Revealing the Role of N Heteroatoms in Noncovalent Aromatic Interactions by Ultrafast Intermolecular Coulombic Decay.

Despite the widely recognized importance of noncovalent interactions involving aromatic rings in many fields, our understanding of the underlying forces and structural patterns, especially the impact of heteroaromaticity, is still incomplete. Here, we investigate the relaxation processes that follow inner-valence ionization in a range of molecular dimers involving various combinations of benzene, pyridine, and pyrimidine, which initiate an ultrafast intermolecular Coulombic decay process. Multiparticle coincidence momentum spectroscopy, combined with ab initio calculations, enables us to explore the principal orientations of these fundamental dimers and, thus, to elucidate the influence of N heteroatoms on the relative preference of the aromatic π-stacking, H-bonding, and CH-π interactions and their dependence on the number of nitrogen atoms in the rings. Our studies reveal a sensitive tool for the structural imaging of molecular complexes and provide a more complete understanding of the effects of N heteroatoms on the noncovalent aromatic interactions at the molecular level.

Functional-group translocation of cyano groups by reversible C-H sampling.

Chemical transformations that introduce, remove or manipulate functional groups are ubiquitous in synthetic chemistry1. Unlike conventional functional-group interconversion reactions that swap one functionality for another, transformations that alter solely the location of functional groups are far less explored. Here, by photocatalytic, reversible C-H sampling, we report a functional-group translocation reaction of cyano (CN) groups in common nitriles, allowing for the direct positional exchange between a CN group and an unactivated C-H bond. The reaction shows high fidelity for 1,4-CN translocation, frequently contrary to inherent site selectivity in conventional C-H functionalizations. We also report the direct transannular CN translocation of cyclic systems, providing access to valuable structures that are non-trivial to obtain by other methods. Making use of the synthetic versatility of CN and a key CN translocation step, we showcase concise syntheses of building blocks of bioactive molecules. Furthermore, the combination of C-H cyanation and CN translocation allows access to unconventional C-H derivatives. Overall, the reported reaction represents a way to achieve site-selective C-H transformation reactions without requiring a site-selective C-H cleavage step.

Overview of 1,5-Selective Click Reaction of Azides with Alkynes or Their Synthetic Equivalents.

Nowadays, the click reaction of azides with alkynes has evolved rapidly and become one of the most efficient methods to synthesize 1,2,3-triazoles, which are an important class of N-containing heterocycles. While the 1,4-selective click reaction of azides with alkynes is well established to synthesize 1,4-substituted 1,2,3-triazoles, the corresponding 1,5-selective click reaction for the generation of 1,5-substituted-1,2,3-triazoles is much less explored, and there is no systematic review for the 1,5-selective click reaction. This timely review summarizes the discovery and development of 1,5-selective click reactions of azides with alkynes for the synthesis of 1,5-substituted 1,2,3-triazoles. The 1,5-selective click reactions will be divided into three types according to the critical reactive intermediates: metallacyclic intermediates, acetylide intermediate, and formal 1,5-selective azide-alkyne cycloaddition. The related mechanistic studies will also be involved in this review.

Structural and dynamical studies of CH-πbonded CH4-C6H6dimer by ultrafast intermolecular Coulombic decay.

The inner-valence ionization and fragmentation dynamics of CH4-C6H6dimer induced by 200 eV electron impact is studied utilizing a multi-particle coincidence momentum spectroscopy. The three-dimensional momentum vectors and kinetic energy release (KER) of the CH4++C6H6+ion pairs are obtained by coincident momentum measurement. Our analysis on the absolute cross sections indicates that the intermediate dication CH4+-C6H6+is preferentially produced by the removal of an inner-valence electron from CH4or C6H6and subsequent relaxation of ultrafast intermolecular Coulombic decay followed by two-body Coulomb explosion. Combining withab initiomolecular dynamics (AIMD) simulations, the real-time fragmentation dynamics including translational, vibrational and rotational motions are presented as a function of propagation time. The revealed fragmentation dynamics are expected to have a potential implication for crystal structure imaging with various radiation sources.

Investigation of VOC characteristics, source analysis, and chemical conversions in a typical petrochemical area through 1-year monitoring and emission inventory.

To effectively investigate the characteristics, source analysis, and chemical conversions of volatile organic compounds (VOCs) pollution in a typical petrochemical area, 81 VOC species from nine sampling sites were collected from 1st January to 31th December 2019 in Jinshan District. Results showed the concentration of VOCs was 51.63 ± 36.05 ppbv, and VOCs were dominated by alkane (40.10%) and alkenes (39.91%). The temporal variations of VOCs showed that the highest average VOC concentration appeared in July, and the lowest concentration of VOCs was in February. The concentration of VOCs was mainly connected with industrial processes and was transported to other areas through the downwind direction. Six PMF-derived sources including petrochemical industry, solvent utilization, vehicle exhaust, fuel evaporation, combustion, and other industry processes, contributing 37.08%, 16.74%, 16.69%, 14.99%, 9.53%, and 4.97%, respectively. Meanwhile, an anthropogenic VOC emission inventory was established by emission factors and the activity statistics for 2019, results indicated that the total emission of VOCs was estimated as 6.22 kt, petrochemical industry was the most important contributor of human-produced VOCs. The LOH concentration was 396.12 ppbv via OH radical loss rate method, and the OFP was 210.44 ppbv based on the MIR factor. Alkenes and aromatics were the important components of O3 formation. This study provides effective information for corresponding governments to establish VOCs contamination control directives.

Re-evaluating the asymmetric economic policy uncertainty, conventional energy, and renewable energy consumption nexus for BRICS.

Economic policy uncertainty has increased throughout the world since the previous few decades. Moreover, economic policy uncertainty significantly influences economic activities that may also produce a strong effect on energy consumption. The objective of the study is to investigate the effect of economic policy uncertainty on renewable and non-renewable energy consumption in the case of BRICS countries, for the period 1991-2019. The outcome of the panel NARDL-PMG modeling technique demonstrates that a positive shock in economic policy uncertainty exerts a negative impact on renewable energy consumption and positive impact on non-renewable energy consumption in the short-run and long-run. However, a negative shock in economic policy uncertainty has a positive impact on renewable energy consumption and negative impact on non-renewable energy consumption in the long run, while this effect becomes statistically insignificant in the short run. Numerical elements of long-run results infer that economic policy uncertainty is more influence on renewable energy compared to non-renewable energy consumption in BRICS in long run. On the basis of findings, the study suggests that the authorities should launch such programs that result in shrinking uncertainties linked with economic policy.

Asymmetric Total Syntheses of (+)-Davisinol and (+)-18-Benzoyldavisinol: A HAT-Initiated Transannular Redox Radical Approach.

The first and asymmetric total syntheses of two C11-oxygenated hetisine-type diterpenoid alkaloids, namely, (+)-davisinol and (+)-18-benzoyldavisinol, is described. The concise synthetic approach features a HAT-initiated transannular redox radical cyclization, an ODI-Diels-Alder cycloaddition, and an acylative kinetic resolution. By incorporating an efficient late-stage assembly of the azabicycle, our strategy would streamline the synthetic design of C20-diterpenoid alkaloids and pave the way for their modular syntheses.

Protonation-Induced Enhanced Optical-Light Photochromic Properties of an Inorganic-Organic Phosphomolybdic Acid/Polyaniline Hybrid Thin Film.

A phosphomolybdic acid/polyaniline (PMoA/PANI) optical-light photochromic inorganic/organic hybrid thin film was successfully synthesized by protonation between the the multiprotonic acid phosphomolybdic acid (H3PO4·12MoO3) and the conductive polymer polyaniline. The stable Keggin-type structure of PMoA was maintained throughout the process. Protonation and proton transfer successfully transformed the quinone structure of eigenstate PANI into the benzene structure of single-polarized PANI in the PMoA/PANI hybridized thin film, and proton transfer transformed the benzene structure of single-polarized PANI back to the quinone structure of eigenstate PANI in the PMoA/PANI hybrid thin film, as verified by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The average distribution of PMoA/PANI was observed by atom force microscopy (AFM). Interestingly, protonation of PMoA caused PANI to trigger transformation of the quinone structure into the single-polarized benzene structure, which enhanced the electron delocalization ability and vastly enhanced the maximum light absorption of the PMoA/PANI hybrid thin film as confirmed by density functional theory (DFT), electrochemistry, and ultraviolet-visible spectroscopy (UV-Vis) studies. Under optical-light illumination, the pale-yellow PMoA/PANI hybrid thin film gradually turned deep blue, thus demonstrating a photochromic response, and reversible photochromism was also observed in the presence of hydrogen peroxide (H2O2) or oxygen (O2). After 40 min of optical-light illumination, 36% of the Mo5+ species in PMoA was photoreduced via a protonation-induced proton transfer mechanism, and this proton transfer resulted in a structural change of PANI, as observed by XPS, generating a dominant structure with high maximum light absorption of 3.46, when compared with the literature reports.

Dataset for NiO/ZnO biomorphic nanocomposite using a poplar tree leaf template to generate an enhanced gas sensing platform to detect n-butanol.

The SEM image data presented in this article was collected by the Scanning electron microscopy (SEM) performed on an XL-30 ESEM FEG scanning electron microscopy. The diameter stastics data was collected and calculated by the Image-Pro Plus software system. The UV-Vis Res spectrum was collected by solid state UV diffuse reflector Shimadzu UV-4100 at wavelength 200-800 nm. The SEM image data showed more details of the poplar tree leave template(PTLT). The diameter stastics data show the diameter averagely distributed in the material. The UV-Vis Res spectrum reflected the physical property of PTLT NiO/ZnO. Interpretation of this data can be found in a research article titled "One-step facile synthesis of a NiO/ZnO biomorphic nanocomposite using a poplar tree leaf template to generate an enhanced gas sensing platform to detect n-butanol" (Qingrui Zeng et al., 2019) [1], Research Article DOI: 10.1016/j.jallcom.2019.05.018•The SEM image provide the more details about the distinction of the PTLT ZnO and conventional ZnO, further present more morphology information of the PTLT biotemplate. Exhibiting a facile and green way for synthesising ZnO and narrow down the size of ZnO crystal, present the advantage of PTLT ZnO in morphology control. Motivating gas sensor researcher to fabricate ZnO by a biotemplate method, which owned biomorphic and extraordinary gas sensing properties.•The UV-Vis Res spectrum present more detail of the energy band information of PTLT ZnO and PTLT NiO/ZnO, which is use for the gas sensing mechanism analysis. Inspiring researcher forcus on the construction on p-n heterojunction type gas sensor to enhance the gas sensing properties.•The material researchers work on the morphic investigation, gas sensor, and application of semiconductor.•These data are benefit for the application of biotemplate method for material fabrication and material application.

Temporal variations in riverine hydrochemistry and estimation of the carbon sink produced by coupled carbonate weathering with aquatic photosynthesis on land: an example from the Xijiang River, a large subtropical karst-dominated river in China.

The coupled carbonate weathering represents a significant carbon sink and can be controlled by the riverine hydrochemical variations. However, magnitudes, variations, and mechanisms responsible for the carbon sink produced by coupled carbonate weathering are unclear. In view of this, temperature, pH, dissolved oxygen, turbidity, electrical conductivity, and discharge of the Xijiang River at Wuzhou Hydrologic Gauging Station was recorded during October 2013 to September 2015 to elucidate the temporal variations in riverine hydrochemistry and their controlling mechanisms. To obtain the complete carbon sink flux (CSF) produced by coupled carbonate weathering with terrestrial aquatic photosynthesis in the river basin, the fluxes of dissolved inorganic carbon (DIC), autochthonous organic carbon (AOC, sourced from the transformation of DIC via aquatic photosynthesis), and sedimentary AOC were all considered. The results show that seasonal hydrochemical variations in the Xijiang River were related not only to dilution effects but also aquatic primary production. These results demonstrate that the variations in discharge caused by rainfall played a dominant role in controlling the variations in the CSF due to the chemostatic behavior of DIC and dissolved organic carbon (DOC). The CSF of the Xijiang River produced by coupled carbonate weathering was calculated as 11.06 t C km-2 a-1, including DIC carbon sink flux of 6.56 t C km-2 a-1, AOC flux (FAOC) of 2.25 t C km-2 a-1, and sedimentary AOC flux (FSAOC) of 2.25 t C km-2 a-1. The FAOC and FSAOC together accounted for approximately 69% of DIC carbon sink flux, or approximately 41% of the CSF, indicating that the riverine AOC flux may be high and must be considered in the estimation of rock weathering-related carbon sinks.

[Clinical application of laryngeal endoscopy in the minimally invasive surgery of laryngeal diseases].

OBJECTIVE: To study the value of laryngeal endoscopic system in the treatment of laryngeal diseases with minimally invasive surgery. METHOD: This paper was to summarized retrospectively the clinical experience of 34 cases suffered from laryngeal diseases treated by minimally invasive surgery with laryngeal endoscopic system. The remain tumor and hemorrhage were treated by microwave machine. The malignant tumors were treated by radiotherapy with 60Co in 40 Gy, postoperatively. RESULT: The tumors were totally resected and no serious complications were revealed. Followed-up these 34 cases, 26 cases with benign pathological changes who had hoarseness preoperatively recovered to normal 1-month after operation. In 2 cases with vocal cord carcinoma at the early stage, the functions and construction of throat were retained and no recurrence was founded after 6-12 month postoperatively. CONCLUSION: The laryngeal endoscopic system is valuable in treating laryngeal pathological regions and early stage carcinoma for its minimally invasion, wide operative field, good illuminative degree and normal construction and function reserved.