Double Direct C-H Bond Arylation of Thiophenes with Aryl Chlorides Catalyzed by the N-Heterocyclic Carbene-PdCl2-1-methylimidazole Complex.

With the combination of the N-heterocyclic carbene-PdCl2-1-methylimidazole complex and Cu2O, we succeeded in the first example of double direct C-H bond arylation reactions between thiophenes and aryl chlorides, giving the desired 2,5-diarylated thiophenes in moderate to high yields under suitable conditions, consistent with the density functional theory calculations.

Metagenomics reveals the variations in functional metabolism associated with greenhouse gas emissions during legume-vegetable rotation process.

Legume-based rotation is commonly recognized for its mitigation efficiency of greenhouse gas (GHG) emissions. However, variations in GHG emission-associated metabolic functions during the legume-vegetable rotation process remain largely uncharacterized. Accordingly, a soybean-radish rotation field experiment was designed to clarify the responses of microbial communities and their GHG emission-associated functional metabolism through metagenomics. The results showed that the contents of soil organic carbon and total phosphorus significantly decreased during the soybean-radish process (P < 0.05), while soil total potassium content and bacterial richness and diversity significantly increased (P < 0.05). Moreover, the predominant bacterial phyla varied, with a decrease in the relative abundance of Proteobacteria and an increase in the relative abundance of Acidobacteria, Gemmatimonadetes, and Chloroflexi. Metagenomics clarified that bacterial carbohydrate metabolism substantially increased during the rotation process, whereas formaldehyde assimilation, methanogenesis, nitrification, and dissimilatory nitrate reduction decreased (P < 0.05). Specifically, the expression of phosphate acetyltransferase (functional methanogenesis gene, pta) and nitrate reductase gamma subunit (functional dissimilatory nitrate reduction gene, narI) was inhibited, indicating of low methane production and nitrogen metabolism. Additionally, the partial least squares path model revealed that the Shannon diversity index was negatively correlated with methane and nitrogen metabolism (P < 0.01), further demonstrating that the response of the soil bacterial microbiome responses are closely linked with GHG-associated metabolism during the soybean-radish rotation process. Collectively, our findings shed light on the responses of soil microbial communities to functional metabolism associated with GHG emissions and provide important insights to mitigate GHG emissions during the rotational cropping of legumes and vegetables.

All-nitrogen spiropentadiene-N5.

Of the pentanitrogen cation (N5 +) family, the only experimentally known isomer is the V-shaped structure 01. Here, we showed that a super-high-energy (∼100 kcal/mol above 01) all-nitrogen spiropentadiene 02 with considerable σ-delocalization deserves pursuit as the first spirocyclic all-nitrogen molecule, at least spectroscopical.

Design of N-N ylide bond-based high energy density materials: a theoretical survey.

The generally encountered contradiction between large energy content and stability poses great difficulty in designing nitrogen-rich high-energy-density materials. Although N-N ylide bonds have been classified as the fourth type of homonuclear N-N bonds (besides >N-N<, -N[double bond, length as m-dash]N-, and N[triple bond, length as m-dash]N), accessible energetic molecules with N-N ylide bonds have rarely been explored. In this study, 225 molecules with six types of novel structures containing N-N ylide bonds were designed using density functional theory and CBS-QB3 methods. To guide future synthesis, the effects of substitution on the thermal stability, detonation velocity, and detonation pressure of the structures were evaluated under the premise that the N-N ylide skeleton remains stable. The calculations show that the bond dissociation energy values of the N-N ylide bonds of the designed 225 structures were in the range of 61.21-437.52 kJ mol-1, except for N-1NNH2. Many of the designed structures with N-N ylide bonds exhibit high detonation properties, which are superior to those of traditional energetic compounds. This study convincingly demonstrates the feasibility of the design strategy of introducing an N-N ylide bond to develop new types of energetic materials.

How stable can the pentanitrogen cation be in kinetics?

For the 22 year-old pentanitrogen cation N5+ (01), we surprisingly found that the previously reported transition states (TSs) do not correspond to N2-extrusion. We located the real N2-extrusion TS, which can well reconcile the hitherto remaining inconsistency between the gas-phase and salt-like forms of 01 both in structure and energetics.

Arylpentazoles with surprisingly high kinetic stability.

The more-than-one-century-old arylpentazoles can only be used in situ in generating the pentazole anion due to their unfavourable kinetic stability. We successfully increased the N2-leaving barrier to reach hitherto the highest value of 40.83 kcal mol-1 at the CBS-QB3 level via a newly proposed co-stabilization method, making the broader applications of arylpentazoles feasible.

A kinetically persistent isomer found for pentazole: a global potential energy surface survey.

Among the N5R family, pentazoles (A1) with a 103-year-old research history remain the only class of kinetically persistent isomers. Aided by the first global isomeric survey and substitution study of N5H at the composite CBS-QB3 level, we predicted a new N5R isomer (C1) with kinetic stability close to pentazoles.