Ultrasound-Responsive Aligned Piezoelectric Nanofibers Derived Hydrogel Conduits for Peripheral Nerve Regeneration.

Nerve guidance conduits (NGCs) have been considered as promising treatment strategy and frontier trend for peripheral nerve regeneration; while their therapeutic outcomes are limited by the lack of controllable drug delivery and available physicochemical cues. Herein, we propose novel aligned piezoelectric nanofibers derived hydrogel NGCs with ultrasound (US)-triggered electrical stimulation (ES) and controllable drug release for repairing peripheral nerve injury. The inner layer of the NGCs was the barium titanate piezoelectric nanoparticles (BTNPs)-doped polyvinylidene fluoride-trifluoroethylene [BTNPs/P(VDF-TrFE)] electrospinning nanofibers with improved piezoelectricity and aligned orientation. The outer side of the NGCs was the thermoresponsive poly(N-isopropylacrylamide) (pNIPAM) hybrid hydrogel with bioactive drug encapsulation. Such NGCs could not only induce neuronal oriented extension and promote neurite outgrowth with US-triggered wireless ES, but also realize the controllable nerve growth factor (NGF) release with the hydrogel shrinkage under US-triggered heating. Thus, the NGC could positively accelerate the functional recovery and nerve axonal regeneration of rat models with long sciatic nerve defects. We believe that the proposed US-responsive aligned piezoelectric nanofibers derived hydrogel NGCs will find important applications in clinic neural tissue engineering. This article is protected by copyright. All rights reserved.

Endovascular thrombectomy in wake-up stroke guided by arterial spin-labeling and fluid-attenuated inversion recovery versus diffusion-weighted imaging mismatch on MRI.

OBJECTIVE: This purpose of this study is to investigate the effectiveness and safety of utilizing the arterial spin-labeling (ASL) combined with diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) combined with DWI double mismatch in the endovascular treatment of patients diagnosed with wake-up stroke (WUS). METHODS: In this single-center trial, patients diagnosed with WUS underwent thrombectomy if acute ischemic lesions were observed on DWI indicating large precerebral circulation occlusion. Patients with no significant parenchymal hypersignal on FLAIR and ASL imaging showing a hypoperfusion tissue to infarct core volume ratio of at least 1.2 were included. The participants were divided into groups receiving endovascular thrombectomy plus medical therapy or medical therapy alone, based on their subjective preference. Functional outcomes were assessed using the ordinal score on the modified Rankin scale (mRs) at 90 days, along with the rate of functional independence. RESULTS: In this study, a total of 77 patients were included, comprising 38 patients in the endovascular therapy group and 39 patients in the medical therapy group. The endovascular therapy group exhibited more favorable changes in the distribution of functional prognosis measured by mRs at 90 days, compared to the medical therapy group (adjusted common odds ratio, 3.25; 95% CI, 1.03 to 10.26; P < 0.01). Additionally, the endovascular therapy group had a higher proportion of patients achieving functional independence (odds ratio, 4.0; 95% CI, 1.36 to 11.81; P < 0.01). Importantly, there were no significant differences observed in the incidence of intracranial hemorrhage or mortality rates between the two groups. CONCLUSION: Guided by the ASL-DWI and FLAIR-DWI double mismatch, endovascular thrombectomy combined with standard medical treatment appears to yield superior functional outcomes in patients with WUS and large vessel occlusion compared to standard medical treatment alone.

Geographic and ethnicity variation in the prevalence of middle-aged and elderly adult obesity in China in 2020.

AIM: The objective of this study is to evaluate the mean body mass index (BMI), general obesity and abdominal obesity in adults aged ≥40 years residing in China in 2020, and to analyse variations in these factors across different geographic areas and subpopulations. METHODS: We utilized data from the National Stroke High-Risk Population Screening programme to calculate and compare the mean BMI and prevalence of obesity across various demographics, including sex, age, urban-rural locality, geographical region (province) and ethnicity status. RESULTS: In our study, we found that the standardized mean BMI level was 24.65 kg/m2 [95% confidence interval (CI): 24.50-22.84] in men and 24.31 kg/m2 (95% CI: 24.15-24.45) in women. Using the criteria from China, we found that the standardized prevalence of general obesity and abdominal obesity was 13.13% (95% CI: 13.05-13.21%) and 33.03% (95 CI: 32.92-33.14%), respectively. Our study also identified significant effects of age, sex, urban-rural locality, province and ethnicity status on the prevalence of obesity. Overall, our study estimated that in 2020, approximately 91.1 million adults aged ≥40 years in China were obese (46.5 million men and 44.6 million women), while 229.2 million adults (110.4 million men and 118.8 million women) were diagnosed with abdominal obesity. CONCLUSION: Our research has revealed compelling new evidence about the obesity epidemic among Chinese adults aged ≥40 years, particularly at the provincial and ethnic levels. As a result, more targeted and effective prevention strategies should be developed to alleviate the burden of obesity.

Mitophagy in Alzheimer's Disease: A Bibliometric Analysis from 2007 to 2022.

Background: The investigation of mitophagy in Alzheimer's disease (AD) remains relatively underexplored in bibliometric analysis. Objective: To delve into the progress of mitophagy, offering a comprehensive overview of research trends and frontiers for researchers. Methods: Basic bibliometric information, targets, and target-drug-clinical trial-disease extracted from publications identified in the Web of Science Core Collection from 2007 to 2022 were assessed using bibliometric software. Results: The study encompassed 5,146 publications, displaying a consistent 16-year upward trajectory. The United States emerged as the foremost contributor in publications, with the Journal of Alzheimer's Disease being the most prolific journal. P. Hemachandra Reddy, George Perry, and Xiongwei Zhu are the top 3 most prolific authors. PINK1 and Parkin exhibited an upward trend in the last 6 years. Keywords (e.g., insulin, aging, epilepsy, tauopathy, and mitochondrial quality control) have recently emerged as focal points of interest within the past 3 years. "Mitochondrial dysfunction" is among the top terms in disease clustering. The top 10 drugs/molecules (e.g., curcumin, insulin, and melatonin) were summarized, accompanied by their clinical trials and related targets. Conclusions: This study presents a comprehensive overview of the mitophagy research landscape in AD over the past 16 years, underscoring mitophagy as an emerging molecular mechanism and a crucial focal point for potential drug in AD. This study pioneers the inclusion of targets and their correlations with drugs, clinical trials, and diseases in bibliometric analysis, providing valuable insights and inspiration for scholars and readers of JADR interested in understanding the potential mechanisms and clinical trials in AD.

China Trends in Physical Inactivity from 2013 to 2019: An Analysis of 4.23 Million Participants.

INTRODUCTION: This study aimed to evaluate recent trends in physical inactivity prevalence by sociodemographic characteristics and the province of China's residence between 2013 and 2019. METHODS: The study included 4,229,616 participants 40 yr or older from 414 geographically defined localities in China during the 7-yr period. Self-reported total physical inactivity was collected to determine the standardized prevalence of physical inactivity. Logistic regression analysis was used to examine the association between physical inactivity and stroke risk, obtaining odds ratios (OR) and 95% confidence intervals (CI). RESULTS: Results showed that the standardized prevalence of physical inactivity increased from 22.12% (95% CI = 21.99%-22.45%) in 2013 to 28.79% (95% CI = 28.48%-29.19%) in 2019, with an absolute difference of 6.67% (95% CI = 6.15% to 7.16%) and a yearly increase rate of 5.03% (95% CI = 4.85% to 5.21%). In 2019, physical inactivity was higher in female and rural participants (female = 29.55%, rural = 29.46%) than in male and urban participants (male = 28.03%, urban = 28.26%). The prevalence of physical inactivity also varied by race/ethnic groups, with the highest prevalence observed among Uyghur (47.21%) and the lowest among Yizu (14.84%). Additionally, the prevalence of physical inactivity differed by province, ranging from 14.44% in Beijing to 50.09% in Tianjin in 2019. Multivariate analyses showed that physical inactivity was associated with a higher risk of stroke (OR = 1.17, 95% CI = 1.12-1.21, P < 0.001). CONCLUSIONS: In conclusion, our study found an overall increase in physical inactivity prevalence among Chinese adults ≥40 yr old from 2013 to 2019, with significant variation across regions, sex, ages, and race/ethnic groups.

miR-218-5p and miR-320a-5p as Biomarkers for Brain Disorders: Focus on the Major Depressive Disorder and Parkinson's Disease.

Depression is one of the early and most persistent non-motor symptoms of Parkinson's disease (PD), which remains ignored, resulting in the underdiagnosis of PD. Unfortunately, scarce studies and the non-availability of diagnostic strategies cause countless complications, highlighting the need for appropriate diagnostic biomarkers. Recently, brain-enriched miRNAs regulating vital neurological functions have been proposed as potent biomarkers for therapeutic strategies. Therefore, the present study is aimed to identify the brain-enriched miR-218-5p and miR-320-5p in the serum of the Chinese depressed PD patients (n = 51) than healthy controls (n = 51) to identify their potency as biomarkers. For this purpose, depressive PD patients were recruited based on HAMA and HAMD scores and miR-218-5p and miR-320-5p and IL-6, and S100B levels were analyzed using real-time PCR (qRT-PCR) and ELISA assay, respectively. In silico analysis was performed to identify key biological pathways and hub genes involved in the psychopathology of depression in PD. Here, we found significantly downregulated miR-218-5p and miR-320-5p following higher levels of IL-6 and S100B in depressed PD patients than in control (p < 0.05). The correlation analysis revealed that both miRNAs were negatively correlated with HAMA and HAMD, and IL-6 scores, along with a positive correlation with PD duration and LEDD medication. ROC analysis showed AUC above 75% in both miRNAs in depressed PD patients, and in silico analysis revealed that both miRNA's targets regulate key neurological pathways such as axon guidance, dopaminergic synapse, and circadian rhythm. Additional analysis revealed PIK3R1, ATRX, BM1, PCDHA10, XRCC5, PPP1CB, MLLT3, CBL, PCDHA4, PLCG1, YWHAZ, CDH2, AGO3, PCDHA3, and PCDHA11 as hub-genes in PPI network. In summary, our findings show that miR-218-5p and miR-320-5p can be utilized as future biomarkers for depression in PD patients, which may aid in the early diagnosis and treatment of Parkinson's disease.

Intravenous Thrombolysis or Medical Management for Minor Strokes.

OBJECTIVE: To evaluate the outcomes of acute ischemic stroke patients with minor deficits treated with either intravenous thrombolysis (IVT) or routine medical management (MM). METHODS: The study included patients with acute ischemic stroke and National Institutes of Health Stroke Scale (NIHSS) scores of 5 or less who were treated with IVT within 4.5 hours from symptom onset and were classified as the IVT group. The MM group consisted of an equal number of patients with minor strokes, matched for sex, age, and severity, who did not receive thrombolysis. Data on patient information were collected for both groups. RESULTS: A total of 26,236 patients were included in this study (13,208 in IVT and 13,208 in MM). Of these patients, 67.9% were men, and the mean age was 67.1 years (standard deviation: 10.9). At 3 months, the IVT group had a higher rate of stroke-independent outcome (Rankin Scale score of 0-2) compared with the MM group (IVT vs. MM: 91.6 vs. 88.6%, absolute difference: 2.5%, 95% confidence interval [CI]: 1.6-3.4%, p = 0.008; adjusted hazard ratio [HR]: 1.2, 95% CI: 1.1-1.4, p = 0.003). Furthermore, there was no significant difference in 3-month mortality rates between the IVT and MM groups (IVT vs. MM: 2.1 vs. 2.5%, absolute difference: -0.6%, 95% CI: -1.1 to 0.3%, p = 0.11; adjusted HR: 0.9, 95% CI: 0.8-1.2, p = 0.09). CONCLUSION: Compared with MM, IVT does not reduce mortality in minor ischemic stroke but improves functional outcomes in minor stroke with an NIHSS score of 3 to 5.

Impact of the COVID-19 pandemic lockdown on hospitalizations for cerebrovascular disease and related in-hospital mortality in China: A nationwide observational study.

BACKGROUND AND PURPOSE: The aim of this nationwide study was to assess the impact of the COVID-19 pandemic on cerebrovascular disease hospitalization rates, out-of-pocket rates, and in-hospital case fatality rates. METHODS: All hospitalizations for cerebrovascular disease from 1599 hospitals from 2019 to 2020 were selected using the International Classification of Diseases, 10th revision, in the Hospital Quality Monitoring System (HQMS). We defined 2019 as the pre-pandemic group and 2020 as the post-pandemic group. Multivariate analyses were done to assess the association between the pandemic and patient outcomes and out-of-pocket rate with odds ratios (OR) and 95% CIs presented. RESULTS: In total, 9 640 788 patients with the cerebrovascular disease were recruited (mean age was 65.7[SE.0.004] years, and 55.7% were male), and data is available for 5145358 patients in 2019 (pre-epidemic) and 4495430 patients in 2020(post-pandemic), indicating a 12.6% decrease. Out-of-pocket rate increase of 9.3% (2020 vs 2019: 34.1%% vs 31.2% [absolute difference, 2.9% {95% CI, 1.3% to 4.5%}, odd ratio {OR}, 1.1{95% CI, 1.0 to 1.1}]. The epidemic has led to an 18.0% increase in in-hospital mortality (2020 vs 2019: 1.1%% vs 0.9% [absolute difference, 0.2% {95% CI, 0.1% to 0.2%}, odd ratio {OR}, 1.1{95% CI, 1.1 to 1.2}]. The epidemic has led to significantly increased in-hospital mortality for patients with stroke but had no significant impact on other cerebrovascular diseases. CONCLUSIONS: During the COVID-19 pandemic lockdown, patients hospitalized for stroke fell by 12.6%, and there were substantial increases in out-of-pocket rates (9.3%) and in-hospital case fatality rates (18.0%).

Network localization of transient global amnesia beyond the hippocampus.

BACKGROUND: Transient global amnesia is common in the older adult, but the cause and mechanism remain unclear. Focal brain lesions allow for causal links between the lesion location and resulting symptoms, and we based on the reported TGA-causing lesions and used lesion network mapping to explore the causal neuroanatomical substrate of TGA. METHODS: Fifty-one cases of transient global amnesias with DWI lesions from the literature were identified, and clinical data were extracted and analyzed. Next, we mapped each lesion volume onto a reference brain and computed the network of regions functionally connected to each lesion location using a large normative connectome dataset. RESULTS: Lesions primarily occurred in the hippocampus, and in addition to the hippocampus, there are also other locations of TGA-causing lesions such as the cingulate gyrus, anterior thalamic nucleus (ATN), putamen, caudate nucleus, corpus callosum, fornix. More than 90% of TGA-causing lesions inside the hippocampus were functionally connected with the default mode network (DMN). CONCLUSION: Structural abnormality in the hippocampus was the most consistently reported in TGA, and besides the hippocampus, lesions occurring at several other brain locations also could cause TGA. The DMN may also be involved in the pathophysiology of TGA. According to the clinical and neuroimaging characteristics, TGA may be a syndrome with multiple causes and cannot be treated simply as a subtype of TIA.

Positive association between omega-3/6 polyunsaturated fatty acids and idiopathic normal pressure hydrocephalus: a mendelian randomization study.

Background: Idiopathic normal pressure hydrocephalus (iNPH) is a common disease among the elderly, which brings great harm to the health of patients and imposes a huge economic burden on the healthcare system. Research has shown that it is possible to prevent iNPH through nutritional and dietary interventions. Intake of omega-3 and omega-6 polyunsaturated fatty acids (PUFAs) can reduce the risk of many diseases. In this study, we aimed to explore the association between omega-3/6 PUFAs and iNPH. Methods: We conducted a two-sample Mendelian randomization (MR) study using summary data from publicly available genome-wide association studies (GWAS) to evaluate the potential impact of omega-3 and omega-6 PUFAs on the risk of iNPH in European populations. Inverse variance weighting was used as the main method for MR analysis, with Wald ratio, weighted median, MR-Egger, simple mode, and weighted mode as supplementary methods. In addition, we performed a series of instrument variable strength evaluations and sensitivity analyses to test the reliability of the study results. Finally, we also conducted a linkage disequilibrium score regression (LDSC) analysis to assess the genetic correlation and distinguish between causal associations and shared genetic variants between PUFAs and iNPH. Results: One SD increase in genetically predicted levels of total omega-3 PUFAs (OR: 0.748; 95% CI: 0.597-0.937; p = 0.012; IVW), DHA (OR: 0.709; 95% CI: 0.532-0.945; p = 0.019; IVW), ALA (OR: 0.001; 95% CI: 1.17E-06-0.423; p = 0.026; Wald ratio), and DHA (OR: 0.709; 95% CI: 0.532-0.945; p = 0.019; IVW) were associated with a reduced iNPH risk. LDSC did not reveal any significant genetic correlations. Conclusion: Higher genetically predicted levels of total omega-3 PUFAs, ALA, DHA, and DPA are associated with a reduced risk of iNPH. These findings have important implications for preventing iNPH and future nutritional guidance.

A New Nano Adjuvant of PF3 Used for an Enhanced Hepatitis B Vaccine.

Recombinant protein vaccines, with highly pure ingredients and good safety, are gradually replacing some attenuated and inactivated vaccines in clinical practice. However, since their low immunogenicity of the recombinant proteins, adjuvants are often needed to enhance immune response after vaccination. Aluminum adjuvant has been widely used in some vaccines for decades, it can induce strong humoral immunity, but the deficiency of cellular immunity limits its application for some vaccines. Therefore, it is urgently needed to develop novel adjuvant to increase not only humoral but also cellular immune response. To address this, we designed and prepared a new nano adjuvant (PF3) through microfluidization by the combination of saponin (Ginsenoside Rg1) and oil-in-water nano emulsion (NE) in the present study. As compared to aluminum adjuvant, PF3 had stronger humoral and cellular immune induction effect because of high cellular uptake and activization of immune response pathways. Furthermore, PF3 showed better immune enhancement and acceptable biosafety equivalent to that of aluminum adjuvant. In addition, no obvious changes of PF3 were observed in size and zeta potential after 12 weeks storage at 4 and 37°C, demonstrating its high stability in vitro. This study provided an adjuvant platform to replace traditional aluminum adjuvant in design of recombinant vaccines.

Experiment and Theory Clarify: Sc+ Receives One Oxygen Atom from SO2 to Form ScO+ , which Proves to be a Catalyst for the Hidden Oxygen-Exchange with SO2.

Using Fourier-transform ion cyclotron resonance mass spectrometry, it was experimentally determined that Sc+ in the highly diluted gas phase reacts with SO2 to form ScO+ and SO. By 18 O labeling, ScO+ was shown to play the role of a catalyst when further reacting with SO2 in a Mars-van Krevelen-like (MvK) oxygen exchange process, where a solid catalyst actively reacts with the substrate but emerges apparently unchanged at the end of the cycle. High-level quantum chemical calculations confirmed that the multi-step process to form ScO+ and SO is exoergic and that all intermediates and transition states in between are located energetically below the entrance level. The reaction starts from the triplet surface; although three spin-crossing points with minimal energy have been identified by computational means, there is no evidence that a two-state scenario is involved in the course of the reaction, by which the reactants could switch from the triplet to the singlet surface and back. Pivotal to the oxygen exchange reaction of ScO+ with SO2 is the occurrence of a highly symmetric four-membered cyclic intermediate by which two oxygen atoms become equivalent.

The association between restless leg syndrome and anxiety in Parkinson's disease: a case-control study.

OBJECTIVE: To shed light on the association between restless leg syndrome (RLS) and anxiety in Parkinson's disease (PD) population. METHODS: This was a case-control study including 129 PD participants with and without anxiety who presented to the Aerospace Center Hospital in Beijing, China. Anxiety was evaluated by using the Beck Anxiety Index score. RLS was assessed using the minimal diagnostic criteria of the International Restless Legs Study Group and RLS symptom frequency and treatment. We then examined the relationship between RLS and anxiety by logistic regression models and subgroup as well as interaction analyses. RESULTS: The proportion of RLS in PD with anxiety was significantly higher in the PD without anxiety (p < 0.001). The multivariate logistic regression models indicated that PD participants with RLS had a 5.98-fold higher risk of anxiety in PD than those without RLS (OR, 6.98; 95% CI, 2.77-17.59). Subgroup analyses indicated that PD with RLS tended to be associated with a greater risk of anxiety in all stratified subgroups (adjusted ORs >1). Furthermore, the interaction analyses revealed no interactive role in the association between RLS and anxiety. CONCLUSIONS: The present case-control study suggests that RLS is an independent risk factor for anxiety in PD patients. Early attention and targeted treatment for RLS may be necessary for mood management in PD. Larger prospective cohort studies are wanted to validate these findings.

Revisiting the Intriguing Electronic Features of the BeOBeC Carbyne and Some Isomers: A Quantum-Chemical Assessment.

Extensive high-level quantum-chemical calculations reveal that the rod-shaped molecule BeOBeC, which was recently generated in matrix experiments, exists in two nearly isoenergetic states, the 5 Σ quintet (5 6) and the 3 Σ triplet (3 6). Their IR features are hardly distinguishable at finite temperature. The major difference concerns the mode of spin coupling between the terminal beryllium and carbon atoms. Further, the ground-state potential-energy surface of the [2Be,C,O] system at 4 K is presented and differences between the photochemical and thermal behaviors are highlighted. Finally, a previously not considered, so far unknown C2v -symmetric rhombus-like four-membered ring 3 [Be(O)(C)Be] (3 5) is predicted to represent the global minimum on the potential-energy surface.

On the Crucial Role of Isolated Electronic States in the Thermal Reaction of ReC+ with Dihydrogen.

Presented here is that isolated, long-lived electronic states of ReC+ serve as the root cause for distinctly different reactivities of this diatomic ion in the thermal activation of dihydrogen. Detailed high-level quantum chemical calculations support the experimental findings obtained in the highly diluted gas phase using FT-ICR mass spectrometry. The origin for the existence of these long-lived excited electronic states and the resulting implications for the varying mechanisms of dihydrogen splitting are addressed.

Counter-Intuitive Gas-Phase Reactivities of [V2 ]+ and [V2 O]+ towards CO2 Reduction: Insight from Electronic Structure Calculations.

[V2 O]+ remains "invisible" in the thermal gas-phase reaction of bare [V2 ]+ with CO2 giving rise to [V2 O2 ]+ ; this is because the [V2 O]+ intermediate is being consumed more than 230 times faster than it is generated. However, the fleeting existence of [V2 O]+ and its involvement in the [V2 ]+ → [V2 O2 ]+ chemistry are demonstrated by a cross-over labeling experiment with a 1:1 mixture of C16 O2 /C18 O2 , generating the product ions [V2 16 O2 ]+ , [V2 16 O18 O]+ , and [V2 18 O2 ]+ in a 1:2:1 ratio. Density functional theory (DFT) calculations help to understand the remarkable and unexpected reactivity differences of [V2 ]+ versus [V2 O]+ towards CO2 .

Artificial Cytochrome c Mimics: Graphene Oxide-Fe(III) Complex-Coated Molecularly Imprinted Colloidosomes for Selective Photoreduction of Highly Toxic Pollutants.

Our previous works showed that the molecularly imprinted TiO2 photocatalyst has been one of the most efficient materials for selective photooxidation of highly toxic organic pollutants (HTOPs) from complicated wastewater. However, some highly toxic pollutants (e.g., heavy metals) are very stable under the oxidizing environment. Therefore, the design of enzyme-like catalysts to selectively reduce highly toxic pollutants is extremely needed. In this work, inspired by the bioreduction ability of cytochrome c (cyt c, a heme containing metalloprotein), we presented a simple and efficient way to generate an artificial cyt c mimic (ACM) using graphene oxide (GO)-Fe(III) complex-coated molecularly imprinted colloidosomes. Prior to loading of Fe(III) centers to GO for constructing ACMs, GO-coated molecularly imprinted colloidosomes were synthesized via Pickering emulsion polymerization. Similar to a nature cyt c, the ACM contained both the molecular recognition element (molecularly imprinted cavity) and the non-heme electron sink (GO-Fe(III) complex), which resulted in the ACMs having good selectivity toward the enzyme-like reduction of the highly toxic target Cr(VI). Moreover, by using HepG2 cells as model cells, the Cr(VI) solution after treating by ACMs was proved to be safe and nontoxic. To confirm that the present method was universal for constructing ACMs, various GO-Fe(III) complex-coated molecularly imprinted colloidosomes, which could selectively photoreduce other highly toxic inorganic ions and organic pollutants, were also investigated. The ACMs described herein will act as a vector that encourages the design of more functional non-heme enzymes in sensing, environmental separation, clinical diagnose, and delivery of therapeutic agents.

Complete cleavage of the N≡N triple bond by Ta2N+ via degenerate ligand exchange at ambient temperature: A perfect catalytic cycle.

An unprecedented, spontaneous, and complete cleavage of the triple bond of N2 in the thermal reaction of 15N2 with Ta214N+ was observed experimentally by Fourier transform ion cyclotron resonance mass spectrometry; mechanistic aspects of the degenerate ligand exchange were addressed by high-level quantum chemical calculations. The "hidden" dis- and reassembly of N2, mediated by Ta2N+, constitutes a full catalytic cycle. A frontier orbital analysis reveals that the scission of the N2 triple bond is essentially governed by the donation of d-electrons from the 2 metal centers into antibonding π*-orbitals of N2 and by the concurrent migration of electrons from bonding π- and σ-orbitals of N2 into empty d-orbitals of the metals. This work may contribute to a rational design of catalysts in order to reduce the still enormous energy demand required for an artificial dinitrogen activation.

A Reaction-Induced Localization of Spin Density Enables Thermal C-H Bond Activation of Methane by Pristine FeC4.

The reactivity of the cationic metal-carbon cluster FeC4 + towards methane has been studied experimentally using Fourier-transform ion cyclotron resonance mass spectrometry and computationally by high-level quantum chemical calculations. At room temperature, FeC4 H+ is formed as the main ionic product, and the experimental findings are substantiated by labeling experiments. According to extensive quantum chemical calculations, the C-H bond activation step proceeds through a radical-based hydrogen-atom transfer (HAT) mechanism. This finding is quite unexpected because the initial spin density at the terminal carbon atom of FeC4 + , which serves as the hydrogen acceptor site, is low. However, in the course of forming an encounter complex, an electron from the doubly occupied sp-orbital of the terminal carbon atom of FeC4 + migrates to the singly occupied π*-orbital; the latter is delocalized over the entire carbon chain. Thus, a highly localized spin density is generated in situ at the terminal carbon atom. Consequently, homolytic C-H bond activation occurs without the obligation to pay a considerable energy penalty that is usually required for HAT involving closed-shell acceptor sites. The mechanistic insights provided by this combined experimental/computational study extend the understanding of methane activation by transition-metal carbides and add a new facet to the dizzying mechanistic landscape of hydrogen-atom transfer.

Reassessment of the Mechanisms of Thermal C-H Bond Activation of Methane by Cationic Magnesium Oxides: A Critical Evaluation of the Suitability of Different Density Functionals.

The mechanisms of the thermal reactions of the two iconic magnesium oxide cations MgO.+ and Mg2 O2.+ with methane have been re-evaluated at the CCSD(T)/CBS//CCSD/def2-TZVP level of theory. For the reaction of MgO.+ with CH4 , only the classical hydrogen-atom transfer (HAT) was found; in contrast, for the Mg2 O2.+ /CH4 couple, both HAT and proton-coupled electron-transfer (PCET) exist as mechanistic variants. In order to evaluate the suitability of density functional theory (DFT) methods, the reactions were computed by using 27 density functionals. The results obtained demonstrate that the various DFT methods often deliver rather different results for both geometric and energetic features. As to the prediction of the apparent barriers, pure functionals give the largest mean absolute errors. BMK, ωB97XD, and the double-hybrid functional mPW2PLYP were confirmed to come closest to the results provided by CCSD(T)/CBS. Thus, mechanistic conclusions based on a single DFT method should be viewed with great caution. In summary, this study may assist in the selection of a suitable quantum chemical method to unravel the mechanistic details of C-H bond activation by charged metal oxides.