The Role of Linear Alkyl and Alkoxy Side Chains in the Modulation of the Structure and Electrical Properties of Bithiophene:a Theoretical Study

2010 ◽  
Vol 63 (8) ◽  
pp. 1297 ◽  
Author(s):  
Gregorio Garcia ◽  
Andrés Garzón ◽  
José M. Granadino-Roldán ◽  
Mónica Moral ◽  
M. Paz Fernández-Liencres ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Molecular Orbital ◽  
Theoretical Perspective ◽  
Reorganization Energy ◽  
Alkyl Derivatives ◽  
Highest Occupied Molecular Orbital ◽  
Delocalization Energy ◽  
Lowest Unoccupied Molecular Orbital ◽  
Homo Lumo

In the present work, we have studied from a theoretical perspective the geometry and electronic properties of 2,2′-bithiophene (BT) and its derivatives 3,4′-alkyl-2,2′-bithiophene (3,4′ABT) and 3,4′-alkoxy-2,2′-bithiophene (3,4′OABT). Properties such as planarity, bond lengths, electron density, highest occupied molecular orbital → lowest unoccupied molecular orbital (HOMO → LUMO) excitation energy and π-delocalization energy, which are related to the electrical conductivity, were calculated and analyzed as a function of both the nature and length of the substituent. The oxidation process was also studied for the single-polaronic state. The ionization potential and the intramolecular reorganization energy were calculated following the semiclassical Marcus treatment. As a conclusion, the introduction of alkoxy chains in 3,4′-positions improves the electrical properties with respect to the bithiophene molecule and the corresponding alkyl derivatives.

scholarly journals Emphasizing the Operational Role of a Novel Graphene-Based Ink into High Performance Ternary Organic Solar Cells

2019 ◽  
Author(s):  
Minas M. Stylianakis ◽  
Dimitriοs M. Kosmidis ◽  
Katerina Anagnostou ◽  
Christos Polyzoidis ◽  
Miron Krassas ◽  
...  
Keyword(s):  
Solar Cells ◽  
Molecular Orbital ◽  
Organic Solar Cells ◽  
High Performance ◽  
Energy Levels ◽  
Fullerene Derivative ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital ◽  
Synthetic Routes

A novel solution-processed graphene-based material was synthesized by treating graphene oxide (GO) with 2,5,7-trinitro-9-oxo-fluorenone-4-carboxylic acid (TNF-COOH) moieties, via simple synthetic routes. The yielded molecule N-[(carbamoyl-GO)ethyl]-N’-[(carbamoyl)-(2,5,7-trinitro-9-oxo-fluorene)] (GO-TNF) was thoroughly characterized and it was shown that it presents favorable highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels to function as a bridge component between the polymeric donor poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl] thieno[3,4-b]thiophenediyl}) (PTB7) and the fullerene derivative acceptor [6,6]-phenyl-C71-butyric-acid-methylester (PC71BM). In this context, a GO-TNF based ink was prepared and directly incorporated within the binary photoactive layer, in different volume ratios (1-3% ratio to the blend), for the effective realization of inverted ternary organic solar cells (OSCs) of the structure ITO/PFN/PTB7:GO-TNF:PC71BM/MoO3/Al. The addition of 2% v/v GO-TNF ink led to a champion power conversion efficiency (PCE) of 8.71% that was enhanced by ~13% as compared to the reference cell.

Investigation of Carbon Monoxide Adsorption on Cationic Gold- Palladium Clusters

2013 ◽  
Vol 68 (10-11) ◽  
pp. 651-658 ◽  
Author(s):  
Yang-Mei Chen ◽  
Xiao-Yu Kuang ◽  
Xiao-Wei Sheng ◽  
Huai-Qian Wang ◽  
Peng Shao ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Molecular Orbital ◽  
Density Functional ◽  
Co Adsorption ◽  
Vibration Strength ◽  
Au Clusters ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital ◽  
Pd Clusters ◽  
Homo Lumo

Density functional calculations have been performed for the carbon monoxide molecule adsorption on AunPd+m(n+m ≤ 6) clusters. In the process of CO adsorption, small Au clusters and Pd clusters tend to be an Au atom and three Pd atoms adsorption, respectively. For the mixed Au-Pd clusters, an Au atom, a Pd atom, two atoms consisted of an Au atom and a Pd atom, two Pd atoms, and three Pd atoms adsorption structures are displayed. The highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps and natural bond orbital charge population are calculated. Moreover, CO adsorption energy, CO stretching frequency, and CO bond length (upon adsorption) are also analysed in detail. The results predict that the adsorption strength of Au clusters with CO and the C-O vibration strength is enhanced and reduced after doping of Pd in the AunPdmCO+ complexes, respectively

STABILITIES AND FRAGMENTATION BEHAVIORS OF Agn CLUSTERS (n = 2–34)

2012 ◽  
Vol 11 (05) ◽  
pp. 953-964 ◽  
Author(s):  
WEI ZHANG ◽  
SHU-YAO YAN ◽  
ZENG-XIA ZHAO ◽  
HONG-XING ZHANG
Keyword(s):  
Molecular Orbital ◽  
Tight Binding ◽  
Silver Cluster ◽  
Dft Method ◽  
Binding Energies ◽  
Silver Clusters ◽  
Fragmentation Channel ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital ◽  
Homo Lumo

A global search on the lowest-energy structures of the medium-sized silver clusters Ag n(n = 21–34) was performed by using a genetic algorithm (GA) coupled with a tight-binding (TB) method. Structures, binding energies per atom, second differences in energies, the energy gaps between the highest occupied molecular orbital and the lowest unoccupied molecular orbital (HOMO–LUMO), and fragmentation behaviors of Ag n(n = 21–34) are investigated by using DFT method. The calculated results show that the neutral silver clusters prefer to decay by evaporation of a monomer except a small sized silver cluster ( Ag 4), which favors a dimmer evaporation. For the collision induced dissociation of cationic silver clusters, decaying a silver atom is found to be the dominant fragmentation channel. But for some small sized cationic silver clusters, a neutral dimmer evaporation is found to be energetically favorable. Our calculated results are consistent with previous studies.

Structural, stability, and vibrational properties of BinPm clusters

2018 ◽  
Vol 32 (10) ◽  
pp. 1850117
Author(s):  
Wanting Shen ◽  
Lihong Han ◽  
Dan Liang ◽  
Chunfang Zhang ◽  
Quhe Ruge ◽  
...  
Keyword(s):  
Optical Properties ◽  
Molecular Orbital ◽  
Binding Energies ◽  
Highest Occupied Molecular Orbital ◽  
Stable Clusters ◽  
Lowest Unoccupied Molecular Orbital ◽  
Energy Gains ◽  
Alloys And Compounds ◽  
Homo Lumo ◽  
Structure Calculations

An in-depth investigation is performed on stability mechanisms, electronic and optical properties of III–V semiconductor vapor phases clusters. First principles electronic structure calculations of CAM-B3LYP are performed on neutral Bi[Formula: see text]P[Formula: see text] (n + m [Formula: see text] 14) clusters. The geometrical evolution of all stable structures remains amorphous as the clusters size increases. Binding energies (BEs), energy gains and highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO–LUMO) gaps confirm that all four-atom structures of Bi[Formula: see text]P[Formula: see text] clusters have more stable optical properties. Orbitals composition and vibrational spectra of stable clusters are analyzed. Our calculations will contribute to the study of diluted bismuth alloys and compounds.

Hückel Molecular Orbital Quantities of {X,Y}-Cyclacene Graphs Under Next-Nearest-Neighbour Approximations in Analytical Forms

2019 ◽  
Vol 74 (6) ◽  
pp. 469-488 ◽  
Author(s):  
Tapanendu Ghosh ◽  
Swapnadeep Mondal ◽  
Sukanya Mondal ◽  
Bholanath Mandal
Keyword(s):  
Molecular Orbital ◽  
Energy Difference ◽  
Triplet States ◽  
Nearest Neighbour ◽  
Geometrical Structures ◽  
Charge Densities ◽  
Absorption Energy ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital ◽  
Homo Lumo

AbstractHückel molecular orbital (HMO) quantities, viz., electron densities, charge densities, bond orders, free valences, total π-electron energies and highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO–LUMO) or band gaps of {X,Y}-cyclacene graphs under next-nearest-neighbour (nnn) approximations are expressed in analytical forms within a certain range of nnn approximation parameter (m). The critical values of m for {X,Y}-cyclacenes with varying X (=C, N, B) and Y (=C, N, B) are calculated. For {X,X}-cyclacenes with a π-electron on each atom, all HMO quantities except total π-electron energies for a given value of m are found to be independent of X. The cyclic dimer (CD) is constructed in obtaining the eigenvalues corresponding to the singular points of the density of states (DOS) of such {X,Y}-cyclacene. Although the HOMO–LUMO gap of the CD differs from that of the cyclacene with a large number of repeating units (i.e. n ⟶ ∞) but becomes the same for m = 0. The analytical expressions can be used for facile computer programming in obtaining the HMO quantities. Such nnn interaction approximations actually release, to some extent, the strain that results in due to the geometrical structures of such cyclacenes, which is evident from the plots of strain energy per segment vs. contribution of such interactions on the total π-electron energy, where the slopes decrease with an increase in m. The vertical absorption energy difference for singlet-triplet states bears excellent linear correlation with the HOMO–LUMO gaps for a certain m value (m = 0.3) in the case of an even n, but for an odd n, such energy difference remains invariant.

A New Class of Solar Cells: Isomeric Boron Carbide Semiconductors with Fourth Quadrant Conductivity

2003 ◽  
Vol 799 ◽  
Author(s):  
Ravi B. Billa ◽  
A. N. Caruso ◽  
J. I. Brand
Keyword(s):  
Boron Carbide ◽  
Molecular Orbital ◽  
Chemical Vapor ◽  
Fourth Quadrant ◽  
Neutron Detectors ◽  
New Class ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital ◽  
Aluminum Substrates ◽  
Homo Lumo

ABSTRACTPreviously, we have made diodes[1,2] and transistors [3] as well as very effective realtime solid state neutron detectors [4] out of semiconducting boron carbide deposited on silicon or silicon carbide‥In this work the recent fabrication of a new class of highly photosensitive boron carbide diodes is discussed. These diodes exploit the electronic behavior differences of the isomers of film precursors, the closo-dicarbododecaboranes. These differences were observed in photoemission and inverse photoemission studies where the HOMO-LUMO (highest occupied molecular orbital-lowest unoccupied molecular orbital) gap variations upon deposition varied strongly with the isomeric configuration. Based on these results, p-n junctions were formed by plasma enhanced chemical vapor of ortho and meta carborane, respectively, on both nickel and aluminum substrates. These diodes exhibit fourth-quadrant conductivity, making them exciting new photovoltaic conversion devices.

Perspectives on the Role of the Frontier Effective-for-Reaction Molecular Orbital (FERMO) in the Study of Chemical Reactivity: An Updated Review

2020 ◽  
Vol 24 (3) ◽  
pp. 314-331 ◽  
Author(s):  
Letícia S. Braga ◽  
Daniel H. S. Leal ◽  
Kamil Kuca ◽  
Teodorico C. Ramalho
Keyword(s):  
Molecular Orbital ◽  
Chemical Reactions ◽  
Chemical Reactivity ◽  
Molecular Orbitals ◽  
Frontier Molecular Orbital ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital

Molecular orbitals are critical in the rationalization of several chemical reactions. Thus, the frontier molecular orbital theory, proposed by Fukui's group, postulated the importance of the Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied Molecular Orbital (LUMO) for chemical reactions. It should be kept in mind, however, that there are limitations of this theory and new perspectives about the chemical reactivity have recently been arisen based on composition and location of other frontier molecular orbitals. In this review, we have reported the development and the most recent applications of the Frontier Effective-for-Reaction Molecular Orbital (FERMO) concept, which describes the breaking and formation of new chemical bonds and can in turn, provide important clues that modulate chemical reactivity of atoms and molecules.

Antiaromatic ions and their value in quantifying aromaticity, as probes of delocalization, and potential as stable diradicals

2012 ◽  
Vol 84 (4) ◽  
pp. 1101-1112 ◽  
Author(s):  
Nancy S. Mills
Keyword(s):  
Chemical Shift ◽  
Molecular Orbital ◽  
Energetic Properties ◽  
Nucleus Independent Chemical Shift ◽  
Highest Occupied Molecular Orbital ◽  
Diradical Character ◽  
Aromatic Species ◽  
Lowest Unoccupied Molecular Orbital ◽  
Homo Lumo

Antiaromatic dications and dianions are available through oxidation or reduction of unsaturated precursors as well as through ionization of diols. Their experimental accessibility allows them to be used to evaluate the effectiveness of theoretical treatments of antiaromaticity such as the nucleus-independent chemical shift (NICS). Because measures of antiaromaticity are generally larger in magnitude than corresponding measures of aromaticity, they demonstrate relationships between different measures of aromaticity–antiaromaticity, such as those based on magnetic and energetic properties, more effectively than do aromatic measures. Antiaromatic species are more sensitive probes of delocalization than are aromatic species, giving the possibility of observation of subtle effects. Antiaromatic species possess a small highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO-LUMO) gap, giving rise to species with diradical character.

Transition metal Mo-doped boron clusters: A computational investigation

2014 ◽  
Vol 13 (05) ◽  
pp. 1450036 ◽  
Author(s):  
Run-Ning Zhao ◽  
Yanhong Yuan ◽  
Ju-Guang Han
Keyword(s):  
Molecular Orbital ◽  
Density Functional ◽  
Natural Populations ◽  
Chemical Hardness ◽  
Functional Theory ◽  
Relative Stabilities ◽  
Boron Clusters ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital ◽  
Homo Lumo

Geometries associated with relative stabilities and energy gaps of the Mo -doped boron clusters have been investigated systematically by using density functional theory. The critical size of Mo -encapsulated B n structures emerges as n = 10, the evaluated relative stabilities in term of the calculated fragmentation energies reveal that the MoB 6 has enhanced stabilities over their neighboring clusters. Furthermore, the calculated polarities of the MoB n reveal that the hypercoordinated planar MoB 10 wheel is a weakened polar molecule and MoB 11 ring is a nonpolar molecule, and aromatic properties are discussed. Additionally, the MoB 10 cluster with smaller highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) gap is supposed to be stronger chemical activity and smaller chemical hardness. Moreover, the recorded natural populations show that the charges transfer from boron framework to Mo atom. It should be pointed out that the remarkable charge-transfer features of MoB n clusters are distinctly similar to those of transitional metal (TM)-doped Si n clusters; growth-pattern of the TMBn depends on the doped TM impurity.

Sign in / Sign up

Export Citation Format

Share Document