6-31G Level Research Articles

Theoretical investigation of protonated thiophene and two of its nitrile substituted derivatives (2-cyanothiophene and 3-cyanothiophene).

Theoretical and experimental spectroscopic data for protonated cyano-thiophenes (R-CNH+ with R = C4H3S), which are needed for their interstellar search and/or detection, are still lacking in the literature. Considering the high abundance and reactivity of H3+ in the interstellar medium (ISM), a quantum chemical investigation on protonated thiophene and two of its nitrile-substituted derivatives (2-cyanothiophene and 3-cyanothiophene) is undertaken for their characterization. The geometrical structures for the title species are calculated at the M06-2X/6-31G(d,p) level of theory, followed by an empirical correction for systematic errors. At the same level of theory, IR and Raman spectra are explored and the rotational parameters are calculated. The proton affinity (PA) of R-CN and the enthalpy, entropy and Gibbs free energy changes (ΔrH, ΔrS and ΔrG) of the reactions producing R-CNH+ are computed at the G2(MP2) and G3B3 levels of theory and at different temperatures. The PA calculations show that the protonation favors the nitrogen atom, while ΔrH, ΔrS, and ΔrG reveal the spontaneous reactions producing R-CNH+ and their neutral forms. In addition, quadrupole hyperfine structures are predicted, while the region where the brightest lines fall at different temperatures is discussed. These results are expected to assist astrophysicists and astrochemists in the search for new species in the ISM.

A DFT study on the oxidation of cyclotrisilene by nitrous oxide: the σ- and π-bonds reactivity

The chemistry of heteroatom analogues of cyclopropane derivatives has been receiving considerable interest because of their unexpected reactivities. Herein, the density functional theory (DFT) method was applied to understand reactivity and selectivity of sigma (σ) and pi (π) bonds in methyl and aryl (2,4,6-iPr3C6H2)-substituted cyclotrisilenes, as silicon analogue of cyclopropane, for the reaction with nitrous oxide. The DFT calculations at the APFD/def2-TZVPP level of theory show that three types of isomers with Si3O subunit can be considered as potential products for methylated system. The further DFT calculations on the proposed reactions favor the π-bond reactivity of the methyl-substituted cyclotrisilene to yield a structure that adopted the cyclic planar-trans geometry with the lower energy barrier and considerably high exergonic nature. Moreover, π-bond reactivity of the cyclotrisilene with aryl group promotes the formation of the folded isomer of the planar-trans structure with only 0.3 kcal mol−1 energy gap at the B3LYP-D3/6-31G(d,p) level of theory. The theoretical results provide a crucial guide for the reaction to be tackled experimentally.

Hydrogen-bonded supramolecular framework, Hirshfeld surface analysis and interaction energy studies on 2-amino-5-chloropyridinium p-toluenesulfonate

In title compound, 2-amino-5-chloropyridinium p-toluenesulfonate C7H7SOC5H5N2Cl+ (I), the anions and cations form an R22 (8) heteromeric dimer through N—H…O hydrogen bonds. 2-Amino-5-chloropyridinium cations and p-toluenesulfonate anions are interlinked through N—H…O and C—H…O hydrogen bonds to develop a two-dimensional supramolecular grid in the crystal structure parallel to the (0 0 1) plane. The formation of π…π and π…Cl inter­actions bridges the two-dimensional supramolecular network developing a three-dimensional packing of the crystal structure. The Hirshfeld surface analysis of the title molecule is carried out to understand various aspects of the intermolecular interaction. Interaction energies are calculated at the dispersion-corrected CE-B3LYP/6-31G(d,p) level of quantum theory for N—H…O, C—H…O, π…π interactions and the effect of interaction energies in the formation of a supramolecular network is studied.

Structural Characterization, Theoretical Investigation and Hirshfeld Surface Analysis of 2,6-(E,E)-bis((thiophene-2-yl)methylene)cyclohexanone

The bis(chalcone) compound, 2,6-(E,E)-bis((thiophene-2-yl)methylene)cyclohexanone, has been synthesized and characterized by FTIR, 1H-NMR, 13C-NMR techniques, X-ray structure analysis. The optimized molecular structure of the studied compound is calculated using DFT/B3LYP with 6-31G (d,p) level. The calculated geometrical parameters are in good agreement with the experimental data obtained from our reported X-ray structure. The calculated IR fundamental bands, 1H and 13C NMR chemical shifts of the compound were assigned and compared with the experimental data. Additionally, frontier molecular orbital energies (HOMO, LUMO), their energy gap (, molecular electrostatic potential analysis of the compound have been calculated by the same method. The molecular electrostatic potential (MEP) was used to visualize the charge distribution on the molecule. In addition, the intercontacts in the crystal structure are analyzed using Hirshfeld surfaces computational method. The title compound (C16H14OS2) crystallizes in the monoclinic chiral space group P21/c with a=15.0492(10)Å, b=12.0085(9)Å, c=7.6283(6) Å, β=95.883(7)o, V=1371.31(17)Å3, Dcalc=1.387g/cm3. The central cyclohexanone ring has a flattened chair conformation and the substituents at the vinyl group of each chalcone moiety exhibit a trans (entgegen) disposition, and the two thiophene rings adopt a syn orientation and are located on the both side of the cyclohexanone. The asymmetric unit of the title compound, C16H14OS2, contains one-half of a molecule. The other half of the molecule is generated with (x,y,-z) symmetry operator. In the molecule there are two weak C-H…S and C-H…O intramolecular and only C-H…O intermolecular hydrogen bonds. In addition, π…π interactions are found in the crystal structure between the thiophene rings.

Calculation of conductive polymer-based SO2 and SO3 gas sensor mechanisms by using the DFT method.

In this study, we carried out with the DTP (dithieno(3,2-b:2,3-d) pyrrole) molecule which is a member of the conductive polymer class that is one of the topics that have been studied prevalently in recent times, and the density functional theory's (DFT) calculation methods were used to shed light on the sensor mechanisms of its interactions with SOx (SO2 and SO3) sulfur oxides. The changes in the geometric and electronic characteristics of a sensor mechanism designed with the DTP molecule when it encountered sulfur oxides were examined. With these changes, the usability of DTP as a sensor material was proven. DTP sensor applications using this method were not investigated in previous studies. The B3LYP 6-31G(d) levels of DFT were used in the calculations. In the calculations, during the interaction between analyte (SO2-SO3) and the conductive polymer DTP (dithieno(3,2-b:2,3-d) pyrrole), especially, the changes in its geometric and electronic structures were observed. With these changes that were observed in the geometric structure, as a result of the interaction between the conductive polymer and gas molecules, the resistance on the polymer's main chain decreased, and conductivity increased. Calculations on the bandgap on HOMO-LUMO energy levels were observed to decrease. Thus, the structural conductivity of the molecule increased. Additionally, the experiments showed that, as a result of interaction with gas molecules, the bandgap in the ionization potential, electron affinity, and HOMO-LUMO energy levels varied. These variations showed the detection mechanisms for sulfur oxides by the DTP (dithieno(3,2-b:2,3-d) pyrrole) molecule that may be used to design sensors.

Theoretical calculation of selenium N-heterocyclic carbene compounds through DFT studies: Synthesis, characterization and biological potential

N-heterocyclic carbene (NHC) is one of the significant class of compounds in the organometallic chemistry. Strong sigma donating property and weak pi-accepting property of NHC makes it prominent, so that they can interact with metals to form the stable organometallic complex. These ligand compounds have capability to release the metal in the form of ion slowly and sustainable rate at any site in the biological system. Selenium is also very active element having highly demanding applications like antioxidant agent and is necessary trace element for human body. In the current research work two new imidazolium salts (as pre ligands) and respective selenium-NHC compounds have been designed and computed theoretically before the synthesis of active compounds among the designed compounds. Compounds, namely ML1, ML2, MC1 ans MC2, on the basis of imidazole unit were designed and computed for different properties, absorption spectra, dipole moment, theoretically estimated biological potentials, and frontier molecular orbitals, by calculating the HOMO/LUMO energy orbitals via Density functional theory method. Density functional method was applied using Gaussian 09 software and Gauss view 5.0 program. Analysis of compounds were done at B3LYP level by using 6-31G (d) level of DFT (Density Functional Theory). Theoretical calculation showed that compounds are highly biologically active, as their synthesis is exigency of the time so these compounds were synthesized. Synthesized compounds were characterized by UV–visible, FT-IR, carbon and proton NMR spectroscopies. Antioxidant and anticancer properties of compounds were calculated and their charactristics were compared with the charactristics of imidazole present in the literature and results were the almost same as calculated by theoretical method.

Influence of CO<sub>2</sub> Molecules Adsorption on the Electronic Properties of Zigzag and Armchair ZnO Nanotubes

Here, the adsorption behavior of the CO2 molecules on electronic properties of zigzag and armchair ZnO nanotubes (ZnONTs) has been studied at M06-2X/6-31G(d) level of theory. It is found that CO2 molecules can be physically adsorbed on the nanotubes. Two minima structures A (monodentate) and B (bidentate) were found on the potential energy surface. Inspection of the results shows that in zigzag and armchair nanotubes, the monodentate complex is more stable than bidentate complex. Also, the stability of complexes increases by increasing the number of CO2 molecules. Comparison of adsorption energies shows that adsorption of CO2 molecules over zigzag (6, 0) model is stronger than armchair (4,4) model. In this work, the various parameters such as electronic chemical potential (m), hardness (ƞ), softness (S), the maximum amount of electronic charge (DNmax), electrophilicity index (ω), dipole moment and work function were investigated to evaluate the reactivity of structures. It is predicted that the conductivity and reactivity of nanotubes increase upon complexation. Based on the natural bond orbital (NBO) analysis, in all complexes charge transfer occurs from CO2 molecules to the nanotube. Theory of atoms in molecules (AIM) was also applied to characterize OCO2… Zn interaction in nanotubes. In addition, the interaction strength is studied through the reduced density gradient (RDG) function. It is predicted that the ZnONTs can be introduced as a favorable candidate in the design and construction of sensors for detecting CO2 molecules.

Theoretical Studies of Structures and Conformational Analysis of Anthracene-2,7-diyl Cyclic Oligomers

Abstract The structures and conformation of anthracene-2,7-diyl cyclic oligomers were investigated by DFT calculations. The energy minimum and transition state structures of the oligomers ranging from pentamer to nonamer were optimized at the M05-2X/6-31G(d) level. The mechanisms of conformational interconversion were analyzed on the basis of the calculated structures and the thermodynamic energies. The number of structures and the conformational flexibility rapidly increased with increasing ring size. In the stable structures, the dihedral angles between the anthracene units were ca. ±40° or ±140°, and the obtuse angles appeared only in large oligomers. We estimated the cavity size of the cyclic oligomers from the calculated structures and their strain energies by thermochemical calculations of the homodesmotic reactions.

Tuning of optoelectronic properties of triphenylamines-based donor materials for organic solar cells

In the present study, four molecules have been designed by substituting various acceptor moieties around the triphenylamine donor moiety like 2-cyano acrylic acid (R), 2-methylene malonitrile (M1), 2-cyano acrylic acid methyl ester(M2), 2-(2-methylene-3-oxo-indan-1-ylidene)-malonitrile (M3), 2-(6,7-difluoro-2-methylene-3-oxo-indan-1-ylidene)-malonitrile (M4), respectively. CAM-B3LYP/6-31G (d, p) level of theory by using density functional theory (DFT) has been used for the investigation of optoelectronic properties of four new triphenylamine (TPA)-based donor materials (M1–M4) for organic solar cells. In comparison with the recently reported reference molecule, the optoelectronic properties of designed molecules were evaluated. M4 showed absorption maxima at 520[Formula: see text]nm due to extended conjugation with bridged thiophene group. Results of reorganization energy calculations also favor M4 exhibiting highest transfer rate of hole as depicted from its low reorganization energy of hole ([Formula: see text].

Prediction of the half-lives of polychlorinated biphenyls based on the IEF-PCM calculations

Three-dimensional structures of 62 polychlorinated biphenyl (PCB) congeners were optimized with the integral equation formalism polarizable continuum model (IEF-PCM) in combination with the density functional theory (DFT) method at 6-31G(d) level. By applying support vector machine (SVM) algorithm, a nonlinear quantitative structure–property relationship (QSPR) model was built to predict half-lives (log [Formula: see text]) of 62 PCBs in juvenile rainbow trout. The optimal SVM model based on the parameters [Formula: see text] of 854.721 and [Formula: see text] of 0.0565 produces the root-mean-square (rms) errors of 0.0352 for the training set and 0.0446 for the test set, which are less than that of the previous models reported. The results suggest that it is feasible to build SVM models for the half-lives of PCBs with IEF-PCM and B3LYP/6-31G(d) for deriving structural descriptors.

Tuning Optoelectronic Properties of Dithienopyrrole Donor Molecules for Organic Solar Cells

Theoretical analysis of physical properties of organic solar cells (OSCs) are important in order to reveal the correlation between power conversion efficiencies (PCE), structure and properties. Five new A‒D‒A type small molecules M1, M2, M3, M4, and M5 were designed by using dithienopyrrole (DTP) as electron rich donor unit with different types of π-spacers and end capped acceptor units. Functional MPW1PW91/6-31G(d,p) level of theory was used to optimize the geometry of all molecules. For excited state calculation TD-MPW1PW91/6-31G(d,p) level of theory was used. The geometries, electronic structures, dipole moment, open circuit voltage, reorganization energies and charge transport properties of designed molecules (M1 $$ - $$ M5) have been scrutinized comparing with the reported compound R. The results revealed that the HOMO energy levels of molecules M1, M2, M3, and M5 were lower while M4 was of high energy level thus facilitate the donation of electron as compared to references molecule R. While LUMO energy level of all the molecules were slightly high energy due electron withdrawing effects of spacer and acceptor moiety. Highest energy gap of HOMO–LUMO was observed in M1 which was 2.48 eV and M3 showed low energy gap (2.11 eV) as compared to other designed molecules. All molecules showed low values for λe, so they have high rate of electron transfer as compared to R. All designed molecules exhibited higher value of dipole moment as compared to reference molecule R except M1. Higher value of dipole moment of donor molecules contrary to reference means good solubility towards organic solvents which is beneficial for further solar cell device fabrication. All designed molecules show higher Voc values except M4 which has comparable Voc with respect to reference molecule R. In short, choice of appropriate electron withdrawing and donating groups is very important for improving power conversion efficiencies of OSCs.

Understanding Inhibition of Steel Corrosion by Some Potent Triazole Derivatives of Pyrimidine through Density Functional Theory and Molecular Dynamics Simulation Studies

Density Functional Theory (DFT) calculation at B3LYP level of theory and 6-31G* basis set was applied on some triazole derivatives of pyrimidine which led to the optimization of their structures, generation of electronic and other important Quantum chemical descriptors such as the energy of the highest occupied molecular orbital (EHOMO), the energy of the lowest unoccupied molecular orbital (ELUMO), energy band gap (ΔE), Dipole Moment (μ), chemical hardness (η), chemical softness (σ), global electronegativity() and number of transferred electrons () using SPARTAN’14 Software. The obtained results shows a good correlation between the chemical structures of the inhibitors and their experimental inhibition efficiencies (%IEs). The ranking of these efficiencies (%IEs) nicely matched with the order of a good number of the generated descriptors but with a varying degree of correlation as majority of the descriptors indicates that I-4 is the best inhibitor among the data set. Furthermore, molecular dynamic (MD) simulations were carried out to search the best adsorption configuration of the inhibitor on the steel (1 1 0) surface using Material Studio 8.0. The obtained results of MD simulations suggest that the interaction was as a results of the chemical adsorption on the steel surface, since the binding energy > 100 Kcalmol-1 for all the inhibitors and the best adsorption energy was found to be -488.07 Kcalmol-1 (I-4). This observation are in good agreement with the DFT results and the experiment findings. Thus; this study provides a valuable approach and new direction to novel steel corrosion inhibitor discovery.

Investi̇gati̇on of pyrazoly derivatives schi̇ff base li̇gands and thei̇r metal complexes used as anti-cancer drug.

In this study, six pyrazole derivatives containing hetero atoms have been analyzed using theoretical calculation method. The ligands were tested by HF, B3LYP and M06-2X methods using 3-21G, 6-31G, 6-31G(d, p), and sdd basis sets. The results showed that Ligand 5 has a HOMO value of -7.470 at HF / 6-31g (d.p) level. These ligands were investigated in IR, NMR, and UV-VIS spectrum, then experimental values were compared with IR and NMR spectrum data. The solvents, whose effects were investigated in UV-VIS spectrum, were gas phase (ε = 1), toluene (ε = 2.3741), chloroform (ε = 4.7113), methanol (ε = 32.613), water (ε = 78.3553), and n-methylformamide-mixture (ε = 181.56). Metal complexes of tested ligands were produced with copper, nickel, and zinc. Lastly, the interactions between these six pyrazole derivatives and three proteins, namely 3dju, 2IJN, and 1JNX, were also examined. Biological and anti-cancer properties of six pyrazole derivatives were analyzed by DockingServer. In docking calculations, Estimated Free Energy of Binding value of Ligand 5 was found to be -4.87, -4.82, -1.73 respectively, which indicated the highest biological activity.

Mechanistic study of the formation of quercetine cycloadducts under microwave conditions: a theoretical approach

A theoretical mechanistic investigation of the cycloaddition reaction of quercetine with 3,5-di-tert-butyl-o-quinone has been carry out employing density functional calculations at M06-2X/6-31G(d,p) level of theory. This computational study was performed in order to gain insight in the energetic and structural parameters that rule the observed experimental selectivity in the synthetised cyclodimers obtained under classical heating and microwave irradiation conditions and the influence of the solvent on their chemical reactivity. The effect of the solvent in the selectivity was studied implicitly using the polarisable continuum model in absence and presence of one explicit solvent’s molecule. The theoretical results explain the main issues of the classical heating and the MWI reaction and suggest that thermal effects are directly responsible for the reaction selectivity observed. The comparison of the mechanistic pathway and the non-covalent interactions, shows that a dioxane assisted mechanism can explain the observed experimental selectivity of the two synthetised compounds, thus the dioxane molecule play a catalytic role on this hetero Diels–Alder reaction.

Characterization of the 2-methylvinoxy radical + O2 reaction: A focal point analysis and composite multireference study

Vinoxy radicals are involved in numerous atmospheric and combustion mechanisms. High-level theoretical methods have recently shed new light on the reaction of the unsubstituted vinoxy radical with O2. The reactions of 1-methylvinoxy radical and 2-methylvinoxy radical with molecular oxygen have experimental high pressure limiting rate constants, k∞, 5-7 times higher than that of the vinoxy plus O2 reaction. In this work, high-level ab initio quantum chemical computations are applied to the 2-methylvinoxy radical plus O2 system, namely, the formation and isomerization of the 1-oxo-2-propylperoxy radical, the immediate product of O2 addition to the 2-methylvinoxy radical. Multireference methods were applied to the entrance channel. No barrier to O2 addition could be located, and more sophisticated treatment of dynamic electron correlation shows that the principal difference between O2 addition to the vinoxy and 2-methylvinoxy radicals is a larger steric factor for 2-methylvinoxy + O2. This is attributed to the favorable interaction between the incoming O2 molecule and the methyl group of the 2-methylvinoxy radical. Via the focal point approach, energetics for this reaction were determined, in most cases, to chemical accuracy. The coupled-cluster singles, doubles, and perturbative triples [CCSD(T)] correlation energy and Hartree-Fock energies were independently extrapolated to the complete basis set limit. A correction for the effect of higher excitations was computed at the CCSDT(Q)/6-31G level. Corrections for the frozen-core approximation, the Born-Oppenheimer approximation, the nonrelativistic approximation, and the zero-point vibrational energy were included. From the 1-oxo-2-propylperoxy radical, dissociation to reactants is competitive with the lowest energy isomerization pathway. The lowest energy isomerization pathway ultimately forms acetaldehyde, CO, and ·OH as the final products.

Prediction of Depuration Rate Constants for Polychlorinated Biphenyl Congeners.

The integral equation formalism polarizable continuum model (IEF-PCM) for solvent effects with the default solvent (water) and solvent parameters, together with the density functional theory method at 6-31G(d) level, was used to optimize molecular structures for polychlorinated biphenyl (PCB) congeners. Four molecular descriptors were selected to develop quantitative structure–activity relationship (QSAR) models for the depuration rate constants (kd) of 63 PCB congeners in a juvenile rainbow trout (Oncorhynchus mykiss). The optimal multiple linear regression (MLR) model has the correlation coefficient R of 0.933 and the root mean square (rms) error of 0.0681 for the total set of 63 PCB congeners. The support vector regression model has R of 0.953 and rms error of 0.0576 for the total set. Both the MLR and SVM QSAR models in this paper were accurate and acceptable compared with other QSAR models for the depuration rate of PCB congeners reported in references. Thus, applying IEF-PCM and B3LYP/6-31G(d) calculations for molecular descriptor derivation of PCB congeners is successful.

Theoretical study of gallium nitride nanocage as a carrier for 5-fluorouracil anticancer drug.

In this paper, the possible interactions between 5-fluorouracil (5FU) as an anticancer drug and gallium nitride (Ga12N12) nanocage (NC) in aqueous solution have been investigated using DFT/CPCM/B3LYP-D/6-31G(d,p) level of theory. Eleven different orientations were used to mimic the 5FU adsorbed on Ga12N12 (5FU@GaNNC). To investigate the interaction mechanism between the two components, the adsorption energies and thermodynamic parameters, the electronic properties such as the energies and orbitals distribution of the highest occupied molecular orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), the HOMO-LUMO energy gaps (Eg), the density of states (DOS), partial DOS (PDOS), and the molecular electrostatic potential (MEP) have been calculated and compared. The natural bond orbitals (NBOs) and the quantum theory of atoms in molecules (QTAIM) calculations have been applied for understanding chemical interactions and chemical bonding. Additionally, some quantum molecular descriptors were calculated for the understanding of molecular reactivity. Main results revealed that (1) the key factor that leads to stabilization of the formed complex/s is the relocation of one of the H atoms that originally belonging to one of the N atoms in 5FU to one of the nearest Ga atoms in GaNNC and (2) the adsorption energies for the eleven adsorbed systems are relatively larger compared with reported similar systems indicating from a theoretical point of view, a probable chemisorption type of adsorption and the privilege of GaNNC as a carrier for 5FU drug. Graphical abstract Simulation of the most stable adsorbed system of 5-fluorouracil anticancer drug on Gallium nitride nanocage.

Catalyst-Dependent Chemoselectivity in the Dirhodium-Catalyzed Cyclization Reactions Between Enodiazoacetamide and Nitrosoarene: A Theoretical Study.

N-O heterocycle compounds play an important role in various fields. Doyle et al. (Cheng et al., 2017) have recently reported an efficient catalyst-controlled selective cyclization reactions of tert-butyldimethylsilyl (TBS)-protected enoldiazoacetamides with nitrosoarenes in which the multifunctionalized products 5-isoxazolones and 1,3-oxazin-4-ones were formed through [3+2]- and [5+1]-cyclizations using Rh2(oct)4 and Rh2(cap)4 as catalysts, respectively. The present work studied the mechanism of the reactions in question and the origins of the catalyst-dependent chemoselectivity by the density functional theory (DFT) calculations at the M06-D3/SMD/6-311+G(d,p)//B3LYP-D3/6-31G(d,p) level of theory. The computed results illustrate the importance of the different dirhodium catalysts to gain diversified N-O heterocycle compounds and suggest the specific interaction between the reactants by the real catalyst model. Meanwhile, it is the steric hindrance and electronic effect of the ligands of dirhodium catalysts that control the reaction mechanism. Furthermore, the other auxiliary theoretical analysis, natural bond orbital calculation and distortion/interaction analysis, make the electronic effects, and steric hindrance more distinct.

1, 3-Dipolar cycloaddition reactions of selected 1,3-dipoles with 7-isopropylidenenorbornadiene and follow-up thermolytic cleavage: A computational study

The mechanism, regio-, stereo-, and enantio-selectivities of the 1,3-dipolar cycloaddition reactions of 7-isopropylidenenorbornadiene (DENBD) with nitrones and azides to form pharmaceutically relevant isoxazolidine and triazole analogues have been studied computationally at the M06/6-31G(d), 6-31G(d,p), 6-311G(d,p), 6–311++G(d,p) and M06-2X/6-31G(d) levels of theory. In the reactions of DENBD with phenyl nitrones, the cycloaddition steps have low activation barriers, with the highest being 16 kcal/mol; and the Diels-Alder cycloreversion steps have generally high barriers, with the lowest being 20 kcal/mol, suggesting that the isolable products in these reactions are the bicyclic isoxazolidine cycloadducts and not the thermolytic products. This is in contrast to the reactions of DENBD with phenyl azide where the isolable products are predicted to be the thermolytic products since the Diels-Alder cycloreversion steps had relatively lower activation barriers. Electron-donating substituents on the dipolarophile substrate favour attack of the nitrone on the least hindered side of the DENBD substrate while electron-withdrawing substituents on the dipolarophile substrate favour attack on the more hindered side of the DENBD, indicating that site-selectivity is affected by nature of substituents. Global reactivity indices calculations are in good agreement with the activation barriers obtained. Analysis of the electrophilic (PK+) and nucleophilic (PK−) Parr functions at the reactive centres reveal that the cycloaddition occurs between atoms with the largest Mulliken and NBO atomic spin densities which agrees well with the energetic trends and the experimental product outcomes.

The AIM, RDG, NBO, Quantum and Structural Study of Adsorption of Phosgene Gas on the Surface of Pristine and Al, P Doped Ga12N12 Nano Cluster: A DFT Method

The main objective of this work is to study the sensivity of pristine, Al, P and Al & P doped Ga12N12 to adsorb phosgene (COCl2) molecule. The interaction of COCl2 from O, C and Cl sites on the surface of Ga12N12 is investigated by applying the density functional theory (DFT) at the cam-B3LYP/6-31G(d) level of theory. The geometrical and electrical structures, quantum descriptive, thermodynamic parameters, solvent effect, atom in molecule theory (AIM), natural bond orbital (NBO), and the reduced density gradient (RDG) are calculated at the above level of theory. The calculated results indicate that the adsorption of COCl2 on the surface of pristine and Al, P and Al & P doped Ga12N12 is exothermic, as well as Al-doped Ga12N12 is more favorable than P and Al & P doped. The recovery time results for adsorption of COCl2 from O site on the surface of Ga12N12, Al-Ga11N12, Ga12N11P and Al-Ga11N11P are 0.103, 4.69×10-7, 3.81×10-12 and 4.31×10-7 respectively. As a result, these nanoclusters can be used as sensor devices toward COCl2 molecule. The deformation energy results reveal that the structural change of Ga12N12 and COCl2 at all adsorption states are not significant. The AIM, RDG and NBO results demonstrate that the intermolecular interaction from O site of COCl2 on the surface of pristine, Al, P and Al & P doped Ga12N12 is stronger than C and Cl atoms sites of COCl2 as it is an electrostatic attractive type. The main objective of this work is to study the sensivity of pristine, Al, P and Al & P doped Ga12N12 to adsorb phosgene (COCl2) molecule. The interaction of COCl2 from O, C and Cl sites on the surface of Ga12N12 is investigated by applying the density functional theory (DFT) at the cam-B3LYP/6-31G(d) level of theory. The geometrical and electrical structures, quantum descriptive, thermodynamic parameters, solvent effect, atom in molecule theory (AIM), natural bond orbital (NBO), and the reduced density gradient (RDG) are calculated at the above level of theory. The calculated results indicate that the adsorption of COCl2 on the surface of pristine and Al, P and Al & P doped Ga12N12 is exothermic, as well as Al-doped Ga12N12 is more favorable than P and Al & P doped. The recovery time results for adsorption of COCl2 from O site on the surface of Ga12N12, Al-Ga11N12, Ga12N11P and Al-Ga11N11P are 0.103, 4.69×10-7, 3.81×10-12 and 4.31×10-7 respectively. As a result, these nanoclusters can be used as sensor devices toward COCl2 molecule.