Direct Observation of All Open-Shell Intermediates in a Photocatalytic Cycle.

Molecular photocatalysis has shown tremendous success in sustainable energy and chemical synthesis. However, visualizing the transient open-shell intermediates in photocatalysis is a significant and long-standing challenge. By employing our recently developed innovative time-resolved electron paramagnetic resonance technique, we directly observed all radicals and radical ions involved in the photocatalytic addition of pempidine to tert-butyl acrylate. The full picture of the photocatalytic cycle is vividly illustrated by the fine structures, chemical kinetics, and dynamic spin polarization of all open-shell intermediates directly observed in this prototypical system. Given the universality of this methodology, we believe it greatly empowers the research paradigm of direct observation in both photocatalysis and radical chemistry.

Phosphorus fertiliser application mitigates the negative effects of microplastic on soil microbes and rice growth.

Soil microplastics (MPs) have attracted widespread attention recently. Most studies have explored how soil MPs affect the soil's physicochemical parameters, matter circulation, and soil microbial community assembly. Similarly, a key concern in agricultural development has been the use of phosphorus (P) fertiliser, which is essential for plant health and development. However, the relationship between MPs and phosphate fertilisers and their effects on the soil environment and plant growth remains elusive. This study assessed the influence of adding low-density polyethylene MPs (1%) with different phosphate fertiliser application rates on microbial communities and rice biomass. Our results showed that MPs changed the structure of soil bacterial and phoD-harbouring microbial communities in the treatment with P fertiliser at the same level and suppressed the interactions of phoD-harbouring microorganisms. In addition, we found that MPs contamination inhibited rice growth; however, the inclusion of P fertiliser in MP-contaminated soils reduced the inhibitory action of MPs on rice growth, probably because the presence with P fertiliser promoted the uptake of NO3--N by rice in MP-contaminated soils. Our results provide further insights into guiding agricultural production, improving agricultural management, and rationally applying phosphate fertilisers in the context of widespread MPs pollution and global P resource constraints.

Effect of different types of biochar on soil properties and functional microbial communities in rhizosphere and bulk soils and their relationship with CH4 and N2O emissions.

Biochar as an agricultural soil amendment plays vital roles in mediating methane (CH4) and nitrous oxide (N2O) emissions in soils. The link between different types of biochar, bulk soil, and rhizosphere microbial communities in relation to CH4 and N2O emissions is being investigated in this study. The rice pot experiment was conducted using biochar at two temperatures (300°C and 500°C) in combination with three biochar levels (0, 2, 10% w/w). Soil properties and the abundance of genes associated with CH4 and N2O emissions from both rhizosphere and bulk soils were investigated. The study also aimed to examine the structure of microbial communities (pmoA, nosZ) in rhizosphere and bulk soils whereas CH4 and N2O emissions were monitored while growing rice. Results showed that biochar at 300°C and 10% incorporation significantly increased the CH4 emissions by up to 59% rise compared to the control group. Random Forest analysis revealed that the ratio of mcrA/pmoA along with the abundance of mcrA from both rhizosphere and bulk soils, the abundance of AOA, TN, DOC, and the community composition of pmoA-harboring microorganisms from both bulk and rhizosphere soils were important predictors of CH4 emissions. Therefore, the ratio of mcrA/pmoA in rhizosphere soil and the abundance of AOA in bulk soil were the main factors influencing CH4 emissions. Variation Partitioning Analysis (VPA) results indicated that the effects of these factors on bulk soil were 9% of CH4 emissions variations in different treatments, which contributed more than rhizosphere soils' factors. Moreover, random forest analysis results indicated that the abundance of AOB in bulk soil was the most important predictor influencing N2O emissions. The VPA result revealed that the factors in rhizosphere soil could explain more than 28% of the variations in N2O emissions. Our study highlights that rhizosphere soil has a more significant effect than bulk soil on N2O production. Our findings further the understanding of the link between bulk and rhizosphere attributes, and their impact on CH4 and N2O emissions in paddy soils. In summary, we recommend the application of biochar at 500°C and 2% incorporation rate for agricultural production in the area.

Visible-Light-Driven Bisfunctionalization of Unactivated Olefins via the Merger of Proton-Coupled Electron Transfer and Carbene Catalysis.

Herein, we reported an N-heterocyclic carbene (NHC) and photo-co-catalyzed alkylacylation of olefins in the presence of the versatile synthon diazo ester, providing a new idea for transient radical generation with the only byproduct being N2. Particularly, this radical process employs traditional carbene precursor diazo esters as the radical source, which is the first case in NHC catalysis. Compared to the previous pathway that produces radicals with large discard fragments, this merged channel possesses great atom economy.

DFT Study on the Mechanism of 4,4'-Bipyridine-Catalyzed Nitrobenzene Reduction by Diboron(4) Compounds.

Diboron(4) compounds serve as useful reagents for borylation, diboration, and reduction in organic synthesis. A variety of pyridine derivatives have been found capable of activating diboron(4) compounds, and different reaction mechanisms have been identified. 4,4'-Bipyridine was found to activate diboron(4) to form N,N'-diboryl-4,4'-bipyridinylidene in 2015, and very recently, it has been found that this transformation is crucial in the 4,4'-bipyridine-catalyzed reduction of nitroarenes by bis(neopentylglycolato)diboron (B2nep2), which features the formation of arylnitrene intermediates. However, the mechanism of N,N'-diboryl-4,4'-bipyridinylidene formation, as well as its role in the transformation of nitroarene to arylnitrene, remains unknown. In this work, we investigated the possible pathways of this intriguing transformation and discovered several important intermediates through density functional theory (DFT) calculations. An N-boryl 4,4'-bipyridyl radical was found to be a crucial intermediate in both the formation of N,N'-diboryl-4,4'-bipyridinylidene and the reduction of nitroarene. A type of single-step reaction with three stages, including a dissociation and two migration steps, was identified in the generation of nitrosobenzene and its reduction. Arylnitrene formation was found to occur on a triplet potential energy surface, and an intersystem crossing was found to be important for achieving a reasonable activation energy barrier for nitrene formation. We anticipate our work to provide deeper insights into the nature of this reaction that could facilitate further rational design of pyridine- and bipyridine-based catalysts.