6-31G Level Research Articles

Smart drug delivery: a DFT study of C24 fullerene and doped analogs for pyrazinamide.

The potential applicability of the C24 nanocage and its boron nitride-doped analogs (C18B3N3 and C12B6N6) as pyrazinamide (PA) carriers was investigated using density functional theory. Geometry optimization and energy calculations were performed using the B3LYP functional and 6-31G(d) basis set. Besides, dispersion-corrected interaction energies were calculated at CAM (Coulomb attenuated method)-B3LYP/6-31G(d,p) and M06-2X/6-31G(d,p) levels of theory. The adsorption energy (E ads), enthalpy (ΔH), and Gibbs free energy (ΔG) values for C24-PA, C18B3N3-PA, and C12B6N6-PA structures were calculated. The molecular descriptors such as electrophilicity (ω), chemical potential (μ), chemical hardness (η) and chemical softness (S) of compounds were investigated. Natural bond orbital (NBO) analysis confirms the charge transfer from the drug molecule to nanocarriers upon adsorption. Based on the quantum theory of atoms in molecules (QTAIM), the nature of interactions in the complexes was determined. These findings suggest that C24 and its doped analogs are promising candidates for smart drug delivery systems and PA sensing applications, offering significant potential for advancements in targeted tuberculosis treatment.

Non-covalent interactions and charge transfer in the CO activation by low-valent group 14 complexes.

The CO activation by low-valent group 14 catalysts encompasses the rupture of varied covalent bonds in a single transition state through a concerted pathway. The bond between the central main group atom and the hydride in the complex is elongated to trigger the formation of the C-H bond with CO accompanied by the concomitant formation of the E-O bond between the complex and CO to lead the corresponding formate product. Prior studies have established that besides the apolar nature of CO , its initial interaction with the complex is primarily governed by electrostatic interactions. Notably, other stabilizing interactions and the transfer of charge between catalysts and CO during the initial phases of the reaction have been ignored. In this study, we have quantified the non-covalent interactions and charge transfer that facilitate the activation of CO by group 14 main group complex. Our findings indicate that electrostatic interactions predominantly stabilize the complex and CO in the reactant region. However, induction energy becomes the main stabilizing force as the reaction progresses towards the transition state, surpassing electrostatics. Induction contributes about 50% to the stabilization at the transition state, followed by electrostatics (40%) and dispersion interactions (10%). Atomic charges calculated with the minimal basis iterative stockholder (MBIS) method reveal larger charge transfer for the back-side reaction path in which CO approaches the catalysts in contrast to the front-side approach. Notably, it was discovered that a minor initial bending of CO to approximately initiates the charge transfer process for all systems. Furthermore, our investigation of group 14 elements demonstrates a systematic reduction in both activation energies and charge transfer to CO while descending in group 14. All studied reactions were characterized along the reaction coordinate obtained with the intrinsic reaction coordinate (IRC) methodology at the M06-2X/6-31g(d,p) level of theory. Gibbs free energy in toluene was computed using electronic energies at the DLPNO-CCSD(T)/cc-pVTZ-SSD(E) level of theory. Vibrational and translational entropy corrections were applied to provide a more accurate description of the obtained Gibbs free energies. To better characterize the changes in the reaction coordinate for all reactions, the reaction force analysis (RFA) has been employed. It enables the partition of the reaction coordinate into the reactant, transition state, and product regions where different stages of the mechanism occur. A detailed characterization of the main non-covalent driving forces in the initial stages of the activation of CO by low-valent group 14 complexes was performed using symmetry-adapted perturbation theory (SAPT). The SAPT0-CT/def2-SVP method was employed for these computations. Charge transfer descriptors based on atomic population using the MBIS scheme were also obtained to complement the SAPT analyses.

Removal of trace Na and K metal ions by resin-grafted crown ether for electronic-grade N-methyl pyrrolidone purification

The semiconductor industry’s rapid evolution necessitates ultra-high-purity N-methyl pyrrolidone (NMP) as an essential electronic-grade solvent. The development of an efficient coordination material to reduce trace metal ions, particularly Na and K metal ions, to below 1 ppb in NMP solution is a significant challenge. To address this, a novel coordination material, St-DVB-g-ACE, has been developed for the removal of Na and K metal ions from NMP. The material was synthesized by grafting 4′-aminobenzo-15-crown-5-ether onto a strong acid gel resin. The resulting St-DVB-g-ACE-3 exhibited excellent coordination performance for Na and K metal ions, with maximum Langmuir adsorption capacities reaching 20,000 μg/g and 33,333 μg/g, respectively. Of particular interest was the ability of St-DVB-g-ACE-3 to reduce all trace metal ions in industrial-grade NMP to below 1 ppb within a fixed bed column, achieving the stringent requirements for electronic-grade NMP at the G3 level. Additionally, the absorbent enhances the purity of NMP from 99.82 % to 99.84 %, indicating that the material is not dissolved and can exist stably in NMP. Its excellent recyclability and reproducibility make it highly practical for industrial use. Density functional theory (DFT) simulation, complemented by spectral analyses, revealed the interaction force and thermodynamic properties between Na and K metal ions and crown ether ring, and illustrated the interaction between anionic sulfonic group (−SO3−) and metal ions. The prepared resin-grafted crown ether adsorbents are highly effective in the thorough removal of trace metal ions from NMP solution, offering a novel and effective method for the production of electronic-grade NMP.

Stepwise Excited-State Intramolecular Double Proton Transfer in 1,8-Dihydroxynaphthalene-2,7-dicarbaldehyde.

We theoretically investigate the salient features of stepwise excited-state intramolecular double proton transfer (ESIDPT) in 1,8-dihydroxynaphthalene-2,7-dicarbaldehyde (DHDA). Surface trajectory simulations using the TD-B3LYP/6-31G(d) level of theory reveal that the proton transfer primarily happens via S1, wherein about ∼42% of trajectories (40 out of 95) show the single proton transfer alone and another ∼32% (30 out of 95) show double proton transfer. The average time scale for the single proton transfer originating from those ∼42% trajectories is ∼147 fs. In the case of double proton transfer, the average time for the first step, i.e., single proton transfer, is ∼54 fs, and the subsequent step, i.e., double proton transfer, completes in ∼151 fs. All three tautomers, i.e., normal, single, and double proton-transferred tautomers, possess a stable minimum in their first singlet excited state. This state has a ππ* character in the former two tautomers, resulting in a dual fluorescence emission phenomenon upon photoexcitation of DHDA.

New combined experimental and DFT studies for adsorption of sole Azo-dye or binary cationic dyes from aqueous solution

Textile-toxic synthetic dyes, which possess complex aromatic structures, are emitted into wastewater from various branches. To address this issue, the adsorption process was applied as an attractive method for the removal of dye contaminants from water in this article. An unprecedented integrated experimental study has been carried out, accompanied by theoretical simulations at the DFT-B3LYP/6-31G (d,P) level of theory to investigate how single Maxilon Blue GRL (MxB) dye or and its mixture with MG (Malachite Green) dyes interact with the adsorbent and compare the obtained results with the data obtained through experimentation. The full geometry optimization revealed the physical adsorption of dyes on the Al2O3 surface. Non-linear optical properties (NLO) results emphasized that the complex MG-Al2O3-MxB is a highly promising material in photo-applications, and the adsorbed binary system is energetically more favorable compared to the adsorbed sole dye system. The experimental results for (MxB) dye adsorption onto γ-Al2O3 affirmed that the optimum conditions to get more than 98% uptake were at dye concentration 100 ppm, pH 10, adsorbent content 0.05 g, and equilibrium time only 20 min. The kinetic and isothermal studies revealed that the adsorption accepted with the pseudo-second-order and Freundlich isotherm model, respectively. The removal efficiency of the mixture of MxB and MG dyes was the highest but did not change clearly with increasing the % of any of them. The details of the interaction mechanisms of the sole and binary dyes were proven.

Theoretical Study of the Mechanism of the Formation of Azomethine Ylide from Isatine and Sarcosine and Its Reactivity in 1,3-Dipolar Cycloaddition Reaction with 7-Oxabenzonorbornadiene.

The reaction mechanism of tthe formation of azomethine ylides from isatins and sarcosine is addressed in the literature in a general manner. This computational study aims to explore the mechanistic steps for this reaction in detail and to assess the reactivity of formed ylide in a 1,3-dipolar cycloaddition reaction with 7-oxabenzonorbornadiene. For this purpose, density functional theory (DFT) calculations at the M06-2X(SMD,EtOH)/6-31G(d,p) level were employed. The results indicate that CO2 elimination is the rate-determining step, the activation barrier for 1,3-dipolar cycloaddition is lower, and the formed ylide will readily react with dipolarophiles. The substitution of isatine with electron-withdrawal groups slightly decreases the activation barrier for ylide formation.

Thermochemical Research on Furfurylamine and 5-Methylfurfurylamine: Experimental and Computational Insights.

The need to transition from fossil fuels to renewables arises from factors such as depletion, price fluctuations, and environmental considerations. Lignocellulosic biomass, being abundant, and quickly renewable, and not interfering with food supplies, offers a standout alternative for chemical production. This paper explores the energetic characteristics of two derivatives of furfural-a versatile chemical obtained from biomass with great potential for commercial sustainable chemical and fuel production. The standard (p° = 0.1 MPa) molar enthalpies of formation of the liquids furfurylamine and 5-methylfurfurylamine were derived from the standard molar energies of combustion, determined in oxygen and at T = 298.15 K, by static bomb combustion calorimetry. Their standard molar enthalpies of vaporization were also determined at the same temperature using high-temperature Calvet microcalorimetry. By combining these data, the gas-phase enthalpies of formation at T = 298.15 K were calculated as -(43.5 ± 1.4) kJ·mol-1 for furfurylamine, and -(81.2 ± 1.7) kJ·mol-1 for 5-methylfurfurylamine. Furthermore, a theoretical analysis using G3 level calculations was performed, comparing the calculated enthalpies of formation with the experimental values to validate both results. This method has been successfully applied to similar molecules. The discussion looks into substituent effects in terms of stability and compares them with similar compounds.

Synthesis, Biological Properties, and Molecular Docking Study of Novel 1,2,3-Triazole-8-quinolinol Hybrids.

A new series of 1,2,3-triazole-8-quinolinol hybrids were synthesized in good yields using monosubstituted acetonitriles and 5-azidomethyl-8-quinolinol as the starting reagents via a one-step protocol. The structures of 1,2,3-triazole-8-quinolinol hybrids were characterized by nuclear magnetic resonance (1H and 13C NMR) spectroscopy and elemental analysis. Antibacterial activity in vitro of all the synthesized hybrids was investigated against Escherichia coli (E. coli), Xanthomonas fragariae (X. fragariae), Staphylococcus aureus (S. aureus), and Bacillus subtilis (B. subtilis) applying the methods of disk diffusion and minimal inhibition concentration (MIC). Hybrid 7 exhibited excellent antibacterial capacity, with an MIC value of 10 μg/mL against S. aureus and 20 μg/mL against B. subtilis, E. coli, and X. fragariae, which were comparable to those that of the standard antibiotic nitroxoline. A structure-activity relationship (SAR) study of 1,2,3-triazole-8-quinolinol hybrids showed that introducing electron-donating substituents in the 1,2,3-triazole ring at the 4-position is important for activity. Quantum chemical calculations have been undertaken to employ the Gaussian software in the B3LYP, HF, and M062X basis sets using 3-21g, 6-31g, and SDD levels to further explain linkages within the antibacterial findings. Furthermore, molecular docking investigations were also conducted to investigate the binding affinities as well as the interactions of some hybrids with the target proteins. An absorption, distribution, metabolism, excretion, and toxicity (ADME/T) investigation was carried out to scrutinize the viability of employing the 1,2,3-triazole-8-quinolinol hybrids as medicines.

Revealing the mechanism, Regio- and stereo selectivity and solvent effects of [3 + 2] cycloaddition reactions involving N-benzyl fluoro nitrone and electron-deficient alkynes

The [3 + 2] cycloaddition reactions (32CA) between N-benzyl fluoro nitrone and electron-deficient dipolarophiles alkynes have been studied using molecular electron density theory at the B3LYP-D3/6-31G(d) level. The findings indicate that, in these 32CA reactions, a one-step mechanism is in play with asynchronous transition states. The topological analyses of these transition states are consistent with the presence of non-covalent interactions at the bonding regions between atoms. The analysis of the energy profile in gas phase and in the presence of solvents indicates a preference for a specific site addition over the others. Parr functions were thus used to justify such regioselectivity. In addition, we show that solvents do not modify the regioselectivity achieved, but it increases the activation energies and reduces the exothermic nature of this 32CA reaction. The present findings are in agreement with the experimental results.

Efficient synthesis, crystallographic study, antimicrobial activity and in silico studies of novel bioactive α-aminophosphonates based on pyridine moiety

This study articulates the synthesis, spectroscopic characterization, antimicrobial evaluation, theoretical calculations, and molecular docking analysis of a novel α-aminophosphonates derived from aminopyridine as potential antibacterial pharmacophore. The structures of all compounds was established using FTIR, 1H, 13C, 31P NMR spectroscopy. A single crystal of the studied compound 3g was selected for X-ray diffraction analysis, it crystallizes in the monoclinic crystal system with P 21/n space group. Theoretical studies based on density functional theory (DFT) at the B3LYP /6-31G (d, p) level of theory was utilized to investigate the stability and electronic properties electronic of the studied α-aminophosphonates. The ADME/toxicity analyzes carried out by Swiss ADME and OSIRIS software show that all synthesized molecules exhibited good pharmacokinetics, bioavailability and had no toxicity profile.

Uncovering the interactions and potentials of magnesium and boron nitride nanostructures for magnesium-ion batteries

In present research paper, relationships between a magnesium atom and a magnesium ion (Mg2+) were examined with four different nanostructures: a boron nitride nanotube and a boron nitride nanocone. Our goal was to determine cell voltage (V) values for Mg-ion batteries (MIBs). We conducted calculations employing ωB97XD level of theory and 6-31G(d) basis set to analyze total energy, optimize the geometry, and examine the frontier molecular orbitals. The DFT calculations provided clarification regarding the energy adsorption changes (Ead) between the Mg2+ ion and nanostructures, indicating that the order of Ead is BN tube > BN cone. However, the nanocone exhibits the highest Vcell value, and alterations in Vcell for Mg-ion batteries follow order of BN cone > BN tube. Present research provides theoretical insights into the potential of magnesium as an anode material in batteries, highlighting its favorable Vcell.

DFT Calculations, Pro-Apoptotic Effects, and Anti-Infective Investigations of Alkaloids Isolated from the Stem Bark Extract of Enantia chlorantha

Fractionation of the stem bark of Enantia chlorantha Oliv yields three alkaloids, palmatine (1), jatrorrhizine (2), columbamine (3), and β-Sitosterol (4). In this investigation, density functional theory (DFT) calculations were carried out to evaluate the electronic structure and properties of 1–4 by DFT-B3LYP/6-31G level of theory using Gaussian 09 software. The highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), HOMO-LUMO energy difference (band gap), hardness (η), softness (S), dipole moment (μ), electronegativity (χ), hydrophobicity (logP), topological surface area (TPSA), and energy gap (Eg) were calculated. The in vitro cytotoxicity of the compounds was investigated against MCF-7 and HCT116 cancer cell lines using Wi-38 cells as a control. The compounds inhibited the proliferation of the MCF-7 and HCT116 cell lines and induced apoptosis via upregulation of caspase-3, Bax, PARP cleavage, and downregulation of Bcl-2. DFT analyses revealed that compounds 1 and 3 have smaller energy gaps, 0.072 and 0.071eV, respectively, with the highest dipole moments; hence, these compounds are more chemically reactive and exhibit better modulation of caspase-3 enzyme and inhibitory activities of the MCF-3 and HCT116 cell lines. The antimicrobial and antiparasitic evaluation of 1–4 showed moderate efficacy against the bacterial strains and moderate antiparasitic activity against Cichlidogyrus tilapia.

Investigating the adsorption potential and sensitivity of pristine along with carbon, boron, and nitrogen substituted hetero-nanocages towards azacitidine drug

The use of nanomaterials as carriers for the delivery of a diverse array of anticancer drugs and their application as effective sensors in clinical environments has been steadily growing as a result of advancements in nanoscience. Using density functional theory at the B3LYP-D3/6-31G(d,p) level, this study made a comparative adsorption efficiency assessment of pure C24 and B12N12 nanocages along with some of their hetero-counterpart nanocages toward the anticancer drug azacitidine. Out of the nanostructures that were examined in this study, B6C6N12 nanocage appeared as the most prominent adsorbent by developing drug delivery conjugated structure that demonstrates the highest degree of stability in adsorbing the azacitidine, making it most suitable for transportation or detection purposes in both gaseous and aqueous environments. The confirmation of the interaction between the azacitidine and the adsorbents is further supported by examining frontier molecular orbitals, natural bond orbital, quantum theory of atoms in molecules, and non-covalent interaction analysis. The simulation of ultraviolet–visible spectra was performed for all systems to assess the feasibility of using ultraviolet–visible spectroscopy to track and monitor the binding of azacitidine to the suggested adsorbents. The findings presented here open up endless possibilities for these nanocages as drug delivery and detection systems of nanomedicine.

Density functional theory and molecular dynamics simulation of water molecules confined between parallel graphene oxide surfaces using new interaction potentials

In this study, the interaction potential of water molecule with a graphene oxide (GO) plate containing OH and O groups has been calculated using the M06-2X/6-31g(d,p) level of theory at different orientations and intermolecular distances and fitted to the Born-Huggins-Meyer (BHM) model. There are good agreements between the calculated and the OPLS-AA and Dreiding models, especially for the GO(O)-H2O interactions. To examine the new computed models, we have used the closer potentials to the OPLS-AA and Dreiding models in the molecular dynamics (MD) simulations. We have calculated several properties using the different obtained interaction potentials including average number of hydrogen bonds per water molecule (〈HB〉) between confined water molecules and between water and GO-surfaces, radial distribution function (RDF), self-diffusion coefficient, and angle distribution function of the confined water molecules between the GO plates. Our results showed good agreements between the OPLS-AA and Dreiding models and some calculated potentials. However, some calculated models showed completely different behavior which discussed in details. According to the results, we concluded that the OH-2 and O1-OH2 models show totally better agreement with the famous force fields than the other calculated potentials. This work provides a simple method for the development of new force fields specifically for these types of systems which are in good agreement with the well-known force fields.

Theoretical and kinetic study of the H-atom abstraction reactions by Ḣ atom from alkyl cyclohexanes.

Reaction kinetics of hydrogen atom abstraction from six alkyl cyclohexanes, methyl cyclohexane (MCH), ethyl cyclohexane (ECH), n-propyl cyclohexane (nPCH), iso-propyl cyclohexane (iPCH), sec-butyl cyclohexane (sBCH) and iso-butyl cyclohexane (iBCH), by the Ḣ atom are systematically studied in this work. The M06-2X method combined with the 6-311++G(d,p) basis set is used to perform geometry optimization, frequency analysis and zero-point energy calculations for all species. The intrinsic reaction coordinate (IRC) calculations are performed to confirm the transition states connecting the reactants and products correctly. One-dimensional hindered rotors are used to treat the low frequency torsional models with potentials scanned at the M06-2X/6-31G level of theory. Electronic single-point energy calculations for all reactants, transition states, and products are performed at the QCISD(T)/CBS level of theory. High-pressure limiting rate constants of 39 reaction channels are obtained using conventional transition state theory with asymmetric Eckart tunneling corrections in the temperature range 298.15-2000 K. Reaction rate rules for H-atom abstraction by the Ḣ atom from alkyl cyclohexanes on primary, secondary and tertiary carbon sites on both the side chain and ring are provided. The obtained rate constants are given by the Arrhenius expression in the temperature range 500-2000 K, which can be used for the combustion kinetics model development for alkyl cyclohexanes.

Theoretical investigation on isomerization and decomposition reactions of pentanol radicals-part II: linear pentanol isomers.

High-level ab initio calculations are conducted for studying the kinetics of three linear pentanol radicals generated through H-atom abstraction reactions. The species involved are optimized using the M06-2X/6-311++G(d,p) level of theory, while a relaxed scan at the M06-2X/6-31g level of theory with 10° increments is used for the hindrance potential for low-frequency torsional modes. Single-point energies for all stationary points are obtained through the QCISD(T) and MP2 methods in combination with cc-pVDZ, cc-pVTZ, and cc-pVQZ basis sets, which can be extrapolated to the complete basis set (CBS) limit. The rate constants and branching ratios for isomerization and decomposition reactions are computed over a temperature range of 250-2000 K and a pressure range of 0.01-100 atm. Isomerization reactions are dominant at low temperatures, while decomposition reactions are more dominant at high temperatures. The branching ratio of the isomerization reaction exhibits a slight decrease with increasing pressure, while the trend for decomposition reactions depends on the type of the breaking bond. Based on the calculations for five branched pentanol radicals in part I, kinetics of linear and branched pentanol radicals are compared in this work and the results reveal that, for the same kind of β-scission reaction at similar positions of linear and branched pentanol radicals, the rate constants of branched ones are faster than those of linear ones at low temperatures. The hydroxyl group adjacent to the breaking bond can increase the β-scission reaction rate constants, while the effect can be ignored when the hydroxyl group is not adjacent to the breaking bond. Moreover, compared to when the hydroxyl group is located in the middle of the carbon chain, its positioning at the chain's end yields a more noticeable impact on the products and rate constants of C-O bond and O-H bond β-scission reactions. Besides, when incorporating calculated rate constants into the CRECK model, the updated mechanism shows a better performance for ignition delay times of 1-pentanol in the NTC range but exhibits lower reactivity at higher temperatures. The simulation of speciation profiles also shows better agreement with the experimental data obtained using a flow reactor.

A computational study photophysical properties of a series phenothiazine-linked-BODIPY as D-D-π-a photosensitizer unit for photo-induced hydrogen production from water

Phenothiazine-derivatives are designed as sensitizers which covalently-linked with BODIPY for application in a system of dye-sensitized photoelectrochemical cells (DSPECs). A series of phenothiazine-linked-BODIPY as D-D-π-A chromophore have been investigated by a computational approach for studying the capability of the photosensitizers for application in photoinduced water splitting hydrogen production in DSPECs. The geometries of sensitizers at the ground state and excited state were optimized by the CAM-B3LYP/6-31G (d,p) level method. The theoretical study has been done in order to investigate the photophysical properties such as absorption profile, HOMO-LUMO energy and surface plots of the photosensitizer. The result of calculation for HOMO-LUMO energy level of each dyes showed that the LUMO energy are ranging more than -2.8 - (-2.86) eV which is higher than -4.0 eV of conduction band of TiO2 as semiconductor in DSPEC, meaning that all these dyes could be used as photosensitizers in DSPECs. In addition, the oscillator strength data of each dyes showed the dyes have absorption profile in visible region, meaning the dyes could harvest higher intensity of sunlight to induce water splitting reaction to produce hydrogen.

A Note on Stability of a Dopant for Perovskite Solar Cells: Dimerization of 2,2′-bis(trifluoromethyl)-[1,1′-biphenyl]-4,4′-diamine Iodine

The note continues with the density-functional theory (DFT) quantum-chemical understanding of perovskite solar cells at molecular level. In particular, 2,2′-bis(trifluoromethyl)-[1,1′-biphenyl]-4,4′-diamine iodine (or BFBAI2, stoichiometry C14H12F6I2N2) is further calculated—the species is known to improve the power conversion efficiency and device stability. The thermodynamic-stability calculations are performed at the M06-2X/3-21G level with anharmonic vibrational analysis (including vibrational-rotational coupling) for construction of the vibrational-rotational partition functions. The dimerization is shown to be an essential feature of BFBAI2 (it is based on the formation of two hydrogen bonds). The BFBAI2 dimerization is described in the terms of the standard Gibbs energy and the related dimerization equilibrium constant. Comparisons are made with the water dimer, commonly used as a model system for hydrogen-bond formation. The equilibrium constants for the water dimerization are consistently lower than for the dimerization of BFBAI2 - as the presence of two hydrogen bonds in the BFBAI2 dimer contributes to the larger stabilization. The dimerization of BFBAI2 upon higher surface coverages represents an additional factor for the layer stabilization as there is decrease in the standard Gibbs energy at moderate temperatures. The dimerization also brings additional features for modulation of surface conditions.

Photophysical properties of four-membered BN3 heterocyclic compounds: theoretical insights.

Understanding the photochemistry of boron nitrogen (BN)-containing compounds is an important aspect to enhance the various optical and electronic applications. In this work, we have explored the structure, bonding, reactivity, electronic absorption (UV-Vis), and light harvesting efficiency (LHE) of a series of BN3 ring and open-chain systems. The frontier molecular orbitals (FMO) analysis found that ring systems have a low HOMO-LUMO energy gap as compared to the open-chain systems which insinuates the feasibility of ring systems in the optoelectronic materials. Also, the molecular electrostatic potential (MEP) maps have been computed to pursue the electrophilic and nucleophilic sites available at the surface of the compound. Interestingly, we have found that the open-chain compounds show more molecular charge distribution range rather than the ring compounds. The investigation of photophysical properties showed that the UV-Vis absorption significantly red-shifted in BN3 ring systems as compared to open-chain counterparts. Furthermore, light harvesting efficiency (LHE) was also found higher in the ring systems as compared to the BN3 open-chain systems. Moreover, the computed structural parameters are found well corroborated with the available X-ray data. Structures of all compounds were optimized by using density functional theory (DFT) method, with M06-2X/6-31G(d,p) level. All the calculations in this work are carried out in Gaussian 16 program package. GaussView6.1 software was used for the modeling of initial geometries and for the plotting of MEP plots. To account the solvent effect on geometries the polarized continuum model (PCM) was used and tetrahydrofuran (THF) taken as solvent. The NBO6.0 program (incorporated in G16 software) was used for the exploration of bonding nature and stabilization energies of B-N bond. The absorption spectra were simulated by using ORCA 4.2 program.

Detailed kinetic mechanism for nitrocellulose low temperature decomposition

In the current investigation a detailed kinetic scheme of nitrocellulose (NC) is developed. Despite being studied for decades, NC did not have a detailed model yet. Thanks to Reaction Mechanism Generator open-source software a NC decomposition scheme has been generated. Optimizations of that model have been performed including intermediates thermodynamic properties calculations with Gaussian 16 at the B3LYP 6-31G(d,p) level of theory. Model reduction and decomposition computations were achieved with Chemkin-Pro. NC detailed mechanism has been optimized thanks to experimental data available in the literature, by slightly adjusting some rate constants of relevant chemical reactions. For instance, mean deviation of NO molar fraction is about 5.64% showing that the model follows the general trend of measured results. The final NC model consists in 62 species and 803 gas phase reactions. Eventually, NC and hexogen (RDX) models have been merged to predict overpressures obtained experimentally on a RDX-NC propellant. Numerical and experimental results have been confronted regarding the ignition temperature, initial pressure and surrounding gas nature. Computed results have been congruent when compared to experimental data, especially under argon atmosphere with an ignition temperature of 1173 K. Evidences from global trends indicate that the developed model can provide encouraging computations results for future research and investigations.