Nitrogen Position Research Articles

A study of donor-acceptor interaction in halogen bonded complexes of N-iodosuccinimide by 14N NQR

Some halogen bonded complexes of N-iodosuccinimide (NIS) with the nitrogen atoms at the donor and acceptor positions have been investigated by 14N nuclear quadrupole resonance (NQR) spectroscopy. The data are analyzed in view of the change of the principal values of the quadrupole coupling tensor produced by halogen bonding. The results show that the deformation of the nitrogen electron orbitals is in the presently studied halogen bonded systems comparable to the one observed in strong hydrogen bonded systems. The order in which the strength of the halogen bond acceptor increases is determined. A possible iodine displacement to a position, which is closer to the acceptor nitrogen atom than to the donor nitrogen atom may occur in the complex NIS-(3-picoline). In all studied complexes the deformation of the nitrogen electron orbitals caused by the halogen bond decreases with increasing temperature at both the donor and acceptor nitrogen positions.

Soil hydrological properties as influenced by long‐term nitrogen application and landscape positions under switchgrass seeded to a marginal cropland

AbstractSwitchgrass (Panicum virgatum L.) has the potential to recover the soil hydrological properties of marginal lands. Nitrogen (N) and landscape position are the key factors in impacting these soil properties under switchgrass. The specific objective of this study was to investigate the responses of N rate (low, 0 kg N/ha and high, 112 kg N/ha) and landscape positions (shoulder and footslope) on near‐surface soil hydrological properties that included: infiltration rate (qs), saturated hydraulic conductivity (Ksat), bulk density (ρb), penetration resistance (SPR), water retention (SWR), pore‐size distribution (PSD), and carbon (C) and nitrogen (N) fractions under switchgrass production. Data showed that, in general, the N and landscape position significantly influenced soil hydrological properties. Higher N rate decreased ρb (1.23 and 1.36 g/cm3 at 0–5 and 5–15 cm, respectively) and SPR (1.06 and 1.53 MPa at 0–5 and 5–15 cm, respectively) at both depths and increased the qs, Ksat and Green–Ampt estimated sorptivity (S) and hydraulic conductivity (Ks) parameters, and SWR (0–5 cm depth) at 0 and −0.4 kPa matric potentials (ψm). Furthermore, footslope position significantly decreased ρb, SPR at 0–5 and 5–15 cm depths, and increased the qs, Ksat, S, Ks, and SWR (0–5 cm depth) at every ψm ranged from 0 to −30.0 kPa. The higher N rate increased the coarse mesopores (60–1,000 μm) and total pores, whereas, footslope position increased the coarse mesopores, micropores (<60 μm), and total pores. Data from this study showed that planting switchgrass with 112 kg N/ha under footslope position helped in improving the soil hydrological properties, those can be beneficial in enhancing the biomass yield under marginal lands.

Base promoted synthesis of novel indole-dithiocarbamate compounds as potential anti-inflammatory therapeutic agents for treatment of acute lung injury

An efficient protocol for highly chemoselective introduction of dithiocarbamate groups to nitrogen position of indoles with bis(dialkylaminethiocarbonyl)disulfides was achieved by employing t-BuOK as a promoter. Based on this methodology, twenty nine novel indole-dithiocarbamate compounds were prepared in moderate to excellent yields at room temperature. All compounds were evaluated for their anti-inflammatory activity. Most of the compounds exhibited high potency on inhibiting the releasing of tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6). Four of them were found to suppress in vitro cytokine production in a dose-dependent manner with IC50 values in the nanomolar range. Additionally, 3-methyl-1H-indol-1-yl dimethylcarbamodithioate (3o) effectively ameliorated histopathological changes of lung tissues and attenuated lipopolysaccharides (LPS)-induced acute lung injury (ALI) in vivo. These data suggest that the new indole-dithiocarbamate derivatives could be particularly useful for further pharmaceutical development for the treatment of ALI.

The long-term effect of legumes as forecrops on the productivity of rotation (winter rape-winter wheat-winter wheat) with nitrogen fertilization

A field experiment was carried out in the years 2012–2018 in Poland in a split-plot design. The aim of the study was to determine the long-term effect of legumes as forecrops on the productivity of rotation with nitrogen fertilization. The rotation included: legumes + spring barley (SB), winter rape (WR), winter wheat (WW) and winter wheat. The study was conducted as a two-factorial field experiment with four replications. The present study showed that legumes as forecrops increased the yield of all after-harvest crops in rotation. Yielding of these crops also depended on nitrogen fertilization and position in the rotation. After comparison of the influence of nitrogen fertilization on yield of cereals, it was observed that the effect of this factor was greater for WW cultivated in the fourth year of rotation than for WW cultivated in the third year of rotation. In relation with control, each dose of nitrogen fertilization caused a significant increase of WR and cereals yield, but the dose of 180 kg N/ha did not increase yield significantly in comparison to the dose of 120 kg N/ha. There was also negative agronomic N-efficiency observed between doses of 120–180 kg N/ha, which means that it is not necessary to use 180 kg N/ha, especially if there are legumes in crop rotation.

DFT study of CO adsorption on nitrogen/boron doped-graphene for sensor applications.

We have performed a Density Functional study of the CO adsorption in B-doped, N-doped and BN-co-doped graphene considering a coronene based model in order to estimate the applications of this systems as CO-sensor. Different monosubstituted, disubstituted and trisubstituted alternatives of combining these two heteroatoms in a substitutional chemical doping and the influence of the relative positions of the heteroatoms are analyzed. In this study, the stability selectivity for CO adsorption and the change in the electric properties for the presence of this molecule, have been evaluated through the calculation of binding energy, CO-adsorption's energy and the gap HOMO-LUMO change due to CO adsorption. The results indicated that, even though all the configurations were stables and was confirmed a CO physical adsorption in all of them, the relative positions of Nitrogen and Boron gave different stabilities and different responses to the CO adsorption. Since monosubstituted Boron-coronene was the second in stability respect to pristine coronene, showed the highest CO adsorption energy and was also the second highest ∆(∆HOMO-LUMO) value, this structure could be potentially a good CO-sensor.

Azaindolo[3,2,1-jk]carbazoles: New Building Blocks for Functional Organic Materials.

The preparation and characterization of 12 azaindolo[3,2,1‐jk]carbazoles is presented. Ring‐closing C−H activation allowed for the convenient preparation of six singly and six doubly nitrogen‐substituted indolo[3,2,1‐jk]carbazole derivatives in which ten of the materials have not been described in the literature before. The detailed photophysical and electrochemical characterization of the developed materials revealed a significant impact of the incorporation of pyridine‐like nitrogen into the fully planar indolo[3,2,1‐jk]carbazole backbone. Furthermore, the nitrogen position decisively impacted intermolecular hydrogen bonding and thus the solid‐state alignment. Ultimately, the versatility of the azaindolo[3,2,1‐jk]carbazoles scaffold makes this class of materials an attractive new building block for the design of functional organic materials.

Crosswise Phthalocyanines with Collinear Functionalization: New Paradigmatic Derivatives for Efficient Singlet Oxygen Photosensitization.

We describe here the preparation of a series of trans-ABAB Zn(II) phthalocyanines (ZnPcs, which combine several interesting features. First, these compounds present high solubility and hindered aggregation, due to the functionalization of two facing isoindole constituents (B) of the ZnPc with bis(trifluoromethylphenyl) units. Second, the other two isoindoles (A) bear extra-annulated phthalimide units containing different substituents in the nitrogen positions, this feature results in a collinear arrangement of a variety of functional groups. Some of these collinearly functionalized ZnPcs are interesting building blocks for constructing either homo- or heteroarrays containing ZnPc units. Furthermore, the amphiphilic nature of some members of the series renders them interesting candidates for photosensitization of singlet oxygen. Photophysical studies on a model compound of the series have shown that these molecules are efficient singlet oxygen photosensitizers in both polar and apolar media, with 1 O2 quantum yields (φΔ ) as high as 0.74.

Impact of heteroatom (S and N) position and change in central ring of anthracene with heterocyclic ring on charge transport and optical properties in anthratetrathiazole (ATTz)

ABSTRACTBased on the results of quantum mechanical calculation extracted with the B3LYP functional at the density functional theory level, the impact of replacement of thiophene with thiazole rings in anthratetrathiophene (ATT) molecule was evaluated. Furthermore, to study the effect of substitution in the central benzene ring of anthracene, cyclic rings with heteroatoms were introduced. The optical and charge transport characteristics were also examined when the position of sulphur and nitrogen at the periphery of anthracene were interchanged. To analyze the electronic transitions in these molecules, TD-DFT calculations were performed. The outcome of the calculations suggest that swapping of the central benzene with hetero-cyclic rings and the change in positions of the sulphur and nitrogen have considerable influence on various properties, i.e. energies of HOMO & LUMO, HOMO-LUMO energy gap, ionization potential (IP), electron affinity (EA), hole extraction potential (HEP), electron extraction potential (EEP) and reorganization energies (λ). Moreover, all the studied molecules posed better hole and electron transport characteristics than standard materials. The smaller values of hole and electron reorganization energies suggest that this analysis offers a supportive background for prospective design and fabrication of high-performance charge-transport materials.HighlightsOn interchanging position of S and N at the periphery of ATTz results, a small change in absorption maxima.Replacement of central six-member ring of anthracene with a five-member ring in ATTz molecule results in blue-shifted absorption.Molecules where sulphur facing outward at the periphery of ATTz are better for hole transporting materials.On changing the position of S-atom (inward to outward position) at the periphery of ATTz lead to destabilization of both HOMO and LUMO levels.

1,2-Αnnulated Adamantane Heterocyclic Derivatives as Anti-Influenza Α Virus Agents

In this report we review our results on the development of 1,2-annulated adamantane heterocyclic derivatives and we discuss the structure-activity relationships obtained from their biological evaluation against influenza A virus. We have designed and synthesized numerous potent 1,2-annulated adamantane analogues of amantadine and rimantadine against influenza A targeting M2 protein the last 20 years. For their synthesis we utilized the key intermediates 2-(2-oxoadamantan-1-yl)acetic acid and 3-(2-oxoadamantan-1-yl)propanoic acid, which were obtained by a simple, fast and efficient synthetic protocol. The latter involved the treatment of protoadamantanone with different electrophiles and a carbon-skeleton rearrangement. These ketoesters offered a new pathway to the synthesis of 1,2-disubstituted adamantanes, which constitute starting materials for many molecules with pharmacological potential, such as the 1,2-annulated adamantane heterocyclic derivatives. To obtain additional insight for their binding to M2 protein three structurally similar 1,2-annulated adamantane piperidines, differing in nitrogen position, were studied using molecular dynamics (MD) simulations in palmitoyl-oleoyl-phosphatidyl-choline (POPC) hydrated bilayers.

The influence of nitrogen position on charge carrier mobility in enantiopure aza[6]helicene crystals.

The properties of an organic semiconductor are dependent on both the chemical structure of the molecule involved, and how it is arranged in the solid-state. It is challenging to extract the influence of each individual factor, as small changes in the molecular structure often dramatically change the crystal packing and hence solid-state structure. Here, we use calculations to explore the influence of the nitrogen position on the charge mobility of a chiral organic molecule when the crystal packing is kept constant. The transfer integrals for a series of enantiopure aza[6]helicene crystals sharing the same packing were analysed in order to identify the best supramolecular motifs to promote charge carrier mobility. The regioisomers considered differ only in the positioning of the nitrogen atom in the aromatic scaffold. The simulations showed that even this small change in the chemical structure has a strong effect on the charge transport in the crystal, leading to differences in charge mobility of up to one order of magnitude. Some aza[6]helicene isomers that were packed interlocked with each other showed high HOMO-HOMO integrals (up to 70 meV), whilst molecules arranged with translational symmetry generally afforded the highest LUMO-LUMO integrals (40-70 meV). As many of the results are not intuitively obvious, a computational approach provides additional insight into the design of new semiconducting organic materials.

Superior oxygen electrocatalysts derived from predesigned covalent organic polymers for zinc-air flow batteries.

Covalent organic polymers (COPs) as emerging porous materials with ultrahigh hydrothermal stability and well-defined and adjustable architectures have aroused great interest in the electrochemical field. Here, we reported a rational design approach for the preparation of a bifunctional electrocatalyst with the assistance of a predesigned bimetallic covalent organic polymer. With the predesigned nitrogen position and structural features of COP materials, the obtained CCOPTDP-FeNi-SiO2 catalyst affords a remarkable bifunctional performance with a positive half-wave potential (0.89 V vs. reversible hydrogen electrode: RHE, superior to the benchmark Pt/C) for ORR activity, and a low overpotential (0.31 V better than the benchmark IrO2) at 10 mA cm-2 for OER activity in alkaline solution. The potential gap between E1/2 and Ej=10 reaches 0.650 V, in line with that observed in the current state-of-the-art bifunctional oxygen electrode materials. Moreover, a homemade rechargeable Zn-air flow battery using the CCOPTDP-FeNi-SiO2 catalyst as an air cathode exhibits an almost twofold power density (112.8 vs. 64.8 mW cm-2) and a lower charge-discharge voltage gap, compared with a commercialized noble Pt/C + IrO2/C-driven Zn-air flow battery. More importantly, the CCOPTDP-FeNi-SiO2-driven battery maintains a better cycling stability compared to a noble metal-driven battery without performance decay. Accordingly, this work will open up new ways for fabricating practical oxygen electrodes for, but not limited to, metal air based battery applications.

Electronic Structure Modulation of Graphitic Carbon Nitride by Oxygen Doping for Enhanced Catalytic Degradation of Organic Pollutants through Peroxymonosulfate Activation.

Oxygen-doped graphitic carbon nitride (O-CN) was fabricated via a facile thermal polymerization method using urea and oxalic acid dihydrate as the graphitic carbon nitride precursor and oxygen source, respectively. Experimental and theoretical results revealed that oxygen doping preferentially occurred on the two-coordinated nitrogen positions, which create the formation of low and high electron density areas resulting in the electronic structure modulation of O-CN. As a result, the resultant O-CN exhibits enhanced catalytic activity and excellent long-term stability for peroxymonosulfate (PMS) activation toward the degradation of organic pollutants. The O-CN with modulated electronic structure enables PMS oxidation over the electron-deficient C atoms for the generation of singlet oxygen (1O2) and PMS reduction around the electron-rich O dopants for the formation of hydroxyl radical (•OH) and sulfate radical (SO4•-), in which 1O2 is the major reactive oxygen species, contributing to the selective reactivity of the O-CN/PMS system. Our findings not only propose a novel PMS activation mechanism in terms of simultaneous PMS oxidation and reduction for the production of nonradical and radical species but also provide a valuable insight for the development of efficient metal-free catalysts through nonmetal doping toward the persulfate-based environmental cleanup.

Instability of two–dimensional structure of dichalcogenin and dipnictogenin octa–heterocyclic systems with 1,2–C6X2(X = O, S, Se, Te, N, P) unsaturated rings

The planar configuration and twisted structures of the dichalcogenin (DCG) and dipnictogenin (DPG) octa–heterocyclic systems with 1,2–C6X2 ring in their main skeleton were computed through ab initio geometry optimization and following frequency calculations. Whereas the C6X2 eight–membered unsaturated rings in the considered compounds are unstable in their planar configurations, the molecules distorted from their planar shape with C2v, high symmetry into the C2, lower symmetry, twisted equilibrium configuration. Based on adiabatic potential energy surface (APES) cross sections, coupling between the ground state (1A1) and 1A2 excited state and the PJTE (1A1 + 1A2 + ···) ⊗ a2 are the reasons for the C6X2 unsaturated rings’ two–dimensional structure instability. Moreover, substitution of two hydrogen atoms in bonding with nitrogen and phosphorus positions of DPGs with halogens significantly changed the effect in the 1,2–diazocine and 1,2–diphosphocine compounds. Furthermore, intramolecular hydrogen bonding in the systems with 1,2–C6X2 (X = O, N) rings affect two–dimensional instability of the molecular structure.

Pyridine vs N-Hydrogenated Pyridine Moieties: Theoretical Study of Stability and Spectroscopy of Nitrogen-Contained Heterocyclic Aromatic Compounds and Graphene Nanoflakes

Nitrogen is one of the most common heteroatom appearing in heterocyclic aromatic compounds (HACs) as well as the frequently applied dopant in graphene nanoflakes/nanoribbons. The pyridine moiety is an intuitive and stable common feature of these compounds; but interestingly, using density functional theory calculations, we found that the N-hydrogenated pyridine moiety could be even more stable in large HACs and in N-doped graphene nanoflakes considering their formation reaction energies. The hydrogenation reaction of the pyridine moiety was calculated to be exothermic for models of four and more fused aromatic rings with specific substitutional positions of nitrogen. This theoretical investigation provides energetic and spectroscopic hints to the existence of the N-hydrogenated pyridine moiety under proper conditions.

Production of corn in Serbia in the light of climate change

This paper presents the basic elements of maize production technology in Serbia. For their good knowledge, it is necessary to be familiar with the basic biological requirements of the species, phenology and its particular requirements for water, heat, soil conditions and mineral nutrition. A special emphasis in this paper is given to recent research by the author regarding the correction of production technology (selection of hybrids, time and density of sowing, etc.) from the aspect of knowing the weather conditions of the year to the moment of sowing and the amount and position of available nitrogen in the soil profile during the spring before sowing. In the light of predicted climate change conditions for the Republic of Serbia, the authors of this paper have proposed and appropriated adaptation measures. The general conclusion is that there are no general recipes for the correct production technology of this plant species, but should be adapted to each specific year, field and hybrid.

Design and Synthesis of Energetic Materials towards Versatile Applications by N-trinitromethyl and N-nitromethyl Functionalization of Nitroimidazoles.

Modifying the properties of energetic materials is important not only for gaining insight into the relationship between structures and properties but also for multiple applications. A new family of energetic compounds, polynitroimidazoles featuring trinitromethyl, nitromethyl and methyl acetate moieties at the nitrogen position of heterocyclic rings were synthesized. The high-energy oxidizers 2-nitro and 4-nitro-1-(trinitromethyl)-1H-imidazoles were obtained by nitration of 1-acetonylpolynitroimidazoles in fuming HNO3 and concentrated H2 SO4 . 4,5-Dinitro-1-(nitromethyl)-1H-imidazole and 4,5-dinitro-1-(acetate methyl)-1H-imidazole were afforded by using 68 % HNO3 and concentrated H2 SO4 through controllable synthesis. All the intermediates and the target compounds were confirmed by X-ray diffraction. It is noteworthy that one of the N-trinitromethyl nitroimidazole derivatives showed high density (ρ: 1.88 g cm-3 ), attractive positive oxygen balance (Ω: +18.3 %) and good detonation performance (D: 9003 m s-1 ) exceeding those of ADN, while N-nitromethyl derivative behaved higher thermal stability and lower sensitivity in contrast to those of NG. N-acetate methyl derivative gave an interesting melt-castable property (Tm.p .: 86 o C, Td : 224 o C), acceptable detonation performance as well as low sensitivity towards impact and friction (IS>40 J, FS>360 N), making it a competitive replacement for DNAN. These chemical and physical properties indicate that these novel materials show promising energetic performance towards future applications.

Beta Diversity Patterns of Post-fire Forests in Central Yunnan Plateau, Southwest China: Disturbances Intensify the Priority Effect in the Community Assembly.

Post-fire succession is an ideal case for studying effects of disturbance on community assembly, and the key is to disentangle the contributions of assembly processes to the variation of community composition, namely beta diversity, and the contingent scales. The central Yunnan Plateau of Southwest China is characterized by monsoon related seasonal drought, and frequent forest fires. We sampled five fire sites burned in different years and a middle aged forest, measured species composition dissimilarity and its species turnover and nestedness components, within each fire site and across all sites. Results indicated species turnover as the primary component of beta diversity within all communities. There was no trend of change with year-since-fire (YSF) in beta diversity among early post-fire communities, but beta diversity in the middle aged community was significantly higher. Species turnover patterns across fire sites revealed a weak dispersal limit effect, which was stronger at lower than upper slope position for woody plants, and reverse for herbs. At the site scale, the species dissimilarity and turnover both enlarged with increasing slope position difference, especially in the middle-aged community, but the species nestedness had no consistent trend among sites, except a decreasing trend in the middle-aged forest. (Partial) Mantel tests indicated habitat filtering [primarily indicating total nitrogen (TN) and slope position] played a much stronger role than dispersal limit and YSF (indicating competition intensity) for the post-fire forest assembly at the landscape scale, for both woody and herbaceous layers. However, at the site scale, Mantel tests indicated a diminishing effect of soil nutrient filtering with increasing YSF, while effects of topography and spatial distance in the middle aged community was stronger. This divergence suggests the primary assembly mechanism gradually shift away from the soil constraint. While the seasonal drought and the mountain topography dominate the environmental legacy, our results imply that fires may reinforce a priority effect in the forests assembly in this region, by creating a habitat filtering (e.g., moisture and nitrogen limitation) effect on species composition in post-fire communities.

Synthesis, spectroscopic characterization and photophysical investigations of new di-(2/3)-pyridine-stilbenes; isomerism, nitrogen position influence and solvent effects

Stilbene analogues with the pyridine ring, that is di-(pyridin-2/3/4-yl)vinyl)benzenes, were synthesized, purified and completely spectroscopically characterized. Upon irradiation these di-(pyridin-3/4-yl)vinyl)benzenes showed no other process but isomerization, in conditions for both intra- and intermolecular reactions. Compound di-(pyridin-2-yl)vinyl)benzene gave by intermolecular cycloaddition reaction, in trace amounts, a dimeric product. This general unreactivity towards photocyclization and photocycloaddition reactions led to further investigations and description of photophysical properties. Quantum yields of photolysis as well as fluorescence were measured and calculated. It was shown that the placement of the nitrogen in the stilbene like system plays an important role in the photophysical properties. The connection between photophysical properties and configurational isomerism was defined. The polarity effect of the medium has a complex influence on the photobehaviour and the measured effects are probably not coming only from polarity.

Synthetic nicotinic/isonicotinic thiosemicarbazides: In vitro urease inhibitory activities and molecular docking studies

Nicotinic and isonicotinic thiosemicarbazide or hydrazine carbothioamides 3–27 were synthesized and the structures of synthetic compounds were elucidated by various spectroscopic techniques such as EI-MS, 1H-, and 13C NMR. Synthetic derivatives were evaluated for their urease inhibitory activity which revealed that except few all derivatives demonstrated excellent inhibition in the range of IC50 values of 1.21–51.42 μM as compared to the standard thiourea (IC50 = 21.25 ± 0.13 μM). Among the twenty-five synthetic derivatives nineteen 1–5, 7, 8, 10, 12, 14–18, 20–22, 24–27 were found to be more active showing IC50 values between 1.13 and 19.74 μM showing superior activity than the standard. Limited structure-activity relationship demonstrated that the positions of substituent as well as position of nitrogen in pyridine ring are very important for inhibitory activity of this class of compound. To verify these interpretations, in silico study was also performed. A good correlation was obtained between the biological evaluation of active compounds and docking study.

Position of Methyl and Nitrogen on Axial Aryloxy Substituents Determines the Crystal Structure of Silicon Phthalocyanines

Phthalocyanines are a class of organometallic compounds that have been investigated extensively for emerging applications such as organic photovoltaics, organic light-emitting diodes, and thin-film transistors. For these applications, the understanding of molecular structures and intermolecular interactions is extremely crucial and is one of the most promising pathways for designing a new generation of functional materials. Here, the crystal structures of six axially substituted silicon phthalocyanines (SiPcs) with aryloxy groups are reported. Three bis(methylphenoxy) SiPcs with varying methyl positions and two bis(pyridoxy) derivatives with varying nitrogen positions are compared to the bare bis(phenoxy) SiPc. Quantitative analysis is conducted to describe the impact of the position and nature of the functional group/atom on the orientation of the axial aryloxy subtituents as well as on the aromaticity and planarity of the SiPc macrocycle. Quantitative analysis of changes in intermolecular interactions, ...