The urgent desire for Halon substitution propels the exploration of potential alternatives, because of the severe damage of Halons to the stratospheric ozone layer. In this paper, the thermal decomposition mechanism, as well as fire-extinguishing mechanism and performance of Trifluoroiodomethane (CF3I) were studied by density functional theory (DFT) calculation and experimental measurements, to analyze the practicability of this proposed Halon substitute. The thermal decomposition products of CF3I can react with active OH· and H· radicals to achieve the purpose of rapidly fire-extinguishing. Besides, through DFT calculation and reaction kinetics analysis, the fire-extinguishing radicals CF3· and I· are more easily generated during the interaction between CF3I and flame, which indicates the chemical- extinguishing mechanism and pronounced fire-extinguishing performance of CF3I. To explore its actual fire-extinguishing effect, the fire-extinguishing concentration (FEC) of CF3I was measured in cup burner. The FEC value of this proposed Halon substitute is 3.42vol% for extinguishment of methane-air flame, which is smaller than those of three HFCs and HFO-1336mzz(Z) and is comparable to that of Halon 1301. These findings suggest the promising applicability of CF3I in practical Halon replacement and the necessity of further evaluation.
R\’enyi complexity ratio of two density functions is introduced for three and multidimensional quantum systems. Localization property of several density functions are defined and five theorems about near continuous property of R\’enyi complexity ratio are proved by Lebesgue measure. Some properties of R\’enyi complexity ratio are demonstrated and investigated for different quantum systems. Exact analytical forms of R\’enyi entropy, R\’enyi complexity ratio, statistical complexities based on R\’enyi entropy for integral order have been presented for solutions of pseudoharmonic and a family of isospectral potentials. Some properties of R\’enyi complexity ratio are verified for six diatomic molecules (CO, NO, N$_2$, CH, H$_2$, and ScH) and for other quantum systems.
We seek to determine the two-way transfer of chemical character due to the coupling occurring between hydrogen-bonds and covalent-bonds known to account for the unusual strength of hydrogen-bonds in water. We have provided a vector-based quantification of the chemical character of uncoupled hydrogen-bonds and covalent-bonds and then determined the effects of two-way coupling consistent with the total local energy density H(rb) < 0 for hydrogen-bonds. We have calculated the precessions Kʹ of the eigenvectors around the bond-path for the Ehrenfest Force F(r) and compared with the corresponding QTAIM Kʹ. In doing so we explain why the Ehrenfest Force F(r) provides insights into the coupling between the hydrogen and covalent bonds whilst QTAIM cannot. Conditions for favorable transfer of electron momentum from the hydrogen atom of a sigma bond to the hydrogen-bond are found, with excellent agreement with the hydrogen-bond BCP and covalent-bond BCP separations providing the theoretical bounds for coupling.
Density functional theory (DFT) calculations were adopted in this work to investigate the ability of the B12N12 fullerene like nano-cage for sensing juglone (Jug) and one of its derivative (Jug-OH) using DFT based methods in gas phase, pentyl ethanoate (PE) and water. Results showed that B12N12 is able to adsorbed Jug preferentially by binding to one of the O-atom of its carbonyl groups. Based on NBO analysis, a charge transfer from the oxygen atoms of Jug and Jug-OH to the anti-bonding orbital of B was revealed. QTAIM analysis showed that the B12N12-Jug and B12N12-Jug-OH complexes are stabilized by a partially covalent B-O bond in addition to attractive non covalent interactions. The ability of Jug, Jug-OH as well as their complexes A and A-OH to scavenge radicals has been investigated via the usual hydrogen atom transfer (HAT) mechanism in the three media of study previously stated. Theoretical results revealed that in PE and water, the complexes are better antioxidant than Jug and Jug-OH. These results provide fundamental knowledge for the development of new antioxidant delivery careers.
Artemisinin is the most successful antimalarial drug against malaria caused by Plasmodium falciparum. Despite its tremendous success and popularity in malaria therapeutics, the molecular mechanism of artemisinin’s activity is still elusive. The activation of artemisinin, i.e., cleavage of the endoperoxide bond at the infected cell that generates radical intermediates and the subsequent chemical rearrangements plays a key role in the antimalarial activities. In this work, applying state-of-the-art computational techniques based on the spin-constraint density functional theory (CDFT) along with ab initio thermodynamics, we have investigated various key steps of the molecular mechanism of artemisinin. The well-accepted artemisinin activation process is the reductive heterolytic scission of the endo-peroxide bond which is followed by subsequent chemical reactions that propagate via mono-radical intermediates. Adopting CDFT methodology, here we have investigated the possible alternative ‘biradical’ intermediates and their mechanistic pathways for the subsequent chemical reactions. The change in Gibbs free energy associated with the activation of artemisinin through homolytic-scissoring (biradical) intermediate is quite competitive and favorable compared to the reductive heterolytic-scissoring (monoradical) process. This indicates the alternative possibilities for the biradical activation process. The reported experimental EPR signals for the biradicals especially for similar anti-malarial drugs like G3-factor support our observations.
In this research, dynamics, and kinetics of some metal-free organic dyes based on triphenylamine having a D-π-A type structure were investigated in the gas phase and solvent (ethanol, dichloromethane, toluene, tetrahydrofuran, chloroform, and dimethylformamide) using the quantum chemistry calculations. These structures consist of triphenylamine as the donor linked to the acceptor units of cyanoacrylic acid and benzoic acid via different π-conjugated systems. The obtained results show that TC601 dye having the ethynyl anthracene phenyl -conjugated system has the preferred charge/hole transfer properties (Ginj/Greg), which in ethanol as the solvent, the lowest values of Ginj and Greg were evaluated. Molecular spectroscopic properties of the studied dyes reveal that H-P and F-P dyes have favorable molar absorption coefficients in all media. Also, the behaviors of the light-harvesting efficiency (LHE) and incident photon to current efficiency (IPCE) as the functions of the wavelength were analyzed, which show that the presence of solvent increases the values of IPCE and LHE for most studied dyes in comparison with the gas phase. Finally, based on different analyses, TC601 as the dye and ethanol as the solvent are proposed as the preferred candidates to be applied in the DSSCs.
N-heterocyclic aromatic in anion-π interaction has been playing a crucial role in a host of chemical and biological processes. In the present contribution, several different complexes composed of N-heterocyclic anthracene C14-2mH10-2mN2m (m = 1, 2, and 3) and chloride anion are investigated at the atomic level. We find that anion-π interactions are enhanced with the increasing number of N atoms. In addition, positions of nitrogen heteroatoms also have a significant effect on this interaction. Contributions of α, β and γ N atoms are in order of Nβ>Nγ>Nα. Moreover, energy decomposition analysis indicates that electrostatic interactions are the dominant stabilizing forces when chloride anion locates above aromatic ring, while the influence of other terms becomes significant when chloride anion deviates from aromatic ring. It is worth noting that dispersion forces play an important role in those anion-π interactions.
We calculate the energy and Shannon entropy for a hydrogen atom confined in a dielectric spherical microcavity for the fist time. In contrast to the hydrogen atom in the vacuum microcavity, some unexpected and interesting phenomena appear: First, the turning radius for the bound energy changes from positive to negative depends on the dielectric constant of the spherical microcavity sensitively. With the increase of the relative dielectric constant, the turning radius gets larger. Second, the dielectric spherical microcavity impacts the rearrangement of the excited state energy, and breaks the energy degeneracy of the excited states. At some given radius, there is energy crossover between different orbital. Third, the dielectric in the spherical microcavity affects the Shannon entropy for the confined hydrogen atom greatly. The Shannon entropy in the vacuum microcavity is the smallest and the Shannon entropy increases with the relative dielectric constant. For smaller size spherical microcavity, the Shannon entropy change is always negative, which suggests that the electron density is localized. With the increase of the radius of the microcavity, the Shannon entropy change becomes positive, and the confinement of the electron density gets delocalized. Our results show that we can control the confining effect of the spherical microcavity on the atom by changing the dielectric. This work can guide the future experimental studies for trapping and manipulating of atoms and molecules in the external environment and has some practical applications in metrology and quantum information processing.
C-radical borylation is an significant approach for the construction of carbon−boron bond. Photochemical borylation of aryl halides successfully applied this strategy. However, precise mechanisms, such as the generation of aryl radicals and the role of base additive(TMDAM) and water, remain controversy in these reactions. In this study, photochemical borylation of aryl halides has been researched by density functional theory (DFT) calculations. Indeed, the homolytic cleavage of the C−X bond under irradiation with UV-light is a key step for generation of aryl radicals. Nevertheless, the generation of aryl radicals may also undergo the process of single electron transfer and the heterolytic carbon-halogen bond cleavage sequence, and the latter is favorable during the reaction.
Within this study, four thermal ring-opening reactions, Reactions (1-4), were selected in order to investigate the phenomenon of torquoselectivity as well as predicting non-competitive or competitive reactions in QTAIM and stress tensor frameworks rather than using conventional methods. The theoretical analysis for these reactions exhibits differently for non-competitive and competitive reactions as well as for the conrotatory preferences either TSOC or TSIC directions by presenting degeneracy or non-degeneracy in their results. The concordant results of stress tensor and QTAIM scalar and vectors with experimental results provide a better understanding of all reactions mechanism. Examination the (rb), ε, H(rb), ℙσ, 3, BPL, and H indicate that Reaction 1 is a competitive and Reactions (2-4) are non-competitive reactions with TSOC, TSOC, and TSIC preference directions respectively.
Diels-Alder cycloaddition reaction is helpful to produce covalent derivatives of fullerene with desirable electronic and physical properties. In the present venture, we have computationally investigated the reactivity of neutral C60 and its Li+ encapsulated derivative towards Multi-Diels-Alder (MDA) reaction with 1,3-butadiene, employing density functional theory (DFT). The computational reports available to date illustrate the functionalization of fullerene surfaces of neutral and encapsulated C60 (Ca and Sm) with two butadiene molecules. In this article, we aim to investigate whether more than two butadiene molecules can be attached to the fullerene surface or not. To do so, we have shown that the MDA reaction initiates with the formation of an encounter complex between the mono-functionalized fullerene product and the second butadiene molecule. In this context, two different approaches, namely ‘Direct’ and ‘Alternative’ have been considered based on the attachment of the second butadiene, i.e., whether it is attached to the opposite or adjacent position of the first functionalization, which eventually produces the same final product. We have explored the MDA reactions by considering a total of four diene molecules that can be embedded successfully on the fullerene surface, with each reaction step having a high degree of exothermicity, thus making the overall reaction thermodynamically facile. In harmony with the mono- and bis-cycloaddition reactions, for MDA reaction also, the positive impact of Li+ encapsulation for enhancing the reactivity of fullerene surface towards butadiene attachment is evident from our study. On-the-fly calculations also suggest the bond preference for [6, 6] connectivity than its [6, 5] counterpart, to be the suitable dienophile, just like the mono- and bis-functionalization reported earlier. Overall, the present study will foresee an extensive idea about the detailed mechanism of the MDA reaction on neutral C60 and Li+@C60 that could encourage the scientists to perform the aforementioned reaction for other fullerene derivatives in the long run.
A systematic first-principles study is performed to investigate the 20-electron transition metal complexes (C5H5)2TM(E1E2)2 (TM = Cr, Mo, W; E1E2 = CO, N2, BF). The bond dissociation energy (De) based on (C5H5)2TM(E1E2)2 → (C5H5)2TM(E1E2) + E1E2 indicates much lower thermodynamic stability of (C5H5)2TM(N2)2 because of poor binding ability of N2 ligands. For the thermodynamic stable (C5H5)2TM(E1E2)2 complexes (TM = Cr, Mo, W; E1E2 = CO, BF), their 20-electron nature is derived from their occupied nonbonding molecular orbital mainly donated by ligands. Furthermore, charge transfer from TMs to the C5H5 ligands is revealed by the atoms in molecules (AIM) theory, leading to the positive charges of the TM atoms. On the other hand, the nature of the TM-E1 bond has been thoroughly analyzed by the energy decomposition analysis (EDA) method. The absolute value of interaction energies (|ΔEint|) between (C5H5)2TM(E1E2) and E1E2 has the same trend as the corresponding bond dissociation energy and Wiberg bond orders of TM-E1 bonds, following the order W > Mo > Cr with same ligands and BF > CO with same TM. Additionally, the largest contribution to the ΔEint values is the repulsive term ΔEPauli. Similar contributions from covalent and electrostatic terms to the TM-E1 bonds were found, which can be described as the classic dative bond with nearly same σ and π contributions. The stronger σ donations and π backdonations in (C5H5)2TM(BF)2 than in (C5H5)2TM(CO)2 indicate much more stability of (C5H5)2TM(BF)2.
The lattice vibration and thermal properties of CdS by first-principles calculations based on density functional theory are especially investigated. The results of phonon spectra show that CdS is thermodynamically stable. Combined with the concept of irreducible representation, the contribution of atoms in CdS to Raman and infrared is analyzed, that is: A1 and E1 participate in Raman vibration, and A1, E1 and E2 participate in infrared vibration. The electronic band structure and optical properties such as dielectric constant, refractive index, reflectivity are determined theoretically using DFT method. The thermal properties of CdS show that Debye temperature, isochoric specific heat capacity and coefficient of thermal expansion increase with the increase of temperature, and then tend to equilibrium. The equilibrium values are 353.13 K, 23.86 cal/cell.K and 1.04×10-4 K-1, respectively. For comparison. piezoelectric semiconductor material CdS power is synthesized by microwave hydrothermal process (temperature at 140°C + time about 15min), with particle size ranges from 50nm to 1000nm. The HRTEM imagine of CdS are experimentally studied to understand the crystal structure, with the growth preference along the plane (1000) and nanocrystal distance of 6.76 Å. This study is of great significance and provides theoretical guidance for further designing CdS matrix composite materials and to improve photoanode performance through doping of CdS and quantum dots co-sensitization.
This study addresses the first-principles analysis using generalized gradient approximation (GGA), which is pillared on density functional theory (DFT), to find the effects of silver (Ag) doping on SrTiO3 structurally, electronically and optical properties. As Ag doping into SrTiO3, we see a small decrease in the volume of unit cell. Moreover, Ag-doping adds new states in SrTiO3 at Brillouin zone symmetry points, transferring host material’s indirect band gap to a direct band gap. Ag doping in SrTiO3 results in the transfer density of states to smaller energies and increase in interaction among Ag atom and its surrounding atoms. Moreover, at the conduction band, the partial density of states (PDOS) of SrTiO3 changes generally. As a result, we conclude that Ag doping has an effect on the electronic band structure of SrTiO3. SrTiO3 doping with Ag has improved optical properties and its ability of converting to direct band gap results it in a perfect choice for optoelectronic applications.
In this study, a theoretical investigation of the photoinduced charge transfer (CT), electron injection, regeneration and Non-linear optical (NLO) of the A1-A4 structures were carried out for optoelectronic applications based on tetrahydroquinoline (C1-1) dye. Besides, a detailed assessment of the association among the electronic structures, chemical hardness, spectral and photovoltaic (PV) presentation were defined in DSSCs. Furthermore, this exploration purposes improved the electron-injection procedure, as well as the light-harvesting efficiency (LHE) of the dyes. For the research purpose, PO3H2, CONHOH, SO2H and OH (A1-A4) chromophores effects among the tetrahydroquinoline moieties related via a thiophene group were used as the electron acceptor group. The density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were executed on the designing dye molecules. The presentation of three functional groups (Becke’s three-parameter and Lee-Yang-Parr (B3LYP), coulomb-attenuating method-B3LYP (CAM-B3LYP) and Head-Gordon model (ωB97XD) were analyzed maximum absorption peak for C1-1. Here, TD-ɷB97XD with the 6-31G(d) combined functional and basis set were provided reliable effects to the C1-1. Therefore, newly designed A1-A4 dyes in absorption spectra were followed by TD-ɷB97XD method. Among these results, A1 dye displays red-shift and higher molar extinction coefficient than the other dyes and C1-1. It is specified that the PO3H2 have better PV properties, compared to literature. The NLO belongings of the A1-A4 sensitizers were derived in the polarizability and first-order hyperpolarizability. The calculated value of A1 dye has best for NLO presentation. The theoretically outcomes were intensely recommended that molecular proposal of the sensitizer has a vital role for the optoelectronic properties.
The present work focuses on the synthesis and characterization of four hydrazone derivatives. The structures of the synthesized compounds were determined through spectroscopic techniques via., EI MS, &1H NMR. The experimental results demonstrate that the obtained compounds successfully synthesize and screened for DPPH free radical scavenging activity, ferrous ion-chelating activity, ferric ion reducing activity, total antioxidant activity, and hydroxyl radical scavenging activity. Density Functional Theory (DFT) calculations were carried out by the Gaussian 09 package by using a hybrid density functional B3LYP (at 6-31G, 6-311G, and 6-31G++(d,p) basis sets) to investigate the electronic, molecular structures and provide useful spectroscopic and structural information. The computational data obtained from 1H NMR calculations were quite compatible with the experimental results. DFT calculations optimized the molecular geometry and estimated the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy of these compounds. Additionally, the charge transfer within the molecule and favorable sites for the electrophilic and nucleophilic attack was explored. Furthermore, the frontier molecular orbital (FMO) calculations were used to calculate different reactivity parameters, i.e., ionization potential, electron affinity, electronegativity, chemical hardness, chemical softness, and electrophilicity index.
Propylene oxide is an important chemical raw material. In this paper, Density Functional Theory (DFT) was used to calculate the epoxidation of propylene on the dimer MoOx by Gaussian 09 software. Firstly, we established the structure of the dimer MoOx/SiO2 and analyzed it, and then calculated the dehydrogenation process of propylene and the formation process of PO. It was found that the activity of O in Mo-O-Si was higher, which was beneficial to the AHS process of C3H6, but the reaction activity of different O substances to the formation of PO was very low. In order to solve this problem, we established a dimer MoOx model with defect sites, and found that the defect sites in the dimer could effectively activate O2 (O2- 2), and the activated material O had high PO selectivity. Compared with process of AHS and the process of PO formation, the energy barrier of PO formation path was very low, which was the main product. At the same time, we also established the MoOx model of Fe doped dimer and the MoOx model of Fe doped defect dimer. It was found that the MoOx clusters were more active due to Fe doping, and the energy barriers of both AHS process and PO formation path were greatly reduced compared with those before doping. The presence of Fe made it easier for the dimer MoOx to form defect sites, which made it easier to activate O2 (O- 2) and reduced the energy barriers of both AHS and PO formation processes.
Cu-Ni-Si alloys have been widely applied in electronic and electrical industries.The effect of precipitation on the microstructure and properties of the alloys are still not well understood. In this study, Cu-Ni-Si alloys were prepared by hot-pressed sintering and elemental copper powders, nickel powders and silicon powders as raw materials. The results show that, there were no Ni-Si intermetallic compounds except the δ-Ni2Si phase in the microstructure by hot-pressed sintered preparation of Cu-Ni-Si alloys. And the distribution of the δ-Ni2Si phase in the alloy was more uniform and smaller. After aging treatment, when the mass ratio of Ni and Si were 2:1 and 3:1, the precipitation of δ-Ni2Si phase was significantly less, and when the mass ratio of Ni and Si were 4:1 and 5:1, the precipitation of δ-Ni2Si phase particles increased significantly.The test results by electrical conductivity and vickers hardness show that after ageing treatment, both the electrical conductivity and vickers hardness of the alloys were greatly improved. When the electrical conductivity was 39.33%IACS, the vickers hardness was 230.95HV, and the Cu-Ni-Si alloy had the best comprehensive performance.