Axially Chiral Nonbenzenoid Nanographene with Second Harmonic Generation Property.

Chiral nanographenes (NGs) have garnered significant interest as optoelectronic materials in recent years. While helically chiral NGs have been extensively studied, axially chiral NGs have only witnessed limited examples, with no prior reports of axially chiral nonbenzenoid NGs. Herein we report an axially chiral nonbenzenoid nanographene featuring six pentagons and four heptagons. This compound, denoted as 2, was efficiently synthesized via an efficient Pd-catalyzed aryl silane homocoupling reaction. The presence of two bulky 3,5-di-tert-butylphenyl groups around the axis connecting the two nonbenzenoid PAH (AHR) segments endows 2 with atropisomeric chirality and high racemization energy barrier, effectively preventing racemization of both R- and S-enantiomers at room temperature. Optically pure R-2 and S-2 were obtained by chiral HPLC separation, and they exhibit circular dichroism (CD) activity at wavelengths up to 660 nm, one of the longest wavelengths with CD responses reported for the chiral NGs. Interestingly, racemic 2 forms a homoconfiguration π-dimer in the crystal lattice, belonging to the I222 chiral space group. Consequently, this unique structure renders crystals of 2 with a second harmonic generation (SHG) response, distinguishing it from all the reported axially chiral benzenoid NGs. Moreover, R-2 and S-2 also exhibit SHG-CD properties.

Unusual Electronic Structures of an Electron Transfer Series of [Cr(µ-η1 : η1 -N2 )Cr]0/1+/2.

In dinitrogen (N2 ) fixation chemistry, bimetallic end-on bridging N2 complexes M(µ-η1 : η1 -N2 )M can split N2 into terminal nitrides and hence attract great attention. To date, only 4d and 5d transition complexes, but none of 3d counterparts, could realize such a transformation. Likewise, complexes {[Cp*Cr(dmpe)]2 (µ-N2 )}0/1+/2+ (1-3) are incapable to cleave N2 , in contrast to their Mo congeners. Remarkably, cross this series the N-N bond length of the N2 ligand and the N-N stretching frequency exhibit unprecedented nonmonotonic variations, and complexes 1 and 2 in both solid and solution states display rare thermally activated ligand-mediated two-center spin transitions, distinct from discrete dinuclear spin crossovers. In-depth analyses using wave function based ab initio calculations reveal that the Cr-N2 -Cr bonding in complexes 1-3 is distinguished by strong multireference character and cannot be described by solely one electron configuration or Lewis structure, and that all intriguing spectroscopic observations originate in their sophisticate multireference electronic structures. More critical is that such multireference bonding of complexes 1-3 is at least a key factor that contributes to their kinetic inertness toward N2 splitting. The mechanistic understanding is then used to rationalize the disparate reactivity of related 3d M(µ-η1 : η1 -N2 )M complexes compared to their 4d and 5d analogs.

Diazulenorubicene as a Non-benzenoid Isomer of peri-Tetracene with Two Sets of 5/7/5 Membered Rings Showing Good Semiconducting Properties.

Non-benzenoid polycyclic aromatic hydrocarbons (PAHs) have received a lot of attention because of their unique optical, electronic, and magnetic properties, but their synthesis remains challenging. Herein, we report a non-benzenoid isomer of peri-tetracene, diazulenorubicene (DAR), with two sets of 5/7/5 membered rings synthesized by a (3+2) annulation reaction. Compared with the precursor containing only 5/7 membered rings, the newly formed five membered rings switch the aromaticity of the original heptagon/pentagon from antiaromatic/aromatic to non-aromatic/antiaromatic respectively, modify the intermolecular packing modes, and lower the LUMO levels. Notably, compound 2 b (DAR-TMS) shows p-type semiconducting properties with a hole mobility up to 1.27 cm2  V-1 s-1 . Moreover, further extension to larger non-benzenoid PAHs with 19 rings was achieved through on-surface chemistry from the DAR derivative with one alkynyl group.

Surface molecular ionization imaging of gold nanocubes.

The near-field enhancement effect in nanoparticles dominates the dynamical response of the atoms and molecules within the nanosystem when interacting with ultrashort laser pulses. In this work, using the single-shot velocity map imaging technique, the angle-resolved momentum distributions of the ionization products from surface molecules in gold nanocubes have been obtained. The far-field momentum distributions of the H+ ions can be linked with the near field profiles demonstrated by a classical simulation considering the initial ionization probability and the Coulomb interactions among the charged particles. This research provides an approach to look at the nanoscale near field distribution in the extreme interactions of femtosecond laser pulses and nanoparticles, paving the way for exploring the complex dynamics.

Insight into the Ligand-to-Ligand Charge-Transfer Process in Rare-Earth-Metal Diradical Complexes.

While a ligand-to-ligand charge-transfer (LLCT) process is an important way to understand the interactions between metal-bridged radicals for late-transition-metal complexes, there is little clear and evident observation of the LLCT process for rare-earth-metal complexes. In this work, rare-earth-metal diradical complexes supported by diazabutadiene (DAD) ligands [(DAD)2RE(BH4)] [RE = Yb (1), Sm (2)] were synthesized and studied. The coordination geometries of 1 and 2 are different due to the different ionic radii. Reduction of 1 or 2 generated monoradical complexes, with one of their DAD radical anions being reduced. In all of the complexes, Sm and Yb remain at the 3+ valence state. In their UV-vis spectra, the LLCT transition of 1 could be clearly observed, but complex 2 did not show the same transition. These results could be related to the geometric structures of the complexes as well as exchange coupling between diradicals, thus clearly expanding the model for late-transition-metal-bridged diradicals to rare-earth systems experimentally.

A Heptacene Analogue Entailing a Quinoidal Benzodi[7]annulene (7/6/7 Ring) Core with a Tunable Configuration and Multiple Redox Properties.

Non-benzenoid acenes containing heptagons have received increasing attention. We herein report a heptacene analogue containing a quinoidal benzodi[7]annulene core. Derivatives of this new non-benzenoid acene were obtained through an efficient synthetic strategy involving an Aldol condensation and a Diels-Alder reaction as key steps. The configuration of this heptacene analogue can be modulated from a wavy to a curved one by just varying the substituents from a (triisopropylsilyl)ethynyl group to a 2,4,6-triisopropylphenyl (Trip) group. When mesityl (Mes) groups are linked to the heptagons, the resulting non-benzenoid acene displays polymorphism with a tunable configuration from a curved to a wavy one upon varying the crystallization conditions. In addition, this new non-benzenoid acene can be oxidized or reduced by NOSbF6 or KC8 to the respective radical cation or radical anion. Compared with the neutral acene, the radical anion shows a wavy configuration and the central hexagon becomes aromatic.

Safety and Efficacy of Stereotaxic Surgery Combined with Urokinase in the Treatment of Ventricular Hemorrhage: A Retrospective Propensity-Matched Score Analysis.

BACKGROUND: Intraventricular hemorrhage (IVH) is a severe and devastating stroke. Research on existing treatment options has been controversial. Therefore, we aimed to evaluate the safety and efficacy of minimally implanted stereotactic puncture combined with urokinase (uPA) in the treatment of IVH. METHODS: The clinical data of 122 IVH patients admitted to our department from 2018 to 2022 were retrospectively analyzed. According to the modified RanKin score (mRS) after 30 days, the patients were divided into good prognosis (mRS 0-3) and poor prognosis (mRS 4-6), and the factors affecting the prognosis were screened by univariate and multivariate analysis, and then the tendency Score matching and paired patient screening were performed for comparative analysis between uPA and non-uPA groups. RESULTS: Patients' age, uPA usage, initial Glasgow Coma Scale and primary blood volume all could affect the mRS score of patients. One hundred patients were finally included, including 50 cases in the uPA group and 50 cases in the non-uPA group. The analysis showed that at follow-up after 30 days, 46.0% of the patients in the uPA group and 28.0% in the non-uPA group had an mRS score of 0-3; however, they were not statistically significantly different. The postoperative hematoma clearance rate in the uPA group was significantly higher than that in the non-uPA group (P < 0.001), and the incidence of postoperative complications was not increased (P > 0.05). CONCIUSIONS: uPA treatment can improve the treatment efficiency. However, its effect in improving patient outcomes does not appear to be significant.

Temperature-dependent photoluminescence properties of single defects in AlGaN micropillars.

Single-photon emitters (SPEs) are attractive as integrated platforms for quantum applications in technologically mature wide-bandgap semiconductors since their stable operation at room temperature or even at high temperatures. In this study, we systematically studied the temperature dependence of the SPE in AlGaN micropillar by experiment. The photoluminescence (PL) spectrum, PL intensity, radiative lifetime and second-order autocorrelation function measurements are investigated over the temperature range from 303 to 373 K. The point defects of AlGaN show strong zero phonon line in the wavelength range of 800-900 nm and highly antibunched photon emission even up to 373 K. Our study reveals a possible mechanism for linewidth broadening in AlGaN SPE at high temperatures. This indicates a possible key for on-chip integration applications based on this material operating at high temperatures.

Dinitrogen Functionalization Affording Chromium Diazenido and Side-on η2-Hydrazido Complexes.

Isolation of key intermediate complexes in dinitrogen functionalization is crucial for elucidating the mechanistic details and further investigation. Herein, the synthesis and characterization of (µ-η1:η1-N2)(η1-N2)-Cr(I) 3 and (η1-N2)2-Cr(0) complexes 4 supported by Cp* (Cp* = C5Me5) and NHC ligands were reported. Further functionalization of Cr(0)-N2 complex 4 with silyl halides delivered the key intermediates in the alternating pathway, the chromium diazenido complex 5 and the chromium side-on η2-hydrazido complex 6. Protonation of 6 led to the quantitative formation of N2H4. Moreover, the [η2-Me3SiNNSiMe3]2- unit in 6 enabled N-C bond formation reactions with CO2 and tBuNCO, giving the corresponding N,O-chelating hydrazidochromium complexes 7 and 8, respectively.

Cerebrospinal fluid drainage and chronic hydrocephalus in aneurysmal subarachnoid hemorrhage patients with intraventricular hemorrhage.

Background: Patients with intraventricular hemorrhage (IVH) are at a higher risk of developing hydrocephalus and often require external ventricular drainage or long-term ventriculoperitoneal shunt surgery. Objective: To investigate whether cerebrospinal fluid drainage in patients with IVH due to aneurysmal subarachnoid hemorrhage (aSAH) reduces the incidence of chronic hydrocephalus. Method: A retrospective analysis was conducted on patients with aSAH treated at our hospital between January 2020 and December 2022. The first analysis compared patients with and without IVH, while the second analysis compared IVH patients with and without chronic hydrocephalus. The third analysis compared IVH patients who underwent in different drainage methods which is lumbar drainage (LD) or external ventricular drainage (EVD). The primary outcome measure was the incidence of chronic hydrocephalus. Result: Of the 296 patients hospitalized with aSAH, 108 (36.5%) had IVH, which was associated with a significantly higher incidence of chronic hydrocephalus compared to patients without IVH (49.1% vs. 16.5%, p < 0.001). Multivariate logistic regression analysis showed that IVH was independently associated with the formation of chronic hydrocephalus (OR: 3.530, 95% CI: 1.958-6.362, p < 0.001). Among the 108 IVH patients, 53 (49.1%) developed chronic hydrocephalus. Multivariate logistic regression analysis revealed that the Hunt Hess grade at admission (OR: 3.362, 95% CI: 1.146-9.863, p = 0.027) and postoperative cerebrospinal fluid drainage (OR: 0.110, 95% CI: 0.036-0.336, p < 0.001) were independent risk factors for the development of chronic hydrocephalus in IVH patients. Among all IVH patients who underwent cerebrospinal fluid drainage, 45 (75%) received continuous lumbar puncture drainage, and 15 (25%) received external ventricular drainage. Univariate analysis did not show a statistically significant difference between the two groups in terms of postoperative chronic hydrocephalus (p = 0.283). However, multivariate logistic regression analysis suggested that the drainage methods of LD and EVD might be associated with the development of chronic hydrocephalus. Conclusion: The presence of IVH increases the risk of chronic hydrocephalus in patients with aSAH, and postoperative cerebrospinal fluid drainage appears to reduce this risk. The specific effects of lumbar puncture drainage and ventricular drainage on the incidence of chronic hydrocephalus require further investigation.

Deciphering the photophysical properties of near-infrared quantum emitters in AlGaN films by transition dynamics.

Point defects in wide bandgap III-nitride semiconductors have been recently reported to be one kind of the most promising near-infrared (NIR) quantum emitters operating at room temperature (RT). But the identification of the point defect species and the energy level structures as well as the transition dynamics remain unclear. Here, the photophysical properties of single-photon emission from point defects in AlGaN films are investigated in detail. According to the first-principles calculations, a three-level model was established to explain the transition dynamics of the quantum emitters. An anti-site nitrogen vacancy complex (VNNGa) was demonstrated to be the most likely origin of the measured emitter since the calculated zero-phonon line (ZPL) and the lifetime of VNNGa in the AlGaN film coincide well with the experimental results. Our results provide new insights into the optical properties and energy level structures of quantum emission from point defects in AlGaN films at RT and establish the foundation for future AlGaN-based on-chip quantum technologies.

Ultra-early endovascular treatment improves prognosis in High grade aneurysmal subarachnoid hemorrhage: A single-center retrospective study.

Background: The long-term survival prognosis of patients with high-grade (Hunt-Hess grade IV-V or World Federation of Neurosurgical Societies grade IV-V) aneurysmal subarachnoid hemorrhage (aSAH) is generally poor, and the association between endovascular treatment timing and the prognosis of high-grade aSAH has not been explored in depth. This retrospective cohort study aimed to determine whether endovascular treatment within 24 h of high-grade aSAH is associated with a better prognosis. Methods: We retrospectively analyzed the clinical data of patients with high-grade aSAH who were admitted to our institution between January 2018 and January 2021. The Modified Rankin Scale score was used to assess the 6-month prognosis of patients. Univariate and multivariate logistic regression analyses were used to identify the factors associated with prognosis. The area under the receiver operating characteristic (ROC) curve was used to assess the model's discriminatory ability. Results: Eighty-six patients were included in the study. In the multivariate analysis, the timing of endovascular treatment (odds ratio = 7.003 [1.800-27.242], P = 0.005) was an independent risk factor for prognosis. The ROC curve showed that the predictive power of the timing of endovascular treatment was 0.744, the best cut-off value was 12.5 h, and the corresponding sensitivity and specificity were 71.4 and 70.5%, respectively. Hydrocephalus (P = 0.005) and pulmonary infection (P = 0.029) were also associated with prognosis. In addition, cerebrospinal fluid drainage immediately after endovascular treatment had a significant effect on reducing hydrocephalus formation. Conclusions: Endovascular therapy within 24 h is feasible and improves the prognosis of patients with high-grade aSAH.

Risk factors for emergency endoscopic variceal ligation treatment failure of acute variceal bleeding.

OBJECTIVE: To determine the risk factors for emergency endoscopic variceal ligation (EVL) failure in acute variceal bleeding (AVB). METHODS: Data from 161 cirrhosis patients with oesophageal variceal bleeding who underwent emergency EVL treatment at the Second Hospital of Hebei Medical University from January 2018 to May 2021 were retrospectively analysed. Enrolled patients were divided into a successful treatment group and a failed treatment group. The variables studied were demographic, clinical, imaging, laboratory, and endoscopic data from the enrolled patients. RESULTS: Of the enrolled patients, 19 patients experienced emergency EVL failure. Of these patients, nine underwent emergency endoscopic treatment again, six patients were treated with a Sengstaken-Blakemore tube for haemostasis and endoscopic treatment, four patients received drug therapy. The presence of portal vein thrombosis (PVT) in the failure group was higher than that in the success group (p < .05). Active bleeding on endoscopy was associated with emergency EVL failure for patients with Child-Pugh class C (p < .05). CONCLUSIONS: Child-Pugh class C with active bleeding on endoscopy or the presence of PVT could increase the risk of emergency EVL failure. The patient's condition should be fully evaluated before emergency endoscopic treatment to reduce the risk of failure.

A perylene five-membered ring diimide for organic semiconductors and π-expanded conjugated molecules.

A perylene five-membered ring diimide, PDI39, was developed as a new electron-deficient building block for n-type semiconductors. The π-expanded conjugated molecules containing azulenes were synthesized from PDI39. These conjugated molecules show helical geometry and near-infrared absorption up to 810 nm.

Hydrogenated Amorphous Titania with Engineered Surface Oxygen Vacancy for Efficient Formaldehyde and Dye Removals under Visible-Light Irradiation.

Hydrogenated crystalized TiO2-x with oxygen vacant (OV) doping has attracted considerable attraction, owing to its impressive photoactivity. However, amorphous TiO2, as a common allotrope of titania, is ignored as a hydrogenated templet. In this work, hydrogenated amorphous TiO2-x (HAm-TiO2-x) with engineered surface OV and high surface area (176.7 cm2 g-1) was first prepared using a unique liquid plasma hydrogenation strategy. In HAm-TiO2-x, we found that OV was energetically retained in the subsurface region; in particular, the subsurface OV-induced energy level preferred to remain under the conduction band (0.5 eV) to form a conduction band tail and deep trap states, resulting in a narrow bandgap (2.36 eV). With the benefits of abundant light absorption and efficient photocarrier transportation, HAm-TiO2-x coated glass has demonstrated superior visible-light-driven self-cleaning performances. To investigate its formaldehyde photodegradation under harsh indoor conditions, HAm-TiO2-x was used to decompose low-concentration formaldehyde (~0.6 ppm) with weak-visible light (λ = 600 nm, power density = 0.136 mW/cm2). Thus, HAm-TiO2-x achieved high quantum efficiency of 3 × 10-6 molecules/photon and photoactivity of 92.6%. The adsorption capabilities of O2 (-1.42 eV) and HCHO (-1.58 eV) in HAm-TiO2-x are both largely promoted in the presence of subsurface OV. The surface reaction pathway and formaldehyde decomposition mechanism over HAm-TiO2-x were finally clarified. This work opened a promising way to fabricate hydrogenated amorphous photocatalysts, which could contribute to visible-light-driven photocatalytic environmental applications.

Plasmon Enhanced Second Harmonic Generation from ZnO Nanofilms on Vertical Au Nanorod Arrays.

Vertically aligned gold nanorod arrays have attracted much attention for their fascinating optical properties. Different from longitudinal surface plasmon wavelength (LSPW) and edge-to-edge spacing of gold nanorods, the role of gold nanorod diameter in plasmonic enhancement ability of vertical gold nanorod arrays has rarely been explored. In this work, we selected gold nanorods with similar LSPW but two different diameters (22 and 41 nm), the optical properties of which are dominated by absorption and scattering cross sections, respectively. The vertically aligned arrays of these gold nanorods formed by evaporation self-assembly are coupled with nonlinear ZnO nanocrystal films spin-coated on their surfaces. It was found that the gold nanorod array with a larger diameter can enhance the second harmonic generation (SHG) of ZnO nanofilm by a factor of 27.0, while it is about 7.3 for the smaller gold nanorod array. Theoretical simulations indicate that such stronger enhancement of the larger vertical gold nanorod array compared with the smaller one is due to its stronger scattering ability and greater extent of near-field enhancement at SHG fundamental wavelength. Our work shows that the diameter of gold nanorods is also an important factor to be considered in realizing strong plasmon enhancement of vertically aligned gold nanorod arrays.

Distance-Dependent Plasmon-Enhanced Fluorescence of Submonolayer Rhodamine 6G by Gold Nanoparticles.

We investigate the fluorescence from submonolayer rhodamine 6G molecules near gold nanoparticles (NPs) at a well-controlled poly (methyl methacrylate) (PMMA) interval thickness from 1.5 to 21 nm. The plasmonic resonance peaks of gold NPs are tuned from 530 to 580 nm by the PMMA spacer of different thicknesses. Then, due to the plasmonic resonant excitation enhancement, the emission intensity of rhodamine 6G molecules at 562 nm is found to be enhanced and shows a decline as the PMMA spacer thickness increases. The variation of spectral intensity simulated by finite-difference time-domain method is consistent with the experimental results. Moreover, the lifetime results show the combined effects to rhodamine 6G fluorescence, which include the quenching effect, the barrier effect of PMMA as spacer layer and the attenuation effect of PMMA films.

Synthesis, Structure, and Magnetic Properties of Rare-Earth Bis(diazabutadiene) Diradical Complexes.

New kinds of diradical rare-earth metal complexes supported by diazabutadiene (DAD) ligands, [(DAD)2LnN(TMS)2] (1; Ln = Dy, Lu; TMS = SiMe3), were synthesized and studied. They showed a new [radical-Ln-radical] alignment with distorted square-pyramidal geometry. Structural and density functional theory analysis illustrated the radical anionic nature of the ligands. Magnetic studies revealed antiferromagnetic coupling of the two radicals in 1-Lu. 1-Dy showed typical single-molecule-magnet (SMM) behavior with an effective energy barrier of 231 K, which is much higher than those of similar radical-containing SMMs. Magnetostructural analysis suggests that the anionic [N(TMS)2]- group plays a vital role in the SMM property. This study provides a new platform for further improving the performance of radical-Ln SMMs.

Polarization control of plasmon-induced transparency in metamaterials with reversibly convertible bright and dark modes.

We numerically demonstrate a Z-shaped metal-based metamaterial to realize an active polarization-controlled plasmon-induced transparency (PIT). The metamaterial unit cell contains two horizontal Au bars and a vertical Au bar. Simply by varying the incident light polarization, a tunable PIT can be achieved due to the reversible conversion of bright and dark modes between the horizontal and vertical Au bars. Moreover, a switchable PIT window modulation can be accomplished via changing the geometrical parameters, and the theoretical fittings according to the coupled Lorentz oscillator model display consistency with the simulated results. Our proposed metamaterials provide a promising strategy for fabricating compact PIT devices such as optical switching, sensing, and selective filters.

Cyclic Bis-alkylidene Complexes of Titanium and Zirconium: Synthesis, Characterization, and Reaction.

Transition-metal alkylidenes have exhibited wide applications in organometallic chemistry and synthetic organic chemistry, however, cyclic Schrock-carbene-like bis-alkylidenes of group 4 metals with a four-electron donor from an alkylidene have not been reported. Herein, the synthesis and characterization of five-membered cyclic bis-alkylidenes of titanium (4 a,b) and zirconium (5 a,b) are reported, as the first well-defined group 4 metallacyclopentatrienes, by two-electron reduction of their corresponding titana- and zirconacyclopentadienes. DFT analyses of 4 a show a four-electron donor (σ-donation and π-donation) from an alkylidene carbon to the metal center. The reaction of 4 a with N,N'-diisopropylcarbodiimide (DIC) leads to the [2+2]-cycloaddition product 6. Compound 4 a reacted with CO, affording the oxycyclopentadienyl titanium complex 7. These reactivities demonstrate the multiple metal-carbon bond character. The reactions of 4 a or 5 a with cyclooctatetraene (COT) or azobenzene afforded sandwich titanium complex 8 or diphenylhydrazine-coordinated zirconacyclopentadiene 9, respectively, which exhibit two-electron reductive ability.