Structure and Stability of Aromatic Nitrogen Heterocycles Used in the Field of Energetic Materials

Understanding the stabilization of nitrogen heterocycles is critical in the field of energetic materials and calls for innovative knowledge of nitrogen aromatics. Herewith, we report for the first time that nitrogen lone pair electron (NLPE) delocalization in five-membered nitrogen heterocycles creates a second σ-aromaticity in addition to the prototypical π-aromaticity. The NLPE delocalization and the attendant dual-aromaticity are enhanced as more carbon atoms in the ring are substituted by unsaturated nitrogen atoms. The presence of adjacent nitrogen atoms in the ring can enhance the aromaticity of the nitrogen heterocycles and improve in-crystal intermolecular binding strength but will decrease the firmness of the individual molecular architecture. Notably, such σ-aromaticity is not present in six-membered nitrogen heterocycles, probably due to the longer bonds and broader regions of their rings; therefore, six-membered heterocycles present overall lower aromaticity than five-membered heterocycles. This work brings new knowledge to nitrogen aromatics and is expected to inspire broad interest in the chemistry community.

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Metallkomplexe von Heteroarenen, VII: Bis(2,3,5,6-tetramethyl-η6-pyrazin)vanadium, der erste Bis(aren)metall-Komplex mit vier N-Atomen in der Koordinationssphäre / Metal Complexes of Heteroarenes, VII: Bis(2,3,5,6-tetramethyl-η6-pyrazine)vanadium, the First Bis(arene)metal Complex with Four N Atoms in the Coordination Sphere

Zeitschrift für Naturforschung B ◽

10.1515/znb-1993-1117 ◽

1993 ◽

Vol 48 (11) ◽

pp. 1581-1588 ◽

Cited By ~ 8

Author(s):

Mathias Nowotny ◽

Christoph Elschenbroich ◽

Andreas Behrendt ◽

Werner Massa ◽

Sigrid Wocadlo

Keyword(s):

Spin Density ◽

Lone Pair ◽

Hyperfine Coupling Constant ◽

Metal Ring ◽

Torsional Angle ◽

Redox Potentials ◽

X Ray Crystallography ◽

Phase Combination ◽

Nitrogen Lone Pair ◽

The Individual

Cocondensation of 2,3,5,6-tetramethyl-pyrazine with vanadium atoms affords [2,3,5,6-(CH3)4-η6-1,4-C4N2]2V (6) which has been studied by X-ray crystallography, EPR-spectro-scopy and cyclic voltammetry. As shown by unequal metal ring-atom distances (V—C = 219.6, V—N = 210.9 pm) the ligand in 6 is folded along the N—N axis (dihedral angle 13.6°). The conformation adopted by the cyclic ligands in the crystal has a torsional angle of 44.2° which comes close to the angle of 45° expected for maximum back-bonding, the filled vanadium orbitals 3 dx2-γ2and 3 dxy interacting separately with unoccupied b3u(π*) orbitals of the individual pyrazine rings. The hyperfine coupling constant a(51V) = 4.45 mT attests to comparatively small spin density at the metal nucleus. It is proposed, that substantial transfer of spin density is effected by V 3dz2→ag(σn+) overlap, the latter function representing the in-phase combination of the nitrogen “lone pair” orbitals. Contrary to bis(η6-phosphinine)vanadium 8, for the pyrazine complex 6 only the anion 6⁻ is formed reversibly in cyclovoltammetry, oxidation to 6+ being irreversible. However, in common with 8, the redox potentials for 6 show pronounced anodic shifts. Attempts towards η6-coordination of 2,4,6-trimethyl-1,3,5-triazine failed. Apparently, the 1:1 ratio of CH3/N is insufficient to furnish the triazine ring with the appropriate combination of π-donor and δ-acceptor properties essential for synergetic bond formation.

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Victorian Pain

10.23943/princeton/9780691174464.001.0001 ◽

2017 ◽

Cited By ~ 1

Author(s):

Rachel Ablow

Keyword(s):

Nineteenth Century ◽

Victorian Literature ◽

Social Life ◽

Charles Darwin ◽

Harriet Martineau ◽

The Status ◽

History Of ◽

The Individual ◽

Natural Philosophers ◽

First Time

The nineteenth century introduced developments in science and medicine that made the eradication of pain conceivable for the first time. This new understanding of pain brought with it a complex set of moral and philosophical dilemmas. If pain serves no obvious purpose, how do we reconcile its existence with a well-ordered universe? Examining how writers of the day engaged with such questions, this book offers a compelling new literary and philosophical history of modern pain. The book provides close readings of novelists Charlotte Brontë and Thomas Hardy and political and natural philosophers John Stuart Mill, Harriet Martineau, and Charles Darwin, as well as a variety of medical, scientific, and popular writers of the Victorian age. The book explores how discussions of pain served as investigations into the status of persons and the nature and parameters of social life. No longer conceivable as divine trial or punishment, pain in the nineteenth century came to seem instead like a historical accident suggesting little or nothing about the individual who suffers. A landmark study of Victorian literature and the history of pain, the book shows how these writers came to see pain as a social as well as a personal problem. Rather than simply self-evident to the sufferer and unknowable to anyone else, pain was also understood to be produced between persons—and even, perhaps, by the fictions they read.

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A University Education

10.1093/oso/9780198767268.001.0001 ◽

2017 ◽

Cited By ~ 7

Author(s):

David Willetts

Keyword(s):

Higher Education ◽

Modern Society ◽

University Education ◽

Modern World ◽

Controversial Issues ◽

The Us ◽

The Individual ◽

The University ◽

First Time ◽

The Relationship

Universities have a crucial role in the modern world. In England, entrance to universities is by nation-wide competition which means English universities have an exceptional influence on schools--a striking theme of the book. This important book first investigates the university as an institution and then tracks the individual on their journey to and through university. In A University Education, David Willetts presents a compelling case for the ongoing importance of the university, both as one of the great institutions of modern society and as a transformational experience for the individual. The book also makes illuminating comparisons with higher education in other countries, especially the US and Germany. Drawing on his experience as UK Minister for Universities and Science from 2010 to 2014, the author offers a powerful account of the value of higher education and the case for more expansion. He covers controversial issues in which he was involved from access for disadvantaged students to the introduction of L9,000 fees. The final section addresses some of the big questions for the future, such as the the relationship between universities and business, especially in promoting innovation.. He argues that the two great contemporary trends of globalisation and technological innovation will both change the university significantly. This is an authoritative account of English universities setting them for the first time in their new legal and regulatory framework.

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The Republic

The Oxford Handbook of Plato ◽

10.1093/oxfordhb/9780190639730.013.11 ◽

2019 ◽

pp. 205-229

Author(s):

Dominic Scott

Keyword(s):

Political Theory ◽

Left Behind ◽

Ideal State ◽

The Republic ◽

Individual Justice ◽

The Individual ◽

Political Right ◽

First Time ◽

The Ideal

This chapter presents a reading of Plato’s Republic. The Republic is among Plato’s most complex works. From its title, the first-time reader will expect a dialogue about political theory, yet the work starts from the perspective of the individual, coming to focus on the question of how, if at all, justice contributes to an agent’s happiness. Only after this question has been fully set out does the work evolve into an investigation of politics—of the ideal state and of the institutions that sustain it, especially those having to do with education. But the interest in individual justice and happiness is never left behind. Rather, the work weaves in and out of the two perspectives, individual and political, right through to its conclusion. All this may leave one wondering about the unity of the work. The chapter shows that, despite the enormous range of topics discussed, the Republic fits together as a coherent whole.

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Biosynthetic strategies for tetramic acid formation

Natural Product Reports ◽

10.1039/d0np00099j ◽

2021 ◽

Author(s):

Xuhua Mo ◽

Tobias A. M. Gulder

Keyword(s):

Molecular Mechanism ◽

Gene Clusters ◽

Acid Formation ◽

Biosynthetic Gene ◽

Tetramic Acid ◽

Biosynthetic Gene Clusters ◽

The Individual ◽

First Time ◽

Acid Unit

Over 30 biosynthetic gene clusters for natural tetramate have been identified. This highlight reviews the biosynthetic strategies for formation of tetramic acid unit for the first time, discussing the individual molecular mechanism in detail.

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Kinetical Study, Thermo-Mechanical Characteristics and Recyclability of Epoxidized Camelina Oil Cured with Antagonist Structure (Aliphatic/Aromatic) or Functionality (Acid/Amine) Hardeners

Polymers ◽

10.3390/polym13152503 ◽

2021 ◽

Vol 13 (15) ◽

pp. 2503

Author(s):

Chiara Di Mauro ◽

Aratz Genua ◽

Alice Mija

Keyword(s):

Disulfide Bonds ◽

Mechanical Characteristics ◽

Dicarboxylic Acids ◽

Thermomechanical Properties ◽

Chemical Recycling ◽

Camelina Oil ◽

Ft Ir ◽

Tan Δ ◽

The Individual ◽

First Time

In an attempt to prepare sustainable epoxy thermosets, this study introduces for the first time the idea to use antagonist structures (aromatic/aliphatic) or functionalities (acid/amine) as hardeners to produce reprocessable resins based on epoxidized camelina oil (ECMO). Two kinds of mixtures were tested: one combines aromatic/aliphatic dicarboxylic acids: 2,2′-dithiodibenzoic acid (DTBA) and 3,3′-dithiodipropionic acid (DTDA); another is the combination of two aromatic structures with acid/amine functionality: DTBA and 4-aminophenyl disulfide (4-AFD). DSC and FT-IR analyses were used as methods to analyze the curing reaction of ECMO with the hardeners. It was found that the thermosets obtained with the dual crosslinked mechanism needed reduced curing temperatures and reprocessing protocols compared to the individual crosslinked thermosets. Thanks to the contribution of disulfide bonds in the network topology, the obtained thermosets showed recycling ability. The final thermomechanical properties of the virgin and mechanical reprocessed materials were analyzed by DMA and TGA. The obtained thermosets range from elastomeric to rigid materials. As an example, the ECMO/DTBA704-AFD30 virgin or reprocessed thermosets have tan δ values reaching 82–83 °C. The study also investigates the chemical recycling and the solvent resistance of these vitrimer-like materials.

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Exploring Secondary Metabolite Profiles of Stachybotrys spp. by LC-MS/MS

Toxins ◽

10.3390/toxins11030133 ◽

2019 ◽

Vol 11 (3) ◽

pp. 133 ◽

Cited By ~ 3

Author(s):

Annika Jagels ◽

Viktoria Lindemann ◽

Sebastian Ulrich ◽

Christoph Gottschalk ◽

Benedikt Cramer ◽

...

Keyword(s):

Secondary Metabolites ◽

Future Research ◽

Structural Modifications ◽

Metabolite Profiles ◽

The Individual ◽

First Time ◽

Analytical Standards ◽

Respective Species

The genus Stachybotrys produces a broad diversity of secondary metabolites, including macrocyclic trichothecenes, atranones, and phenylspirodrimanes. Although the class of the phenylspirodrimanes is the major one and consists of a multitude of metabolites bearing various structural modifications, few investigations have been carried out. Thus, the presented study deals with the quantitative determination of several secondary metabolites produced by distinct Stachybotrys species for comparison of their metabolite profiles. For that purpose, 15 of the primarily produced secondary metabolites were isolated from fungal cultures and structurally characterized in order to be used as analytical standards for the development of an LC-MS/MS multimethod. The developed method was applied to the analysis of micro-scale extracts from 5 different Stachybotrys strains, which were cultured on different media. In that process, spontaneous dialdehyde/lactone isomerization was observed for some of the isolated secondary metabolites, and novel stachybotrychromenes were quantitatively investigated for the first time. The metabolite profiles of Stachybotrys species are considerably influenced by time of growth and substrate availability, as well as the individual biosynthetic potential of the respective species. Regarding the reported adverse effects associated with Stachybotrys growth in building environments, combinatory effects of the investigated secondary metabolites should be addressed and the role of the phenylspirodrimanes re-evaluated in future research.

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Taming nitroformate through encapsulation with nitrogen-rich hydrogen-bonded organic frameworks

Nature Communications ◽

10.1038/s41467-021-22475-8 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Jichuan Zhang ◽

Yongan Feng ◽

Richard J. Staples ◽

Jiaheng Zhang ◽

Jean’ne M. Shreeve

Keyword(s):

Thermal Stability ◽

Hydrogen Bonds ◽

Self Assembly ◽

Energetic Materials ◽

Decomposition Temperature ◽

High Oxygen Content ◽

The Poor ◽

Simple Preparation ◽

First Time ◽

Hydrogen Bonded

AbstractOwing to its simple preparation and high oxygen content, nitroformate [−C(NO2)3, NF] is an extremely attractive oxidant component for propellants and explosives. However, the poor thermostability of NF-based derivatives has been an unconquerable barrier for more than 150 years, thus hindering its application. In this study, the first example of a nitrogen-rich hydrogen-bonded organic framework (HOF-NF) is designed and constructed through self-assembly in energetic materials, in which NF anions are trapped in pores of the resulting framework via the dual force of ionic and hydrogen bonds from the strengthened framework. These factors lead to the decomposition temperature of the resulting HOF-NF moiety being 200 °C, which exceeds the challenge of thermal stability over 180 °C for the first time among NF-based compounds. A large number of NF-based compounds with high stabilities and excellent properties can be designed and synthesized on the basis of this work.

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Age-Graded Transitions and Turning Points in Polish Offenders’ Criminal Careers from the Standpoint of Life Course Theory

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph18116010 ◽

2021 ◽

Vol 18 (11) ◽

pp. 6010

Author(s):

Krzysztof Pękala ◽

Andrzej Kacprzak ◽

Piotr Chomczyński ◽

Jakub Ratajczak ◽

Michał Marczak ◽

...

Keyword(s):

Life Course ◽

Turning Points ◽

Criminal Activity ◽

Juvenile Detention ◽

Criminal Careers ◽

Social Adaptation ◽

Life Course Theory ◽

The Individual ◽

Individual Choices ◽

First Time

Both juvenile and adult criminal careers show regularities in the origins of delinquency, the dynamics of the criminal pathway, and the turning points that lead to desistance/persistence in crime. Research shows that family, education, and friendship environments contribute significantly to the individual choices that create criminal biographies. Our aim was to apply core aspects of life course theory (LCT): trajectory, the aged-graded process, transitions, institutions, and ultimately how desistance/persistence factor into explaining the criminal careers of Polish offenders. The research is based on in-depth interviews (130) carried out with both offenders (90) and experts (40). The offenders were divided into two groups: 30 were juveniles, and 60 were adults of whom half were sentenced for the first time (30) and half were recidivists (30) located in correctional institutions or released. The experts group (40) includes psychologists, educators, social rehabilitators, and prison and juvenile detention personnel working with offenders. We used triangulation of researcher, data, and methodology. Our data revealed that similar biographical experiences characterized by an early socialization, family and friends-based circles laid the groundwork for their entry and continued participation in criminal activity. Juvenile and adult first-time sentenced offenders led criminal careers significantly different from those of recidivists, who faced problems with social adaptation caused by lack of family and institutional support.

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Structure and bonding in cyclic phosphoramidates as determined by carbon-13 magnetic resonance

Canadian Journal of Chemistry ◽

10.1139/v79-004 ◽

1979 ◽

Vol 57 (1) ◽

pp. 21-26 ◽

Cited By ~ 5

Author(s):

Gerald W. Buchanan ◽

Frederick G. Morin

Keyword(s):

Magnetic Resonance ◽

Nitrogen Atom ◽

Electron Pair ◽

Chemical Shifts ◽

Lone Pair ◽

Ring Conformation ◽

Delocalized Electron ◽

Nitrogen Lone Pair ◽

Structure And Bonding

13C chemical shifts and 13C–31P couplings are reported for 11 cyclic phosphoramidates of ring sizes from four to nine. Vicinal couplings are compared with those of carbocyclic analogs and provide insight regarding the degree of nitrogen lone pair derealization into the N—P bond. For six-membered and larger rings, there appears to be nearly complete lone pair delocalization, i.e., a trigonal planar nitrogen atom. In azetidine derivatives the nitrogen lone pair remains localized, giving rise to a highly puckered ring conformation. Pyrrolidine derivatives are viewed as having a nitrogen with a partially delocalized electron pair.

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