Quantum Chemical Calculations of Reorganization Energy for Self-Exchange Electron and Hole Transfers of Aromatic Diamines as Electron-donor Molecules

2011 ◽  
Vol 1286 ◽  
Author(s):  
Qi Wei ◽  
Khishigjargal Tegshjargal ◽  
Davaasambuu Sarangerel ◽  
Chimed Ganzorig
Keyword(s):  
Electron Transfer ◽  
Density Functional ◽  
Light Emitting Diode ◽  
Reorganization Energy ◽  
Electron Transfer Reaction ◽  
Basis Set ◽  
Aromatic Diamine ◽  
Aromatic Diamines ◽  
Organic Light Emitting Diode ◽  
Electron Transfer Theory

ABSTRACTReorganization energy is one of the important factors to decide the rate of electron transfer according to the Marcus theory. Small reorganization energy is highly desirable in design of optoelectronic and electronic devices like as organic light emitting diode. For this reason, reorganization energy of aromatic diamine derivatives, N,N′-diphenyl-N,N′-bis(3-methylphenyl)- (1,1′-biphenyl)-4,4′-diamine (TPD) and 4,4′-diphenyl-N,N,N′,N′-tetraphenylbenzidine (DTPB) have been studied theoretically by self-exchange electron transfer theory. By executing the Gaussian 03 calculation we can easily figure out the optimization point which needed for calculation of the inner reorganization energy (λ) of self-exchange electron transfer reaction. Also ionization potential and electron affinities of these molecules can be calculated at the density functional theory level with basis set 6-31G** and 6-31G* using Gaussian 03 software on the basis of ab initio method. It gives possibility to develop a semi-empirical model for the observed absorption and photoluminescence spectrum.

scholarly journals Green One-Pot Synthesis of Coumarin-Hydroxybenzohydrazide Hybrids and Their Antioxidant Potency

Antioxidants ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1106
Author(s):  
Marko R. Antonijević ◽  
Dušica M. Simijonović ◽  
Edina H. Avdović ◽  
Andrija Ćirić ◽  
Zorica D. Petrović ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Electron Transfer ◽  
Density Functional ◽  
Electron Transfer Reaction ◽  
Hydrogen Atom Transfer ◽  
Special Importance ◽  
Theory Approach ◽  
One Pot ◽  
Antioxidant Potency

Compounds from the plant world that possess antioxidant abilities are of special importance for the food and pharmaceutical industry. Coumarins are a large, widely distributed group of natural compounds, usually found in plants, often with good antioxidant capacity. The coumarin-hydroxybenzohydrazide derivatives were synthesized using a green, one-pot protocol. This procedure includes the use of an environmentally benign mixture (vinegar and ethanol) as a catalyst and solvent, as well as very easy isolation of the desired products. The obtained compounds were structurally characterized by IR and NMR spectroscopy. The purity of all compounds was determined by HPLC and by elemental microanalysis. In addition, these compounds were evaluated for their in vitro antioxidant activity. Mechanisms of antioxidative activity were theoretically investigated by the density functional theory approach and the calculated values of various thermodynamic parameters, such as bond dissociation enthalpy, proton affinity, frontier molecular orbitals, and ionization potential. In silico calculations indicated that hydrogen atom transfer and sequential proton loss–electron transfer reaction mechanisms are probable, in non-polar and polar solvents respectively. Additionally, it was found that the single-electron transfer followed by proton transfer was not an operative mechanism in either solvent. The conducted tests indicate the excellent antioxidant activity, as well as the low potential toxicity, of the investigated compounds, which makes them good candidates for potential use in food chemistry.

Mechanistic Study of ROS-photogeneration by Pterin

Pteridines ◽  
2011 ◽  
Vol 22 (1) ◽  
pp. 73-76 ◽  
Author(s):  
Hong-Fang Ji ◽  
Liang Shen
Keyword(s):  
Electron Transfer ◽  
Density Functional ◽  
Transfer Reaction ◽  
Direct Electron Transfer ◽  
Density Functional Theory Calculations ◽  
Electron Transfer Reaction ◽  
Mechanistic Study ◽  
Functional Theory ◽  
Direct Energy ◽  
Electronic Parameters

Abstract Pterins are widespread in biological systems and possess photosensitizing activities. In the present study, the photosensitization mechanism of acid form of pterin (PTA) and basic form of pterin (PTB) is investigated by means of density functional theory calculations. The reactive oxygen species-photogenerating pathways of the lowest triplet excited (T1) state PTA and PTB are proposed as follows. Through direct energy transfer, both T1 state PTA and PTB can photogenerate 1O2. Two possible O2 .−-generating pathways are proposed according to the electronic parameters of PTA and PTB: i) direct electron transfer from T1 state PTA and PTB to 3O2 and the electron transfer reaction is more favorable energetically for PTB in comparison with PTA; and ii) electron transfer from anion radical of PTA and PTB to 3O2.

scholarly journals Unified Mechanistic Understanding of CO2 Reduction to CO on Transition Metal and Single Atom Catalysts

2021 ◽  
Author(s):  
Sudarshan Vijay ◽  
Wen Ju ◽  
Sven Brückner ◽  
Peter Strasser ◽  
Karen Chan
Keyword(s):  
Electron Transfer ◽  
Electronic Structure ◽  
Transition Metal ◽  
Density Functional ◽  
Co2 Reduction ◽  
Electron Transfer Reaction ◽  
Dipole Field ◽  
Single Atom ◽  
Activity Measurements ◽  
Carbon Catalysts

<p>CO is the simplest product from CO<sub>2</sub> electroreduction (CO<sub>2</sub>R), but the identity and nature of its rate limiting step remains controversial. Here we investigate the activity of both transition metals (TMs) and metal-nitrogen doped carbon catalysts (MNCs), and a present unified mechanistic picture of CO<sub>2</sub>R to for both these classes of catalysts. By consideration of the electronic structure through a Newns-Andersen model, we find that on MNCs, like TMs, electron transfer to CO<sub>2</sub><sub> </sub>is facile, such that CO<sub>2</sub> (g) adsorption is driven by adsorbate dipole-field interactions. Using density functional theory with explicit consideration of the interfacial field, we find CO<sub>2</sub> * adsorption to generally be limiting on TMs, while MNCs can be limited by either CO<sub>2</sub>* adsorption or by the proton-electron transfer reaction to form COOH*. We evaluate these computed mechanisms against pH-dependent experimental activity measurements on CO<sub>2</sub>R to CO activity for Au, FeNC, and NiNC. We present a unified activity volcano that, in contrast to previous analyses, includes the decisive CO<sub>2</sub>*<sub> </sub>and COOH* binding strengths as well as the critical adsorbate dipole-field interactions. We furthermore show that MNC catalysts are tunable towards higher activity away from transition metal scaling, due to the stabilization of larger dipoles resulting from their discrete and narrow <i>d</i>-states. The analysis suggests two design principles for ideal catalysts: moderate CO<sub>2</sub>* and COOH* binding strengths as well as large dipoles on the CO<sub>2</sub>*<sub> </sub>intermediate. We suggest that these principles can be exploited in materials with similar electronic structure to MNCs, such as supported single-atom catalysts, molecules, and nanoclusters, 2D materials, and ionic compounds towards higher CO<sub>2</sub>R activity. This work captures the decisive impact of adsorbate dipole-field interactions in CO<sub>2</sub>R to CO and paves the way for computational-guided design of new catalysts for this reaction.</p>

scholarly journals Distal [FeS]-Cluster Coordination in [NiFe]-Hydrogenase Facilitates Intermolecular Electron Transfer

2017 ◽  
Author(s):  
Alexander Petrenko ◽  
Matthias Stein
Keyword(s):  
Electron Transfer ◽  
Density Functional ◽  
Electric Energy ◽  
Reorganization Energy ◽  
Outer Sphere ◽  
Intermolecular Electron Transfer ◽  
Sulfur Cluster ◽  
Donor And Acceptor ◽  
Marcus Equation ◽  
Hydrogenase Enzyme

Biohydrogen is a versatile energy carrier for the generation of electric energy from renewable sources. Hydrogenases can be used in enzymatic fuel cells to oxidize dihydrogen. The rate of electron transfer (ET) at the anodic side between the [NiFe]-hydrogenase enzyme distal iron&ndash;sulfur cluster and the electrode surface can be described by the Marcus equation. All parameters for the Marcus equation are accessible from Density Functional Theory (DFT) calculations. The distal cubane FeS-cluster has a three-cysteine and one-histidine coordination [Fe4S4](His)(Cys)3 first ligation sphere. The reorganization energy (inner- and outer-sphere) is almost unchanged upon a histidine-to-cysteine substitution. Differences in rates of electron transfer between the wild-type enzyme and an all-cysteine mutant can be rationalized by a diminished electronic coupling between the donor and acceptor molecules in the [Fe4S4](Cys)4 case. The fast and efficient electron transfer from the distal iron&ndash;sulfur cluster is realized by a fine-tuned protein environment, which facilitates the flow of electrons. This study enables the design and control of electron transfer rates and pathways by protein engineering.

scholarly journals Free Radical Scavenging Activity of Dihydrocaffeic Acid: A Quantum Chemical Approach

2021 ◽  
Vol 33 (4) ◽  
pp. 937-944
Author(s):  
K. Senthilkumar ◽  
S.S. Naina Mohammed ◽  
S. Kalaiselvan
Keyword(s):  
Electron Transfer ◽  
Quantum Chemical ◽  
Density Functional ◽  
Radical Scavenging ◽  
Hydrogen Atom Transfer ◽  
Basis Set ◽  
Published Data ◽  
Chemical Calculation ◽  
Neutral Radical ◽  
Donor And Acceptor

Based on density functional theory (DFT), to investigate relationships between the antioxidant activity and structure of dihydrocaffeic acid, quantum chemical calculation is used. The optimized structures of the neutral, radical and ionic forms have been carried out by DFT-B3LYP method with the 6-311G(d,p) basis set. Reaction enthalpies related with the hydrogen atom transfer (HAT), single electron transfer proton transfer (SET-PT) and sequential proton loss and electron transfer (SPLET) were calculated in gas and water phase. The HOMO-LUMO energy gap, electron affinity, electronegativity, ionization energy, hardness, chemical potential, global softness and global electrophilicity were calculated by using the same level of theory. Surfaces with a molecular electrostatic potential (MEP) were studied to determine the reactive sites of dihydrocaffeic acid. The difference in energy between the donor and acceptor as well as the stabilization energy was determined through the natural bond orbital (NBO) analysis. The Fukui index (FI) based on electron density was employed to predict reaction sites. Reaction enthalpies are compared with previously published data for phenol and 3,4-dihydroxycinnamic acid.

scholarly journals The photo-physical study of the interaction of riboflavin with Nicotine in bicontinuous microemulsion

2017 ◽  
Vol 6 (6) ◽  
pp. 267-275
Author(s):  
Maurice Ohaekeleihem Iwunze
Keyword(s):  
Electron Transfer ◽  
Free Energy ◽  
Rate Constant ◽  
Reorganization Energy ◽  
Outer Sphere ◽  
Electron Transfer Reaction ◽  
Microemulsion System ◽  
Quenching Rate ◽  
Bicontinuous Microemulsion ◽  
Bimolecular Quenching

Steady-state fluorescence spectroscopy was used to study the interaction of riboflavin with nicotine in a bicontinuous microemulsion system made up of 42.11:13.70:21.34:22.85 % w/w of water: oil: surfactant: cosurfactant. The surfactant used is cetyltrimethylammonium bromide (CTAB), the oil is tetradecane and the cosurfactant is 1-pentanol. It is observed that the interaction of riboflavin and nicotine in the prepared microemulsion lead to the quenching of riboflavin fluorescence. The bimolecular quenching rate constant, kq, of riboflavin by nicotine was observed as 4.15 x 109 M-1 s -1 with an efficiency of 56 %. The mechanism of the reaction is proposed to be diffusion limited in an activated electron transfer reaction in a solvent separated (outer-sphere) scheme. The electron transfer rate constant, kET, was calculated as 5.89 x 109 s -1 with an activation rate constant, ka, of 9.52 x 109 s -1 . The calculated solvent reorganization energy, λs, of the reaction was 1.09 eV, the free energy of interaction, ΔGo , is -2.9 eV and the free energy of activation, ΔG*, was calculated as 0.75 eV.

Theoretical Study on Benzazole Derivatives for Use in Blue Thermally Activated Delayed Fluorescence Emitters

2015 ◽  
Vol 15 (10) ◽  
pp. 7819-7822 ◽  
Author(s):  
Dong Yuel Kwon ◽  
Geon Hyeong Lee ◽  
Young Sik Kim
Keyword(s):  
Density Functional Theory ◽  
Molecular Orbital ◽  
Density Functional ◽  
Light Emitting Diode ◽  
Energy Difference ◽  
Delayed Fluorescence ◽  
Functional Theory ◽  
Thermally Activated Delayed Fluorescence ◽  
Organic Light Emitting Diode ◽  
Thermally Activated

Four novel thermally activated delayed fluorescence (TADF) materials with 9,10-dihydro-9,9- dimethylacridine (DMAC) and phenylindolo(2,3-a)carbazole (PIC) as electron donors and benzazole derivatives (BO, and BT) as electron acceptors (DMAC-BO, DMAC-BT, PIC-BO, and PIC-BT) were designed and theoretically investigated for use as a blue organic light emitting diode (OLED) emitter. Using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations, we calculated the electron distribution of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), and the energy of the lowest singlet (S1) and the lowest triplet (T1) excited states. All the dyes had a small spatial overlap between the HOMO and LUMO because of the relatively large dihedral angle between the phenyl ring and the acceptor moiety. In terms of the energy difference (ΔEST) between the S1 state and the T1 state, DMAC-BO and DMAC-BT showed the small ΔEST (0.18 eV and 0.21 eV, respectively). However, PIC-BO and PIC-BT showed the large ΔEST (0.62 eV and 0.61 eV, respectively). Among the TADF materials, we showed that DMAC-BO would have the best TADF properties in terms of small ΔEST and blue OLED emitters

Ab initio study of C20 nanocluster effects on electrochemical properties of tetraphenylporphyrin

2018 ◽  
Vol 22 (08) ◽  
pp. 640-645
Author(s):  
Saeid Ekrami ◽  
Hamid Reza Shamlouei
Keyword(s):  
Electron Transfer ◽  
Electrochemical Properties ◽  
Density Functional ◽  
Transfer Reaction ◽  
Dft Method ◽  
Electron Transfer Reaction ◽  
Ionic Character ◽  
Transfer Energy ◽  
Solvent Type ◽  
The Density Functional Theory

The Density Functional Theory (DFT) method was employed to study the properties of the C[Formula: see text] complex with tetraphenylporphyrin (TPP). Calculations were performed in vacuum and in the presence of different solvents. Strong interaction between the C[Formula: see text] cluster and TPP molecule was observed. To understand the effect of C[Formula: see text] on electrochemical properties of TPP, electron transfers from and toward the porphyrin and C[Formula: see text]-TPP complex were studied. It was shown that the presence of C[Formula: see text] influences the electron transfer reaction toward the porphyrin molecule and causes transfer of one and two electrons to C[Formula: see text]-porphyrin, which is more favorable compared with porphyrin alone. However, C[Formula: see text] has slight effect on electron transfer from porphyrin and on positive ion formation. The effect of solvent type on electron transfer energy was studied for these reactions, and it was shown that solvents with higher permittivity have lower electron transfer reaction energy, which may be predicted from ionic character of the products.

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