Selective reduction of CO(2) with silanes over platinum nanoparticles immobilised on a polymeric monolithic support under ambient conditions.

Here, we demonstrate the use of Pt(0) nanoparticles immobilised on a polymeric monolithic support as a ligand-free heterogeneous catalytic system for the reduction of (13) CO2 at room temperature and atmospheric pressure. The described system effectively reduces (13) CO2 with dihydrosilanes as the hydrogen source to yield a mixture of silylformates, silylacetals and methoxysilanes, which upon further hydrolysis with D2 O, produces their respective C1-type products, that is H(13) COOD, (13) CH2 (OD)2 and (13) CH3 OD. If a monohydrosilane was used as the hydrogen source, a selective reduction of (13) CO2 to a product mixture of only silylformates was observed. Addition of diethylamine to this reaction mixture results in the formation of H(13) COOH and Et2 N(13) CHO. This robust catalytic system is not only maintenance-free and simple to handle, as compared with organometallic and organocatalyst systems, but also shows 3- to 11-fold better catalytic activity and exhibits higher turnover numbers (TONs) up to 21 900 (activity=6.22 kg CO 2 gPt (-1) bar(-1) ).

Ring-opening metathesis polymerization-derived, lectin-functionalized monolithic supports for affinity separation of glycoproteins.

Lectin-functionalized monolithic columns were prepared within polyether ether ketone (PEEK) columns (150 × 4.6 mm id) via transition metal-catalyzed ring-opening metathesis polymerization of norborn-2-ene (NBE) and trimethylolpropane-tris(5-norbornene-2-carboxylate) (CL) using the first-generation Grubbs initiator RuCl2 (PCy3 )2 (CHPh) (1, Cy = cyclohexyl) in the presence of a macro- and microporogen, i.e. of 2-propanol and toluene. Postsynthesis functionalization was accomplished via in situ grafting of 2,5-dioxopyrrolidin-1-yl-bicyclo[2.2.1]hept-5-ene-2-carboxylate to the surface of the monoliths followed by reaction with α,ω-diamino-poly(ethyleneglycol). The pore structure of the poly(ethyleneglycol)- derivatized monoliths was investigated by electron microscopy and inverse-size exclusion chromatography, respectively. The amino-poly(ethyleneglycol) functionalized monolithic columns were then successfully used for the immobilization of lectin from Lens culinaris hemagglutinin. The thus prepared lectin-functionalized monoliths were applied to the affinity chromatography-based purification of glucose oxidase. The binding capacity of Lens culinaris hemagglutinin-immobilized monolithic column for glucose oxidase was found to be 2.2 mg/column.

Ring-opening metathesis polymerization-derived large-volume monolithic supports for reversed-phase and anion-exchange chromatography of biomolecules.

Preparative-scale monolithic columns up to 433.5 mL in volume were prepared via transition metal-catalyzed ring-opening metathesis polymerization (ROMP) from norborn-2-ene (NBE) and trimethylolpropane-tris(5-norbornene-2-carboxylate) (CL) using the 1(st)-generation Grubbs initiator RuCl(2)(PCy(3))(2)(CHPh) (Cy = cyclohexyl) (1) in the presence of a macro- and microporogen, i.e. of 2-propanol and toluene. To prepare large-volume monoliths, bulk polymerizations were completed within borosilicate or PEEK column formats with diameters in the range of 3 to 49 mm. The pore structure of the large-volume monoliths was investigated by electron microscopy and inverse-size exclusion chromatography (ISEC), respectively. Monolithic columns with inner diameters (I.D.s) in the range of 10-49 mm were tested for the separation of a mixture of five proteins, i.e., insulin, cytochrome C, lysozyme, conalbumin, and ß-lactoglobulin. Preparative separation of these proteins was achieved within less than 12 min in a 433.5 mL monolithic column by applying gradient elution in the RP-HPLC mode. Furthermore, weak and strong anion exchangers were prepared via post-synthesis grafting of bicyclo[2.2.1]hept-5-en-2-yl-methyl-N,N-dimethylammonium hydrochloride (4) and bicyclo[2.2.1]hept-5-en-2-ylmethyl-N,N,N-trimethylammonium iodide (5), respectively. The weak and strong anion exchangers were used for the preparative-scale separation of 5'-phosphorylated oligodeoxythymidylic acid fragments of d[pT](12-18) at pH values ranging from 5 to 9.

Functional monolithic materials for boronate-affinity chromatography via Schrock catalyst-triggered ring-opening metathesis polymerization.

Monolithic polymeric materials are prepared via ring-opening metathesis copolymerization of norborn-2-ene with 1,4,4a,5,8,8a-hexahydro-1,4,5,8-exo,endo-dimethanonaphthalene in the presence of macro- and microporogens, that is, of n-hexane and 1,2-dichloroethane, using the Schrock catalyst Mo(N-2,6-(2-Pr)(2) -C(6) H(3) )(CHCMe(2) Ph)(OCMe(3) )(2) . Functionalization of the monolithic materials is accomplished by either terminating the living metal alkylidenes with various functional aldehydes or by post-synthesis grafting with norborn-5-en-2-ylmethyl-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzoate. Finally, boronate-grafted monolithic columns (100 × 3 mm i.d.) are successfully applied to the affinity chromatographic separation of cis-diol-based biomolecules.

Ring-opening metathesis polymerization based pore-size-selective functionalization of glycidyl methacrylate based monolithic media: access to size-stable nanoparticles for ligand-free metal catalysis.

Monolithic polymeric supports have been prepared by electron-beam-triggered free-radical polymerization using a mixture of glycidyl methacrylate and trimethylolpropane triacrylate in 2-propanol, 1-dodecanol, and toluene. Under appropriate conditions, phase separation occurred, which resulted in the formation of a porous monolithic matrix that was characterized by large (convective) pores in the 30 µm range as well as pores of <600 nm. The epoxy groups in pores of >7 nm were hydrolyzed by using poly(styrenesulfonic acid) (Mw = 69,400 g mol(-1), PDI=2.4). The remaining epoxy groups inside pores of <7 nm were subjected to aminolysis with norborn-5-en-2-ylmethylamine (2) and provided covalently bound norborn-2-ene (NBE) groups inside these pores. These NBE groups were then treated with the first-generation Grubbs initiator [RuCl2 (PCy3 )2 (CHPh)]. These immobilized Ru-alkylidenes were further used for the surface modification of the small pores by a grafting approach. A series of monomers, that is, 7-oxanorborn-5-ene-2,3-dicarboxylic anhydride (3), norborn-5-ene-2,3-dicarboxylic anhydride (4), N,N-di-2-pyridyl-7-oxanorborn-5-ene-2-carboxylic amide (5), N,N-di-2-pyridylnorborn-5-ene-2-carboxamide (6), N-[2-(dimethylamino)ethyl]bicyclo[2.2.1]hept-5-ene-2-carboxamide (7), and dimethyl bicyclo[2.2.1]hept-5-en-2-ylphosphonate (8), were used for this purpose. Finally, monoliths functionalized with poly-5 graft polymers were used to permanently immobilize Pd(2+) and Pt(4+), respectively, inside the pores. After reduction, metal nanoparticles 2 nm in diameter were formed. The palladium-nanoparticle-loaded monoliths were used in both Heck- and Suzuki-type coupling reactions achieving turnover numbers of up to 167,000 and 63,000, respectively.

Comparative study on the separation behavior of monolithic columns prepared via ring-opening metathesis polymerization and via electron beam irradiation triggered free radical polymerization for proteins.

Monolithic columns have been prepared via ring-opening metathesis polymerization using different monomers and crosslinkers, i.e. norborn-2-ene, 1,4,4a,5,8,8a-hexahydro-1,4,5,8-exo,endo-dimethanonaphthalene, cyclooctene and tris(cyclooct-4-en-1-yloxy)methylsilane. 2-Propanol and toluene were used as macro- and microporogens. Alternatively, monolithic supports were realized via electron beam triggered free radical polymerization using trimethylolpropane triacrylate and ethylmethacrylate. Here, 2-propanol, 1-dodecanol and toluene were used as porogens. The three monolithic supports were structurally characterized by inverse size exclusion chromatography and investigated for their separation capabilities for a series of proteins. Separation efficiencies are discussed within the context of the different structural features of the monolithic supports and are compared to the separation data obtained on a commercial silica-based Chromolith RP-18e column.

Ring-opening metathesis polymerization-derived monolithic strong anion exchangers for the separation of 5'-phosphorylated oligodeoxythymidylic acids fragments.

Ring-opening metathesis polymerization (ROMP) derived monoliths were prepared from 5-norborn-2-enemethyl bromide (NBE-CH(2)Br) and tris(5-norborn-2-enemethoxy)methylsilane ((NBE-CH(2)O)(3)SiCH(3)) within the confines of surface-silanized borosilicate columns (100 mm × 3 mm I.D.), applying Grubbs' first generation benzylidene-type catalyst [RuCl(2)(PCy(3))(2)(CHPh)]. Two monoliths of the same recipe were converted into strong anion-exchangers applying two different approaches. Monolith I was prepared by a two-step reaction of the poly(NBE-CH(2)-Br) moieties with diethyl amine forming a weak-anion exchanger followed by reaction (quaternization) with ethyl iodide. Monolith II was prepared via a single-step reaction of the poly(NBE-CH(2)-Br) moieties with triethyl amine. The resulting monolithic anion-exchangers prepared demonstrated a good aptitude for the anion-exchange separation of single-stranded nucleic acids (ss-DNA). However, monolith II showed superior separation efficiency compared to monolith I indicated by sharper analyte peaks and better resolution values for the 5'-phosphorylated oligodeoxythymidylic acids fragments. On monolith II, the seven fragments of [d(pT)(12-18)] were baseline separated in less than 9 min. The influence of the buffer pH on the separation efficiency was studied applying a phosphate (0.05 mol/L, pH 7 and 8) and Tris-HCl buffer (0.05 mol/L, pH 9), respectively.

Electron beam triggered, free radical polymerization-derived monolithic capillary columns for high-performance liquid chromatography.

Monolithic capillary columns were prepared via electron beam triggered free radical polymerization within the confines of 0.2 and 0.1mm I.D. capillary columns using ethyl methacrylate and trimethylolpropane triacrylate as monomers as well as 2-propanol, 1-dodecanol and toluene as porogenic system. The influence of column diameter on reproducibility and separation performance was investigated. For evaluation, a protein standard consisting of five proteins in the range of 5800-66,000 g mol(-1) was used. Reproducibility was checked by determining the relative standard deviations in retention times, peak widths at half height, asymmetry and resolution. Excellent run-to-run reproducibility was found for both 0.2 and 0.1mm I.D. columns; batch-to-batch reproducibility was good for both column types. In order to enhance the non-polar character of the monolithic columns, lauryl methacrylate-based capillary columns were prepared. These were successfully used for the separation of proteins and a cytochrome c digest.

Separation behavior of electron-beam curing derived, acrylate-based monoliths.

Electron beam (EB) curing-derived monolith materials were prepared from ethyl methacrylate (EMA), trimethylolpropane triacrylate (TMPTA), 2-propanol, 1-dodecanol, and toluene within the confines of 3 mmx100 mm id glass columns, applying a total dose of 22 kGy for curing. Monolithic columns were checked for their separation behavior for selected dansylated (DNS)-amino acids as well as for cyclophilin 18. Their separation performance was compared to that of a C18-modified silica-based rigid rod (Chromoliths). In the separation of dansylated amino acids, retention times were reduced on EB-derived columns, where the peak resolution was significantly better than on a Chromolith. This finding was attributed to a larger fraction of small pores (<2.15 nm) in the EB curing-derived monoliths. Finally, EB curing-derived monoliths have been used to separate cyclophilin 18 from crude cell lysis mixtures.