Probing the Electron Accepting Ability of Phosphaphenalenes.

Phosphaphenalenes, extended π conjugates with the incorporation of phosphorus, are attractive avenues towards molecular materials for the applications in organic electronics, but their electron accepting ability have not been investigated. In this study, we present systematic studies on the reductive behavior of a representative phosphaphenalene and its oxide by chemical and electrochemical methods. The chemical reduction of the phosphaphenalene by alkali metals reveals the facile P‒C bond cleavage to form phosphaphenalenide anion, which functions as a transfer block for structure modification on the phosphorus atom. In contrast, the pentavalent P-oxide reacts with one or two equivalents of elemental sodium to form stable radical anion and dianion salts, respectively.

Phosphorene Supported Single-Atom Catalysts for CO Oxidation: A Computational Study.

Single-atom catalysts (SACs) have attracted extensive attention owing to their high catalytic activity. The development of efficient SACs is crucial for applications in heterogeneous catalysis. In this article, the geometric configuration, electronic structure, stabilitiy and catalytic performance of phosphorene (Pn) supported single metal atoms (M=Ru, Rh, Pd, Ir, Pt, and Au) have been systematically investigated using density functional theory calculations and ab initio molecular dynamics simulations. The single atoms are found to occupy the hollow site of phosphorene. Among the catalysts studied, Ru-decorated phosphorene is determined to be a potential catalyst by evaluating adsorption energies of gaseous molecules. Various mechanisms including the Eley-Rideal (ER), Langmuir-Hinshelwood (LH) and trimolecular Eley-Rideal (TER) mechanisms are considered to validate the most favourable reaction pathway. Our results reveal that Ru-Pn exhibits outstanding catalytic activity toward CO oxidation reaction via TER mechanism with the corresponding rate-determining energy barrier of 0.44 eV, making it a very promising SAC for CO oxidation under mild conditions. Overall, this work may provide a new avenue for the design and fabrication of two-dimensional materials supported SACs for low-temperature CO oxidation.

The df-d Dative Bonding in a Uranium-Cobalt Heterobimetallic Complex for Efficient Nitrogen Fixation.

Single transition-metal site catalysts with s-, p-, or d-block atom anchor for nitrogen fixation have been extensively studied, and yet the studies of the f-block atom anchor are rarely reported. Thus, we investigate the feasibility of using a newly synthesized U-Co complex featuring a single CoI site coordinated by tetrakis(phophinoamide) and an UIV anchor for N2-to-NH3 conversion by theoretical modeling. We characterize the evolution of oxidation states of U and Co along the reaction pathways from ab initio density matrix renormalization group (DMRG) calculations, and we find that the variation of the Co → U dative bond is correlated with the changes of oxidation states. Both uranium and cobalt can serve as electron reservoirs to facilitate breaking the N-N bond. Our study demonstrates the viability of metal → metal dative bonds, particularly the df-d one, for the reduction of N2 to NH3, and thus, this opens up a new avenue to the rational design of efficient catalyst for nitrogen fixation.

Activity Origin of the Nickel Cluster on TiC Support for Nonoxidative Methane Conversion.

Designing an active and selective catalyst for nonoxidative conversion of methane under mild conditions is critical for natural gas utilization as a chemical feedstock. Here, we demonstrate that the origin of the selective nonoxidative conversion of methane by the titanium carbide supported nickel cluster arises from the formation of a nickel carbide site under the reaction conditions, which could stabilize the CHx intermediate to facilitate the C-C coupling, but further coking is rather limited. The reaction mechanism reveals that the C2 products can be formed via a key -CHx-CH3 intermediate. In addition, we demonstrate that boration of the nickel cluster site can improve the methane conversion toward C2 products. That higher activity and selectivity from the moderate rise in d orbital energy levels can therefore be considered as a descriptor of the catalyst effectiveness. These findings provide an understanding of the dynamic behavior of the single nickel cluster toward methane conversion to C2 products and guidance for their future rational design.

The protective effects and underlying mechanisms of dapagliflozin on diabetes-induced testicular dysfunction.

Male diabetic individuals present a marked impairment in fertility; however, knowledge regarding the pathogenic mechanisms and therapeutic strategies is unsatisfactory. The new hypoglycemic drug dapagliflozin has shown certain benefits, such as decreasing the risk of cardiovascular and renal events in patients with diabetes. Even so, until now, the effects and underlying mechanisms of dapagliflozin on diabetic male infertility have awaited clarification. Here, we found that dapagliflozin lowered blood glucose levels, alleviated seminiferous tubule destruction, and increased sperm concentrations and motility in leptin receptor-deficient diabetic db/db mice. Moreover, the glucagon-like peptide-1 receptor (GLP-1R) antagonist exendin (9-39) had no effect on glucose levels but reversed the protective effects of dapagliflozin on testicular structure and sperm quality in db/db mice. We also found that dapagliflozin inhibited the testicular apoptotic process by upregulating the expression of the antiapoptotic protein B-cell lymphoma 2 (BCL2) and X-linked inhibitor of apoptosis protein (XIAP) and inhibiting oxidative stress by enhancing the antioxidant status, including total antioxidant capacity, total superoxide dismutase (SOD) activity, and glutathione peroxidase (GPx) activity, as well as decreasing the level of 4-hydroxynonenal (4-HNE). Exendin (9-39) administration partially reversed these effects. Furthermore, dapagliflozin upregulated the glucagon-like peptide-1 (GLP-1) level in plasma and GLP-1R expression by promoting AKT8 virus oncogene cellular homolog (Akt) phosphorylation in testicular tissue. Exendin (9-39) partially inhibited Akt phosphorylation. These results suggest that dapagliflozin protects against diabetes-induced spermatogenic dysfunction via activation of the GLP-1R/phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway. Our results indicate the potential effects of dapagliflozin against diabetes-induced spermatogenic dysfunction.

A 13-million turnover-number anionic Ir-catalyst for a selective industrial route to chiral nicotine.

Developing catalysts with both useful enantioselectivities and million turnover numbers (TONs) for asymmetric hydrogenation of ketones is attractive for industrial production of high-value bioactive chiral entities but remains a challenging. Herein, we report an ultra-efficient anionic Ir-catalyst integrated with the concept of multidentate ligation for asymmetric hydrogenation of ketones. Biocatalysis-like efficacy of up to 99% ee (enantiomeric excess), 13,425,000 TON (turnover number) and 224 s-1 TOF (turnover frequency) were documented for benchmark acetophenone. Up to 1,000,000 TON and 99% ee were achieved for challenging pyridyl alkyl ketone where at most 10,000 TONs are previously reported. The anionic Ir-catalyst showed a novel preferred ONa/MH instead of NNa/MH bifunctional mechanism. A selective industrial route to enantiopure nicotine has been established using this anionic Ir-catalyst for the key asymmetric hydrogenation step at 500 kg batch scale, providing 40 tons scale of product.

Surface enrichment of Ir on the IrRu alloy for efficient and stable water oxidation catalysis in acid.

Inducing the surface enrichment of active noble metal can not only help to stabilize the catalyst but also modify the catalytic performance of the catalyst through electronic and geometric effects. Herein, we report the in situ surface enrichment of Ir on IrRu alloy during the oxygen evolution reaction (OER). The surface enrichment of Ir was probed by ex situ high-resolution transmission electron microscopy (HRTEM), in situ X-ray absorption spectroscopy (XAS), and electrochemical Cu stripping, leading to complementary characterizations of the dynamic reconstruction of the IrRu alloy during OER. Guided by the density functional theory (DFT), an IrRu alloy with low Ir content (20 wt%) was constructed, which displayed a low overpotential of only 230 mV to deliver an OER current density of 10 mA cm-2 in 0.1 M HClO4 solution and maintained stable performance for over 20 h. To investigate the practical application potential, a proton exchange membrane (PEM) water electrolyzer using the IrRu alloy as the anode catalyst was assembled, which required a low cell voltage of only 1.48 V to generate a current density of 1 A cm-2.

A general strategy for preparing pyrrolic-N4 type single-atom catalysts via pre-located isolated atoms.

Single-atom catalysts (SACs) have been applied in many fields due to their superior catalytic performance. Because of the unique properties of the single-atom-site, using the single atoms as catalysts to synthesize SACs is promising. In this work, we have successfully achieved Co1 SAC using Pt1 atoms as catalysts. More importantly, this synthesis strategy can be extended to achieve Fe and Ni SACs as well. X-ray absorption spectroscopy (XAS) results demonstrate that the achieved Fe, Co, and Ni SACs are in a M1-pyrrolic N4 (M= Fe, Co, and Ni) structure. Density functional theory (DFT) studies show that the Co(Cp)2 dissociation is enhanced by Pt1 atoms, thus leading to the formation of Co1 atoms instead of nanoparticles. These SACs are also evaluated under hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), and the nature of active sites under HER are unveiled by the operando XAS studies. These new findings extend the application fields of SACs to catalytic fabrication methodology, which is promising for the rational design of advanced SACs.

LDC000067 suppresses RANKL-induced osteoclastogenesis in vitro and prevents LPS-induced osteolysis in vivo.

Bone homeostasis requires a dynamic balance between osteogenesis and osteoclastogenesis, and osteolytic disorders are mainly attributed to aberrant osteoclastogenesis and bone resorption. Accumulating evidence has demonstrated that cyclin-dependent kinase 9 (CDK9) regulates some inflammatory diseases without affecting the cell cycle. Whether the specific inhibitor of CDK9, LDC000067 (abbreviated as LDC067), helps to prevent from osteolytic disorders has not been fully elucidated. Interestingly, this study demonstrated that LDC067 inhibited receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis and bone resorption in vitro, and suppressed the expression of osteoclast-related marker genes such as cathepsin K (CTSK), tartrate-resistant acid phosphatase (TRAP), dendrite cell-specific transmembrane protein (DC-STAMP), V-ATPase D2, calcitonin receptor (CTR) and nuclear factor of activated T cells cytoplasmic 1 (NFATc1). The bone protective effects of LDC067 can be partly explained by its suppression of nuclear factor-kappa B (NF-κB)-mediated NFATc1 activation via AKT signalling pathway. In keeping with the results obtained in vitro, inhibition of CDK9 with LDC067 was observed to delay subchondral osteolysis and substantially ameliorate LPS-induced osteolysis in murine calvaria. Collectively, these results highlight the positive effects of LDC067 in preventing osteolytic disorders and indicate that this CDK9 inhibitor may a promising therapeutic agent.

Effective formation of stable and versatile double-stranded ß-sheets templated by a hydrogen-bonded duplex.

We report herein an effective approach that is generally applicable for constructing double-stranded ß-sheets composed of tetra- and penta-peptides based on a hydrogen-bonded duplex template, regardless of their amino acid sequences and α-helical or ß-sheet propensities.