Coordination-induced switch between the singly occupied and the lowest unoccupied molecular orbitals in two methylviologen-derived chromophores

1996 ◽  
pp. 1197-1204 ◽  
Author(s):  
Eberhard Waldhör ◽  
Mthembeni M. Zulu ◽  
Stanislav Zalis ◽  
Wolfgang Kaim
Keyword(s):  
Molecular Orbitals ◽  
Lowest Unoccupied Molecular Orbitals

scholarly journals Molecular Structure Modulated Trap Distribution and Carrier Migration in Fluorinated Epoxy Resin

Molecules ◽  
2020 ◽  
Vol 25 (13) ◽  
pp. 3071 ◽  
Author(s):  
Jin Li ◽  
Yufan Wang ◽  
Zhaoyu Ran ◽  
Hang Yao ◽  
Boxue Du ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Surface Charge ◽  
Epoxy Resin ◽  
Mobility Model ◽  
Molecular Orbitals ◽  
Chemical Calculation ◽  
Dissipation Process ◽  
Highest Occupied Molecular Orbitals ◽  
Lowest Unoccupied Molecular Orbitals ◽  
Positively Charged

Surface charge accumulation on epoxy insulators is one of the most serious problems threatening the operation safety of the direct current gas-insulated transmission line (GIL), and can be efficiently inhibited by the surface modification technology. This paper investigated the mechanisms of fluorination modulated surface charge behaviors of epoxy resin through quantum chemical calculation (QCC) analysis of the molecular structure. The results show that after fluorination, the surface charge dissipation process of the epoxy sample is accelerated by the introduced shallow trap sites, which is further clarified by the carrier mobility model. The electron distribution probability of the highest occupied molecular orbitals (HOMO) under positive charging and the lowest unoccupied molecular orbitals (LUMO) under negative charging shows distinctive patterns. It is illustrated that electrons are likely to aggregate locally around benzenes for the positively charged molecular structure, while electrons tend to distribute all along the epoxy chain under negatively charging. The calculated results verify that fluorination can modulate surface charge behaviors of epoxy resin through redesigning its molecular structure, trap distribution and charging patterns.

Observational studies of imperfect carbon cage structures of C 60 by high-resolution scanning tunnelling microscopy

1994 ◽  
Vol 444 (1921) ◽  
pp. 325-332 ◽  
Keyword(s):  
High Resolution ◽  
Molecular Orbitals ◽  
Scanning Tunnelling Microscopy ◽  
Carbon Cage ◽  
Scanning Tunnelling ◽  
Tunnelling Microscopy ◽  
Dynamics Simulations ◽  
First Time ◽  
Highest Occupied Molecular Orbitals ◽  
Lowest Unoccupied Molecular Orbitals

Anomalies in the morphology of the carbon cage of C 60 clusters have been investigated with atomic level resolution using high-resolution scanning tunnelling microscopy. The imperfect carbon cages have been resolved in the finest detail, which, for the first time, provide a remarkable confirmation of a variety of theoretical defect structures recently predicted by molecular dynamics simulations. The observed tunnelling spectra are consistent with the theoretical contention that the gap between the highest occupied molecular orbitals (HOMO) and the lowest unoccupied molecular orbitals (LUMO) for the clusters is decreased with the presence of defects.

scholarly journals Energy-level alignment at interfaces between manganese phthalocyanine and C60

2017 ◽  
Vol 8 ◽  
pp. 927-932 ◽  
Author(s):  
Daniel Waas ◽  
Florian Rückerl ◽  
Martin Knupfer ◽  
Bernd Büchner
Keyword(s):  
Energy Level ◽  
Photoelectron Spectroscopy ◽  
Energy Difference ◽  
Molecular Orbitals ◽  
Organic Photovoltaic ◽  
Photovoltaic Devices ◽  
Organic Photovoltaic Devices ◽  
Energy Level Alignment ◽  
Organic Heterojunctions ◽  
Lowest Unoccupied Molecular Orbitals

We have used photoelectron spectroscopy to determine the energy-level alignment at organic heterojunctions made of manganese phthalocyanine (MnPc) and the fullerene C60. We show that this energy-level alignment depends upon the preparation sequence, which is explained by different molecular orientations. Moreover, our results demonstrate that MnPc/C60 interfaces are hardly suited for application in organic photovoltaic devices, since the energy difference of the two lowest unoccupied molecular orbitals (LUMOs) is rather small.

scholarly journals ЦЕЛЕНАПРАВЛЕННЫЙ ПОИСК ВЕЩЕСТВ В РЯДУ ПРОИЗВОДНЫХ 3-АРИЛ(АРАЛКИЛ)КСАНТИНА, ОБЛАДАЮЩИХ АНТИРАДИКАЛЬНОЙ АКТИВНОСТЬЮ В ОТНОШЕНИИ СУПЕРОКСИД-РАДИКАЛА

2016 ◽  
Author(s):  
V. P. Ryzhenko ◽  
O. A. Ryzhov ◽  
S. V. Levich ◽  
I. F. Belenichev ◽  
К. V. Aleksandrova
Keyword(s):  
Linear Dependence ◽  
Quantum Chemical ◽  
Molecular Orbitals ◽  
Frontier Molecular Orbitals ◽  
Chemical Methods ◽  
Quantum Chemical Methods ◽  
Semi Empirical ◽  
Lowest Unoccupied Molecular Orbitals

<p>The aim of the research was to study the basic descriptors of frontier molecular orbitals of 3- aryl (aralkyl) xanthine using semi-empirical quantum- chemical methods and substantiate their impact on the manifestation of anti-radical activity.</p><p>Comparison of received data and calculated descriptors values revealed linear dependence of anti-radical activity on the highest occupied and lowest unoccupied molecular orbitals energy values.</p>

New Quantum Chemical Method for Assessing the Relative Activity of Antioxidants

2019 ◽  
pp. 96-104 ◽  
Author(s):  
T.A. Yarkova ◽  
A.M. Gyulmaliev
Keyword(s):  
Antioxidant Activity ◽  
Quantum Chemical ◽  
Chemical Potential ◽  
Relative Activity ◽  
Molecular Orbitals ◽  
Chemical Hardness ◽  
Test Substance ◽  
Lowest Unoccupied Molecular Orbitals ◽  
Electronic Chemical Potential ◽  
Electronic Chemical

A new method for evaluating the antioxidant activity of organic compounds based on quantum chemical calculations of their electronic structure using the DFT B3LYP/6-31G (d, p) method has been proposed. The geometric parameters of antioxidant molecules were optimized and the reactivity indices were determined from the energy values of the highest occupied and the lowest unoccupied molecular orbitals: absolute electronegativity; electronic chemical potential; absolute "chemical hardness". The found indicators allow us to quantify the antioxidant activity by building their dependence on the energy of the lower vacant molecular orbitals. The correlation of the obtained parameters with the standard, such as trolox, allows determining the relative antioxidant activity of the test substance.

Orbital interactions. VIII. Competition kinetic measurements of the Birch reduction of some compounds having the bicyclo[2,2,1]heptadiene framework as a means of investigating orbital interactions through space in these systems

1980 ◽  
Vol 33 (4) ◽  
pp. 785 ◽  
Author(s):  
MN Paddon-Row ◽  
R Hartcher
Keyword(s):  
Rate Constants ◽  
Relative Rate ◽  
Butyl Alcohol ◽  
Molecular Orbitals ◽  
Kinetic Measurements ◽  
Birch Reduction ◽  
Orbital Interactions ◽  
Relative Rate Constants ◽  
Lowest Unoccupied Molecular Orbitals

Relative rate constants for the Birch reduction (Li/liq. NH3/t-butyl alcohol) of norbornadiene (1),1,4-dihydro-1,4-methanonaphthalene (3), 9-(1-methylethylidene)-1,4-dihydro-1,4-methanonaphthalene(5), 1,4- dihydro-1,4-epoxynaphthalene (7), lithium benzoate, α-methylstyrene, and the hexahydrobenzenomethanoanthracene(20a), were obtained and compared with that obtained for the reduction of norbornene from an earlier study. Compounds (1), (3) and (5) were some 105 times more readily reduced than norbornene. These results are best explained in terms of the presence of through-space interactions operating between the two lowest unoccupied molecular orbitals in these molecules. The Birch reduction of (7) gave mainly 1,4-dihydronaphthalene (17).A mechanism for this reaction is presented.

Mesogenic complementary absorbing dyads based on porphyrin and perylene units

2018 ◽  
Vol 22 (01n03) ◽  
pp. 221-232
Author(s):  
Xiangfei Kong ◽  
Hongkang Gong ◽  
Shengping Dai ◽  
Wei Yao ◽  
Linping Mu ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Emission Spectra ◽  
Molecular Orbitals ◽  
Resonance Spectroscopy ◽  
Response Curves ◽  
Scanning Calorimetry ◽  
Broad Absorption ◽  
Active Materials ◽  
Highest Occupied Molecular Orbitals ◽  
Lowest Unoccupied Molecular Orbitals

Five novel dyads, consisting of a tetraphenylporphyrine unit connected to a perylene monoimide diester unit via a flexible bridge -CONH-(CH[Formula: see text]- (n [Formula: see text] 4, 6, 8, 10 and 12), have been synthesized. Their structures were characterized by [Formula: see text]C and [Formula: see text]H nuclear magnetic resonance spectroscopy, infrared spectroscopy, mass spectrometry and elemental analysis. The UV-vis absorption spectra revealed these dyads have broad optical absorption in the ultraviolet and visible regions due to the complementary absorption of the two units. The differential scanning calorimetry traces and polarized optical microscopy textures showed all these dyads have columnar liquid crystal phases. Cyclic voltammetry revealed the highest occupied molecular orbitals of the dyads located on the porphyrin units, and the lowest unoccupied molecular orbitals located on the perylene units. In addition, these results were in agreement with that of the theoretical modeling. When excited at 423 or 473 nm, the photoluminescent emission spectra showed that the degree of fluorescence quenching of porphyrin units increased as the spacers became shorter. This quenching was ascribed to intramolecular photoinduced electron transfer, which also induced the dyad molecules to form the charge-separated states. The charge-separated molecules were further confirmed by the photocurrent response curves. These behaviors of broad absorption of the ultraviolet-visible light, yielding the charge-separated states of the molecules when excited and the formation of columnar liquid crystal phase made these dyads candidates for single-component photovoltaic active materials.

Control of electroluminescence in a molecular photodiode by gate voltage

2020 ◽  
Vol 34 (19n20) ◽  
pp. 2040063
Author(s):  
E. Petrov ◽  
V. Leonov ◽  
Y. Shevchenko ◽  
V. Snitsarev
Keyword(s):  
Bias Voltage ◽  
Gate Voltage ◽  
Energy Levels ◽  
Molecular Orbitals ◽  
Orbital Energy ◽  
Electrode Surfaces ◽  
Kinetics Of ◽  
Lowest Unoccupied Molecular Orbitals ◽  
Resonant Mechanism

The role of the gate voltage in the regulation of electroluminescence (EL) of a molecular photodiode with asymmetric localization of electron density on the frontier highest occupied and lowest unoccupied molecular orbitals of the photochromic molecule is considered. It is shown that the gate voltage can have a significant effect on the formation of EL in devices where one of the orbital energy levels are outside the gap between the biased Fermi levels of the electrodes. The role of the gate voltage consists in shifting the position of the orbital energy levels until both frontier levels fall into the gap and thereby provide a resonant mechanism for the formation of EL. This leads to the inclusion of EL at a lower bias voltage than that which includes EL at zero gate voltage. In addition, the shift in energy levels caused by the gate voltage explains the mechanism for controlling the kinetics of bipolarity formation. The effect is carried out by turning on and off the resonant hopping’s of the electron between the conducting states of the electrodes and molecular orbitals localized at different distances from the electrode surfaces.

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