If the Crown Fits: Sterically Demanding N-Heterocyclic Carbene Promotes the Formation of Au8Pt Nanoclusters.

While N-heterocyclic carbenes (NHCs) have recently been shown to be effective ligands for gold nanoclusters, very few examples of heterometallic clusters incorporating nongroup 11 metals are known. We present herein an Au-Pt NHC cluster featuring a crown-shaped [Au8Pt(NHC)8]2+ core, produced in high yield without the need for chromatographic purification. The method was largely independent of the substitution pattern of the NHC backbone; however, bulky wingtip groups were needed for clean conversion to the Au8Pt cluster. Clusters were characterized using single crystal X-ray diffraction, multinuclear nuclear magnetic resonance, electrospray ionization mass spectroscopy, and ultraviolet-visible spectroscopy, and electrochemical features of the cluster are also presented. A detailed analysis of the in-progress reaction mixture by ESI-MS supports the direct involvement of Au-H species as intermediates in cluster formation. These studies further demonstrate that NHC wingtip sterics play a key part in determining the nature of the initial cluster species, providing critical information for the generation of new NHC-stabilized nanoclusters.

Tailored Design of Mesoporous Nanospheres with High Entropic Alloy Sites for Efficient Redox Electrocatalysis.

High Entropy Alloys (HEAs) are a versatile material with unique properties, tailored for various applications. They enable pH-sensitive electrocatalytic transformations like hydrogen evolution reaction (HER) and hydrogen oxidation reactions (HOR) in alkaline media. Mesoporous nanostructures with high surface area are preferred for these electrochemical reactions, but designing mesoporous HEA sis challenging. To overcome this challenge, a low-temperature triblock copolymer-assisted wet-chemical approach is developed to produce mesoporous HEA nanospheres composed of PtPdRuMoNi systems with sufficient entropic mixing. Owing to active sites with inherent entropic effect, mesoporous features, and increased accessibility, optimized HEA nanospheres promote strong HER/HOR performance in alkaline medium. At 30 mV nominal overpotential, it exhibits a mass activity of ≈167 (HER) and 151 A gPt -1 (HOR), far exceeding commercial Pt-C electrocatalysts (34 and 48 A gPt -1) and many recently reported various alloys. The Mott-Schottky analysis reveals HEA nanospheres inherit high charge carrier density, positive flat band potential, and smaller charge transfer barrier, resulting in better activity and faster kinetics. This micelle-assisted synthetic enable the exploration of the compositional and configurational spaces of HEAs at relatively low temperature, while simultaneously facilitating the introduction of mesoporous nanostructures for a wide range of catalytic applications.

Close Stacking of Antiaromatic Ni(II) Norcorrole Originating from a Four-Electron Multicentered Bonding Interaction.

A π-conjugated molecule with one electronic spin often forms a π-stacked dimer through molecular orbital interactions between two unpaired electrons. The bonding is recognized as a multicentered two-electron interaction between the two π-conjugated molecules. Here, we disclose a multicentered bonding interaction between two antiaromatic molecules involving four electrons. We have synthesized an antiaromatic porphyrin analogue, Ni(II) bis(pentafluorophenyl)norcorrole. Its dimer adopts a face-to-face stacked structure with an extremely short stacking distance of 2.97 Å. The close stacking originates from a multicenter four-electron bonding interaction between the two molecules. The bonding electrons were experimentally observed via synchrotron X-ray diffraction analysis and corroborated by theoretical calculations. The intermolecular interaction of the molecular orbitals imparts the stacked dimer with aromatic character that is distinctly different from that of its monomer.

First-principles studies of enhanced oxygen reduction reactions on graphene- and nitrogen-doped graphene-coated platinum surfaces.

Developing innovative platinum-based electrocatalysts and enhancing their efficiency are crucial for advancing high-performance fuel cell technology. In this study, we employed DFT calculations to provide a theoretical basis for interpreting the impact of graphene coatings on various Pt surfaces on oxygen reduction reaction (ORR) catalytic activity, which are currently applied as protective layers in experiments. We comprehensively assess the geometric and electronic properties of Pt(100), Pt(110), and Pt(111) surfaces in comparison to their graphene-coated counterparts, revealing different adsorption behaviors of O2 across these surfaces. The ORR mechanisms on different Pt surfaces show distinct rate-determining steps, with Pt(111) showing the highest ORR activity, followed by Pt(110) and Pt(100). Graphene coatings play a key role in enhancing charge transfer from the surface, resulting in modifications of O2 adsorption. Despite influencing ORR kinetics, these graphene-coated surfaces demonstrate competitive catalytic activity compared to their bare counterparts. Notably, Pt(111) with a graphene coating exhibits the lowest activation energy among graphene-coated surfaces. Our calculations also suggest that the ORR can occur directly on non-defective Pt@graphene surfaces rather than being restricted to exposed Pt centers due to point defects on graphene. Furthermore, our work highlights the potential of nitrogen doping onto the Pt(111)@C surface to further enhance ORR activity. This finding positions nitrogen-doped Pt@C as a promising electrocatalyst for advancing electrochemical technologies.

Effect of porphyrin ligands on the catalytic CH4 oxidation activity of monocationic µ-nitrido-bridged iron porphyrinoid dimers by using H2O2 as an oxidant.

The µ-nitrido-bridged iron phthalocyanine homodimer is a potent molecule-based CH4 oxidation catalyst that can effectively oxidize chemically stable CH4 under mild reaction conditions in an acidic aqueous solution including an oxidant such as H2O2. The reactive intermediate is a high-valent iron-oxo species generated upon reaction with H2O2. However, a detailed comparison of the CH4 oxidation activity of the µ-nitrido-bridged iron phthalocyanine dimer with those of µ-nitrido-bridged iron porphyrinoid dimers containing one or two porphyrin ring(s) has not been yet reported, although porphyrins are the most important class of porphyrinoids. Herein, we compare the catalytic CH4 and CH3CH3 oxidation activities of a monocationic µ-nitrido-bridged iron porphyrin homodimer and a monocationic µ-nitrido-bridged heterodimer of an iron porphyrin and an iron phthalocyanine with those of a monocationic µ-nitrido-bridged iron phthalocyanine homodimer in an acidic aqueous solution containing H2O2 as an oxidant. It was demonstrated that the CH4 oxidation activities of monocationic µ-nitrido-bridged iron porphyrinoid dimers containing porphyrin ring(s) were much lower than that of a monocationic µ-nitrido-bridged iron phthalocyanine homodimer. These findings suggested that the difference in the electronic structure of the porphyrinoid rings of monocationic µ-nitrido-bridged iron porphyrinoid dimers strongly affected their catalytic light alkane oxidation activities.

Stereochemistry-Dependent Labeling of Organelles with a Near-Infrared-Emissive Phosphorus-Bridged Rhodamine Dye in Live-Cell Imaging.

The development of near-infrared (NIR) fluorophores that have both excellent chemical stability and photostability, as well as efficient cell permeability, is highly demanded. In this study, we present phospha-rhodamine (POR) dyes which display significantly improved performance for protein labeling. This is achieved by incorporating a 2-carboxy-3-benzothiophenyl group at the 9-position of the xanthene scaffold. The resulting cis and trans isomers were successfully isolated and structurally characterized using X-ray diffraction. The HaloTag ligand conjugates of the two isomers exhibited different staining abilities in live cells. While the cis isomer showed non-specific accumulation on the organelle membranes, the trans isomer selectively labeled the HaloTag-fused proteins, enabling the long-term imaging of cell division and the 5-color imaging of cell organelles. Molecular dynamics simulations of the HaloTag ligand conjugates within the lipid membrane suggested that the cis isomer is more prone to forming oligomers in the membrane. In contrast, the oligomerization of the trans isomer is effectively suppressed by its interaction with the lipid molecules. By taking advantage of the superior labeling performance of the trans isomer and its NIR-emissive properties, multi-color time-lapse super-resolution 3D imaging, namely super-resolution 5D-imaging, of the interconnected network between the endoplasmic reticulum and microtubules was achieved in living cells.

Characterizing after-hours hematology/oncology clinic calls.

BACKGROUND: After-hour calls can be resource intensive and remain a significant challenge to medical practices, though they have historically been poorly or non-reimbursable services. This study reviews after-hour calls from hematology/oncology patients at a cancer center to characterize after-hour care needs, identify care gaps, and look for opportunities to improve outpatient healthcare delivery. METHODS: This descriptive, retrospective Institutional Review Board-approved study analyzed patient calls between June 2015 to February 2021 in an academic hematology/oncology practice. Data from 500 calls were reviewed and cataloged into a database including patient demographics, clinical history, and information surrounding the call (e.g., primary reason for the call, outcome of the call). Calls were also categorized as being urgent or not from a patient or provider's perspective. RESULTS: Among 500 calls, representing 398 unique patients, the average patient was 62 years old and 52% of calls were from females. Most calls were made to report symptoms (65%), followed by calls to follow-up on labs, tests, or imaging (13%), and clarifying treatment plans (10%). Oncology patients represented 67% of calls and hematology (malignant and benign) patients represented 33%. More specifically, patients with gastrointestinal cancer (25%), hematologic malignancies (24%), and thoracic cancer (13%) represented the diagnoses with the highest call volume. CONCLUSIONS: This study explores the complexity and variety of after-hour cancer patient calls. By systematically exploring patient calls, this data can provide insight into patients' needs outside of regular clinic times and help practices develop strategies to anticipate these needs, reduce after-hour call burden, and improve overall quality of care.