Construction of Annulated Spiro[4.4]-nonane-diones via the Tandem [4 + 2]-Cycloaddition/Aromatization Reaction.

A method for the synthesis of both symmetric and asymmetric fused spiro[4.4]-nonane-dione derivatives has been developed. It is based on a Diels-Alder reaction of spiro[4.4]nona-2,7-diene-1,6-dione as a dienophile component followed by immediate aromatization of the adduct. An active diene component can be generated using the tetrabromoxylene/NaI system, the 1,3-diphenylisobenzofuran/BF3 system, or substituted cyclones.

Metalloligand-based coordination polymer embedding the nitrosyl ruthenium complex for photoactive materials with bound nitric oxide.

The stability of a photoactivated isonitrosyl state was boosted by confining a pre-designed bicarboxylate ligand with a ruthenium nitrosyl fragment in a 2D metal-organic framework. The novel Zn/Ru-based MOF, {Zn[RuNO(H2O)(inic)2(OH)2]2}·12H2O (inic = isonicotinate), was obtained with enhanced isonitrosyl stability by 30 K (up to 200 K) compared to the related ruthenium-only complex.

Rb9-xAg3+xSc2(WO4)9: a new glaserite-related structure type, rubidium disorder, ionic conductivity.

A new triple tungstate Rb9-xAg3+xSc2(WO4)9 (0 ≤ x ≤ 0.15) synthesized by solid state reactions and spontaneous crystallization from melts presents a new structure type related to those of Cs7Na5Yb2(MoO4)9 and Na13Sr2Ta2(PO4)9. The title compound in centrosymmetric space group Cmcm contains dimers of two ScO6 octahedra sharing corners with three bridging WO4 tetrahedra. Three pairs of opposite terminal WO4 tetrahedra are additionally linked by AgO2 dumbbells to form {Ag3[Sc2(WO4)9]}9- groups, which together with some rubidium ions are packed in pseudohexagonal glaserite-like layers parallel to (001), but stacking of the layers is different in these three structures. In the title structure, the layers stack with a shift along the b axis and their interlayer space contains disordered Rb+ cations partially substituted by Ag+ ions. Almost linear chains of incompletely filled close Rb3a-Rb3d positions (the shortest distances Rb-Rb are 0.46 to 0.64 Å) are found to locate approximately along the b axis. This positional disorder and the presence of wide common quadrangular faces of Rb2 and Rb3a-Rb3d coordination polyhedra favor two-dimensional ionic conductivity in the (001) plane with Rb+ and Ag+ carriers, which was confirmed with bond valence sum (BVS) maps. Electrical conductivity measurements on Rb9Ag3Sc2(WO4)9 ceramics revealed a first-order superionic phase transition at 570 K with a sharp increase in the electrical conductivity. The conductivity σi = 1.8 × 10-3 S cm-1 at 690 K is comparable with the value of 1.0 × 10-3 S cm-1 (500 K) observed earlier for rubidium-ion transport in pyrochlore-like ferroelectric RbNbWO6.

Chiral C2-Symmetric Diimines with 4,5-Diazafluorene Units.

A synthetic approach to a new group of stable chiral C2-symmetric diimines with the 4,5-diazafluorene core has been developed based on condensation of dipinodiazafluorene with aromatic diamines. The chemical structures of new compounds were proven by spectroscopic methods and X-ray crystallography. All the compounds form solvates with organic solvents (chloroform, benzene, 1,4-dioxane) and water. Specific spectral data of the new compounds are explained using calculated data (DFT). Diimines of the pinodiazafluorene series give colored reactions with transition metal ions and can be regarded as prospective polydentate ligands with interesting luminescent and chiroptical properties.

Semiclathrate Hydrates in Tri-n-butylphosphine Oxide (TBPO)-Water and TBPO-Water-Methane Systems.

In the present work, we studied semiclathrate hydrates in the TBPO-H2O and TBPO-H2O-CH4 systems. The stoichiometry, temperature, and enthalpy of dissociation of TBPO semiclathrate hydrate crystals formed in the TBPO-H2O binary system were found to be TBPO·33.6 ± 0.9H2O, 280.0 K, and 253.1 ± 4.7 J g-1, respectively. The crystal structure determined by single crystal XRD analysis (150 K) was the orthorhombic with space group Pbam and unit cell parameters a = 19.9313(8) Å, b = 23.4660(7) Å, and c = 12.1127(5) Å. The structural stoichiometry is TBPO·34.5H2O. The TBPO guest molecules arrangement within the host water framework has been refined for the first time. The discrepancy between the analytically measured and structural stoichiometry is likely to be attributed to the structure defects, which cannot be revealed by the routine single-crystal XRD analysis. The methane capacity of TBPO + CH4 double hydrate was measured by the thermovolumetric method in the range 14.9-55.8 wt % TBPO aqueous solution at a methane pressure of 8.5 ± 0.5 MPa and temperature of 274 ± 1 and 286 ± 1 K. The maximum included methane volumes of 61.6-74.6 mL/g were observed for the TBPO + CH4 double hydrates synthesized from ∼26-30 wt % TBPO aqueous solutions. Powder X-ray diffraction measurements of the hydrate samples used in the thermovolumetric experiments revealed that the TBPO + CH4 double hydrate has the same structural characteristics as the simple TBPO hydrate. The study of the Raman spectra of the TBPO + CH4 double hydrate and TBPO simple hydrate showed that in the TBPO + CH4 double hydrate CH4 molecules selectively occupy the small D cages. The results of the present study did not confirm the earlier suggestion of the formation of several structural types of hydrates in the TBPO-H2O system. The obtained results indicate that the TBPO-H2O binary system has a potential for application in gas separation and as cold storage and transportation media.

1,2,4-Triphospholyl anions - versatile building blocks for the formation of 1D, 2D and 3D assemblies.

The potential of K[P3C2R2] (R = (t)Bu, Mes) as building blocks in metallo-supramolecular chemistry was investigated and self-assembly processes with Cu(i) halides resulted in the formation of a large variety of unprecedented one-, two- and even three-dimensional aggregates. The 3D networks showed an interesting topological similarity to allotropes of carbon: diamond and the theoretically proposed polybenzene. Furthermore, the negative charge of the phospholyl ligand favoured the generation of cationic CuaXb (a > b, X = Cl, Br, I) assemblies, a challenging area within the well-studied coordination chemistry of CuX units. In addition, the 1D strands were also characterized in solution, revealing the presence of oligomeric units.

Calorimetric and structural studies of tetrabutylammonium bromide ionic clathrate hydrates.

In the present work, characteristic properties of tetrabutylammonium bromide (TBAB) ionic clathrate hydrates structures were studied by single-crystal X-ray structure analysis. The structures of three different tetragonal TBAB ionic clathrate hydrates that were formed in our experiments were based on the same water lattice of tetragonal structure I (TS-I) differing in the ways of including bromide anions and arranging tetrabutylammonium cations. We demonstrated that (1) Br(-) can be included into the water lattice, replacing two water molecules, (2) the butyl group of the cation can be inserted not only in large T and P cavities but also in small D cavities of the water lattice TS-I, and (3) one of the reasons for polytypism of ionic clathrate hydrates on the basis of TS-I is the occurrence of alternative modes of arrangements of four-compartment cavities in adjacent layers of the water framework. The compositions of three TBAB ionic clathrate hydrates TBAB·38.1H2O, TBAB·32.5H2O, and TBAB·26.4H2O were determined by chemical analysis, and their enthalpies of fusion were measured by differential scanning calorimetry (DSC). From the obtained results, the enthalpies of the TBAB hydrate formation from TBAB and water were calculated thermodynamically.

Physicochemical and structural studies of clathrate hydrates of tetrabutylammonium polyacrylates.

In this work, physicochemical and structural studies have been carried out for semiclathrate hydrates of linear (un-cross-linked) and cross-linked tetrabutylammonium polyacrylates with different degrees of cross-linking of the polymeric guest molecules (n = 0.5, 1, 2, 3%) and different degrees of substitution of proton ions of carboxylic groups in poly(acrylic acid) for TBA cations (x = 1, 0.8, 0.6). The changes in the hydrates' stability and composition depending on the outlined parameters were examined in the course of phase diagram studies of the binary systems water-tetrabutylammonium polyacrylates using differential thermal analysis method and calorimetric measurements of fusion enthalpies of the hydrates. Phase diagram studies of the binary system water-linear tetrabutylammonium polyacrylate revealed the formation of four hydrates. Based on the data of chemical analysis of hydrate crystals the compositions of all hydrates have been determined. Single-crystal X-ray diffraction studies revealed a tetragonal structure, space group 4/m, and unit cell parameters are close for different hydrates and lie in the ranges a = 23.4289-23.4713 Å and c = 12.3280-12.3651 Å (150 K). The structure can be related to tetragonal structure I typical for the clathrate hydrates of tetraalkylammonium salts with monomeric anions. Powder X-ray diffraction analyses confirmed the identity of the above crystal structure to that of the hydrates with cross-linked tetrabutylammonium polyacrylates. The behavior of TBA polyacrylate hydrates under the pressure of methane was studied and quantitative assessment of the gas content in the hydrates was made using volumetric analysis method.