Impurity doping has been widely used to endow semiconductor nanocrystals with novel optical, electronic, and magnetic functionalities. Here, we introduce a new family of doped NCs offering unique ...insights into the chemical mechanism of doping, as well as into the fundamental interactions between the dopant and the semiconductor host. Specifically, by elucidating the role of relative bond strengths within the precursor and the host lattice, we develop an effective approach for incorporating manganese (Mn) ions into nanocrystals of lead-halide perovskites (CsPbX3, where X = Cl, Br, or I). In a key enabling step not possible in, for example, II–VI nanocrystals, we use gentle chemical means to finely and reversibly tune the nanocrystal band gap over a wide range of energies (1.8–3.1 eV) via postsynthetic anion exchange. We observe a dramatic effect of halide identity on relative intensities of intrinsic band-edge and Mn emission bands, which we ascribe to the influence of the energy difference between the corresponding transitions on the characteristics of energy transfer between the Mn ion and the semiconductor host.
A manganese‐catalyzed regio‐ and stereoselective hydroarylation of allenes is reported. The C−H functionalization method provides access to various alkenylated indoles in excellent yields. Moreover, ...a hydroarylation/cyclization cascade involving an unexpected C−N bond cleavage and aryl shift has been developed, which provides a new synthetic approach to substituted pyrroloindolones.
Which way to go: An efficient, scalable, regio‐, and stereoselective manganese‐catalyzed C−H arylation of allenes is reported. When trisubstituted allenes are used, a C−H functionalization/C−N bond cleavage/cyclization cascade affords pyrroloindolones. Mechanistic studies suggest that a manganacycle is formed during the catalytic cycle.
The development of efficient water oxidation catalysts based on inexpensive and Earth-abundant materials is a prerequisite to enabling water splitting as a feasible source of alternative energy. In ...this work, we report the synthesis of ternary cobalt manganese phosphide nanoparticles from the solution-phase reaction of manganese and cobalt carbonyl complexes with trioctylphosphine. The CoMnP nanoparticles (ca. 5 nm in diameter) are nearly monodisperse and homogeneous in nature. These CoMnP nanoparticles are capable of catalyzing water oxidation at an overpotential of 0.33 V with a 96% Faradaic efficiency when deposited as an ink with carbon black and Nafion. A slight decrease in activity is observed after 500 cycles, which is ascribed to the etching of P into solution, as well as the oxidation of the surface of the nanoparticles. Manganese-based ternary phosphides represent a promising new system to explore for water oxidation catalysis.
The first example of a base metal (manganese) catalyzed acceptorless dehydrogenative coupling of methanol and amines to form formamides is reported herein. The novel pincer complex ...(iPr‐PNHP)Mn(H)(CO)2 catalyzes the reaction under mild conditions in the absence of any additives, bases, or hydrogen acceptors. Mechanistic insight based on the observation of an intermediate and DFT calculations is also provided.
Back to basics: An acceptorless dehydrogenative coupling of methanol and amines to form formamides that is catalyzed by a well‐defined manganese pincer complex (see scheme) is reported. Mechanistic insight based on the observation of an intermediate and density functional calculations is also provided.
Biomass-derived ethanol is an important renewable feedstock. Its conversion into high-quality biofuels is a promising route to replace fossil resources. Herein, an efficient manganese-catalyzed ...Guerbet-type condensation reaction of ethanol to form 1-butanol was explored. This is the first example of upgrading ethanol into higher alcohols using a homogeneous non-noble-metal catalyst. This process proceeded selectively in the presence of a well-defined manganese pincer complex at the parts per million (ppm) level. The developed reaction represents a sustainable synthesis of 1-butanol with excellent turnover number (>110 000) and turnover frequency (>3000 h–1). Moreover, mechanistic studies including control experiments, NMR spectroscopy, and X-ray crystallography identified the essential role of the “N–H moiety” of the manganese catalysts and the major reaction intermediates related to the catalytic cycle.
Nitrogen-doped porous hollow carbon spheres were fabricated via hydrothermal pre-carbonization and pyrolysis carbonization using yeast cell templates. After that, the MnO2 nanowires were deposited by ...the in-situ hydrothermal reaction. By controlling the reaction concentration, various MnO2 nanostructures with different morphologies and electrochemical properties were obtained. The as-prepared sample exhibited an ultrahigh specific capacitance of 255 F g-1 at a current density 1 A g-1 in 1 M Na2SO4 electrolyte. The MnO2/HCS-30 material was used as the positive electrode, and the HCS was used as the negative electrode to assemble the asymmetric supercapacitor. The maximum energy density operating at the 2.0 V voltage window is 41.4 Wh kg−1 at a power density of 500 W kg−1 and still maintains 23.0 Wh kg−1 at a power density of 7901 W kg−1. Moreover, it displayed excellent cycle stability, retained approximately 93.9% of the capacitance after 5000 cycles. This work innovatively combines biomass and energy, provides an environmentally benign strategy and new insights for the preparation of electrode materials.
An asymmetric supercapacitors based on MnO2@Biological cell template synthesized nitrogen-doped porous hollow carbon spherical composites exhibited high energy and power density and an excellent cycle stability. Display omitted
•N-doped porous hollow carbon spheres were synthesized based on yeast templates.•The MnO2 nanowires were anchored by one-step hydrothermal deposition.•The prepared composite material exhibited a unique hollow structure.•As-prepared asymmetric supercapacitors exhibited excellent capacitive behavior.
We report the hydrogenation of carbamates and urea derivatives, two of the most challenging carbonyl compounds to be hydrogenated, catalyzed for the first time by a complex of an earth-abundant ...metal. The hydrogenation reaction of these CO2-derived compounds, catalyzed by a manganese pincer complex, yields methanol in addition to amine and alcohol, which makes this methodology a sustainable alternative route for the conversion of CO2 to methanol, involving a base-metal catalyst. Moreover, the hydrogenation proceeds under mild pressure (20 bar). Our observations support a hydrogenation mechanism involving the Mn–H complex. A plausible catalytic cycle is proposed based on informative mechanistic experiments.
The first manganese‐catalyzed hydrogenation of esters to alcohols has been developed. The combination of Mn(CO)5Br with HN(CH2CH2P(Et)2)2 leads to a mixture of cationic and neutral Mn PNP pincer ...complexes, which enable the reduction of various ester substrates, including aromatic and aliphatic esters as well as diesters and lactones. Notably, related pincer complexes with isopropyl or cyclohexyl substituents showed very low activity.
A manganese‐catalyzed hydrogenation of esters to alcohols has been developed. The combination of Mn(CO)5Br with HN(CH2CH2P(Et)2)2 led to a cationic and a neutral Mn PNP pincer complex, which both enable the reduction of various aromatic and aliphatic esters as well as diesters and lactones.
A new hydrogenation catalyst based on a manganese complex of a chiral P,N,N ligand has been found to be especially active for the hydrogenation of esters down to 0.1 mol % catalyst loading, and gives ...up to 97 % ee in the hydrogenation of pro‐chiral deactivated ketones at 30–50 °C.
Non‐precious metal for valuable catalysis: A new manganese catalyst for enantioselective ketone hydrogenation has been developed (see scheme). This catalyst also hydrogenates esters at low catalyst loadings for an earth‐abundant metal system.
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