of thiourea and substituted thioureas are reported. The sulfur ligands include thiourea (tu), 1-methyl-2-thiourea (mtu), 1,3-dimethyl-2-thiourea (dmtu), 1,1,3,3-tetramethyl-2-thiourea (tmtu), and 2-imidazolidinethione (N,N'-ethylenethiourea, etu). Synthesis was effected by dissolving AgCN in an aqueous solution of ligand. Two different complexes were obtained by the reaction of AgCN with tu. Complex 1a: (AgCN)(tu), monoclinic, P2(1)/c, a = 9.3851 (6) A, b = 8.2782 (5) A, c = 7.1178 (5) A, beta = 94.591 (1) degree, and Z = 4. Complex 1b: (AgCN)(tu)2, triclinic, P1, a = 7.9485 (14) A, b = 9.431 (2) A, c = 12.771 (2) A, alpha = 85.695 (3) degrees, beta = 81.210 (4) degrees, gamma = 77.987 (2) degrees, and Z = 4. Complex 2: (AgCN)(mtu), triclinic, P1, a = 4.113 (2) A, b = 9.472 (4) A, c = 9.679 (4) A, alpha = 113.918 (5) degrees, beta = 98.188 (6) degrees, gamma = 97.725 (6) degrees, and Z = 2. Complex 3 (AgCN)2(dmtu)2, monoclinic, P2(1)/m, a = 7.1482 (7) A, b = 14.776 (2) A, c = 7.3366 (7) A, beta = 92.418 (2) degrees, and Z = 2. Complex 4: (AgCN)(tmtu), orthorhombic, P2(1)2(1)2(1), a = 8.823(6) A, b = 10.209 (2) A, c = 10.362 (2) A, and Z = 4. Complex 5: (AgCN)2(etu)2, triclinic, P1, a = 6.8001 (2) A, b = 8.6154 (1) A, c = 13.4747 (3) A, alpha = 71.720 (1) degree, beta = 79.906 (1) degree, gamma = 75.885 (2) degrees, and Z = 2. All of the structures involve either one- or two-dimensional polymeric arrays held together by bridging S and CN groups. There is, however, no similarity between any two of the arrays. Four of the five ligands used also form similar complexes with CuCN. For one ligand, tmtu, the structures are isomorphous. For the other three, not only are the structures not isomorphous, the m/n ratio in (MCN)mLn when M is Ag is different from that when M is Cu.     

Studies on structures of some platinum complexes with 1,1-cyclopropanedicarboxylate

The crystal structures of [Pt(NH3)2CPrDCA].H2O (I), [Pt(CH3NH2)2CPrDCA] (II), and [Pt(dmbn) CPrDCA].2.5H2O (III) (where CPrDCA is 1,1-cyclopropanedicarboxylate; dmbn is 2,3-dimethyl-2,3-butyldiamine) are determined. Compound I crystallizes in the orthorhombic space group Pnma with the cell dimensions: a = 6.517(2), b = 9.709(3), c = 14.205(5) A, Z = 4, R = 0.058. Compound II is monoclinic with space group P2(1)/n, a = 9.648(3), b = 8.720(2), c = 12.770(4) A, beta = 107.12(2), Z = 4, R = 0.059. Compound III belongs to the monoclinic system space group P2(1)/m with the cell dimensions: a = 6.494(1), b = 19.638(3), c = 6.606(1)A, beta = 94.44(1), Z = 2, R = 0.038. Electronic structures of the complexes are studied and the correlation between structure of the amine ligands and biological activity of the complexes is explored.     

钼簇合物的簇解反应和两个多钼酸盐化合物的晶体结构

含μ-Cl桥的三核钼簇阴离子[Mo~3(μ~3-O)(μ-Cl)~3(μ-OAc)~3Cl~3]^-在Fe^3^+作用下发生簇解反应, 形成钼同多酸盐[FeCl(DMF)~5][Mo~6O~1~9]。在合成[Mo~3(μ~3-S)(μ-S~2)~3(dtp)~3Cl]簇合物的反应中如果有CuI存在, 则形成钼磷杂多酸盐(Et~4N)~4[PMo~1~2O~4~0](DMF)~2。本文报道这两个多钼酸盐化合物的晶体结构, 并讨论有关的簇解反应。     

Syntheses,structures, and characterization of new lead(II)-tellurium(IV)-oxide halides: Pb3Te2O6X2 and Pb3TeO4X2 (X = Cl or Br)

The syntheses, structures, and characterization of four new lead(II)-tellurium(IV)-oxide halides, Pb(3)Te(2)O(6)X(2) and Pb(3)TeO(4)X(2) (X = Cl or Br) are reported. The materials are synthesized by solid-state techniques, using Pb(3)O(2)Cl(2) or Pb(3)O(2)Br(2) and TeO(2) as reagents. The compounds have three-dimensional structural topologies consisting of lead-oxide halide polyhedra connected to tellurium oxide groups. In addition, the Pb(2+) and Te(4+) cations are in asymmetric coordination environments attributable to their stereoactive lone pair. We also demonstrate that Pb(3)Te(2)O(6)X(2) and Pb(2)TeO(4)X(2) can be interconverted reversibly through the loss or addition of TeO(2). X-ray data: Pb(3)Te(2)O(6)Cl(2), monoclinic, space group C2/m (No. 12), a = 16.4417(11) A, b = 5.6295(4) A, c = 10.8894(7) A, beta = 103.0130(10) degrees, Z = 4; Pb(3)Te(2)O(6)Br(2), monoclinic, space group C2/m (No. 12), a = 16.8911(8) A, b = 5.6804(2) A, c = 11.0418(5) A, beta = 104.253(2) degrees, Z = 4; Pb(3)TeO(4)Cl(2), orthorhombic, space group Bmmb (No. 63), a = 5.576(1) A, b = 5.559(1) A, c = 12.4929(6) A, Z = 4; Pb(3)TeO(4)Br(2), orthorhombic, space group Bmmb (No. 63), a = 5.6434(4) A, b = 5.6434(5) A, c = 12.9172(6) A, Z = 4.     

Studies on the effect of column angle in figure-8 centrifugal counter-current chromatography

The performance of the figure-8 column configuration in centrifugal counter-current chromatography was investigated by changing the angle between the column axis (a line through the central post and the peripheral post on which the figure-8 coil is wound) and the centrifugal force. The first series of experiments was performed using a polar two-phase solvent system composed of 1-butanol-acetic acid-water (4:1:5, v/v) to separate two dipeptide samples, Trp-Tyr and Val-Tyr, at a flow rate of 0.05 ml/min at 1000 rpm. When the column angle was changed from 0° (column axis parallel to the centrifugal force) to 45° and 45° to 90° (column axis perpendicular to the centrifugal force), peak resolution (Rs) changed from 1.93 (Sf=37.8%) to 1.54 (Sf=30.6%), then to 1.31 (Sf=40.5%) with the lower mobile phase and from 1.21 (Sf=38.8%) to 1.10 (Sf=34.4%), then to 0.99 (Sf=42.2%) with the upper mobile phase, respectively, where the stationary phase retention, Sf, is given in parentheses. The second series of experiments was similarly performed with a more hydrophobic two-phase solvent system composed of hexane-ethyl acetate-methanol-0.1M hydrochloric acid (1:1:1:1, v/v) to separate three DNP-amino acids, DNP-glu, DNP-β-ala and DNP-ala, at a flow rate of 0.05 ml/min at 1000 rpm. When the column angle was altered from 0° to 45° and 45° to 90°, Rs changed from 1.77 (1st peak/2nd peak) and 1.52 (2nd peak/3rd peak) (Sf=27.3%) to 1.24 and 1.02 (Sf=35.4%), then to 1.69 and 1.49 (Sf=42.1%) with the lower mobile phase, and from 1.73 and 0.84 (SF=41.2%) to 1.44 and 0.73 (Sf=45.6%), then to 1.21 and 0.63 (Sf=55.6%) with the upper mobile phase, respectively. The performance of figure-8 column at 0° and 90° was also compared at different flow rates. The results show that Rs was increased with decreased flow rate yielding the highest value at the 0° column angle with lower mobile phase. The overall results of our studies indicated that a 0° column angle for the figure-8 column enhances the mixing of two phases in the column to improve peak resolution while decreasing the stationary phase retention by interrupting the laminar flow of the mobile phase.     

3D architectures of iron molybdate: phase selective synthesis, growth mechanism, and magnetic properties

Monoclinic and orthorhombic Fe(2)(MoO(4))(3) microsized particles with complex 3D architectures have been selectively prepared by a template-free hydrothermal process. The pH value, reaction time, temperature, and molybdenian source have crucial influence on the phase formation, shape evolution, and microstructures. Monoclinic Fe(2)(MoO(4))(3) particles obtained at pH 1 and pH 1.65 display ferromagnetic ordering at 10.4 K and 10.5 K, respectively, and the ferromagnetic component is determined to be 0.0458 mu(B) and 0.0349 mu(B) per Fe-ion at 10 K, respectively. For orthorhombic beta-Fe(2)(MoO(4))(3), antiferromagnetic ordering was observed about 12 K. At higher temperatures, beta-Fe(2)(MoO(4))(3) began to follow the Curie-Weiss law with theta=-70 K. Such 3D architectures of monoclinic and orthorhombic beta-Fe(2)(MoO(4))(3) microparticles with unique shapes and structural characteristics may find applications as catalysts and as well as in other fields.     

Crown Inclusion Compounds with 3,4-Diamino-1,2,5-Oxadiazole. X-Ray Structures of Its 1:1 Inclusion Complexes with 15-Crown-5 and Benzo-15-crown-5

The X-ray crystal structures of two closely related molecular complexes of 15-crown-5 and benzo-15-crown-5 with 3,4-diamino-1,2,5-oxadiazole are reported (I and II). Both complexes are of 1:1 stoichiometry with the host–guest alternation in the infinitechains formed due to the unsymmetrical H-bonding patterns between the components. Crystals of I are monoclinic, P2_1/c, a = 7.856(3), b = 12.994(1), c = 16.033(1) , = 94.79(2)°, Z = 4, final R-factor is 0.0488. Crystals of II are orthorhombic, P2₁2₁2₁, a = 8.260(4), b = 15.692(5),c = 13.955(7) , Z = 4, final R-factor is 0.0522.     

Heterometallic polymeric clusters containing tetraselenotungstate anion: one-dimensional helical chain [[La(Me2SO)8

[PPh4]2[WSe4] reacts with an equivalent of [Ag(MeCN)4][ClO4] in DMF to afford a linear polymeric cluster [[Ph4P][(mu-WSe4)Ag]]n (1). Treatment of cluster 1 with excess La(NO3)3.3H2O in Me2SO solution resulted in the formation of a helical chain polymeric cluster [[La(Me2SO)8][(mu-WSe4)3Ag3]]n (2). Cluster 2 crystallizes in the monoclinic space group P2(1/n) with four formula units in a cell of dimensions a = 12.7642(5) A, b = 24.1725(9) A, c = 19.4012(7) A, and beta = 103.546(11) degrees. Refinement by full-matrix least-squares techniques gave final residuals R = 0.0540 and Rw = 0.1116 for 494 variables and 7593 reflections (Fo(2) > 2.0sigma(Fo(2))). The anion [[(mu-WSe4)3Ag3]]n(3n-) in 2 can be described as a butterfly-type SeWSe3Ag2 basic repeating unit linked through interactions with a Ag atom of one fragment and a Ag atom of another to form an intriguing helical array. The CuCN, KCN, and [Et4N]2[WSe4] reaction system resulted in the formation of a novel three-dimensional cluster [[Et4N]2[(mu4-WSe4)Cu4(CN)4]]n (4) either in DMF/2-picoline or in solid at 80 degrees C. Cluster 4 crystallizes in the orthorhombic space group Fddd with cell constants a = 11.090(2) A, b = 23.206(5) A, c = 23.910(5) A, and Z = 8. Anisotropic refinement with 1510 reflections (Fo(2) > 2.0sigma(Fo(2))) and 82 parameters for all non-hydrogen atoms yielded the values of R = 0.0428 and Rw = 0.0887. The anion structure of 4 is built up from a WSe4Cu4 unit bridged by cyanide ligands to form a three-dimensional cross framework. The air- and moisture-stable polymeric clusters easily decompose into small molecular clusters when treated with ligands such as PPh3 and pyridine (Py). Cluster 2 exhibits both strong optical absorption and an optical self-focusing effect (effective alpha2 = 2.2 x 10(-9) m2.W(-1), n2 = 6.8 x 10(-15) m2.W(-1); examined in a 0.13 mM DMF solution). Cluster 4 shows good photostability in the process of measurement and a large optical limiting effect (the limiting threshold is ca. 0.2 J.cm(-2)).     

Nitrogen-rich salts based on energetic nitroaminodiazido[1,3,5]triazine and guanazine

Highly dense nitrogen-rich ionic compounds are potential high-performance energetic materials for use in military and industrial venues. Guanazinium salts with promising energetic anions and a family of energetic salts based on nitrogen-rich cations and the 6-nitroamino-2,4-diazido[1,3,5]triazine anion (NADAT) were prepared and fully characterized by elemental analysis, IR spectroscopy, (1)H NMR and (13)C NMR spectroscopy, and differential scanning calorimetry (DSC). The crystal structures of neutral NADAT (2) and its biguanidinium salt 5 were determined by single-crystal X-ray diffraction (2: orthorhombic, Pnma; 5: monoclinic, P2(1)). Additionally, the isomerization behavior of 2 in solution was investigated by proton-decoupled (13)C and (15)N NMR spectroscopy. All the new salts exhibit desirable physical properties, such as relatively high densities (1.63-1.78 g cm(-3)) and moderate thermal stabilities (T(d) = 130-196 °C for 3-10 and 209-257 °C for 11-15). Theoretical performance calculations (Gaussian 03 and Cheetah 5.0) gave detonation pressures and velocities for the ionic compounds 3-15 in the range of 21.0-30.3 GPa and 7675-9048 m s(-1), respectively, which makes them competitive energetic materials.     

Combined structural refinement of Bi3.5La0.5Ti3O12 using neutron and X-ray powder diffraction data

A combined structural refinement of Bi3.5La0.5Ti3O12 against both neutron and X-ray diffraction data was performed at 298 K on the basis of the Raman study. The upshift of Raman peaks suggested that the substitution sites of La atoms in Bi3.5La0.5Ti3O12 were only the Bi sites in the perovskite units. Of the two crystal structural models (orthorhombic and monoclinic systems) considered for the crystal structural system of Bi3.5La0.5Ti3O12, the weighted R factor, Rwp, and goodness-of-fit indicator, S (=Rwp/Re), of the monoclinic system were lower than those of the orthorhombic one. The final Rwp and S values based on the monoclinic system were 7.04% (6.34 and 7.76% for the neutron data and the X-ray data, respectively) and 1.45, respectively. The lattice parameters obtained from the combined structural refinement were a = 5.4321(1) A, b = 5.4161(1) A, and c = 32.8614(3) A. The beta angle was 89.95(4) degrees . Spontaneous polarizations calculated from the refined structural parameters were 27.0 microC/cm2 for the monoclinic system and 1.8 microC/cm2 for the orthorhombic one.