Ultra-stable ring-type organosilicas with click modifiable groups : application as catalytic support and HPLC packing

Organosilicas or polysilsesquioxane frameworks are attractive alternatives for commonly applied silica-based materials. Within these hybrid materials, the structural properties and robustness of inorganic supports are combined with embedded organic functionalities. Due to their resulting hydrolytic stability and functional versatility, organosilicas have successfully been applied in many fields of research. In this work, a deliberate suggestion towards an ultimate organosilica precursor in terms of versatility and stability is made. Subsequently, this new precursor is transformed into two distinctly different but highly adapted materials for further application. To serve as a catalytic support, a Periodic Mesoporous Organosilica (PMO), possessing highly uniform and ordered pores, is developed. Employing ‘click’ chemistry this material is further converted into a solid ligand able to accomodate a Ru(III)-complex. Such heterogeneous catalyst is found active in alcohol oxidation reactions performed in water at room temperature. Next to this, multiple approaches were investigated to obtain spherical and porous particles used as ultra-stable reverse-phase HPLC packing. The unprecedented stability of the organosilica at both high and low pH holds high promise for the development of new chromatographic methods. Its high-temperature stability, on the other hand, offers opportunities for extremely fast separations with a reduced amount of organic modifier

A novel Malonamide Periodic Mesoporous Organosilica (PMO) for controlled Ibuprofen release

Controlled drug release gained a sharply increasing interest over recent years. Multiple materials have been screened as possible drug carriers, ranging from biodegradable polymers to hydroxyapatite[1]. Periodic Mesoporous Organosilicas are valuable alternatives as they possess a high chemical and thermal stability combined with a biocompatible nature[2]. Furthermore, their large internal surface area permits a high drug loading. Careful selection of the organic ‘bridged’ functionality allows a controlled release with respect to external stimuli, such as pH or temperature, of the drugs which are adsorbed via weak and reversible interactions, e.g. H-bonding, ionic and hydrophobic-phobic interaction[3]. In this contribution a novel malonamide (MA-PMO) and a methyl-malonamide PMO (mMA-PMO) bearing a high amount of functionalities, capable of multiple intramolecular interactions, are developed and thoroughly characterized[4]. Subsequently, these hybrid materials are evaluated in the controlled drug release of Ibuprofen

A novel malonamide Periodic Mesoporous Organosilica (PMO) for controlled ibuprofen release

Controlled drug release gained a sharply increasing interest over recent years. Multiple materials have been screened as possible drug carriers, ranging from biodegradable polymers to hydroxyapatite[1]. Periodic Mesoporous Organosilicas are valuable alternatives as they possess a high chemical and thermal stability combined with a biocompatible nature[2]. Furthermore, their large internal surface area permits a high drug loading. Careful selection of the organic ‘bridged’ functionality allows a controlled release with respect to external stimuli, such as pH or temperature, of the drugs which are adsorbed via weak and reversible interactions, e.g. H-bonding and hydrophobic-phobic interaction[3]. In this contribution a novel malonamide (MA-PMO) and a methyl-malonamide PMO (mMA-PMO) bearing a high amount of H-bond donors and acceptors is developed and thoroughly characterised. Subsequently, these hybrid materials are evaluated in the controlled drug release of Ibuprofen

A Novel Malonamide Periodic Mesoporous Organosilica (PMO) for tuneable ibuprofen release

Incorporation of organic functionalities within porous materials is a very elegant manner to control the administration of therapeutic drugs. Delayed drug-release profile originates from weak and reversible interactions (e.g., electrostatic, hydrophobic–hydrophobic and H-bonding interaction) between the modified carrier and the drug molecule. Two new silsesquioxane PMO precursors were synthesized in a quick and facile Schotten-Baumann reaction of (3-aminopropyltriethoxy)silane and (N-methyl-3-aminopropyltrimethoxy)-silane with malonylchloride, respectively. Based on these bis(3-(triethoxysilyl)propyl)malonamide (MA) and N,N-dimethyl-N,N-bis(3-(triethoxysilyl)propyl)malonamide (mMA) precursors, an extensive range of 2D hexagonal PMOs with high functional loading was obtained by the co-condensation with tetraethyl orthosilicate (TEOS) in a typical PMO synthesis (acidic medium, P123, KCl). The materials showed good ordering up to 20 mol% of functional loading, a large surface area (up to 550 m2/g) and wide pores (∼7 nm). The malonamide-type PMOs are capable to adsorb large amounts of ibuprofen (130 mg/g) as a hydrophobic model drug. Release experiments are performed in a phosphate buffer solution at pH 7.4 and show a controlled desorption of Ibuprofen over 24 hours; a largely expanded times pan compared to mesoporous silicas. Moreover, we are able to tune the release profile by varying the content of organic bridges in the PMO pores

Influence of aqueous precursor chemistry on the growth process of epitaxial SrTiO3 buffer layers

In this Article, epitaxial thin films of SrTiO3 were prepared on single crystalline (100) LaAlO3 by an aqueous chemical solution deposition method. By using different chelating agents to stabilize the metal ions in water, the impact of the precursor chemistry on the microstructural and crystalline properties of the films was studied. Thorough investigation of the precursor by means of infrared and Raman spectroscopy as well as thermogravimetric analysis revealed that stable precursors can be obtained in which strontium ions can be either free in the solution or stabilized by one of the chelating agents. This stabilization of strontium ions appeared to be essential in order to obtain single phase SrTiO3 films. Precursors in which Sr2+ remained as free ions showed SrO microcrystal segregation. Precursors in which both metal ions were stabilized gave rise to strongly textured, dense, and terraced SrTiO3 films, allowing subsequent deposition of YBa2Cu3O7-delta with superior superconducting performances

One-pot preparation of Ni-Cu nanoparticles supported on γ-Al2O3 as selective and stable catalyst for the Guerbet reaction of 1-octanol

This paper reports on the "in-situ" preparation deposition and reduction of Ni-Cu nanoparticles (NPs) on gamma-Al2O3 as support, using a green and elegant one pot synthesis approach. Pristine and supported Ni-Cu NPs were evaluated as (de)hydrogenation catalysts for the Guerbet reaction of 1-octanol and compared with a classic impregnated and "ex-situ" reduced NiCu on gamma-Al2O3 catalyst. XRD reavealed that the degree of Ni-Cu nano alloying was insignificant in the one pot preparation method, resulting in Ni-Cu nanocomposites, while the degree of nano alloying was resp. low and very high in the pristine nanoparticles (NPs) and the classic impregnated catalyst. The degree of reduction was very similar for both the in situ and ex situ reduction treatments of the supported catalysts as demonstrated by H-2 chemisorption. The "in-situ" prepared supported NiCu NPs showed an enhanced kinetics when compared to the unsupported pristine Ni-Cu NPs, showing a beneficial effect of the metal support interaction, however the classic impregnated catalyst showed overall the best kinetics, selectivity and stability for the Guerbet reaction of 1-octanol

Heterogeneous Ru(III) oxidation catalysts via 'click' bidentate ligands on a periodic mesoporous organosilica support

A 100% monoallyl ring-type Periodic Mesoporous Organosilica (PMO) is prepared as a novel, versatile and exceptionally stable catalytic support with a high internal surface area and 5.0 nm pores. Thiol-ene 'click' chemistry allows straightforward attachment of bifunctional thiols (-NH2, -OH, -SH) which, exploiting the thioether functionality formed, give rise to 'solid' bidentate ligands. [Ru(acac)(2)(CH3CN)(2)]PF6 is attached and complex formation on the solid is studied via density functional theory. All resulting solid catalysts show high activity and selectivity in alcohol oxidation reactions performed in green conditions (25 degrees C/water). The PMO catalysts do not leach Ru during reaction and are thus easily recuperated and re-used for several runs. Furthermore, oxidation of poorly water-soluble (+/-)-menthol illustrates the benefits of using hydrophobic PMOs as catalytic supports