scholarly journals Electrochemical and Spectroelectrochemical Studies on the Reactivity of Perimidine–Carbazole–Thiophene Monomers towards the Formation of Multidimensional Macromolecules versus Stable π-Dimeric States

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2167
Author(s):  
Malgorzata Czichy ◽  
Patryk Janasik ◽  
Pawel Wagner ◽  
David L. Officer ◽  
Mieczyslaw Lapkowski
Keyword(s):  
Conjugated Polymer ◽  
Density Functional ◽  
Radical Cations ◽  
Covalent Bonding ◽  
Oxidation States ◽  
Solid Product ◽  
Functional Theory ◽  
Subsequent Oxidation ◽  
Molecular Ordering ◽  
Significant Difference

During research on cross-linked conducting polymers, double-functionalized monomers were synthesized. Two subunits potentially able to undergo oxidative coupling were used—perimidine and, respectively, carbazole, 3,6-di(hexylthiophene)carbazole or 3,6-di(decyloxythiophene)carbazole; alkyl and alkoxy chains as groups supporting molecular ordering and 14H-benzo[4,5]isoquinone[2,1-a]perimidin-14-one segment promoting CH⋯O interactions and π–π stacking. Electrochemical, spectroelectrochemical, and density functional theory (DFT) studies have shown that potential-controlled oxidation enables polarization of a specific monomer subunit, thus allowing for simultaneous coupling via perimidine and/or carbazole, but mainly leading to dimer formation. The reason for this was the considerable stability of the dicationic and tetracationic π-dimers over covalent bonding. In the case of perimidine-3,6-di(hexylthiophene)carbazole, the polymer was not obtained due to the steric hindrance of the alkyl substituents preventing the coupling of the monomer radical cations. The only linear π-conjugated polymer was obtained through di(decyloxythiophene)carbazole segment from perimidine-di(decyloxythiophene)-carbazole precursor. Due to the significant difference in potentials between subsequent oxidation states of monomer, it was impossible to polarize the entire molecule, so that both directions of coupling could be equally favored. Subsequent oxidation of this polymer to polarize the side perimidine groups did not allow further crosslinking, because rather the π–π interactions between these perimidine segments dominate in the solid product.

A Combined ab initio and Density Functional Study of the Electronic Structure of Thymine and 2-Thiothymine Radicals

2003 ◽  
Vol 68 (12) ◽  
pp. 2322-2334 ◽  
Author(s):  
Robert Vianello ◽  
Zvonimir B. Maksić
Keyword(s):  
Ab Initio ◽  
Spin Density ◽  
Density Functional ◽  
Radical Cations ◽  
Functional Study ◽  
Theory Approach ◽  
Functional Theory ◽  
Adiabatic Ionization Potential ◽  
Highest Occupied Molecular Orbital ◽  
Positively Charged

The electronic and energetic properties of thymine (1) and 2-thiothymine (2) and their neutral and positively charged radicals are considered by a combined ab initio and density functional theory approach. It is conclusively shown that ionization of 1 and 2 greatly facilitates deprotonation of the formed radical cations thus making the proton transfer between charged and neutral precursor species thermodynamically favourable. The adiabatic ionization potential of 1 and 2 are analysed. It appears that ADIP(1) is larger than ADIP(2) by 10 kcal/mol, because of greater stability of the highest occupied molecular orbital (HOMO) of the former. It is also shown beyond any doubt that the spin density in neutral and cationic radical of 2 is almost exclusively placed on the σ-3p AO of sulfur implying that these two systems represent rather rare sigma-radicals. In contrast, the spin density of radicals of 1 is distributed over their π-network.

Density functional theory study on the structural, reactivity, and electronic properties of all mono-, di-, tri-, tetra-, and penta-fluoroanilines as monomers for conducting polymers

2012 ◽  
Vol 90 (10) ◽  
pp. 902-914 ◽  
Author(s):  
Hossein Shirani Il Beigi
Keyword(s):  
Density Functional Theory ◽  
Conducting Polymers ◽  
Structural Properties ◽  
Density Functional ◽  
Dipole Moments ◽  
Radical Cations ◽  
The Other ◽  
Functional Theory ◽  
Density Distributions ◽  
Electric Polarizabilities

Electrical and structural properties of mono-, di-, tri-, tetra-, and penta-fluoroanilines as candidate monomers for new conducting polymers have been investigated using hybrid density functional theory (B3LYP/6–311+G**) based methods. The effects of the number and position of the fluorine atoms on the electrical and structural properties of fluoroanilines and their radical cations have also been investigated. The values of the vibrational frequencies, charge and spin-density distributions, ionization potentials, dipole moments, electric polarizabilities, HOMO-LUMO gaps, and the NICS values of these compounds have been calculated and analyzed as well. The results showed that the double bonds in 2-fluoroaniline and 2,5-difluoroaniline are more delocalized compared with other fluoroanilines; therefore, these molecules have the most aptitude for the electropolymerization reactions. The frequency analysis showed that the electrochemical stability of 2-fluoroaniline is greater than the other fluoroanilines. Also, this molecule possesses the largest NICS value compared to the other fluoroanilines. Consequently, 2-fluoroaniline has the largest ring current and the highest conductivity among all other monomers. Based on the results obtained, 2-fluoroaniline and 2,5-difluoroaniline are the best candidate monomers among all fluoroanilines for the synthesis of corresponding conducting polymers.

Cleavage of neutral alkenes and alkene radical cations; hybrid Hartree-Fock/density functional theory results

1998 ◽  
Vol 76 (12) ◽  
pp. 1817-1826
Author(s):  
Leif A. Eriksson ◽  
C. Magnus Jansson ◽  
Donald R. Arnold ◽  
Russell J. Boyd
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Radical Cations ◽  
Functional Theory ◽  
Hartree Fock

First-principles study of oxygen and hydrogen adsorption on Pt(111) and PtML/Pd(111) surfaces

2015 ◽  
Vol 29 (31) ◽  
pp. 1550199 ◽  
Author(s):  
J. L. Nie ◽  
L. Ao ◽  
X. T. Zu
Keyword(s):  
Density Functional Theory ◽  
First Principles ◽  
Density Functional ◽  
Hydrogen Adsorption ◽  
Chemical Interaction ◽  
Energy Difference ◽  
Covalent Bonding ◽  
Oxygen Molecule ◽  
First Principles Calculations ◽  
Functional Theory

In this paper, first-principles calculations based on density functional theory (DFT) have been performed to investigate the adsorption of oxygen and hydrogen on [Formula: see text] and [Formula: see text] surfaces covered by monolayer (ML) of [Formula: see text]. The results have shown that the oxygen molecule tends to adsorb on fcc site on both surfaces at the coverage of 0.25 ML, which becomes degeneration with hcp site when the coverage increases to 1 ML. For both oxygen and hydrogen, the adsorption on [Formula: see text] surface are stronger than those on [Formula: see text] surface. The adsorption energy difference for oxygen on the two surfaces is [Formula: see text][Formula: see text]0.2 eV at the coverage of 1 ML, which increases to [Formula: see text][Formula: see text]0.6 eV with the coverage decreasing to 0.25 ML. The similar energy difference was also found for hydrogen adsorption. The density of states analysis have demonstrated the chemical interaction of adsorbed oxygen with both pure [Formula: see text] and [Formula: see text] surfaces with certain shift of [Formula: see text] states to lower level compared to isolated oxygen. For hydrogen adsorption, the hybridization of [Formula: see text] with [Formula: see text] states were observed for both surfaces, indicating the covalent bonding component of H–Pt bond.

ENERGETICS AND STRUCTURAL INSIGHTS OF MOLECULAR CONDUCTORS USING DENSITY FUNCTIONAL THEORY METHODS: 1,3-DITHIOLE-2-THIONE, 1,3-DITHIOLE-2-ONE, 1,3-DIOXOLE-2-ONE, AND 1,3-DIOXOLE-2-THIONE

2009 ◽  
Vol 08 (06) ◽  
pp. 1185-1195 ◽  
Author(s):  
R. L. PRASAD ◽  
A. KUSHWAHA ◽  
RAJENDRA PRASAD ◽  
S. JAISWAL ◽  
R. A. YADAV
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Energy Requirement ◽  
Radical Cations ◽  
Geometrical Parameters ◽  
Dft Methods ◽  
Molecular Conductors ◽  
Relaxation Energy ◽  
Functional Theory ◽  
Hartree Fock

Computations were carried out employing the restricted Hartree–Fock (RHF) and density functional theory (DFT) methods to investigate the geometries and energies for the 1,3-dithiole-2-thione (DTT), 1,3-dithiole-2-one (DTO), 1,3-dioxole-2-thione (DOT), and 1,3-dioxole-2-one (DOO) molecules and their radical cations. The geometrical parameters of all the four molecules suggest a finite extent of extended conjugation across the molecules. The radical cations of the DTT and DOT molecules exhibit increased extent of conjugation compared to their neutral analogues. However, on going from the neutral DOO and DTO molecules to their radical cations, the extent of conjugation across the ions decreases and two unsaturated sites become isolated from each other. Requirement of the relaxation energy for the formation of radical cation is much lower for the DTT and DOT molecules compared to that for the DOO and DTO molecules. Smaller relaxation energy requirement favors minimal resistance to charge transport along the molecular stacking. Therefore, it is speculated that the DTT and DOT molecules are better molecular conductors as compared to the DOO and DTO molecules.

Ab Initio Calculations of Electronic and Magnetic Properties of AlMnO3 Perovskite Manganites

2015 ◽  
Vol 754-755 ◽  
pp. 757-761
Author(s):  
Abdullah Chik ◽  
S. Saad ◽  
Cheow Keat Yeoh ◽  
R.M. Zaki ◽  
F. Che Pa
Keyword(s):  
Density Functional Theory ◽  
Magnetic Properties ◽  
Electronic Structure ◽  
Ground State ◽  
Density Functional ◽  
Covalent Bonding ◽  
Perovskite Manganites ◽  
Functional Theory ◽  
Cubic Crystal ◽  
Energy Approximation

The electronic structure of the perovskite manganites AlMnO3cubic crystal was presented. The calculations were made within density functional theory and PBE exchange correlations energy approximation. It was found that the crystal exhibit covalent bonding between Mn and O with superexchange mechanism. At groundstate, AlMnO3stabilizes in antiferromagnetic structure with semi metallic like nature at the ground state.

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