scholarly journals (4n +2)π Huckel’s rule of Bn NnC(8-2n) H8 as anti-cancer heterocyclic systems

2020 ◽  
Vol 11 (29) ◽  
pp. 129-150
Author(s):  
Neda SamieiSoofi ◽  
Majid Monajjemi
Keyword(s):  
Aromatic Ring ◽  
Current Density ◽  
Ring Current ◽  
Ring Currents ◽  
Anti Cancer ◽  
Whole Space ◽  
Homo And Lumo ◽  
Localized Orbital ◽  
Homo Lumo ◽  
Magnetic Mechanism

Replacing of Boron and nitrogen atoms in [8] annulene molecule help us for explaining the details of mentioned magnetic mechanism concerning the ring currents of the carbon disappearing in the isoelectronic azabora-hetero-cycles variants (Bn Nn C(8-2n) H82-,n=0,1,2,3 and4 The (4n+2)π systems aromatic on variants of BnNnC(8-2n) H8 (n=0, 1 ,2,3 and 4) via the localized orbital by considering the current density induced have been studied. It has been predicted a four-electron dia-tropic (aromatic) ring current for (4n+2) π aza-bora-hetero-cycles variants of BnNnC (8-2n) H8(n=0,1 ,2,4) and a two-electron para-tropic (anti-aromatic) current for (4n) π. HOMO and LUMO energies and also HOMO/LUMO overlapping in whole space have been calculated. Two forms can be considered, first the HOMO–LUMO transition leads to a para-tropic contribution, and second HOMO–LUMO+1 transitions to the dia-tropic contributions. In addition, the NICS and SNICS values confirm the amounts of aromaticity and anti-aromaticity in those rings.

scholarly journals Ellipticity, PDI and FLU, Evaluation of Aromaticity Indexes During Substituting B &N Atoms in Poly-Annulene

2020 ◽  
Vol 11 (1) ◽  
pp. 8298-8317
Keyword(s):  
Density Functional ◽  
Ring Current ◽  
Chemical Shifts ◽  
Density Functional Calculation ◽  
Close Relationship ◽  
Whole Space ◽  
Homo And Lumo ◽  
Localized Orbital ◽  
Derivatives Of ◽  
Homo Lumo

A close relationship between chemical shift and magnetic criteria for aromaticity arouses a deeper view for probing and modeling of induced current density in π systems through external magnetic fields. The (4n+2)π systems aromatic are studied on variants of Azabora Derivatives of [8] Annulene (BnNnC(8-2n)H8) via the localized orbital localization (LOL) and electron localized function (ELF) by considering the density functional calculation. By this work, it has been predicted a four-electron dia-tropic (aromatic) ring current for (4n+2) π variants of Bn NnC(8-2n) H8 and a two-electron para-tropic (anti-aromatic) current for (4n) π. With the HOMO and LUMO energies and also HOMO/LUMO overlapping in whole space, it is possible to predict the transition states from delocalized to-localized currents in all variant mentioned compounds in the viewpoint of aromaticity and anti-aromaticity. In addition, the nucleus independent chemical shifts (NICS), HOMA, Ellipticity, Aromatic Fluctuation index (FLU), and para delocalization index (PDI) values confirm the amounts of aromaticity and anti-aromaticity in those rings.

Coherent Ring Currents in Chiral Aromatic Molecules Induced by Linearly Polarized UV Laser Pulses

2013 ◽  
Vol 543 ◽  
pp. 381-384 ◽  
Author(s):  
Manabu Kanno ◽  
Hirohiko Koho ◽  
Hirobumi Mineo ◽  
Sheng Hsien Lin ◽  
Yuichi Fujimura
Keyword(s):  
Aromatic Ring ◽  
Quantum Dynamics ◽  
Ring Current ◽  
Molecular System ◽  
Laser Pulses ◽  
Uv Laser ◽  
Aromatic Molecules ◽  
Ring Currents ◽  
Linearly Polarized ◽  
Coherent Ring

In recent years, laser control of electrons in molecular system and condensed matter has attracted considerable attention with rapid progress in laser science and technology [. In particular, control of π-electron rotation in photo-induced chiral aromatic molecules has potential utility to the next-generation ultrafast switching devices. In this paper, we present a fundamental principle of generation of ultrafast coherent ring currents and the control in photo-induced aromatic molecules. This is based on quantum dynamics simulations of π-electron rotations and preparation of unidirectional angular momentum by ultrashort UV laser pulses properly designed. For this purpose, we adopt 2,5-dichloro [(3,6) pyrazinophane (DCPH) fixed on a surface, which is a real chiral aromatic molecule with plane chirality. Here π electrons can be rotated along the aromatic ring clockwise or counterclockwise by irradiation of a linearly polarized laser pulse with the properly designed photon polarization direction and the coherent ring current with the definite direction along the aromatic ring is prepared. This is contrast to ordinary ring current in an achiral aromatic ring molecule with degenerate electronic excited state, which is prepared by a circularly polarized laser [2]. In this case, π electrons rotate along the Z-axis of the laboratory coordinates, while for the present case electrons rotate along the z-axis in molecular Cartesian coordinates. It should be noted that signals originated from the coherent ring currents prepared by linearly polarized ultrashort UV lasers are specific to the chiral molecule of interest.

scholarly journals Magnetically induced ring currents in naphthalene-fused heteroporphyrinoids

2021 ◽  
Author(s):  
Markus Rauhalahti ◽  
D Sundholm ◽  
Mikael P. Johansson
Keyword(s):  
Current Density ◽  
Quantum Chemical ◽  
Ring Current ◽  
Induced Current ◽  
Ring Currents ◽  
Induced Currents

The magnetically induced current density of an intriguing naphthalene-fused heteroporphyrin have been studied, using the quantum-chemical, gauge-including magnetically induced currents (GIMIC) method. The ring-current strengths and current-density pathways for the...

Aromaticity, π-electron delocalization, and ring currents

2007 ◽  
Vol 79 (6) ◽  
pp. 969-979 ◽  
Author(s):  
Patrick W. Fowler ◽  
Mark Lillington ◽  
Leif P. Olson
Keyword(s):  
Current Density ◽  
Vector Potential ◽  
Ring Current ◽  
Computational Cost ◽  
Electron Delocalization ◽  
Induced Current ◽  
Simple Interpretation ◽  
Cyclic System ◽  
Ring Currents ◽  
Highest Occupied Molecular Orbital

The magnetic criterion of aromaticity is based on the ability of a cyclic system to support a ring current. If the ring current has the diatropic sense, the system is aromatic; if the sense is paratropic, the system is antiaromatic. Attribution of aromaticity ab initio therefore reduces to the calculation and visualization of induced current density. This can be achieved at modest computational cost within the ipsocentric approach, where current density at any point in space is calculated with that point as origin of vector potential. This choice leads to accurate maps of current density and a uniquely simple interpretation in terms of nonredundant orbital contributions governed by translational and rotational selection rules. For example, four-electron diatropicity and two-electron paratropicity are predicted for delocalized forms of [4n+2]- and [4n]-annulenes, respectively. A new application to homoaromatic systems is described. Two model tris-homoaromatics, both neutral molecules, are shown to exhibit a through-space, highest occupied molecular orbital (HOMO)-dominated, four-electron ring current, in a direct analogy with the conventional "aromatic" benzene π-current.

scholarly journals Molecular structure, NBO analysis, first hyper polarizability, and homo-lumo studies of π-extended tetrathiafulvalene (EXTTF) derivatives connected to π-nitro phenyl by density functional method

2018 ◽  
Vol 6 (1) ◽  
pp. 114
Author(s):  
Tahar Abbaz ◽  
Amel Bendjeddou ◽  
Didier Villemin
Keyword(s):  
Density Functional ◽  
Density Functional Method ◽  
Nbo Analysis ◽  
Functional Method ◽  
Total Charge ◽  
Linear Optics ◽  
Functional Theory ◽  
Non Linear Optics ◽  
Homo And Lumo ◽  
Homo Lumo

In these study we have been obtained the structural properties of (exTTF) derivatives 1-4 by using B3LYP/6-31G(d,p) of Density Functional Theory (DFT) utilizing Becke three exchange functional and Lee Yang Paar correlation functional. The calculation of first hyperpolarizability shows that the molecules are attractive molecules for future applications in non-linear optics. Molecular electrostatic potential (MEP) at a point in the space around a molecule gives an indication of the net electrostatic effect produced at that point by the total charge distribution of the molecule. The calculated HOMO and LUMO energies show that charge transfer occurs within these molecules. 

scholarly journals The distribution of the ring current: Cluster observations

2011 ◽  
Vol 29 (9) ◽  
pp. 1655-1662 ◽  
Author(s):  
Q.-H. Zhang ◽  
M. W. Dunlop ◽  
M. Lockwood ◽  
R. Holme ◽  
Y. Kamide ◽  
...  
Keyword(s):  
Current Density ◽  
Ring Current ◽  
Local Times ◽  
Distribution Profile ◽  
Full Circle ◽  
Equatorial Current ◽  
The Mean ◽  
Current Flows ◽  
First Time

Abstract. Extending previous studies, a full-circle investigation of the ring current has been made using Cluster 4-spacecraft observations near perigee, at times when the Cluster array had relatively small separations and nearly regular tetrahedral configurations, and when the Dst index was greater than −30 nT (non-storm conditions). These observations result in direct estimations of the near equatorial current density at all magnetic local times (MLT) for the first time and with sufficient accuracy, for the following observations. The results confirm that the ring current flows westward and show that the in situ average measured current density (sampled in the radial range accessed by Cluster ~4–4.5 RE) is asymmetric in MLT, ranging from 9 to 27 nA m−2. The direction of current is shown to be very well ordered for the whole range of MLT. Both of these results are in line with previous studies on partial ring extent. The magnitude of the current density, however, reveals a distinct asymmetry: growing from 10 to 27 nA m−2 as azimuth reduces from about 12:00 MLT to 03:00 and falling from 20 to 10 nA m−2 less steadily as azimuth reduces from 24:00 to 12:00 MLT. This result has not been reported before and we suggest it could reflect a number of effects. Firstly, we argue it is consistent with the operation of region-2 field aligned-currents (FACs), which are expected to flow upward into the ring current around 09:00 MLT and downward out of the ring current around 14:00 MLT. Secondly, we note that it is also consistent with a possible asymmetry in the radial distribution profile of current density (resulting in higher peak at ~4–4.5 RE). We note that part of the enhanced current could reflect an increase in the mean AE activity (during the periods in which Cluster samples those MLT).

Meso-alkynyl corroles and their cobalt(III), manganese(III) and gallium(III) complexes

2020 ◽  
Vol 24 (05n07) ◽  
pp. 737-749
Author(s):  
Michael Haas ◽  
Sabrina Gonglach ◽  
Wolfgang Schöfberger
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Density Functional ◽  
Theoretical Study ◽  
Lumo Energy ◽  
Functional Theory ◽  
Energy Gaps ◽  
Peak Broadening ◽  
Homo And Lumo ◽  
Homo Lumo

We report routes towards synthesis of novel [Formula: see text]-conjugated freebase cobalt, copper, gallium and manganese meso-alkynylcorroles. UV-vis spectra show that extensive peak broadening, red shifts, and changes in the oscillator strength of absorptions increase with the extension of [Formula: see text]-conjugation. Using density functional theory (DFT), we have carried out a first theoretical study of the electronic structure of these metallocorroles. Decreased energy gaps of about 0.3–0.4 eV between the HOMO and LUMO orbitals compared to the corresponding copper, gallium and manganese meso-5,10,15 triphenylcorrole are observed. In all cases, the HOMO energies are nearly unperturbed as the [Formula: see text]-conjugation is expanded. The contraction of the HOMO–LUMO energy gaps is attributed to the lowered LUMO energies.

scholarly journals First current density measurements in the ring current region using simultaneous multi-spacecraft CLUSTER-FGM data

2005 ◽  
Vol 23 (5) ◽  
pp. 1849-1865 ◽  
Author(s):  
C. Vallat ◽  
I. Dandouras ◽  
M. Dunlop ◽  
A. Balogh ◽  
E. Lucek ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Current Density ◽  
Ring Current ◽  
Magnetic Activity ◽  
Activity Level ◽  
Local Current Density ◽  
Magnetospheric Configuration And Dynamics ◽  
Local Current ◽  
Current Region ◽  
First Time

Abstract. The inner magnetosphere's current mapping is one of the key elements for current loop closure inside the entire magnetosphere. A method for directly computing the current is the multi-spacecraft curlometer technique, which is based on the application of Maxwell-Ampère's law. This requires the use of four-point magnetic field high resolution measurements. The FGM experiment on board the four Cluster spacecraft allows, for the first time, an instantaneous calculation of the magnetic field gradients and thus a measurement of the local current density. This technique requires, however, a careful study concerning all the factors that can affect the accuracy of the J estimate, such as the tetrahedral geometry of the four spacecraft, or the size and orientation of the current structure sampled. The first part of this paper is thus providing a detailed analysis of the method accuracy, and points out the limitations of this technique in the region of interest. The second part is an analysis of the ring current region, which reveals, for the first time, the large latitudinal extent of the ring current, for all magnetic activity levels, as well as the latitudinal evolution of the perpendicular (and parallel) components of the current along the diffuse auroral zone. Our analysis also points out the sharp transition between two distinct plasma regions, with the existence of high diamagnetic currents at the interface, as well as the filamentation of the current inside the inner plasma sheet. A statistical study over multiple perigee passes of Cluster (at about 4 RE from the Earth) reveals the azimuthal extent of the partial ring current. It also reveals that, at these distances and all along the evening sector, there isn't necessarily a strong dependence of the local current density value on the magnetic activity level. This is a direct consequence of the ring current morphology evolution, as well as the relative positioning of the spacecraft with respect to the bulk of the ring current. It also proves the existence of a substantial ring current at these distances, all over the evening and the post-midnight sector. Keywords. Magnetospheric physics (Current systems; Energetic particles, trapped; Magnetospheric configuration and dynamics)

scholarly journals Study of the applicability of the curlometer technique with the four Cluster spacecraft in regions close to Earth

2012 ◽  
Vol 30 (3) ◽  
pp. 597-611 ◽  
Author(s):  
S. Grimald ◽  
I. Dandouras ◽  
P. Robert ◽  
E. Lucek
Keyword(s):  
Magnetic Field ◽  
Current Density ◽  
Ring Current ◽  
Current System ◽  
Sufficient Conditions ◽  
Magnetic Activity ◽  
Inner Magnetosphere ◽  
Good Proxy ◽  
The Magnetic Field ◽  
Magnetospheric Current System

Abstract. Knowledge of the inner magnetospheric current system (intensity, boundaries, evolution) is one of the key elements for the understanding of the whole magnetospheric current system. In particular, the calculation of the current density and the study of the changes in the ring current is an active field of research as it is a good proxy for the magnetic activity. The curlometer technique allows the current density to be calculated from the magnetic field measured at four different positions inside a given current sheet using the Maxwell-Ampere's law. In 2009, the CLUSTER perigee pass was located at about 2 RE allowing a study of the ring current deep inside the inner magnetosphere, where the pressure gradient is expected to invert direction. In this paper, we use the curlometer in such an orbit. As the method has never been used so deep inside the inner magnetosphere, this study is a test of the curlometer in a part of the magnetosphere where the magnetic field is very high (about 4000 nT) and changes over small distances (ΔB = 1nT in 1000 km). To do so, the curlometer has been applied to calculate the current density from measured and modelled magnetic fields and for different sizes of the tetrahedron. The results show that the current density cannot be calculated using the curlometer technique at low altitude perigee passes, but that the method may be accurate in a [3 RE; 5 RE] or a [6 RE; 8.3 RE] L-shell range. It also demonstrates that the parameters used to estimate the accuracy of the method are necessary, but not sufficient conditions.

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