Geminal-atom catalysis for cross-coupling.

Single-atom catalysts (SACs) have well-defined active sites, making them of potential interest for organic synthesis1-4. However, the architecture of these mononuclear metal species stabilized on solid supports may not be optimal for catalysing complex molecular transformations owing to restricted spatial environment and electronic quantum states5,6. Here we report a class of heterogeneous geminal-atom catalysts (GACs), which pair single-atom sites in specific coordination and spatial proximity. Regularly separated nitrogen anchoring groups with delocalized π-bonding nature in a polymeric carbon nitride (PCN) host7 permit the coordination of Cu geminal sites with a ground-state separation of about 4 Å at high metal density8. The adaptable coordination of individual Cu sites in GACs enables a cooperative bridge-coupling pathway through dynamic Cu-Cu bonding for diverse C-X (X = C, N, O, S) cross-couplings with a low activation barrier. In situ characterization and quantum-theoretical studies show that such a dynamic process for cross-coupling is triggered by the adsorption of two different reactants at geminal metal sites, rendering homo-coupling unfeasible. These intrinsic advantages of GACs enable the assembly of heterocycles with several coordination sites, sterically congested scaffolds and pharmaceuticals with highly specific and stable activity. Scale-up experiments and translation to continuous flow suggest broad applicability for the manufacturing of fine chemicals.

Evidence for electron-hole crystals in a Mott insulator.

The coexistence of correlated electron and hole crystals enables the realization of quantum excitonic states, capable of hosting counterflow superfluidity and topological orders with long-range quantum entanglement. Here we report evidence for imbalanced electron-hole crystals in a doped Mott insulator, namely, α-RuCl3, through gate-tunable non-invasive van der Waals doping from graphene. Real-space imaging via scanning tunnelling microscopy reveals two distinct charge orderings at the lower and upper Hubbard band energies, whose origin is attributed to the correlation-driven honeycomb hole crystal composed of hole-rich Ru sites and rotational-symmetry-breaking paired electron crystal composed of electron-rich Ru-Ru bonds, respectively. Moreover, a gate-induced transition of electron-hole crystals is directly visualized, further corroborating their nature as correlation-driven charge crystals. The realization and atom-resolved visualization of imbalanced electron-hole crystals in a doped Mott insulator opens new doors in the search for correlated bosonic states within strongly correlated materials.

Highly Selective On-Surface Ring-Opening of Aromatic Azulene Moiety.

Controllable ring-opening of polycyclic aromatic hydrocarbons plays a crucial role in various chemical and biological processes. However, breaking down aromatic covalent C-C bonds is exceptionally challenging due to their high stability and strong aromaticity. This study presents a seminal report on the precise and highly selective on-surface ring-opening of the seven-membered ring within the aromatic azulene moieties under mild conditions. The chemical structures of the resulting products were identified using bond-resolved scanning probe microscopy. Furthermore, through density functional theory calculations, we uncovered the mechanism behind the ring-opening process and elucidated its chemical driving force. The key to achieving this ring-opening process lies in manipulating the local aromaticity of the aromatic azulene moiety through strain-induced internal ring rearrangement and cyclodehydrogenation. By precisely controlling these factors, we successfully triggered the desired ring-opening reaction. Our findings not only provide valuable insights into the ring-opening process of polycyclic aromatic hydrocarbons but also open up new possibilities for the manipulation and reconstruction of these important chemical structures.

Simultaneously Engineering the First and Second Coordination Shells of Single Iron Catalysts for Enhanced Oxygen Reduction.

The atomically dispersed Fe-N4 active site presents enormous potential for various renewable energy conversions. Despite its already remarkable catalytic performance, the local atomic microenvironment of each Fe atom can be regulated to further enhance its efficiency. Herein, a novel conceptual strategy that utilizes a simple salt-template polymerization method to simultaneously adjust the first coordination shell (Fe-N3 S1 ) and second coordination shell (C-S-C, a structure similar to thiophene) of Fe-N4 isolated atoms is proposed. Theoretical studies suggest that this approach can redistribute charge density in the MN4 moiety, lowering the d-band center of the metal site. This weakens the binding of oxygenated intermediates, enhancing oxygen reduction reaction (ORR) activity when compared to only implementing coordination shell regulation. Based on the above discovery, a single Fe atom electrocatalyst with the optimal Fe-N3 S1 -S active moiety incorporated in nitrogen, sulfur co-doped graphene (Fe-SAc/NSG) is designed and synthesized. The Fe-SAc/NSG catalyst exhibits excellent alkaline ORR activity, exceeding benchmark Pt/C and most Fe-SAc ORR electrocatalysts, as well as superior stability in Zn-air battery. This work aims to pave the way for creating highly active single metal atom catalysts through the localized regulation of their atomic structure.

Direct Observation of Hollow Bimetallic Nanoparticle Formation through Galvanic Replacement and Etching Reactions.

Hollow bimetallic nanoparticles (NPs) formed from metal oxide NP templates are widely used catalysts for hydrogen evolution and CO2 reduction reactions. Despite their importance in catalysis, the details of how these NPs form on the NP templates remain unclear. Here, using in situ liquid-phase transmission electron microscopy (TEM) imaging, we describe the conversion of Cu2O template NPs to hollow PdCu NPs. Our observations show that a polycrystalline PdCu shell forms on the surface of the template via a galvanic replacement reaction while the template undergoes anisotropic etching. This study provides important insights into the synthesis of hollow metallic nanostructures from metal oxide templates.

Chemotherapy and targeted therapy for advanced biliary tract cancers: an umbrella review.

BACKGROUND: Malignant tumors of the biliary system are characterized by a high degree of malignancy and strong invasiveness, and they are usually diagnosed at late stages with poor prognosis. For patients with advanced biliary tract cancer, chemotherapy and targeted therapy are two of the options available to improve prognosis and delay tumor progression. This study aimed to comprehensively evaluate the safety and effectiveness of various chemotherapy schemes for the treatment of advanced biliary tract cancer in published systematic reviews and meta-analyses (SRoMAs). METHODS: An umbrella review method was adopted, which aims to summarize the existing evidence from multiple studies around a research topic. SRoMAs up to April 9, 2022, were identified using PubMed, Web of Science, the Cochrane database, and manual screening. Eligible studies were screened according to inclusion and exclusion criteria. This study had been registered at PROSPERO (CRD42022324548). For each eligible study, we extracted the data of general characteristics and the main findings. The methodological quality of the included studies were assessed by the AMSTAR2 scale, and the quality of evidence was evaluated by the GRADE tools. RESULTS: A total of 1833 articles were searched; 14 unique articles with 94 outcomes were identified by eligibility criteria. The incidence of skin rash (RR = 18.11, 95% CI 5.13-63.91, GRADE: Moderate) and diarrhea (RR = 2.48, 95% CI 1.2-5.10, GRADE: Moderate) was higher in patients receiving gemcitabine-based chemotherapy plus targeted therapy than in patients receiving gemcitabine monotherapy. The number of patients receiving gemcitabine-based chemotherapy who developed leukopenia (OR = 7.17, 95% CI 1.43-36.08, GRADE: Moderate), anemia (OR = 7.04, 95% CI 2.59-19.12, GRADE: High), thrombocytopenia (RR = 2.45, 95% CI 1.39-4.32, GRADE: Moderate), and neutropenia (RR = 3.30, 95% CI 1.04-10.50, GRADE: Moderate) was significantly higher than that of patients who received gemcitabine-free regimens. In addition, patients receiving S-1 monotherapy had significantly better ORR (RR = 2.46, 95% CI 1.27-4.57, GRADE: Moderate) than patients receiving S-1 + gemcitabine. Patients receiving fluoropyrimidine-based chemotherapy had longer OS (HR = 0.83, 95% CI 0.7-0.99, GRADE: Moderate), higher DCR (0R = 5.18, 95% CI 3.3-10.23, GRADE: Moderate), and higher ORR (0R = 3.24, 95% CI 1.18-8.92, GRADE: Moderate) compared with patients who received 5-FU/LV monotherapy or supportive therapy. Surprisingly, we found evidence that gemcitabine-based chemotherapy did not improve postoperative patients' OS (HR = 0.91, 95% CI 0.74-1.12, GRADE: Moderate) when compared with best supportive care. CONCLUSIONS: This study comprehensively evaluated the safety and efficacy of chemotherapy or targeted therapy regimens for advanced biliary tract cancer and found 11 outcomes with "Moderate" or "High" levels; however, most of the outcomes were still at "low" or "very low" levels. More randomized controlled studies are needed in the future to further summarize high levels of evidence.

Epidemiology, risk factors, diagnosis, and treatment of intra-abdominal traumatic neuromas - a narrative review.

Traumatic neuroma (TN) is a disorganized proliferation of injured nerves arising from the axons and Schwann cells. Although TN rarely occurs in the abdominal cavity, the incidence of TN may be underestimated because of the large number of asymptomatic patients. TN can cause persistent pain, which seriously affects quality of life. TN of the biliary system can cause bile duct obstruction, leading to acute cholangitis. It is difficult to differentiate TN from malignancies or recurrence of malignancy, which results in a number of patients receiving aggressive treatment. We collected cases reports of intra-abdominal TN over the past 30 years form PubMed and cases diagnosed in our medical center over the past 20 years, which is the largest case series of intra-abdominal TN to the best of our knowledge. In this review, we discuss the epidemiology, pathophysiology, risk factors, classification, diagnosis, and management of intra-abdominal TN.

Timing of surgery in patients with synchronous colorectal cancer liver metastases undergoing neoadjuvant chemotherapy: a propensity score analysis.

BACKGROUND: The optimal timing of surgery after neoadjuvant chemotherapy (NAC) in patients with synchronous colorectal cancer liver metastases (SLM) remains controversial. We plan to analyze whether the choice of different surgical timings will have different effects on the perioperative and oncologic outcomes of patients. METHOD: We retrospectively collected all patients who met the inclusion and exclusion criteria from 2010 to 2020 in West China Hospital. Patients were grouped according to time interval (TI) after NAC to surgery. The perioperative and oncologic outcomes of the two groups were compared after propensity score matching. Univariate and multivariate analyzes were used to screen factors associated with prognosis. RESULT: Among 255 enrolled patients, 188 were matched with comparable baseline (94 each group). Patients in the 6≦TI≦8 group had longer operation time, less intraoperative blood loss, and less postoperative complications than those in the 4≦TI < 6 group. However, the overall survival (OS) (p = 0.012) and disease-free survival (DFS) (p = 0.013) of the patients in the 4≦TI < 6 group were better than those in the 6≦TI≦8 group. Subgroup analysis found that the above conclusions still apply in age ≥ 60, non-anemic patients, and patients who underwent R0 resection. OS was inversely correlated with TI in patients without preoperative jaundice. DFS was negatively correlated with TI in patients with preoperative jaundice. Multivariate analysis showed that the prolongation of TI after NAC to surgery was an independent prognostic risk factor for OS and DFS. CONCLUSIONS: Patients with SLM may be a better choice for surgery within 4-6 weeks after receiving NAC. Although patients with SLM undergoing surgery 4-6 weeks after NAC has a higher rate of postoperative complications, radical surgery is still recommended for a better survival benefit.

Gate-Tunable Resonance State and Screening Effects for Proton-Like Atomic Charge in Graphene.

The ability to create a robust and well-defined artificial atomic charge in graphene and understand its carrier-dependent electronic properties represents an important goal toward the development of graphene-based quantum devices. Herein, we devise a new pathway toward the atomically precise embodiment of point charges into a graphene lattice by posterior (N) ion implantation into a back-gated graphene device. The N dopant behaves as an in-plane proton-like charge manifested by formation of the characteristic resonance state in the conduction band. Scanning tunneling spectroscopy measurements at varied charge carrier densities reveal a giant energetic renormalization of the resonance state up to 220 meV with respect to the Dirac point, accompanied by the observation of gate-tunable long-range screening effects close to individual N dopants. Joint density functional theory and tight-binding calculations with modified perturbation potential corroborate experimental findings and highlight the short-range character of N-induced perturbation.

Prognostic value of exosomal noncoding RNA in hepatocellular carcinoma: a meta-analysis.

High morbidity, recurrence and mortality make hepatocellular carcinoma (HCC) a leading cause of cancer-related burden and deaths. The lack of prognostic evaluation methods weakened the therapeutic efficacy for HCC. Exosomal noncoding RNAs (ncRNAs) play a key role in cancer development. Our meta-analysis aimed to assess the prognostic value of exosome-transferred noncoding RNAs in predicting the outcomes of patients with HCC. We obtained 16 articles from PubMed, Web of Science, Scopus, and EMBASE up to 4 November 2021. The ncRNAs were divided into three parts: microRNAs (miRNA), long noncoding RNAs (lncRNA), and circular RNAs (circRNA). In the pooled hazard ratios (HRs), upregulated miRNAs were 3.06 (95% CI = 2.51-3.73), downregulated miRNAs were 3.28 (95% CI = 2.61-4.11), lncRNAs were 3.34 (95% CI = 1.87-5.96), and circRNAs were 1.76 (95% CI = 1.36-2.14). As the results of subgroup analysis, upregulated miRNAs had a pooled HR of 3.10 (95% CI = 1.66-5.81), and the HR of downregulated miRNAs was 3.04 (95% CI = 2.17-4.28) for multivariate analysis of overall survival (OS). Meanwhile, upregulated miRNAs had a pooled HR of 2.61 (95% CI = 1.89-3.60), and the HR of downregulated miRNAs was 3.77 (95% CI = 1.11-12.73) for multivariate analysis of other endpoints. Remarkably, miR-21 has a pooled HR of 2.48 (95%CI = 1.52-4.05, I2 = 0) for disease-free survival (DFS). In conclusion, the expression of exosomal noncoding RNAs can be used to evaluate the prognosis of patients with HCC. Exosome-transferred miR-21 might serve as a potential prognostic biomarker in HCC.

Degradation Chemistry and Kinetic Stabilization of Magnetic CrI3.

The discovery of the intrinsic magnetic order in single-layer chromium trihalides (CrX3, X = I, Br, and Cl) has drawn intensive interest due to their potential application in spintronic devices. However, the notorious environmental instability of this class of materials under ambient conditions renders their device fabrication and practical application extremely challenging. Here, we performed a systematic investigation of the degradation chemistry of chromium iodide (CrI3), the most studied among CrX3 families, via a joint spectroscopic and microscopic analysis of the structural and composition evolution of bulk and exfoliated nanoflakes in different environments. Unlike other air-sensitive 2D materials, CrI3 undergoes a pseudo-first-order hydrolysis in the presence of pure water toward the formation of amorphous Cr(OH)3 and hydrogen iodide (HI) with a rate constant of kI = 0.63 day-1 without light. In contrast, a faster pseudo-first-order surface oxidation of CrI3 occurs in a pure O2 environment, generating CrO3 and I2 with a large rate constant of kCr = 4.2 day-1. Both hydrolysis and surface oxidation of CrI3 can be accelerated via light irradiation, resulting in its ultrafast degradation in air. The new chemical insights obtained allow for the design of an effective stabilization strategy for CrI3 with preserved optical and magnetic properties. The use of organic acid solvents (e.g., formic acid) as reversible capping agents ensures that CrI3 nanoflakes remain stable beyond 1 month due to the effective suppression of both hydrolysis and oxidation of CrI3.

Printable two-dimensional superconducting monolayers.

Two-dimensional superconductor (2DSC) monolayers with non-centrosymmetry exhibit unconventional Ising pair superconductivity and an enhanced upper critical field beyond the Pauli paramagnetic limit, driving intense research interest. However, they are often susceptible to structural disorder and environmental oxidation, which destroy electronic coherence and provide technical challenges in the creation of artificial van der Waals heterostructures (vdWHs) for devices. Herein, we report a general and scalable synthesis of highly crystalline 2DSC monolayers via a mild electrochemical exfoliation method using flexible organic ammonium cations solvated with neutral solvent molecules as co-intercalants. Using NbSe2 as a model system, we achieved a high yield (>75%) of large-sized single-crystal monolayers up to 300 µm. The as-fabricated, twisted NbSe2 vdWHs demonstrate high stability, good interfacial properties and a critical current that is modulated by magnetic field when one flux quantum fits to an integer number of moiré cells. Additionally, formulated 2DSC inks can be exploited to fabricate wafer-scale 2D superconducting wire arrays and three-dimensional superconducting composites with desirable morphologies.

Electronic Self-Passivation of Single Vacancy in Black Phosphorus via Ionization.

We report that monoelemental black phosphorus presents a new electronic self-passivation scheme of single vacancy (SV). By means of low-temperature scanning tunneling microscopy and noncontact atomic force microscopy, we demonstrate that the local reconstruction and ionization of SV into negatively charged SV^{-} leads to the passivation of dangling bonds and, thus, the quenching of in-gap states, which can be achieved by mild thermal annealing or STM tip manipulation. SV exhibits a strong and symmetric Friedel oscillation (FO) pattern, while SV^{-} shows an asymmetric FO pattern with local perturbation amplitude reduced by one order of magnitude and a faster decay rate. The enhanced passivation by forming SV^{-} can be attributed to its weak dipolelike perturbation, consistent with density-functional theory numerical calculations. Therefore, self-passivated SV^{-} is electrically benign and acts as a much weaker scattering center, which may hold the key to further enhance the charge mobility of black phosphorus and its analogs.

On-surface synthesis of graphene nanostructures with π-magnetism.

Graphene nanostructures (GNs) including graphene nanoribbons and nanoflakes have attracted tremendous interest in the field of chemistry and materials science due to their fascinating electronic, optical and magnetic properties. Among them, zigzag-edged GNs (ZGNs) with precisely-tunable π-magnetism hold great potential for applications in spintronics and quantum devices. To improve the stability and processability of ZGNs, substitutional groups are often introduced to protect the reactive edges in organic synthesis, which renders the study of their intrinsic properties difficult. In contrast to the conventional wet-chemistry method, on-surface bottom-up synthesis presents a promising approach for the fabrication of both unsubstituted ZGNs and functionalized ZGNs with atomic precision via surface-catalyzed transformation of rationally-designed precursors. The structural and spin-polarized electronic properties of these ZGNs can then be characterized with sub-molecular resolution by means of scanning probe microscopy techniques. This review aims to highlight recent advances in the on-surface synthesis and characterization of a diversity of ZGNs with π-magnetism. We also discuss the important role of precursor design and reaction stimuli in the on-surface synthesis of ZGNs and their π-magnetism origin. Finally, we will highlight the existing challenges and future perspective surrounding the synthesis of novel open-shell ZGNs towards next-generation quantum technology.

On-Surface Synthesis and Characterization of [7]Triangulene Quantum Ring.

The ability to engineer geometrically well-defined antidots in large triangulene homologues allows for creating an entire family of triangulene quantum rings (TQRs) with tunable high-spin ground state, crucial for next-generation molecular spintronic devices. Herein, we report the synthesis of an open-shell [7]triangulene quantum ring ([7]TQR) molecule on Au(111) through the surface-assisted cyclodehydrogenation of a rationally designed kekulene derivative. Bond-resolved scanning tunneling microscopy (BR-STM) unambiguously imaged the molecular backbone of a single [7]TQR with a triangular zigzag edge topology, which can be viewed as [7]triangulene decorated with a coronene-like antidot in the center. Additionally, dI/dV mapping reveals that both inner and outer zigzag edges contribute to the edge-localized and spin-polarized electronic states of [7]TQR. Both experimental results and spin-polarized density functional theory calculations indicate that [7]TQR retains its open-shell septuple ground state (S = 3) on Au(111). This work demonstrates a new route for the design of high-spin graphene quantum rings for future quantum devices.

Machine Vision Automated Chiral Molecule Detection and Classification in Molecular Imaging.

Scanning probe microscopy (SPM) is recognized as an essential characterization tool in a broad range of applications, allowing for real-space atomic imaging of solid surfaces, nanomaterials, and molecular systems. Recently, the imaging of chiral molecular nanostructures via SPM has become a matter of increased scientific and technological interest due to their imminent use as functional platforms in a wide scope of applications, including nonlinear chiroptics, enantioselective catalysis, and enantiospecific sensing. Due to the time-consuming and error-prone image analysis process, a highly efficient analytic framework capable of identifying complex chiral patterns in SPM images is needed. Here, we adopted a state-of-the-art machine vision algorithm to develop a one-image-one-system deep learning framework for the analysis of SPM images. To demonstrate its accuracy and versatility, we employed it to determine the chirality of the molecules comprising two supramolecular self-assemblies with two distinct chiral organization patterns. Our framework accurately detected the position and labeled the chirality of each molecule. This framework underpins the tremendous potential of machine learning algorithms for the automated recognition of complex SPM image patterns in a wide range of research disciplines.

Mixed adenoneuroendocrine carcinomas of stomach and ampulla of vater after curative-intent resection: a single center cases series.

BACKGROUND: Mixed adenoneuroendocrine carcinoma is a rare clinical manifestation, especially in the gastric and ampullary. The purpose of this study was to investigate the clinicopathological features and prognosis of mixed adenoneuroendocrine carcinoma in the gastric and ampullary and summarize related treatment suggestions. METHODS: In all, 32 cases of mixed adenoneuroendocrine carcinoma in the gastric and ampullary that were diagnosed from resected specimens were analyzed from 2009 to 2015. The corresponding demographic, clinicopathological and survival data were retrospectively reviewed. RESULTS: The 1-year, 3-year and 5-year survival rates were 78.1%, 28.1 and 9.4%, respectively, and the median overall survival was 28.0 months. In all, 75.0% (24/32) had lymph node metastasis at the time of initial diagnosis. A multivariate analysis revealed that TNM stage (HR 6.444 95%CI 1.477-28.121 P = 0.013), lymph nodes metastasis (HR10.617 95%CI 1.409-79.997 P = 0.022), vascular invasion (HR 5.855 95%CI 1.719-19.940 P = 0.005), grade of the adenocarcinoma component (HR 3.876 95%CI 1.451-10.357 P = 0.007) and CD56 positivity (HR 0.265 95%CI 0.100-0.705 P = 0.008) were independent predictors of overall survival. CONCLUSIONS: Mixed adenoneuroendocrine carcinoma is an aggressive clinical entity with a poor prognosis. Taking both the neuroendocrine component and the adenocarcinoma component into consideration of optimal treatment is strongly recommended.

Tailoring long-range superlattice chirality in molecular self-assemblies via weak fluorine-mediated interactions.

Controllable fabrication of enantiospecific molecular superlattices is a matter of imminent scientific and technological interest. Herein, we demonstrate that long-range superlattice chirality in molecular self-assemblies can be tailored by tuning the interplay of weak intermolecular non-covalent interactions between hexaphenylbenzene-based enantiomers. By means of high-resolution scanning tunneling microscopy measurements, we demonstrate that the functionalization of a hexaphenylbenzene-based molecule with fluorine (F) atoms leads to the formation of molecular self-assemblies with distinct long-range chiral recognition patterns. We employed density functional theory calculations to quantify F-mediated lone pair F⋯π, C-H⋯F, and F⋯F interactions attributed to the distinct enantiospecific molecular self-organizations. Our findings underpin a viable route to fabricate long-range chiral recognition patterns in supramolecular assemblies by engineering the weak non-covalent intermolecular interactions.

The preoperative elevated plasma fibrinogen level is associated with the prognosis of hilar cholangiocarcinoma.

PURPOSE: Elevated fibrinogen (Fbg) levels contribute to tumor progression and metastasis. However, little is known regarding the association of the clinicopathological characteristics and the prognosis of hilar cholangiocarcinoma (HC) with plasma fibrinogen. METHODS: Data on the plasma Fbg levels, clinicopathological characteristics, and overall survival were retrospectively collected. Plasma fibrinogen concentrations over 4.0 g/L were classified as hyperfibrinogen, elevated fibrinogen, or abnormal fibrinogen levels. We then analyzed the relationships among plasma fibrinogen level, clinicopathological features, and patient prognosis. RESULTS: A total of 171 HC patients were included. An elevated plasma fibrinogen level was associated with lymph-node metastasis (P < 0.001), the AJCC stage (P < 0.001), the surgical margin (P = 0.005), and vascular invasion (P = 0.027). Univariate analyses revealed that preoperative plasma fibrinogen (P < 0.001), operative blood loss (P = 0.044), vascular invasion (P < 0.001), CA19-9 (P = 0.003), surgical margin (P < 0.001), T stage (P < 0.001), histologic differentiation (P = 0.007), and lymph-node metastasis (P < 0.001) were associated with OS. The survival time of patients with high Fbg levels was shorter than that of patients with normal fibrinogen levels (P < 0.001). Furthermore, a multivariate analysis showed that fibrinogen was negatively and independently associated with the HC prognosis (P = 0.029). CONCLUSIONS: An elevated plasma Fbg level was associated with lymph-node metastasis, vascular invasion, the surgical margin, and the tumor stage, and the Fbg level might therefore be an independent factor associated with poor outcomes in HC patients.

Real-Space Imaging of a Single-Molecule Monoradical Reaction.

Organic radicals consisting of light elements exhibit a low spin-orbit coupling and weak hyperfine interactions with a long spin coherence length, which are crucial for future applications in molecular spintronics. However, the synthesis and characterization of these organic radicals have been a formidable challenge due to their chemical instability arising from unpaired electrons. Here, we report a direct imaging of the surface chemical transformation of an organic monoradical synthesized via the monodehydrogenation of a chemically designed precursor. Bond-resolved scanning tunneling microscopy unambiguously resolves various products formed through a complex structural dissociation and rearrangement of organic monoradicals. Density functional theory calculations reveal detailed reaction pathways from the monoradical to different cyclized products. Our study provides unprecedented insights into complex surface reaction mechanisms of organic radical reactions at the single molecule level, which may guide the design of stable organic radicals for future quantum technology applications.