Highly functionalized bridged silsesquioxanes

The objective of this work was to synthesize functionalized mesoporous silsesquioxanes with high concentrations of amine groups. During typical sol–gel syntheses, these materials are obtained by co-condensation of organic precursors with suitable linkers, such as tetraethoxysilane, necessary to prevent the mesoporous structure from collapsing. Thus, concentrations of amine groups in organosilicas usually do not exceed 2.7–3.4 mmol g⁻¹. The use of bridged bis-trimethoxysilanes, however, allowed formation of mesoporous materials with no linker. Polycondensation of bis-trimethoxysilanes containing amine groups was conducted in acidic, neutral and basic media, resulting in high yields of solid bridged silsesquioxanes. Gelation occurred quickly if no acid or base was added to the reaction mixture. The hybrid organic/inorganic nature of obtained materials was confirmed by FT-IR and MAS CP NMR spectroscopy. Elemental analysis showed that amino group concentration in the products was 3.3–4.1 mmol g⁻¹. Measurement of particle size distribution confirmed that choice of reaction media significantly affects particle sizes and agglomeration degrees, with the largest agglomerates (up to 50 μm) formed in basic media. A morphology study, using small-angle X-Ray scattering, displayed two-level fractal structures composed of aggregated 6.5–10.5 nm particles. Reactions in the presence of a surfactant resulted in formation of mesoporous structures. Furthermore, the obtained bridged silsesquioxanes were thermally stable down to 260 °C, but could reversibly absorb water and CO₂ at temperatures below 120 °C. Thus, condensation of the bridged precursor without a linker resulted in formation of a highly functionalized mesoporous material.     

Mixed complexes of palladium(II) with 1-aminoethylidene-1,1-diphosphonic acid and glycine

The complexing of palladium(II) with two biological active reagents: glycine (Gly, HA) and 1-aminoethylidene-1,1-diphosphonic acid (AEDP, H₄L) at concentrations of chloride ions (0.15 mol/L) corresponding to physiological levels is studied by means of spectrophotometry, pH potentiometry, and ³¹P NMR spectroscopy. The formation constants for mixed complexes with compositions of [PdH₂LA]^? (log?? = 43.7) and [PdHLA]^2? (log?? = 39.05) are determined. The both ligands are found to be coordinated to palladium(II) in a bidentant-cyclic manner: through amine nitrogen and the oxygen atom of the carboxyl group (in the case of Gly), or through the phosphonic group (in the case of AEDP). A diagram of the distribution of equilibrium concentrations of the complexes depending on pH is calculated for the system K₂[PdCl₄]: Gly: AEDP = 1: 1: 1. It is demonstrated that there are complexes with compositions of [PdHLA]^2?, [PdA₂], and [Pd(HL)₂]^4? in solutions with $C_{Cl^ - } = 0.15 mol/L$ and pH 6?C7.     

Protic Oligosilsesquioxane Dicationic Ionic Liquids with Two Types of Ionic Sites in Organic Frame

Theoretical and Experimental Chemistry - A method of synthesis of oligomeric siloxane protic ionic liquids capable of condensation reactions has been developed as starting compounds in the...     

Protic cationic oligomeric ionic liquids of the urethane type

Protic oligomeric cationic ionic liquids of the oligo(ether urethane) type are synthesized via the reaction of an isocyanate prepolymer based on oligo(oxy ethylene)glycol with M = 1000 with hexamethylene-diisocyanate followed by blocking of the terminal isocyanate groups with the use of amine derivatives of imidazole, pyridine, and 3-methylpyridine and neutralization of heterocycles with ethanesulfonic acid and p-toluenesulfonic acid. The structures and properties of the synthesized oligomeric ionic liquids substantially depend on the structures of the ionic groups. They are amorphous at room temperature, but ethanesulfonate imidazolium and pyridinium oligomeric ionic liquids form a low melting crystalline phase. The proton conductivities of the oligomeric ionic liquids are determined by the type of cation in the temperature range 80–120°C under anhydrous conditions and vary within five orders of magnitude. The resulting compounds are thermally stable up to 200–270°C.