Temperature-responsive poly(N-vinylcaprolactam) microgels containing encapsulated enzymes are synthesized via precipitation polymerization initiated by glucose oxidase in aqueous medium.
The substitution of pure metal particles by metal phosphides in catalysis represents a promising opportunity to lower the required metal quantity in the context of a sustainable use of metal resources. Herein we show the synthesis of palladium phosphide, Pd 3 P, supported on silica, which is tested as catalyst for the Wacker-Tsuji-oxidation of styrene to acetophenone. The synthesized catalyst is characterized by PXRD, SEM-EDX, FTIR, ICP-AES and XPS measurements. Four different reaction systems are investigated in this study including different co-catalysts and reaction media. Conversions of styrene up to 95 % with a selectivity of 73 % towards acetophenone are observed using Pd 3 P/SiO 2 as catalyst, CuCl 2 as co-catalyst and O 2 as oxidant. An enhanced selectivity up to 100 % towards acetophenone is obtained in other reaction systems. The use of Pd 3 P/SiO 2 leads to an optimized selectivity and conversion in the oxidation reaction in comparison with the purely Pd-based system Pd/ SiO 2 . These results give an insight on how the incorporation of phosphorus has a great effect on the performance of heterogeneous catalysts.
In the current work the tautomeric equilibrium between tetraphenyldiphosphoxane (Ph2P–O–PPh2, POP) and tetraphenyldiphosphine monoxide (Ph2P–P(=O)Ph2, PPO) in the absence and presence of transition metal precursors is investigated. Whereas with hard...
Herein, the synthesis of amylose‐coated, temperature‐responsive poly(N‐vinylcaprolactam) (VCL)‐based copolymer microgels by enzyme‐catalyzed grafting‐from polymerization with phosphorylase b from rabbit muscle is reported. The phosphorylase is able to recognize the oligosaccharide maltoheptaose as primer and attach glucose units from the monomer glucose‐1‐phosphate to it, thereby forming amylose chains while releasing inorganic phosphate. Therefore, to enable the phosphorylase‐catalyzed grafting‐from polymerization of glucose‐1‐phosphate from the PVCL‐based microgels, the maltoheptaose primer is covalently attached to the microgel in the first synthesis step. This is realized by adding N‐(2‐aminoethyl)methacrylamide (AEMAA) as a comonomer to the PVCL microgel to integrate primary amino groups and subsequent coupling of maltoheptaonolactone. Both the PVCL/AEMAA microgel as well as the obtained microgel–maltoheptaose construct are characterized in detail by dynamic light scattering, electrophoretic mobility measurements, IR spectroscopy, and atomic force microscopy. From the microgel–maltoheptaose construct, the grafting‐from polymerization of glucose‐1‐phosphate is performed by the addition of phosphorylase b. Atomic force microscopy images clearly demonstrate the formation of an amylose shell around the microgels. The developed amylose‐coated microgels open up promising application possibilities, for example, as colloidal scavengers, since amylose helices can serve as host molecules for inclusion of hydrophobic guest molecules.
Da Metalle wie Osmium rarer und somit teuer sind als Metalle wie Aluminium, versuchen Forscher, Katalysatoren mit geringen Metallanteilen zu entwickeln, die die gleiche katalytische Aktivität haben. Ein Ergebnis sind Einzelatomkatalysatoren.
In the current work, the rational synthesis of trinuclear copper complexes, incorporating acute bite angle POP-and PSP-type ligands, is reported. The in situ formation of POP (Ph 2 P−O−PPh 2 ) or PSP (Ph 2 P−S−PPh 2 ) ligands in the presence of a copper(I) precursor gave access to various trinuclear copper complexes of the form [Cu 3 (μ 3 -Hal) 2 (μ-PXP) 3 ]PF 6 [X = O; Hal = Cl (1), Br (2), I (3) and X = S; Hal = Cl (5), Br (6), I ( 7)]. Related iodide-containing complexes and clusters, such as [Cu 4 (μ 3 -I) 4 (Ph 2 PI) 4 ] (4) and [Cu 3 (μ 3 -I) 2 (μ-I)(μ-PSP) 2 ] (8), could also be obtained via the variation of the reaction stoichiometry. The investigation of the photo-optical properties by photo-luminescence spectroscopy has demonstrated that the phosphorescence in the visible region can be switched off through the mere change of the heteroatom in the ligand backbone (POP vs PSP ligand scaffold). Theoretical studies have been conducted to complement the experimental photo-optical data with detailed insights into the occurring electronic transitions. Consequently, this systematic study paves the way for tuning the photo-optical properties of transition metal complexes in a more rational way.
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