Grubbs-Hoveyda type catalysts bearing a dicationic N-heterocyclic carbene for biphasic olefin metathesis reactions in ionic liquids.

The novel dicationic metathesis catalyst [(RuCl2(H2ITapMe2)(=CH-2-(2-PrO)-C6H4))(2+) (OTf(-))2] (Ru-2, H2ITapMe2 = 1,3-bis(2',6'-dimethyl-4'-trimethylammoniumphenyl)-4,5-dihydroimidazol-2-ylidene, OTf(-) = CF3SO3 (-)) based on a dicationic N-heterocyclic carbene (NHC) ligand was prepared. The reactivity was tested in ring opening metathesis polymerization (ROMP) under biphasic conditions using a nonpolar organic solvent (toluene) and the ionic liquid (IL) 1-butyl-2,3-dimethylimidazolium tetrafluoroborate [BDMIM(+)][BF4 (-)]. The structure of Ru-2 was confirmed by single crystal X-ray analysis.

First acyclic diene metathesis polymerization under biphasic conditions using a dicationic ruthenium alkylidene: access to high-molecular-weight polymers with very low ruthenium contamination.

The acyclic diene metathesis (ADMET) polymerization of 6-hydroxy-1,10-undecadiene (M1) and 6-acetoxy-1,10-undecadiene (M2) by the action of two different catalysts, i.e., the second-generation Grubbs-Hoveyda system ([RuCl2(IMesH2)(CH-2-(2-PrO-C6H4)]) (1) and the dicationic ruthenium alkylidene [Ru(DMF)3(IMesH2)(CH-2-(2-PrO-C6H4)] (2, IMesH2 = 1,3-dimesitylimidazolin-2-ylidene) is reported. Biphasic conditions using 1-butyl-2,3-dimethylimidazolium tetrafluoroborate ([BDMIM(+)BF4(-)]) and 1,2,4-trichlorobenzene (TCB) are applied. Under the chosen conditions (T = 75 °C, 20 mbar), the use of catalyst 1 results only in the formation of low-molecular-weight polymers (Mn ≤ 10,000 g mol(-1)), while catalyst 2 allows for the high yield synthesis of high-molecular-weight polymers (Mn ≤ 40,000 g mol(-1), yields ≤ 99%). Irrespective of the catalyst used, all polymers display a high trans-content (>95%). Notably, Ru-contamination of the target polymers without any additional purification is as low as 1.2 ppm with catalyst 2. Together with the high yields and high molecular weights, the low Ru-contaminations clearly illustrate the advantages of the biphasic setup.

A dicationic ruthenium alkylidene complex for continuous biphasic metathesis using monolith-supported ionic liquids.

A dicationic ruthenium-alkylidene complex [Ru(dmf)(3)(IMesH(2))(=CH-2-(2-PrO)-C(6)H(4))][(BF(4))(2)] (1; IMesH(2) =1,3-dimesitylimidazolin-2-ylidene) has been prepared and used in continuous metathesis reactions by exploiting supported ionic-liquid phase (SILP) technology. For these purposes, ring-opening metathesis polymerization (ROMP)-derived monoliths were prepared from norborn-2-ene, tris(norborn-5-ene-2-ylmethyloxy)methylsilane, and [RuCl(2)(PCy(3))(2)(CHPh)] (Cy=cyclohexyl) in the presence of 2-propanol and toluene and surface grafted with norborn-5-en-2-ylmethyl-N,N,N-trimethylammonium tetrafluoroborate ([NBE-CH(2)-NMe(3)][BF(4)]). Subsequent immobilization of the ionic liquid (IL), 1-butyl-2,3-dimethylimidazolium tetrafluoroborate ([BDMIM][BF(4)]), containing ionic catalyst 1 created the SILP catalyst. The use of a second liquid transport phase, which contained the substrate and was immiscible with the IL, allowed continuous metathesis reactions to be realized. High turnover numbers (TONs) of up to 3700 obtained in organic solvents for the ring-closing metathesis (RCM) of, for example, N,N-diallyltrifluoroacetamide, diethyl diallylmalonate, diethyl di(methallyl)malonate, tert-butyl-N,N-diallylcarbamate, N,N-diallylacetamide, diphenyldiallylsilane, and 1,7-octadiene, as well as in the self-metathesis of methyl oleate, could be further increased by using biphasic conditions with [BDMIM][BF(4)]/heptane. Under continuous SILP conditions, TONs up to 900 were observed. Due to the ionic character of the initiator, catalyst leaching into the transport phase was very low (<0.1 %). Finally, the IL can, together with decomposed catalyst, be removed from the monolithic support by flushing with methanol. Upon reloading with [BDMIM][BF(4)]/1, the recycled support material again qualified for utilization in continuous metathesis reactions.

The softer and more hydrophobic the better: influence of the side chain of polymethacrylate nanoparticles for cellular uptake.

Intracellular uptake of nanoparticles is highly interesting for labeling of cells, drug delivery, or non-viral gene delivery. In this study we have synthesized a wide variety of poly(alkyl methacrylate) nanoparticles with the same size and investigated their uptake into cells. The nanoparticles were prepared from alkylmethacrylates with different linear and branched ester chains as well as from benzylmethacrylate using the miniemulsion polymerizaiton technique. By adding a fluorescent dye as a marker, the internalization of the nanoparticles could be investigated quantitatively with flow cytometry and qualitatively with confocal laser scanning microscopy. With increasing side chain of the ester and therefore increasing hydrophobicity and at glass transition temperature (T(g)), below the incubation temperature of 37 degrees C the uptake of the nanoparticles into cells is favored.