The structures and interactions of systems formed by the MPBCP (meta-Phenylene-Bridged Cyclic Oligopyrrole) functionalized with lanthanum atom were studied for investigating the abilities of MPBCP, [La-MPBCP]+3 and La-MPBCP to absorb biogas (CO2, N2, H2 and CH4) using density functional theory. The Eads calculated values for biogas molecules on [La-MPBCP]+3 and La-MPBCP showed that these gas molecules have favorable interactions with the lanthanum atom coordinated on the MPBCP. CO2 molecule shows strong interactions, with Eads values of -28.63 and -15.95 kcal/mol. In the case of H2 molecule, the Eads is lower with values of -7.51 and -5.28. It is easy to observe the CO2 molecule on the [La-MPBCP]+3 system has four times higher energy value than adsorption energy for the H2 molecule. The natural bond orbital analysis reveals that gas molecules are electron donator in the systems and the acceptor orbitals belong to lanthanum atom. Computational studies suggest that CO2, N2, CH4 and H2 molecules on [La-MPBCP]+3 and La-MPBCP present physisorption. Our findings divulge promising potential of the [La-MPBCP]+3 as an adsorber/separator CO2/H2.
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.
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.
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.
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.
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.
We investigated the electronic and mechanical properties of single-walled carbon nanotubes (SWCNTs) with different tube diameters using density functional theory (DFT) and molecular dynamics (MD) simulation, respectively. The carbon nanotubes’ electronic properties were derived from the index number ( n 1 , n 2 ), lattice vectors, and the rolled graphene sheet orientation. For (6,1) SWCNT, ( n 1 - n 2 )/3 is a non-integer, so the expected characteristic is semiconducting. We have considered (6,1) Chiral SWCNT with different diameters ‘d’ (4.68 Å, 4.90 Å, 5.14 Å, 5.32 Å, 5.53 Å) corresponds to respective bond-lengths ‘ δ ’(1.32 Å, 1.36 Å, 1.45 Å, 1.50 Å and 1.56 Å) and then analyze the electronic properties from the Linear Combination of Atomic Orbitals (LCAO) based on DFT. We have used both the DFT-1/2 and GGA exchange energy correlation approximations for our calculation and compared the results. In both cases, the energy band gap is decreasing order with the increase in bond lengths. The lowest value of formation energy was obtained at the bond length δ = 1.45 Å ( d = 5.14 Å). For the mechanical properties, we have calculated Young’s Modulus using Molecular Dynamic simulations. From our calculation, we have found that the (6,1) SWCNT with bond length 1.45 Å ( d = 5.14 Å) has Young’s modulus value of 1.553 TPa.
The structural, electronic, optical, and electrical properties of CuO were studied using the density functional theory (DFT) based on the Full Potential Linearized Augmented Plane Wave (FP-LAPW) method as implemented in the Wien2k code. The structural parameters are optimized by using the 4D-optimize option and the PBE-sol functional. The electronic and optical properties were analysed adopting Generalized Gradient approximation plus the screened Coulomb interaction (GGA+U) and the modified Becke-Johnson (GGA-TB-mBJ) potential for comparison. The calculated band energies have been used with the Boltzmann transport equation to calculate the thermoelectric properties. It is shown that the gap energy obtained by the (TB-mBJ) approximation potential is 2.02 eV more close to the experimental values comparing to that given by the GGA+U (Eg=1.57 eV). The optical properties reveal a high absorption coefficient in the UV region with an average transmittance of around 65% in the visible range, which covers a high range of light using TB-mBJ exchange potential and an average reflectivity of approximately 18% in visible light. The CuO conductivity is limited by the carrier mobility at low temperature and primarily defined by the carrier concentration at high temperature. These properties make CuO a promising material for solar cell applications as an absorbent layer and antireflection coating.
Theoretical calculations involving singlet molecular oxygen (O2(1g)) are challeng- ing due to their inherent multi-reference character. We have tested the quality of re- stricted and unrestricted DFT geometries obtained for the reaction between singlet oxy- gen and a series of alkenes (propene, 2-methylpropene, trans-butene, 2-methylbutene and 2,3-dimethylbutene) which are able to follow the ene-reaction. The electronic en- ergy of the obtained geometries are rened using 3 dierent methods which account for the multi-reference character of singlet oxygen. The results show that the mechanism for the ene-reaction is qualitatively dierent when either one or two allylic-hydrogen groups are available for the reaction. When one allylic-hydrogen group is available the UDFT calculations predict a stepwise addition forming a biradical intermediate, while, the RDFT calculations predict a concerted reaction where both hydrogen abstrac- tion and oxygen addition occur simultaneously. When two allylic-hydrogen groups are available for the reaction then UDFT and RDFT predict the same reaction mechanism, namely that the reaction occurs as a stepwise addition without a stable intermediate between the two transition states. The calculated rate constants are in reasonable agreement with experimental data, except for trans-butene where the calculated rate constant is three orders of magnitude lower than the experimental one. In conclusion we nd that the simple bypassing scheme tested in this paper is a robust approach for calculations of reaction involving singlet oxygen in the limit that the transition state processes low multi-reference character. 2