Relating nucleus independent chemical shifts with integrated current density strengths

2021 ◽  
Author(s):  
Slavko Radenković ◽  
Slađana Đorđević
Keyword(s):  
Chemical Shift ◽  
Current Density ◽  
Chemical Shifts ◽  
The Other ◽  
Induced Current ◽  
Nucleus Independent Chemical Shift ◽  
Other Hand

Indices based on the nucleus independent chemical shift (NICS) are the most frequently used in analysis of magnetic aromaticity. The magnetically induced current density, on the other hand, is a...

Relativistic effects on the aromaticity of E3M3H3 (E = C–Pb; M = N–Bi) benzene analogues

2020 ◽  
Vol 22 (40) ◽  
pp. 22973-22978 ◽  
Author(s):  
Ricardo Pino-Rios ◽  
Alejandro Vásquez-Espinal ◽  
Luis Alvarez-Thon ◽  
William Tiznado
Keyword(s):  
Chemical Shift ◽  
Current Density ◽  
Relativistic Effects ◽  
Induced Current ◽  
Nucleus Independent Chemical Shift

The relativistic effects on the aromaticity of a set of benzene analogues, E3M3H3 (E = C–Pb; M = N–Bi) heterocycles, using magnetically induced current density (MICD) and the NICSzz component of the conventional nucleus independent chemical shift (NICS), is hereby examined.

Synthesis and electronic properties of meso-tetra(3,4,5-trimethoxy)phenyl-porphyrin and -tetrabenzoporphyrin and their phosphorus complexes

2020 ◽  
Vol 24 (01n03) ◽  
pp. 105-111
Author(s):  
Taniyuki Furuyama ◽  
Yuichi Takahashi ◽  
Tomoteru Fukumura ◽  
Ana C. C. Bacilla ◽  
Nagao Kobayashi
Keyword(s):  
Chemical Shift ◽  
Molecular Orbital ◽  
Electronic Absorption ◽  
Current Density ◽  
Magnetic Circular Dichroism ◽  
Induced Current ◽  
Mo Calculations ◽  
Metal Free ◽  
Nucleus Independent Chemical Shift ◽  
Td Dft

meso-Tetra(3,4,5-trimethoxy)phenyl-porphyrin and -tetrabenzoporphyrin and their phosphorus complexes were synthesized and their electronic absorption and magnetic circular dichroism (MCD) spectra discussed based on TD-DFT molecular orbital (MO) calculations. Nucleus-independent chemical shift (NICS) and anisotropy of the induced current density (ACID) calculations were also carried out for metal-free (and phosphorus) tetrabenzoporphyrins in order to discuss the aromaticity and flow of electrons in the molecule.

17O and 13C NMR spectra of some geminal diacetates

1988 ◽  
Vol 53 (3) ◽  
pp. 588-592 ◽  
Author(s):  
Antonín Lyčka ◽  
Josef Jirman ◽  
Jaroslav Holeček
Keyword(s):  
13C Nmr ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
The Other ◽  
13C Nmr Spectra ◽  
Other Hand ◽  
Carboxylic Esters ◽  
C Nmr ◽  
Oxygen Atoms

The 17O and 13C NMR spectra of eight geminal diacetates RCH(O(CO)CH3)2 derived from simple aldehydes have been measured. In contrast to the dicarboxylates R1R2E(O(CO)R3)2, where E = Si, Ge, or Sn, whose 17O NMR spectra only contain a single signal, and, on the other hand, in accordance with organic carboxylic esters, the 17O NMR spectra of the compound group studied always exhibit two well-resolved signals with the chemical shifts δ(17O) in the regions of 183-219 ppm and 369-381 ppm for the oxygen atoms in the groups C-O and C=O, respectively.

scholarly journals Relativity or aromaticity? A first-principles perspective of chemical shifts in osmabenzene and osmapentalene derivatives

2020 ◽  
Vol 22 (19) ◽  
pp. 10863-10869 ◽  
Author(s):  
Cina Foroutan-Nejad ◽  
Jan Vícha ◽  
Abhik Ghosh
Keyword(s):  
Current Density ◽  
First Principles ◽  
Chemical Shifts ◽  
Induced Current ◽  
Aromatic System ◽  
System P

The topology of the magnetically induced current density in osmabenzene suggests that the molecule is a novel type of Craig–Möbius aromatic system.

Growth of Epitaxial Site-Engineered Bi4Ti3O12-Basded Thin Films by Mocvdand Their Characterization

2002 ◽  
Vol 748 ◽  
Author(s):  
Hiroshi Funakubo ◽  
Tomohiro Sakai ◽  
Takayuki Watanabe ◽  
Minoru Osada ◽  
Masato Kakihana ◽  
...  
Keyword(s):  
Thin Films ◽  
Leakage Current ◽  
Leakage Current Density ◽  
Current Density ◽  
Spontaneous Polarization ◽  
Chemical Vapor ◽  
The Other ◽  
Other Hand ◽  
La Substitution ◽  
Lower Temperature

ABSTRACTThin films of BIT, La-substituted BIT (BLT) and La- and V-cosubstituted BIT(BLTV) were epitaxially grown on SrRuO3//SrTiO3 substrates at 850°C by metalorganic chemical vapor deposition (MOCVD), and their electrical properties were systematically compared. All films on (100), (110) and (111)-oriented substrates were epitaxially grown with (001)-, (104)-/(014)-and (118) –preferred orientations, respectively. The leakage current density of the BLTV film was almost the same with that of the BLT film, but was smaller than that of BIT film, suggesting that the La substitution contributed to the decrease of the leakage current density especially in pseudoperovskite layer. Spontaneous polarization of the BLTV film was estimated to be almost the same with the BLT film but was smaller that that of the BIT film. This is explained by the decrease of Tc with the La substitution, while V did not contribute to the change of the Curie temperature (Tc ). On the other hand, the coercive field (Ec) value of the BLTV was smaller than that of the BIT and the BLT films. As a result, La substitution contributed to the decrease of the leakage current density together with the decrease of the spontaneous polarization due to the decrease of the Tc. On the other hand, V substitution contributes to the decrease of the defects that suppress the domain motion and increases the Ec value. Therefore, each substitution of La and V plays different roles and this contribution is remarkable for the films deposited at lower temperature.

Carbon-13 Substituent-Induced Chemical Shifts: Monosubstituted Benzene Derivatives

1992 ◽  
Vol 57 (3) ◽  
pp. 497-507 ◽  
Author(s):  
Otto Exner ◽  
Miloš Buděšínský
Keyword(s):  
Benzene Ring ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
The Other ◽  
Correlation Equations ◽  
Benzene Derivatives ◽  
Complex Mechanism ◽  
Monosubstituted Benzene ◽  
Resonance Effects ◽  
Other Hand

Carbon-13 NMR spectra of twelve monosubstituted benzene derivatives were measured in deuterochloroform. Together with the literature data a set of 35 systematically chosen substituents was obtained on which some thirty correlation equations were tested. As anticipated only substituent chemical shifts (SCS) in the position 4 are controlled by inductive and resonance effects, and can be correlated by dual substituent parameters (DSP). For the other positions DSP were not successful and more sophisticated equations are not much telling. On the other hand, the direct relations between two series of SCS are usually more precise and simple to understand. It is concluded that SCS in benzene ring need not be controlled by too complex mechanism but simply by different factors than by inductive and resonance effects.

Numerical Study of Different Anode and Cathode Channel Design on the Performance of Piezoelectric Proton Exchange Membrane Fuel Cells (PZT-PEMFCs)

2009 ◽  
Author(s):  
Hsiao-Kang Ma ◽  
Jyun-Sheng Wang ◽  
Shih-Han Huang ◽  
Yu-Jen Huang ◽  
Yao-Zong Kuo
Keyword(s):  
Water Vapor ◽  
Flow Field ◽  
Current Density ◽  
Vibration Frequency ◽  
Electrochemical Reaction ◽  
Flow Fields ◽  
The Other ◽  
Open Area ◽  
Current Output ◽  
Other Hand

Previous studies [18, 19] have indicated that a novel ribbed PZT-PEMFC design has been developed, and that a three-dimensional, transitional model has been successfully built to study its major characteristics and fuel cell performance. A ribbed cathode channel can reduce internal resistance and double current density. At a higher PZT vibration frequency (f = 64 Hz), an air-breathing PZT-PEMFCs device compresses more oxygen into the catalyst layer and thus enhances the electrochemical reaction, resulting in a higher current output. On the other hand, the accumulated water vapor may be pumped out from the cathode channel during the compression process. Previous studies [11, 12] also demonstrated that serpentine and interdigitated flow fields could induce better performance than other flow fields in traditional PEMFCs, such as parallel and pin-type. In this study, the 3-D theoretical model of PZT-PEMFCs has been successfully developed in order to investigate the effects of anode and cathode channel designs on the performance of PZT-PEMFCs. Different cathode open area ratios, which are 80.5%, 63.2%, 47.9%, and 34.7%, were chosen for consideration of current density, PZT vibration frequency, and species concentrations. The results show that the cathode open area ratio of 47.9% is a better choice than 80.5%, 63.2%, or 34.7%. The results also establish that a lower vibration frequency may draw less air into the cathode channel, cause water vapor accumulation in the space of the electrochemical reaction area, and ultimately cause a drop in current over time. On the other hand, the designs of the anode flow field are found to have a big influence on the current density and water vapor profiles. The simulation results prove that the interdigitated flow field in the anode side, which is different from the traditional PEMFCs, performs much better than the serpentine and parallel flow fields.

Bismuth composition control of SrBi2TaNbO9 thin films by heat treating Bi2O3-inserted heterostructure

1999 ◽  
Vol 14 (7) ◽  
pp. 2986-2992 ◽  
Author(s):  
Yoon-Baek Park ◽  
Jeon-Kook Lee ◽  
Hyung-Jin Jung ◽  
Jong-Wan Park
Keyword(s):  
Thin Films ◽  
Leakage Current ◽  
Leakage Current Density ◽  
Current Density ◽  
Ferroelectric Properties ◽  
Stoichiometric Composition ◽  
Heat Treating ◽  
The Other ◽  
Composition Control ◽  
Other Hand

Ferroelectric properties of SrBi2TaNbO9 (SBTN) thin films were changed by the amount of Bi content in SBTN. We proposed that the addition of excess Bi to the SBTN thin films could be accomplished by heat treating the SBTN/Bi2O3/SBTN heterostructure fabricated by the radio frequency magnetron sputtering method. The Bi composition was controlled by changing the thickness of the inserted Bi2O3 from 50 to 400Å in the SBTN/Bi2O3/SBTN heterostructure. As the thickness of Bi2O3 films was increased from 0 to 100 Å, the grain grew faster and the ferroelectric properties improved. On the other hand, when the thickness, of Bi2O3 films was thicker than 150 Å, the ferroelectric properties deteriorated. In particular, when a 400 Å Bi2O3 layer was inserted between SBTN films, a Bi2Pt phase appeared and the Bi2O3 films remained between SBTN films, resulting in poor ferroelectric properties. A Bi2Pt phase was formed by the reaction between the platinum bottom electrode and Bi2O3 films. On the other hand, the leakage current density of SBTN thin films decreased with the increase of inserted Bi2O3 film thickness. As the thickness of inserted Bi2O3 films was increased from 0 to 50 Å, leakage current density abruptly decreased because Bi content of the SBTN thin films was increased from 8 mol% deficient to stoichiometric composition. As the thickness of inserted Bi2O3 films increased from 100 to 400 Å, leakage current density gradually decreased because the remaining Bi2O3 layer in SBTN thin films increased.

scholarly journals THE EFFECTS OF CURRENT FLOW ON BIOELECTRIC POTENTIAL

1936 ◽  
Vol 19 (4) ◽  
pp. 633-672 ◽  
Author(s):  
L. R. Blinks
Keyword(s):  
Current Density ◽  
Current Flow ◽  
The Other ◽  
Bioelectric Potential ◽  
Threshold Density ◽  
Other Hand ◽  
Outward Currents ◽  
Inward Currents ◽  
Sigmoid Curve ◽  
Current Flows

The effect of direct current flow upon the potential difference across the protoplasm of impaled Valonia cells was studied. Current density and direction were controlled in a bridge which balanced the ohmic resistances, leaving the changes (increase, decrease, or reversal) of the small, normally negative, bioelectric potential to be recorded continuously, before, during, and after current flow, with a string galvanometer connected into a vacuum tube detector circuit. Two chief states of response were distinguished: State A.—Regular polarization, which begins to build up the instant current starts to flow, the counter E.M.F. increasing most rapidly at that moment, then more and more slowly, and finally reaching a constant value within 1 second or less. The magnitude of counter E.M.F. is proportional to the current density with small currents flowing in either direction across the protoplasm, but falls off at higher density, giving a cusp with recession to lower values; this recession occurs with slightly lower currents outward than inward. Otherwise the curves are much the same for inward and outward currents, for different densities, for charge and discharge, and for successive current flows. There is a slight tendency for the bioelectric potential to become temporarily positive following these current flows. Records in the regular state (State A) show very little effect of increased series resistance on the time constant of counter E.M.F. This seems to indicate that a polarization rather than a static capacity is involved. State B.—Delayed and non-proportional polarization, in which there is no counter E.M.F. developed with small currents in either direction across the protoplasm, nor with very large outward currents. But with inward currents a threshold density is reached at which a counter E.M.F. rather suddenly develops, with a sigmoid curve rising to high positive values (200 mv. or more). There is sometimes a cusp, after which the P.D. remains strongly positive as long as the current flows. It falls off again to negative values on cessation of current flow, more rapidly after short flows, more slowly after longer ones. The curves of charge are usually quite different in shape from those of discharge. Successive current flows of threshold density in rapid succession produce quicker and quicker polarizations, the inflection of the curve often becoming smoothed away. After long interruptions, however, the sigmoid curve reappears. Larger inward currents produce relatively little additional positive P.D.; smaller ones on the other hand, if following soon after, have a greatly increased effectiveness, the threshold for polarization falling considerably. The effect dies away, however, with very small inward currents, even as they continue to flow. Over a medium range of densities, small increments or decrements of continuing inward current produce almost as regular polarizations as in State A. Temporary polarization occurs with outward currents following soon after the threshold inward currents, but the very flow of outward current tends to destroy this, and to decondition the protoplasm, again raising the threshold, for succeeding inward flows. State A is characteristic of a few freshly gathered cells and of most of those which have recovered from injuries of collecting, cleaning, and separating. It persists a short time after such cells are impaled, but usually changes over to State B for a considerable period thereafter. Eventually there is a reappearance of regular polarization; in the transition there is a marked tendency for positive P.D. to be produced after current flow, and during this the polarizations to outward currents may become much larger than those to inward currents. In this it resembles the effects of acidified sea water, and of certain phenolic compounds, e.g. p-cresol, which produce State A in cells previously in State B. Ammonia on the other hand counteracts these effects, producing delayed polarization to an exaggerated extent. Large polarizations persist when the cells are exposed to potassium-rich solutions, showing it is not the motion of potassium ions (e.g. from the sap) which accounts for the loss or restoration of polarization. It is suggested that inward currents restore a protoplasmic surface responsible for polarization by increasing acidity, while outward currents alter it by increasing alkalinity. Possibly this is by esterification or saponification respectively of a fatty film. For comparison, records of delayed polarization in silver-silver chloride electrodes are included.

Aromaticity of C20H10-xFx Corannulene: A Comparative Study by NICS and EFG Methods

2019 ◽  
Vol 16 (7) ◽  
pp. 592-599
Author(s):  
Farrokh Roya Nikmaram ◽  
Khadijeh Kalateh
Keyword(s):  
Density Functional Theory ◽  
Chemical Shift ◽  
Comparative Study ◽  
Density Functional ◽  
The Other ◽  
Electron Delocalization ◽  
Hydrogen Atoms ◽  
Aim Analysis ◽  
Functional Theory ◽  
Nucleus Independent Chemical Shift

Corannulene (C20H10) and its fluorinated derivatives, C20H10-xFx (x=1-10), are investigated at the B3LYP/6-31G level of density functional theory. The degree of electron delocalization is evaluated using Nucleus Independent Chemical Shift (NICS) method, Electric Field Gradient (EFG) method and factor of Ellipticity (ε). In this study, the benzene is the scale of comparison as a more aromatic structure. The aromaticity has been evaluated at three points of structures; center of five-member ring (5-MR), center of fluorine-substituted ring (6-MR), and center of other six-member rings. This comparison shows that substitution of fluorine for four and five hydrogen atoms in the Corannulene structure, C20H10-xFx (x=4, 5), results in more aromaticity compared to the other substitutions, and C20H10 and C20H10-xFx (x=1, 3) are more antiaromatic. It seems that the EFG method is more reliable for forecasting the aromaticity of structures, than NICS method. The factor of Ellipticity and bond lengths resulted from Atom in Molecule (AIM) analysis support the EFG method.

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