No abstract

SBA-15 mesoporous silicates with surface functional groups were synthesized by cohydrolysis of tetraethoxyorthosilicate and ethyl-, carboxylate-, and ethylenediaminetriacetic acid-functionalized organosilanes (ETES, CTES, EDATAS, respectively) using the nonionic surfactant poly(ethylene oxide)−poly(propylene oxide)−poly(ethylene oxide) triblock copolymer (PEO20PPO70PEO20, Pluronic P123). X-ray diffraction revealed that silicates synthesized with up to 5% (wt/wt total silica) of added functionalized silane yielded ordered mesoporous materials with P 6 m m hexagonal symmetry. Further increasing the amount of added functionalized silanes to 20% resulted in a significant decrease in the structural ordering of the resulting silicate. Surface areas, pore volumes, and pore diameters were determined from nitrogen gas adsorption/desorption isotherms. Pore size contraction was observed as the wt % of added ETES was increased but not for the silicates formed with added CTES or EDATAS, with the exception of the silicate formed using 20% added EDATAS. Inclusion of 1,3,5-trimethylbenzene (TMB) during synthesis resulted in silicates with larger pore sizes but a loss of structural order. Appreciable adsorption of copper ions from solution was observed only for the EDATAS-functionalized silicates. X-ray photoelectron spectroscopy of Cu2+-bound EDATAS-functionalized silicates revealed an Cu/N ratio of 0.15, smaller than expected for 1:1 stoichiometry of copper ions and etylenediaminetriacetic acid groups. Adsorption isotherms for Cu2+ binding to EDATAS-functionalized silicates were fit to a double-component Langmuir equation. Binding constants, but not capacity, were dependent on the amount of added EDATAS used in the synthesis and were several orders of magnitude smaller than that reported for structurally similar nonimmobilized HEDTA.

Synthetic routes to alkyl and aryl substituted dithiophosphinate salts that contain non-coordinating PPh(4)(+) counter cations are reported. In general, these compounds can be prepared via a multi-step procedure that starts with reacting secondary phosphines, i.e. HPR(2), with two equivalents of elemental S. The synthetic transformation proceeds by oxidation of the phosphine followed by insertion of S into the H-P bond. This approach was used to synthesize a series of dithiophosphinic acids that were fully characterized, namely HS(2)P(p-CF(3)C(6)H(4))(2), HS(2)P(m-CF(3)C(6)H(4))(2), HS(2)P(o-MeC(6)H(4))(2) and HS(2)P(o-MeOC(6)H(4))(2). Although the insertion step was found to be much slower than the oxidation reaction, the formation of (NH(4))S(2)PR(2) from HPSR(2) occurred rapidly upon addition of NH(4)OH. Subsequent cation exchange reactions proceeded readily with PPh(4)Cl in water, under air and at ambient conditions to provide analytically pure samples of [PPh(4)][S(2)PR(2)] (R = p-CF(3)C(6)H(4), m-CF(3)C(6)H(4), o-CF(3)C(6)H(4), o-MeC(6)H(4), o-MeOC(6)H(4), Ph, and Me, 1b-7b, respectively), which were characterized by elemental analysis, multinuclear NMR, and IR spectroscopy. In addition, S(2)PPh(2)(-) and dithiophosphinates with ortho-substituted aryl groups (3b-6b) were characterized by X-ray crystallography. As opposed to the acids, which have short P=S double bonds and long P-SH single bonds, the metric parameters for the S atoms in S(2)PR(2)(-) are equivalent. In addition, the presence of large non-coordinating PPh(4)(+) cations guard against intermolecular P-S···X interactions and ensure that the P-S bond is isolated. These S(2)PR(2)(-) anions, which can be prepared in large quantities and isolated in crystalline form, are attractive for spectroscopic and theoretical studies because the P-S interaction can be probed independently in the absence of intermolecular interactions.

Six N-substituted polybenzimidazole organosilane derivatives (-CH 2 SiMe 2 R; R ) methyl, vinyl, allyl, hexyl, phenyl, and decyl) were synthesized, and they are more soluble in common organic solvents (tetrahydrofuran and chloroform) than the parent polybenzimidazole. Our polymer modification pathway provides a straightforward synthesis that can be carried out at room temperature/pressure and give moderate yields. Solution 1 H NMR spectra of both the parent and deprotonated polybenzimidazoles are reported. On the basis of the NMR analysis in CDCl 3 , nearly all of the benzimidazole N-H positions (two ligands per repeat unit) are substituted by the organosilane moieties. Some of the modified polymers have comparable thermal properties to the parent polymer, and the average molecular weights are higher for the substituted polybenzimidazoles than the parent PBI.