Revisiting the phosphonium salt chemistry for P-doped carbon synthesis: toward high phosphorus contents and beyond the phosphate environment.

The introduction of phosphorus and nitrogen atoms in carbo-catalysts is a common way to tune the electronic density, and thereby the reactivity, of the material, as well as to introduce surface reactive sites. Numerous environments are reported for the N atoms, but the P-doping chemistry is less explored and focuses on surface POx groups. A one-step synthesis of P/N-doped carbonaceous materials is presented here, using affordable and industrially available urea and tetrakis(hydroxymethyl)phosphonium chloride (THPC) as the N and P sources, respectively. In contrast to most of the synthetic pathways toward P-doped carbonaceous materials, the THPC precursor only displays P-C bonds along the carbon backbone. This resulted in unusual phosphorus environments for the materials obtained from direct thermal treatment of THPC-urea, presumably of type C-P-N according to 31P NMR and XPS. Alternatively, the in situ polymerization and calcination of the precursors were run in calcium chloride hydrate, used as a combined reaction medium and porogen agent. Following this salt-templating strategy led to particularly high phosphorus contents (up to 18 wt%), associated with porosities up to 600 m2 g-1. The so-formed P/N-doped porous materials were employed as metal-free catalysts for the mild oxidative dehydrogenation of N-heterocycles to N-heteroarenes at room temperature and in air.

Phosphine-Enhanced Semi-Hydrogenation of Phenylacetylene by Cobalt Phosphide Nano-Urchins.

Transition metal phosphides are promising, selective, and air-stable nanocatalysts for hydrogenation reactions. However, they often require fairly high temperatures and H2 pressures to provide quantitative conversions. This work reports the positive effect of phosphine additives on the activity of cobalt phosphide nano-urchins for the semi-hydrogenation of phenylacetylene. While the nanocatalyst's activity was low under mild conditions (7 bar of H2 , 100 °C), the addition of a catalytic amount of phosphine remarkably increased the conversion, e. g., from 13 % to 98 % in the case of Pn Bu3 . The heterogeneous nature of the catalyst was confirmed by negative supernatant activity tests. The catalyst integrity was carefully verified by post-mortem analyses (TEM, XPS, and liquid 31 P NMR). A stereo-electronic map was proposed to rationalize the activity enhancement provided over a selection of nine phosphines: the strongest effect was observed for low to moderately hindered phosphines, associated with strong electron donor abilities. A threshold in phosphine stoichiometry was revealed for the enhancement of activity to occur, which was related to the ratio of phosphine to surface cobalt atoms.

Frequency-encoded two-photon excited fluorescence microscopy.

Two-photon excited fluorescence (2PEF) microscopy is the most popular non-linear imaging method of biomedical samples. State-of-the art 2PEF microscopes use multiple detectors and spectral filter sets to discriminate different fluorophores based on their distinct emission behavior (emission discrimination). One drawback of 2PEF is that fluorescence photons outside the filter transmission range are inherently lost, thereby reducing the imaging efficiency and speed. Furthermore, emission discrimination of different fluorophores may fail if their emission profiles are too similar. Here, we present an alternative 2PEF method that discriminates fluorophores based on their excitation spectra (excitation discrimination). For excitation we use two lasers of different wavelengths (ω1, ω2) resulting in excitation energies at 2ω1, 2ω2, and the mixing energy ω1+ω2. Both lasers are frequency encoded (FE) by an intensity modulation at distinct frequencies while all 2PEF emission is collected on a single detector. The signal is fed into a lock-in-amplifier and demodulated at various frequencies simultaneously. A customized nonnegative matrix factorization (NNMF) then generates fluorescence images that are free of cross talk. Combining FE-2PEF with multiple detectors has the potential to enable the simultaneous imaging of an unprecedented number of fluorophores.

Phosphine-Catalyzed Activation of Phenylsilane for Benzaldehyde Reduction.

Hydrosilylation reactions are commonly used for the reduction of carbonyl bonds in fine chemistry, catalyzed by transition metal complexes. The current challenge is to expand the scope of metal-free alternative catalysts, including in particular organocatalysts. This work describes the organocatalyzed hydrosilylation of benzaldehyde with a phosphine, introduced at 10 mol%, and phenylsilane at room temperature. The activation of phenylsilane was highly dependent on the physical properties of the solvent such as the polarity, and the highest conversions were obtained in acetonitrile and propylene carbonate with yields of 46 % and 97 %, respectively. The best results of the screening over 13 phosphines and phosphites were obtained with linear trialkylphoshines (PMe3 , Pn Bu3 , POct3 ), indicating the importance of their nucleophilicity, with yields of 88 %, 46 % and 56 %, respectively. With the help of heteronuclear 1 H-29 Si NMR spectroscopy, the products of the hydrosilylation (PhSiH3-n (OBn)n ) were identified, allowing a monitoring of the concentration in the different species, and thereby of their reactivity. The reaction displayed an induction period of ca. 60 min, followed by the sequential hydrosilylations presenting various reaction rates. In agreement with the formation of partial charges in the intermediate state, we propose a mechanism based on a hypervalent silicon center via the Lewis base activation of the silicon Lewis acid.

Percutaneous Axillary Artery Puncture: An Efficient Approach for Upper Extremity Access.

BACKGROUND: The aim was to analyze the anatomic feasibility of the percutaneous axillary access (PAXA) using cadaverous models and then to analyze the complications associated with PAXA during Fenestrated or Branched Endovascular Aneurysm Repair (F/BEVAR) procedures. METHODS: Cadaverous models were used to analyze axillary pedicle after a PAXA on an initial anatomical investigation. A subclavian approach was performed after puncture to assess the injuries caused by the needle. Then, in an observational study, patients who underwent F/BEVAR using a PAXA between July 2019 and July 2021 were included. PAXA-related events and complications were monitored. RESULTS: Eleven dissections were performed on cadavers. The axillary vein was injured twice (18.2%); the puncture site on the axillary artery was found on the arterial proximal part, behind the clavicle. Fifty-three patients underwent a F/BEVAR using a PAXA. The mean (SD) age of patients was 74.5 (9.7) years. Most indications for endovascular repair were para-renal aneurysms (66%). Two Proglide® closure devices served to close arterial access in all procedures. Adjunct balloon inflation was used in 19 (35.8%) patients. There were 5 (9.4%) PAXA-related events included preoperative blush in 2 (3.8%) patients, axillary artery dissection in 2 (3.8%), and 1 (1.9%) axillary artery stenosis. Five patients (9.4%) had a postoperative axillary hematoma without need for additional surgical procedure. No PAXA-related complication was found after discharge (mean [SD] 11.7 [7.4] months following surgery). CONCLUSIONS: Percutaneous axillary artery access was an efficient upper extremity access and associated with a low rate of PAXA-related events.

Interdisciplinary Round-Robin Test on Molecular Spectroscopy of the U(VI) Acetate System.

A comprehensive molecular analysis of a simple aqueous complexing system-U(VI) acetate-selected to be independently investigated by various spectroscopic (vibrational, luminescence, X-ray absorption, and nuclear magnetic resonance spectroscopy) and quantum chemical methods was achieved by an international round-robin test (RRT). Twenty laboratories from six different countries with a focus on actinide or geochemical research participated and contributed to this scientific endeavor. The outcomes of this RRT were considered on two levels of complexity: first, within each technical discipline, conformities as well as discrepancies of the results and their sources were evaluated. The raw data from the different experimental approaches were found to be generally consistent. In particular, for complex setups such as accelerator-based X-ray absorption spectroscopy, the agreement between the raw data was high. By contrast, luminescence spectroscopic data turned out to be strongly related to the chosen acquisition parameters. Second, the potentials and limitations of coupling various spectroscopic and theoretical approaches for the comprehensive study of actinide molecular complexes were assessed. Previous spectroscopic data from the literature were revised and the benchmark data on the U(VI) acetate system provided an unambiguous molecular interpretation based on the correlation of spectroscopic and theoretical results. The multimethodologic approach and the conclusions drawn address not only important aspects of actinide spectroscopy but particularly general aspects of modern molecular analytical chemistry.