scholarly journals Current vortices in aromatic carbon molecules

2020 ◽  
Vol 102 (7) ◽  
Author(s):  
Thomas Stegmann ◽  
John A. Franco-Villafañe ◽  
Yenni P. Ortiz ◽  
Michael Deffner ◽  
Carmen Herrmann ◽  
...  
Keyword(s):  
Aromatic Carbon ◽  
Carbon Molecules

scholarly journals Current Vortices in Aromatic Carbon Molecules

2019 ◽  
Author(s):  
Thomas Stegmann ◽  
John A. Franco-Villafañe ◽  
Yenni P. Ortiz ◽  
Michael Deffner ◽  
Carmen Herrmann ◽  
...  
Keyword(s):  
Density Functional ◽  
Nearest Neighbor ◽  
Tight Binding ◽  
Electron System ◽  
Aromatic Carbon ◽  
Robust Property ◽  
Local Current ◽  
Ring Structures ◽  
Carbon Molecules ◽  
Current Flows

<div><div><div><p>The local current flow through three small aromatic carbon molecules, namely benzene, naphthalene and anthracene, is studied. Applying density functional theory and the non-equilibrium Green’s function method for transport, we demonstrate that pronounced current vortices exist at certain electron energies for these molecules. The intensity of these circular currents, which appear not only at the anti-resonances of the transmission but also in vicinity of its maxima, can exceed the total current flowing through the molecular junction and generate considerable magnetic fields. The π electron system of the molecular junctions is emulated experimentally by a network of macroscopic microwave resonators. The local current flows in these experiments confirm the existence of current vortices as a robust property of ring structures. The circular currents can be understood in terms of a simple nearest-neighbor tight-binding Hückel model. Current vortices are caused by the interplay of the complex eigenstates of the open system which have energies close-by the considered electron energy. Degeneracies, as observed in benzene and anthracene, can thus generate strong circular currents, but also non-degenerate systems like naphthalene exhibit current vortices. Small imperfections and perturbations can couple otherwise uncoupled states and induce circular currents.</p></div></div></div>

scholarly journals Current Vortices in Aromatic Carbon Molecules

2019 ◽  
Author(s):  
Thomas Stegmann ◽  
John A. Franco-Villafañe ◽  
Yenni P. Ortiz ◽  
Michael Deffner ◽  
Carmen Herrmann ◽  
...  
Keyword(s):  
Density Functional ◽  
Nearest Neighbor ◽  
Tight Binding ◽  
Electron System ◽  
Aromatic Carbon ◽  
Robust Property ◽  
Local Current ◽  
Ring Structures ◽  
Carbon Molecules ◽  
Current Flows

<div><div><div><p>The local current flow through three small aromatic carbon molecules, namely benzene, naphthalene and anthracene, is studied. Applying density functional theory and the non-equilibrium Green’s function method for transport, we demonstrate that pronounced current vortices exist at certain electron energies for these molecules. The intensity of these circular currents, which appear not only at the anti-resonances of the transmission but also in vicinity of its maxima, can exceed the total current flowing through the molecular junction and generate considerable magnetic fields. The π electron system of the molecular junctions is emulated experimentally by a network of macroscopic microwave resonators. The local current flows in these experiments confirm the existence of current vortices as a robust property of ring structures. The circular currents can be understood in terms of a simple nearest-neighbor tight-binding Hückel model. Current vortices are caused by the interplay of the complex eigenstates of the open system which have energies close-by the considered electron energy. Degeneracies, as observed in benzene and anthracene, can thus generate strong circular currents, but also non-degenerate systems like naphthalene exhibit current vortices. Small imperfections and perturbations can couple otherwise uncoupled states and induce circular currents.</p></div></div></div>

Substrate channels revealed in the trimericLactobacillus reuteribacterial microcompartment shell protein PduB

2012 ◽  
Vol 68 (12) ◽  
pp. 1642-1652 ◽  
Author(s):  
Allan Pang ◽  
Mingzhi Liang ◽  
Michael B. Prentice ◽  
Richard W. Pickersgill
Keyword(s):  
Tandem Repeats ◽  
Lactobacillus Reuteri ◽  
Protein Complexes ◽  
Protein Subunits ◽  
Shell Protein ◽  
Domain Structures ◽  
Bacterial Microcompartment ◽  
Major Shell ◽  
Carbon Molecules ◽  
Trimeric Structure

Lactobacillus reuterimetabolizes two similar three-carbon molecules, 1,2-propanediol and glycerol, within closed polyhedral subcellular bacterial organelles called bacterial microcompartments (metabolosomes). The outer shell of the propanediol-utilization (Pdu) metabolosome is composed of hundreds of mainly hexagonal protein complexes made from six types of protein subunits that share similar domain structures. The structure of the bacterial microcompartment protein PduB has a tandem structural repeat within the subunit and assembles into a trimer with pseudo-hexagonal symmetry. This trimeric structure forms sheets in the crystal lattice and is able to fit within a polymeric sheet of the major shell component PduA to assemble a facet of the polyhedron. There are three pores within the trimer and these are formed between the tandem repeats within the subunits. The structure shows that each of these pores contains three glycerol molecules that interact with conserved residues, strongly suggesting that these subunit pores channel glycerol substrate into the metabolosome. In addition to the observation of glycerol occupying the subunit channels, the presence of glycerol on the molecular threefold symmetry axis suggests a role in locking closed the central region.

Equilibrium Constants for Dehydration of Water Adducts of Aromatic Carbon−Carbon Double Bonds

2002 ◽  
Vol 124 (29) ◽  
pp. 8561-8574 ◽  
Author(s):  
Joykrishna Dey ◽  
AnnMarie C. O'Donoghu ◽  
Rory A. More O'Ferrall
Keyword(s):  
Equilibrium Constants ◽  
Double Bonds ◽  
Aromatic Carbon

Nucleophile/Electrophile Combinations in Aromatic Substitution: From Wheland to Wheland–Meisenheimer Intermediates Using Strongly Activated Arenes

Synthesis ◽  
2017 ◽  
Vol 49 (15) ◽  
pp. 3347-3356 ◽  
Author(s):  
Gabriele Micheletti ◽  
Carla Boga
Keyword(s):  
Nitrogen Atom ◽  
Carbon Atom ◽  
Short Review ◽  
Alkyl Halides ◽  
Aryl Halides ◽  
Aromatic Substitution ◽  
Aromatic Carbon ◽  
Isolation And Characterization ◽  
Acyl Halides

This short review provides an overview on the interaction between 1,3,5-triaminobenzene derivatives and different kinds of electrophiles. Due to the ambident reactivity of these nucleophiles (i.e., at the nitrogen atom of the substituents and at the aromatic carbon atom) different compounds can be obtained. Particular attention is devoted to the detection, isolation, and characterization of covalent intermediates of aromatic substitution, starting from Wheland intermediates until the first detection and characterization of Wheland–Meisenheimer intermediates.1 Introduction2 Reactions between 1,3,5-Triaminobenzene Derivatives and Charged Electrophiles2.1 The Proton as an Electrophile2.2 Arenediazonium Salts as Electrophiles3 Reactions between 1,3,5-Triaminobenzene Derivatives and Neutral­ Electrophiles3.1 Alkyl Halides as Electrophiles3.2 Acyl Halides and Sulfonyl Chlorides as Electrophiles3.3 Aryl Halides and Heteroaryl Halides as Electrophiles3.4 Polynitroheteroaromatics as Electrophiles4 Conclusion

scholarly journals C2 and Diffuse Interstellar Bands

2013 ◽  
Vol 9 (S297) ◽  
pp. 121-124 ◽  
Author(s):  
M. Kaźmierczak ◽  
M. Schmidt ◽  
T. Weselak ◽  
G. Galazutdinov ◽  
J. Krełowski
Keyword(s):  
Interstellar Clouds ◽  
Physical Conditions ◽  
Diffuse Interstellar Bands ◽  
Carbon Molecules ◽  
Long Chain

AbstractC2, the simplest multicarbon molecule is a useful astronomical tool, because the analysis of its lines allows to determine the physical conditions in interstellar clouds. C2 abundances give information about the chemistry of interstellar clouds, especially on the pathway to the formation of long-chain carbon molecules, which may be connected with carriers of diffuse interstellar bands (Douglas 1977, Thorburn et al. 2003). Here we summarize all relations between C2 and diffuse interstellar bands (DIBs).

Introduction: Why oxygen chemstry?

1992 ◽  
Author(s):  
Donald T. Sawyer ◽  
R. J. P. Williams
Keyword(s):  
Organic Chemistry ◽  
Nineteenth Century ◽  
Chemical Properties ◽  
First Year ◽  
Chemistry Curriculum ◽  
Design And Synthesis ◽  
Carbon Molecules ◽  
Living Organisms ◽  
Fixed Array ◽  
Oxygen Atoms

The fundamental premise of chemistry is that all matter consists of molecules. The physical and chemical properties of matter are those of the constituent molecules, and the transformation of matter into different materials (compounds) is the result of their reactions to form new molecules. A molecule consists of two or more atoms held in a relatively fixed array via valence-electron orbital overlap (covalent bonds; chemical bonds). In the nineteenth century chemists focused on the remarkable diversity of molecules produced by living organisms, which have in common the presence of tetravalent carbon atoms. As a result the unique versatility of carbon for the design and synthesis of new molecules was discovered, and the subdiscipline of organic chemistry (the science of carbon-containing molecules) has become the dominant part of the discipline. Clearly, the results from a focus on carbon-based chemistry have been immensely useful to science and to society. Although most molecules in biological systems [and produced by living organisms (particularly aerobic systems)] contain oxygen atoms as well as carbon and hydrogen (e.g., proteins, nucleic acids, carbohydrates, lipids, hormones, and vitamins), there has been a long tradition in all of chemistry to treat oxygen atoms as “neutral counterweights” for the “important,” character-determining elements (C, H, Al, Si, Fe, I) of the molecule. Thus, chemists have tended to take the most important element (oxygen) for granted. The chemistry curriculum devotes one or two year-courses to the chemistry of carbon (“Organic Chemistry”), but only a brief chapter on oxygen is included in the first-year and the inorganic courses. However, if the multitude of hydrocarbon molecules is from the incorporation of oxygen atoms in single-carbon molecules argues against the assignment of a “neutral character” for oxygen atoms [e.g., Cn(graphite), CH4(g), CH3OH(1), CH2(O)(1), HC(O)OH(1), (HO)2C(O)(aq), CO(g), CO2(g)]. Just as the focus of nineteenth century chemists on carbon-containing molecules has produced revolutionary advances in chemical understanding, and yielded the technology to synthesize and produce useful chemicals, polymers, and medicinals; I believe that a similar focus on oxygen chemistry is appropriate and will have analogous rewards for chemistry, biochemistry, and the chemical process technologies.

Sign in / Sign up

Export Citation Format

Share Document