The unique architecture of α-cationic phosphanes, in which one or more positively charged groups are directly attached to the phosphorus center dramatically affects both the physicochemical properties of the corresponding ligands and their donor/acceptor properties. Specifically, the introduction of charges increase the solubility of the resulting ligand in polar media allowing the derived metal complexes to be utilized in highly polar solvents such as ionic liquids, or to be easily separated from typical organic media. On the other hand, the presence of a cationic group in close proximity to the donor position weakens the σ-donor ability of the P-atom when compared with neutral analogues, and concomitantly enhances the π-acceptor character of the resulting ligand. In this Highlight Review these aspects are overviewed, putting special emphasis on the implications for transition metal catalyzed processes. Recent developments are critically evaluated and future perspectives for this exciting area of ligand design are discussed.
Soluble organic semiconductors have been widely researched for a wide range of application scenarios, such as organic field-effect transistors (OFETs), organic light-emitting diodes and solar cells. Due to their unique characteristics and great potentials as a platform for exploiting charge transport, two-dimensional (2D) organic crystals are emerging to investigate the device physics in OFETs, which is essential for functional device applications. Here, 2D organic crystalline films are briefly introduced from the deposition to the applications in electronic devices.
Nonaqueous synthesis of magnetite particles offers great opportunities to achieve the particle size control and surface modification since potential reaction media are hugely abundant. Herein epichlorohydrin (ECH), a versatile industrial chemical, was employed as a functional solvent for the first time to directly synthesize modified Fe3O4 microspheres (Fe3O4-op-ECH) with the reduced particle size of ca. 0.25 µm and enhanced Cu2+ exchange capacity of 44.9 mg/g. The Cu2+-exchanged Fe3O4-op-ECH was demonstrated as a potential Fenton-like catalyst for wastewater treatment by catalytic degradation of metronidazole with H2O2.
Direct observation of the crystal domains of organometal halide perovskite MAPbI3 (MA: CH3NH3+) was carried out by high resolution transmission electron microscopy (HR-TEM) followed by focused ion beam processing of the sample specimen. The resulting image clearly showed that the linkage of PbI6 octahedron framework is very robust in contrast with methyl ammonium cation. The chemical bonding energy also supported this physical behavior leading to the initial stage of thermal decomposition of perovskite.
Naphtho[1,2-b]furans were synthesized via a Pd-catalyzed reaction of diazonaphthoquinones and terminal alkynes in the presence of CuI and diisopropylamine. This method was then successfully applied to the synthesis of natural product, furomollugin.
In its crystalline form, spirooxazine does not usually exhibit photochromism. However, a crystalline spherulite spirooxazine film has been found to exhibit coloration upon irradiation with a continuous ultraviolet (UV) light and decoloration under dark conditions at room temperature, thereby indicating the occurrence of photochromism. The construction of different replicable microreliefs was successfully achieved by alternately irradiating with patterned UV light and heating the film to its melting point.
The extremely hydrophobic zinc oxide micro/nanostructures with microscale bundles and nanoscale rods were obtained by sol-gel method and hydrothermal method on stainless steel surfaces. The prepared extremely hydrophobic zinc oxide films were proven to possess excellent anti-biofilm property, which may lead to some new promising applications for inhibiting biofilm formation.
In this paper, a method is presented for the preparation of a transparent thin solid film by stacking α-zirconium phosphate nanosheets (αZrPNSs), and intercalating with cationic free-base porphyrin (TMPyP) molecules at the interlayer space. The αZrPNSs staked solid films with high transparency were firstly prepared by the filtration-film transfer method of a αZrPNSs colloid suspension. Immersion of the transparent film into a mixed aqueous solution of the TMPyP and n-butylamine was found to be the most effective intercalation method. In this film, the TMPyP cations existed as monomer species.
5,17-Difunctionalized calixarenes 1a,b were found to function as low molecular-weight organic gelators. They formed organogels with a variety of organic solvents. SEM images showed 1a formed stacked structures in the xerogels. Single-crystal X-ray analysis of 1c as well as AFM, XRD, and SAXS measurements of 1a indicated that the xerogels contained lamellar structures of the calixarenes.
We theoretically studied reaction paths of Wöhler's urea synthesis using the artificial force induced reaction method and the rate constant matrix contraction method. The systematic search resulted in a reaction path network consisting of 885 local minima. The network includes not only paths giving the main product, urea, but also those leading to a byproduct, carbonic acid. The reaction path network thus provided an entire picture of the mechanism of Wöhler's urea synthesis including the reaction selectivity.
A Nafion thin film on a platinum surface is a model for a reaction center in a catalyst layer of a polymer electrolyte fuel cell (PEFC). The cross-sectional structure of a Nafion film in a humidity chamber is unveiled by neutron reflectometry using a contrast variation method. A condensed layer of Nafion molecules approximately 3 nm in thickness is found on the platinum surface, where a depletion layer of water is formed. Because a similar dense layer of Nafion was observed at the Nafion/platinum interface when the Nafion surface was in contact with bulk water in a trough, the Nafion molecules should be tightly bound to the platinum surface. This segregated layer of the composition would be an activation barrier to oxygen diffusion from air to the platinum catalyst in a PEFC cathode.
A new sesquiterpene (1) and a new natural product, β-triketone-based derivative (2), along with five known compounds (3–7) were isolated from the leaves of Rhodomyrtus tomentosa. Their structures were identified by extensive spectroscopic analysis (IR, UV, NMR, ECD, and HRESIMS). In addition, compounds 1 and 6 exhibited weak inhibitory effects on HeLa cells, and 3 showed weak anti-inflammatory activity.
Salicylate decarboxylase (Sdc, EC 18.104.22.168) from the yeast Trichosporon moniliiforme WU-0401 catalyzes the carboxylation of phenol to salicylic acid and is applicable to enzymatic Kolbe-Schmitt reaction. Based on the 3D-modeling of Sdc, we generated a Sdc mutant, K23A-Sdc, by site-directed mutagenesis for expansion of the entrance region connecting to the substrate access tunnel. K23A-Sdc catalyzed the carboxylation of o-cresol to 3-methyl salicylic acid (3-MS), whereas Sdc showed negligible and slight activity toward o-cresol and 3-MS, respectively. Simultaneously, K23A-Sdc showed approximately 5.8-fold more decarboxylation activity toward 3-MS than Sdc. These results clearly indicate that K23A-Sdc acquired novel substrate specificity by substitution of only one amino acid residue (23rd lysine residue to alanine residue), around the substrate entrance region but not at the active center of Sdc.
A one-step in-situ activation process has been adopted for the synthesis of micro and mesoporous carbon from neem leaves for use as a matrix for a sulfur cathode. The neem leaf micro and mesoporus carbon (NLMC) exhibits high surface area and also the graphitic nature of carbon. The sulfur infused NLMC-4 exhibits a high discharge capacity of 1396 mAh g−1 at a current rate of 0.1 C with promising cyclic stability (506 mAh g−1 @1C after 200 cycles). The porous structure of NLMC prevents polysulfide dissolution and increases the ion and electron mobility resulting in the superior electrochemical performance of sulfur cathode.