Electron Affinity Values Research Articles

Azaacenes Based Electroactive Materials: Preparation, Structure, Electrochemistry, Spectroscopy and Applications-A Critical Review.

This short critical review is devoted to the synthesis and functionalization of various types of azaacenes, organic semiconducting compounds which can be considered as promising materials for the fabrication of n-channel or ambipolar field effect transistors (FETs), components of active layers in light emitting diodes (LEDs), components of organic memory devices and others. Emphasis is put on the diversity of azaacenes preparation methods and the possibility of tuning their redox and spectroscopic properties by changing the C/N ratio, modifying the nitrogen atoms distribution mode, functionalization with electroaccepting or electrodonating groups and changing their molecular shape. Processability, structural features and degradation pathways of these compounds are also discussed. A unique feature of this review concerns the listed redox potentials of all discussed compounds which were normalized vs. Fc/Fc+. This required, in frequent cases, recalculation of the originally reported data in which these potentials were determined against different types of reference electrodes. The same applied to all reported electron affinities (EAs). EA values calculated using different methods were recalculated by applying the method of Sworakowski and co-workers (Org. Electron. 2016, 33, 300–310) to yield, for the first time, a set of normalized data, which could be directly compared.

Recent Advances in Molecular Design of Organic Thermoelectric Materials

Recent Advances in Molecular Design of Organic Thermoelectric Materials

GENERAL CHARACTERIZATION AND IONIZATIONRECOMBINATION PROPERTIES OF ELECTRONEGATIVE ELEMENTS PRESENT IN PLASMA DISCHARGES AT PLASMA CURRENT SWITCH OPERATION. PART I

Based on literary sources, we present here the data on electron affinity values for a variety of negative atomic ions, and also, for some molecules and radicals being of interest for current experimental studies. Besides, the ionization potentials are given for nearly all ionization states of some electronegative elements (C, O, F, Cl). For the said elements, the ionization-recombination parameters and the dependences of the fractional values (ionic fraction) for ionization states and on the electron temperature within the framework of ionization equilibrium are given. A comparison is carried out between the calculated and experimental distributions of the fractions of multicharged C+4 ions versus electron temperature.

Electrophilic Properties of 2'-Deoxyadenosine···Thymine Dimer: Photoelectron Spectroscopy and DFT Studies.

The anion radical of the 2′-deoxyadenosine···thymine (dAT•–) pair has been investigated experimentally and theoretically in the gas phase. By employing negative-ion photoelectron spectroscopy (PES), we have registered a spectrum typical for the valence-bound anion, featuring a broad peak at the electron-binding energy (EBE) between ∼1.5 and 2.2 eV with the maximum at ∼1.9 eV. The measured value of the adiabatic electron affinity (AEA) for dAT was estimated to be ∼1.1 eV. Calculations performed at the M06-2X/6-31++G(d,p) level revealed that the structure, where thymine is coordinated to the sugar of dA by two hydrogen bonds, is responsible for the observed PES signal. The AEAG and the vertical detachment energy of 0.91 and 1.68 eV, respectively, calculated for this structure reproduce the experimental values well. The role of the possible proton transfer in the stabilization of anionic radical complexes is discussed.

Electron Transport in Naphthalene Diimide Derivatives

Two naphthalene diimides derivatives containing two different (alkyl and alkoxyphenyl) N-substituents were studied, namely, N,N′-bis(sec-butyl)-1,4,5,8-naphthalenetetracarboxylic acid diimide (NDI-s-Bu) and N,N′-bis(4-n-hexyloxyphenyl)-1,4,5,8-naphthalenetetracarboxylic acid diimide (NDI-4-n-OHePh). These compounds are known to exhibit electron transport due to their electron-deficient character evidenced by high electron affinity (EA) values, determined by electrochemical methods and a low-lying lowest unoccupied molecular orbital (LUMO) level, predicted by density functional theory (DFT) calculations. These parameters make the studied organic semiconductors stable in operating conditions and resistant to electron trapping, facilitating, in this manner, electron transport in thin solid layers. Current–voltage characteristics, obtained for the manufactured electron-only devices operating in the low voltage range, yielded mobilities of 4.3 × 10−4 cm2V−1s−1 and 4.6 × 10−6 cm2V−1s−1 for (NDI-s-Bu) and (NDI-4-n-OHePh), respectively. Their electron transport characteristics were described using the drift–diffusion model. The studied organic semiconductors can be considered as excellent candidates for the electron transporting layers in organic photovoltaic cells and light-emitting diodes

Методы спектроскопии диссоциативного захвата электронов и теории функционала плотности для моделирования биологической активности производных хиноксалина

The molecules of 2-methylquinoxalin and 2,3-dimethylquinoxalin were studied by mass spectrometry of negative ions of resonant capture of slow (0-15 eV) electrons. These compounds have antimicrobial, antifungal, bactericidal and preservative properties, and are widely used in medicine and the food industry. The average lifetime of molecular negative ions (NI)relative to electron auto-cleavage is measured experimentally. The most probable structures of fragment ions ([M – H]–, formed during the decay of molecular NI, are revealed. Within the framework of the Arrhenius approximation, the value of the adiabatic electron affinity (EAa) was estimated. It is found that the theoretical values of EAa calculated by the B3LYP/6-31+G(d) method with minimal addition of diffuse functions as the difference between the total energies of the neutral molecule and the radical anion correlate with the values of EAa obtained from the experiment.

Experimental Studies of Electron Affinity and Work Function from Aluminium on Oxidized Diamond (100) and (111) Surfaces

Three different procedures are used to deposit aluminium onto O‐terminated (100) and (111) boron‐doped diamond, with the aim of producing a thermally stable surface with low work function and negative electron affinity. The methods are 1) deposition of a > 20 nm film of Al by high‐vacuum evaporation followed by HCl acid wash to remove excess metallic Al, 2) deposition of <3 Å of Al by atomic layer deposition, and 3) thin‐film deposition of Al by electron beam evaporation. The surface structure, work function, and electron affinity are investigated after annealing at temperatures of 300, 600, and 800 °C. Except for loss of excess O upon first heating, the Al + O surfaces remain stable up to 800 °C. The electron affinity values are generally between 0.0 and −1.0 eV, and the work function is generally 4.5 ± 0.5 eV, depending upon the deposition method, coverage, and annealing temperature. The values are in broad agreement with those predicted by computer simulations of Al + O (sub)monolayers on a diamond surface.

Preparation and investigation of phenanthroimidazole-based derivative

The synthesis and properties of N-(4-(tert-butyl)phenyl)-2′-(1-(4-(tert-butyl)phenyl)-1H-phenanthro[9,10-d]imidazol-2-yl)-N-(2-ethylhexyl)-[1,1′-biphenyl]-2-carboxamide were described. The practical characteristics of derivative were investigated by thermal, electrochemical and photophysical measurements and the data were compared with the theoretical values calculated by density functional theory. Compound exhibited high thermal stability with 5% weight loss temperature of 370 °C. Ionization potential value of compound estimated by cyclic voltammetry was found to be 5.48 eV. The high triplet energy (2.82 eV) and high electron affinity values (3.14 eV) of derivative were also observed.

Experimental and Computational Studies on the Electrochemical Behavior of Carvacrol and Menthol

In this study, the effects of solvent on the electrode potentials of menthol and carvacrol species were investigated experimentally and computationally and their antioxidant properties were compared in different solvents by calculating the half-wave potential E1/2 of species, Vand Dissociative Energy (BDE), Ionization Energy (IE), and Electron Affinity (EA). Electrochemical behavior of menthol and carvacrol species in four solvents (MeOH, EtOH, DMSO, and Heptane) were studied using cyclovoltametric technique in a glass electrode as a working electrode and the calculations for obtaining the electrode potential were performed using DFT functional including B3LYP with 6-311+G(d,p)basis set and PCM and IEFPCM models for calculation of solvent energy. Finally, the results were compared and confirmed by experimental methods. Where in the compound carvacrol represent more properties antioxidant than menthol due to lower values E1/2 in gas and solution phases. Also, the lower BDE in the gas phase is 80.19 kcal/mol compared with menthol (98.91 kcal/mol). Moreover, compound carvacrol has the IE value of 1.12 eV smaller than menthol and has the EA value of 0.35 eV higher than menthol. Calculations show that the model had no effect on computational results. Also, according to the results, the antioxidant properties of carvacrol in non-polar solvents were higher due to the smaller amount of E1/2.

Electron affinities for highly charged groups 15 and 16 anions

Electron affinity, electronegativity, and electrophilicity are chemical concepts that have been related to electron accepting power of chemical species. In the literature, although there are many theoretical approaches proposed to calculate the electronegativity and electrophilicity of atoms, ions, and molecules, just a few approaches suggested are related to the prediction of sequential electron affinities of atoms. In the present work, the electron affinities for highly charged groups 15 and 16 anions are calculated by the semi-empirical (PM6) method. The obtained values are compared with those from literature. So far, the authors are concerned, the third and fourth electron affinities for S, P, As and Sb are calculated for the first time. It is well-known that in the calculation of the lattice energy of any inorganic ionic crystal via Born-Haber thermochemical cycle, many parameters regarding any crystal the atoms forming the crystal are considered. One of these parameters is electron affinity. It should be noted that our electron affinity values calculated are in good agreement with both experimental data, other theoretical approaches, and the data obtained in the light of the Born- Haber cycle.

Integrating redox-response in crown ethers by disulfide incorporation: a computational approach

Reducing properties are investigated for the minimum energy conformers of selected thiacrown systems with redox-responsive disulfide linkage. The adiabatic electron affinity values of the investigated host systems in the gas phase lie in a range that makes them capable to undergo reversible redox reactions. In water, these show a high propensity to get reduced. Their binding energy with different alkali metal ions (Li+, Na+, and K+) is also determined under gas and aqueous phase conditions. The computational analysis reveals the weak metal binding interactions of disulfide systems than the parent thiacrown ethers. Such weak interaction energies in host-guest complexes indicate the possibility of reversible complexation-decomplexation. This assumably assists the fast release of guest molecules from the disulfide systems in response to the redox stimuli. Possibilities of incorporating such disulfide incorporated moieties in thiacalixarenes are also discussed. The results discussed in the present work are valuable for further development in the practical applications of crown ether–based host materials.

Does confinement alter the ionization energy and electron affinity of atoms?

Confinement causes drastic changes in bonding, reactivity and dynamics. Alkali metal atoms are excellent reducing agents due to their low ionization energies. On the other hand, high electron affinity values allow the halogen atoms to behave as powerful oxidizing agents. In this article, we have shown that those properties get changed in a confined environment created by two fullerenes differing in size.

Design and simulation of Sb2S3 solar cells based on monolayer graphene as electron transport layer

In Sb2S3 solar cells, the p-n junction are generally formed by combination of p-type Sb2S3 absorber layer and n-type materials, such as CdS and TiO2. In this study, the design and simulation of the Sb2S3 solar cells with graphene as electron transport layer were performed. The device performance parameters with respect to the electron affinity of monolayer graphene, the doping concentration, thickness and bulk defect density of Sb2S3 layer were examined and optimized. The simulation results revealed that the performance of Sb2S3 solar cells could be improved by using a monolayer graphene with lower value of electron affinity. The optimum doping concentration of Sb2S3 absorber layer was found to be 1017 cm−3. Also, the optimum Sb2S3 absorber layer thickness was found to be 0.7 μm when the bulk defect density and the corresponding carrier diffusion length were 1015 cm−3 and 1.6 μm, respectively. According to the optimum values of different variables, the conversion efficiency of the Sb2S3 solar cells could be achieved as high as 23.30%. These results showed that the monolayer graphene could be served as an efficient and inexpensive electron transport layer.

How the stability, reactivity and optical response of the protonated base pairs differ with other biologically important adenine–thymine pairs: a DFT and TD-DFT approach

The chemical behaviour of six biologically important Adenine (A)–Thymine (T) base pairs formed as a result of the interaction between Watson–Crick(WC) type Adenine, Thymine, rare Adenine (A*) and rare Thymine (T*) bases have been studied using density functional theory (DFT) and time-dependent DFT (TD-DFT). The geometrical optimization and other relevant properties have been calculated by employing the hybrid functional CAM-B3LYP and M06-2X with 6-311++G(d,p) basis set for the reliable treatment of dispersion interaction in the gas phase. The energetic parameters show that the A*T* base pair has the highest binding energy. The characteristic Raman modes due to stretching vibrations show significant change for conformational and structural alteration. The absorption spectra of all AT conformers belong to the UV region and the excitations are due to π → π* and π → ryd* transitions. A distinct absorption peak has been observed for the protonated base pairs at a relatively higher wavelength. Natural transition orbital and molecular orbital analysis define charge transfer states associated with the electronic transitions. The lowest ionization potential, positive electron affinity and least value of hardness of the A*T* compared to the other AT base pairs suggest more reactivity of A*T* base pair than the others in chemical and biological reactions. Naturally, these structural rearrangements affect various biological and chemical processes, therefore, this study may be helpful to find out the best fit between the structurally flexible ligand and receptor and how the interaction will affect the chemistry of these important molecules.

Synthesis and characterization of solution processable, high electron affinity molecular dopants

New organic-soluble dopants have record high electron affinity values and show outstanding doping performance with high ionization energy co-polymers.

Efficient EOM-CC-based Protocol for the Calculation of Electron Affinity of Solvated Nucleobases: Uracil as a Case Study.

We present an explicit solvation protocol for the calculation of electron affinity values of the solvated nucleobases. The protocol uses a quantum mechanics/molecular mechanics (QM/MM) approach based on the newly implemented domain-based pair natural orbital EOM-CCSD (equation-of-motion coupled-cluster single-double) method. The stability of the solvated nucleobase anion is sensitive to the local distribution of the water molecules around the nucleobase, and the calculated electron affinity values converge slowly with respect to the number of snapshots and the size of the water box. The use of nonpolarizable water molecules leads to an overestimation of the electron affinity and makes the result sensitive to the size of the QM region in the QM/MM calculation. The electron affinity values, although sensitive to the size of the basis set, lead to an almost constant blue shift of the electron affinity upon the increase in the basis set. The present protocol allows for a controllable description of the various parameters affecting the electron affinity value, and the calculated adiabatic electron affinity values are in excellent agreement with experimental results.

Quantum‐chemical investigation of the phosphine ligand effects on the structure and electronic properties of a rhenabenzyne complex

AbstractThis study examined the effects of phosphine ligand on the structure and electronic properties of (C5H4)Re(PX3)3Cl rhenabenzyne complexes (X = H, F, Cl, Me) using the hybrid density functional MPW1PW91. Variations in the structure, dipole moment, electronic spatial extent (ESE), and aromaticity of the title complex were studied. In addition, adiabatic and vertical ionization potential and electron affinity values of these complexes were calculated. Correlations between the calculated parameters and Tolman cone angles (θ), Tolman's Electronic Parameter (TEP), as well as the Crabtree's DFT Electronic Parameter (CEP) of the phosphine ligands were illustrated. The para‐delocalization index (PDI) was used to investigate aromaticity in these systems. Natural bond orbital analysis (NBO) was employed for a comprehensive insight into the nature of the bonds in these complexes.

Fabrication of AlGaAs/GaAs/diamond heterojunctions for diamond-collector HBTs

Diamond is a highly attractive ultrawide bandgap semiconductor for next-generation high-power switching devices and RF devices for its superior physical and electrical properties. However, the lack of effective n-type dopants in diamond has limited the material to only unipolar p-type device applications. Heterostructure bipolar devices that use better n-type semiconductors together with p-type diamond is an approach to get high performance devices. In this work, p–n–p AlGaAs/GaAs/diamond heterojunction bipolar transistors (HBTs) are proposed and fabricated using a grafting technique. The double-heterojunction is formed by transferring an AlGaAs(p-type)/GaAs(n-type) membrane onto single-crystalline p-type doped diamond with an electron affinity of 0.32 eV. The epitaxial AlGaAs/GaAs emitter-base p–n junction shows an ideality factor of 1.09 with an Ion/Ioff of 1.53 × 107 at ± 1.5 V. The grafted GaAs/diamond n–p junction shows an ideality factor of 3.67 with an Ion/Ioff of 3.74 × 1010 at ± 5.2 V. Due to the valence-band energy barrier of 0.3 eV between the GaAs base and the diamond collector, the measured current gain for the HBT is slightly below unity. Simulations show that by reducing the electron affinity value of the p-type diamond, the base-collector energy barrier height can be correspondingly reduced, and high current gain can be expected.

Theoretical prediction of delivery and adsorption of various anticancer drugs into pristine and metal-doped graphene nanosheet

ABSTRACT The mechanism of this study is utilized the pristine GNS and metal-doped GNS as a carrier to the (5-FU, 6-MP, GB, and CP) anticancer drugs. We used the DFT method, which implemented in the Quantum espresso package, to calculate various electronic properties computed. These impurities altered the behavior of the GNS from metal to semiconductor. Metal-doped GNS and anticancer drugs/pristine GNS became more stable and lower reactivity due to the total energy of these structures increased compared to the pristine GNS. The electronic band gap of the anticancer drugs/pristine GNS rehabilitated and opened. Furthermore, the metal-doped GNS as a carrier to the anticancer drugs was an exothermic process. Then, anticancer drugs/metal-doped GNS thermodynamically stable due to these structures have negative adsorption energies. Besides, we detected that these complex structures were required higher energy to donating/accepting and electron to become cation/anion due to these structures have a lower value of the electron affinity and higher value of the chemical hardness. Moreover, there was a great interaction between pristine GNS and metal impurities; also between metal-doped GNS and anticancer drugs. Then, GNS and metal-doped GNS have been used as drug delivery systems.

Charge transfer and opto-electronic properties of some newly designed polycatenar discotic liquid crystal derivatives: a DFT study.

Herein, we demonstrate effect of substituents on optoelectronic properties of discotic liquid crystals (DLCs) by using density functional theory (DFT) calculations at B3LYP/Lanl2Z level of theory. Three parent DLCs, namely, (1) benzene-1,3,5-triyl tris(3,5-dialkoxybenzoate), (2) N1, N3, N5-tris(3-alkoxyphenyl)benzene-1,3,5-tricarboxamide, and (3) trialkyl 4, 4', 4″-(benzenetricarbonyltris (azanediyl)) tribenzoate benzoate and their -N and -S group derivatives of 1, 2, and 3, were investigated to observe the change in optoelectronic response of these systems. The frontier molecular orbital studies and electron affinity values indicate that the studied compounds are stable against the oxygen and moisture present in air. The calculated charge transfer integrals, electron, and hole mobility values revealed that parent DLCs and their derivatives can be employed as an effective n-type material for OLEDs; however, derivatives have enhanced charge transfer values compared with their parents. For better understanding of the thermochemistry and effect of substituents, frequency calculations were carried out. P1-D4 derivative having R = -NH-CO-CH3 terminal group came out to be theoretically the most favored having the lowest ΔG value. Computed UV/visible spectroscopic analysis showed minimum absorbance and maximum transmittance for derivative P2-D1 having -S-NH2 substituent. Molecular electrostatic potential surfaces mapped at potential range, i.e., - 8.531e-3esu to + 8.531e-3esu, describe electrophilic and nucleophilic characteristics. Introduction of electron donor groups enhanced electrical conductivity, excitation energy, and charge transfer integral, thus increasing optoelectronic properties of DLCs. However, these claims require further experimental verification.