Quantum Chemical Study Research Articles

Quantum Chemical Study of the Cycloaddition Reaction of Tropone with 1,1-Diethoxyethene Catalyzed by B(C6F5)3 or BPh3.

Cycloaddition reaction of tropone with 1,1-diethoxyethene catalyzed by Lewis acid (LA), B(C6F5)3 or BPh3, was examined by using ωB97X-D-level density functional theory (DFT) calculations. In the absence of LA, the reaction proceeds in a stepwise fashion to form two chemical bonds, first between the C2 atom in tropone and the C2 atom in ethene and then between the C5 atom in the former and the C1 atom in the latter. When B(C6F5)3 is attached to the O atom in tropone, the C5 atom in tropone is attacked preferentially by the C1 atom in ethene in the second stage. The attack of the O atom in tropone is shown to be less likely; thus, the [4 + 2] addition is favored in the B(C6F5)3-catalyzed reaction. In contrast, the attack of the O atom in the BPh3-attached tropone to the C1 atom in ethene is preferred over the attack of the C5 atom, indicating that the [8 + 2] cycloaddition instead of the [4 + 2] cycloaddition proceeds in the BPh3-catalyzed reaction. Whether the C1 atom in ethene is attacked by C5 or by O in the second bond formation step is shown in this study to be governed mainly by the nucleophilicity of σ-lone pair electrons of the carbonyl O atom of tropone in the presence of LA. These results are consistent with the experiments reported by Li and Yamamoto.

Mechanism of One-Pot Stereoselective Assembly of Spiroketal Derivatives from Cyclohexanone and Phenylacetylene in KOH/DMSO: a Quantum Chemical Study

Mechanism of One-Pot Stereoselective Assembly of Spiroketal Derivatives from Cyclohexanone and Phenylacetylene in KOH/DMSO: a Quantum Chemical Study

Exploring the cutting-edge properties of 3-nitrophthalic acid single crystal: growth, structure, optical and quantum chemical studies

Exploring the cutting-edge properties of 3-nitrophthalic acid single crystal: growth, structure, optical and quantum chemical studies

Insight into Corrosion Inhibition Efficiency of Imidazole-Based Molecules: A Quantum Chemical Study

Insight into Corrosion Inhibition Efficiency of Imidazole-Based Molecules: A Quantum Chemical Study

An azo coupling of berberine derivatives: an experimental and quantum-chemical study

An azo coupling of berberine derivatives: an experimental and quantum-chemical study

Advances in the chemistry of 1,2,3,4-tetrazines

The experimental and theoretical chemistry of 1,2,3,4-tetrazines have been actively studied in the last 20 years. The increasing interest in this class of compounds is due to the fact that the 1,2,3,4-tetrazine ring is a promising building block for the development of energetic and physiologically active compounds. The review considers various types of 1,2,3,4-tetrazines including completely unsaturated nonannulated tetrazines and their <i>N</i>-oxides; nitrogen-substituted tetrazines; annulated tetrazines with a nitrogen atom common to two heterocycles; 1,2,3,4-tetrazine 1,3-dioxides fused to benzene, pyridine, 1,2,3-triazole or 1,2,5-oxadiazole ring; and also 1,2,3,4-tetrazine 1,3-dioxide fused to one more 1,2,3,4-tetrazine 1,3-dioxide ring. Methods of synthesis and reactivity of these compounds, their crystallographic features, spectral characteristics and thermal stability are described. The results of quantum chemical studies for 1,2,3,4-tetrazine derivatives are presented. The prospects of using 1,2,3,4-tetrazines as energetic compounds are discussed.<br> The bibliography includes 189 references.

Effect of ionic liquid as corrosion inhibitor for 6061 aluminium alloy-(electrochemical and quantum chemical approaches)

ABSTRACT Ionic liquid 1,3-dimethylimidazolium dimethyl phosphate (DIDP) is used as a possible green inhibitor for the corrosion control of 6061 aluminium alloy in 0.25 mol/L HCl is described in the study. Study involved electrochemical methods carried out at various temperatures by changing the concentrations of DIDP. Kinetic and thermodynamic parameters were determined using the Arrhenius rate law and transition state equations, respectively. Physisorption of the inhibitor takes place and the adsorption follows Freundlich isotherm. Surface morphology was studied by scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy-dispersive X-ray analysis (EDAX) techniques. Quantum chemical studies were done by the density functional theory (DFT). The maximum inhibition efficiency of DIDP on 6061 aluminium alloy was about 78% for the concentration of 1000 ppm at 303 K. The mechanistic aspects of DIDP adsorption onto the metal surface were supported by quantum chemical studies. HOMO and LUMO of the optimized structure and quantum chemical descriptors confirmed the adsorption of the inhibitor on the metal surface. Mulliken charge population was used to identify the DIDP molecule’s high electron density region, and Fukui indices confirmed the interaction between metal and inhibitor.

Gas-phase formation route for trans-HC(O)SH and its isomers under interstellar conditions: a state-of-the-art quantum-chemical study

ABSTRACT Sulphur is an important and ubiquitous element of the interstellar medium (ISM). Despite its importance, its chemistry still needs to be elucidated, with one of the main issues being the missing sulphur problem. In this work, small molecular species, already detected in the ISM (SH, OH, H2CS, H2CO, H2S, H2O, HCS/HSC, and HCO), were combined to set five different gas-phase reactions for the formation of isomers belonging to the CH2SO family, with one of its member, namely trans-HC(O)SH, already identified as well. Through a state-of-the-art computational study, it has been found that, thermochemically, only one of the reactions considered is open in the ISM conditions: H2CS + OH can produce cis/trans-HC(S)OH and cis/trans-HC(O)SH via hydrogen-atom loss. Kinetically, the favoured product is trans-HC(S)OH followed by trans-HC(O)SH. In view of the recent detection of this latter, our study suggests that trans-HC(S)OH is a good candidate for astronomical observations. Since this species has never been studied experimentally, as a first step towards its laboratory characterization, accurate estimates of the rotational constants have been provided.

Mechanistic Analysis of Alkyne Haloboration: A DFT, MP2, and DLPNO-CCSD(T) Study.

Stereocontrol of the alkyne haloboration reaction has received attention in many experimental but few theoretical studies. Here we present a detailed quantum-chemical study of mechanisms leading to Z versus E isomers of haloboration products, considering acetylene and propyne combined with BCl3, BBr3, and BI3. Calculations using B3LYP-D3, MP2, and DLPNO-CCSD(T) methods are used to study polar reactions between the alkyne and BX3 in the absence and presence of an additional halide anion whose content in the reaction mixture can be controlled experimentally. The formation of anti-haloboration products via radical mechanisms is also explored, namely, by adding BX3 to (Z)-halovinyl radical. For the anti-haloboration of propyne, the radical route is prohibited by the regiochemistry of the initiating halopropenyl radical, while the polar route is unlikely due to a competitive allene generation. In contrast, energetically accessible routes exist for both syn- and anti-bromoboration of acetylene; hence, careful control of reaction conditions is necessary to steer the stereochemical outcome. Methodologically, MP2 results correspond better to the DLPNO-CCSD(T) energies than the B3LYP-D3 results in terms of both reaction barrier heights and relative ordering of energetically close stationary points.

Molecular Dynamics and Quantum Chemical Studies on Piperine, a Naturally Occurring Alkaloid

Piperine (a naturally occurring alkaloid), is a biologically active natural product belonging to the alkaloid series of compounds. In this study, the spectral characterization of piperine isolated from black pepper has been performed using FT-IR, 1H-NMR, and 13C-NMR. To explain spectral features, we have calculated the vibrational frequencies of the optimized structure of piperine using the B3LYP/6-311 + G(d,p) level of theory and NMR spectra using the GIAO method. All vibrational modes of the title molecule have been assigned based on potential energy distribution. The calculated scaled wavenumbers and NMR chemical shifts show good agreement with the experimental FT-IR and NMR data, respectively. To assess the bioactivity of piperine, we have first performed molecular docking using the ITK receptor and subsequently, the molecular dynamics simulation of the resulting complex for 100 ns. The results suggest the potential of piperine for possible anti-inflammatory action.

Quantum-Chemical Study of C–H Bond Activation in Methane on Ni–Cu Oxide and Sulfide Clusters

Quantum-Chemical Study of C–H Bond Activation in Methane on Ni–Cu Oxide and Sulfide Clusters

How generic is iodide-tagging photoelectron spectroscopy: An extended investigation on the Gly·X- (Gly = glycine, X = Cl or Br) complexes.

We report a joint negative ion photoelectron spectroscopy (NIPES) and quantum chemical computational study on glycine-chloride/bromide complexes (denoted Gly·X-, X = Cl/Br) in close comparison to the previously studied Gly·I- cluster ion. Combining experimental NIPE spectra and theoretical calculations, various Gly·X- complexes were found to adopt the same types of low-lying isomers, albeit with different relative energies. Despite more congested spectral profiles for Gly·Cl- and Gly·Br-, spectral assignments were accomplished with the guidance of the knowledge learned from Gly·I-, where a larger spin-orbit splitting of iodine afforded well-resolved, recognizable spectral peaks. Three canonical plus one zwitterionic isomer for Gly·Cl- and four canonical conformers for Gly·Br- were experimentally identified and characterized in contrast to the five canonical ones observed for Gly·I- under similar experimental conditions. Taken together, this study investigates both genericity and variations in binding patterns for the complexes composed of glycine and various halides, demonstrating that iodide-tagging is an effective spectroscopic means to unravel diverse ion-molecule binding motifs for cluster anions with congested spectral bands by substituting the respective ion with iodide.

Non-Conjugated Bis-(Dithienylethene)-Naphthalenediimide as a Dynamic Anti-Counterfeiting Agent: Driving the Wheel of Photoswitching Enactment.

Photochromic fluorescent molecules dramatically extend their fields of applications ranging from optical memories, bioimaging, photoswitches, photonic devices, anti-counterfeiting technology and many more. Here, we have logically designed and synthesized a triazole appended bis-(dithienylethene)-naphthalenediimide based photo-responsive material, 5, which demonstrated fluorescence enhancement property upon photocyclization (ΦF =0.42), with high photocyclization (44 s, ksolution =0.0355 s-1 , ksolid =0.0135 s-1 ) and photocycloreversion (160 s, ksolution =0.0181 s-1 , ksolid =0.0085 s-1 ) rate and decent photoreaction quantum yield (Φo→c =0.93 and Φc→o =0.11). The open isomer almost converted to the closed isomer at photo-stationary state (PSS) with distinct color change from colorless to blue with 92.85 % conversion yield. A reversible noninvasive modulation of fluorescence through efficient photoinduced electron transfer (PET) process was observed both in solution as well as in solid state. The fluorescence modulation through PET process was further corroborated with thermodynamic calculations using the Rehm-Weller equation and quantum chemical studies (DFT). The thermally stable compound 5 exhibits high fatigue resistance property (up to 50 cycles) both in solution and solid state. Furthermore, the compound 5 was successfully applied as erasable ink and in deciphering secret codes (Quick Response/bar code) portending potential promising application in anti-counterfeiting.

Isolation, vibrational analysis, quantum chemical studies, nature of bonding, and molecular docking studies of triterpenoid isolates from Ganoderma lucidum as potent typhoid fever agent

The bacteria Salmonella Typhi is the source of the dangerous and perhaps fatal disease known as typhoid fever. Typhoid fever treatment is difficult despite the availability of potent medications due to the rise of multi-drug resistance strains. Herein, the extraction, LC-MS and FT-IR spectral characterization, density functional theory (DFT) and molecular docking investigation of 3,15-dihydroxy-11-toxolanost-8,24-dien-26-oic acid (C30H45O5) [MDC_1], Ganoderic acid F (C32H41O9) [MDC_2], and Ganolucidic acid E (C30H43O5) [MDC_3] isolated compounds from G. lucium against Salmonella Typhi enzyme, DNA gyrase B is presented along with the influence of solvation in polar and non-polar solvents. The FT-IR spectral results show that the triterpenoid extract of G. lucidum contains oxygen atoms, which mainly exist in functional groups (such as CO, O–H, C–O) and are consistent with the general molecular structures of triterpenoids. The reactivity parameters in the gas phase show that MDC_1 and MDC_3 have higher energy gaps whereas MD_2 has the lowest energy gap, indicating that it is more reactive than the other complexes. The energy gap of the compounds in solvent also shows a little shift, compared to the energy gap in Ethanol and Heptane, respectively. The results of the molecular docking study revealed several small molecules with strong binding affinities for the protein targets, suggesting that they could be used as potential therapeutics for typhoid fever. Therefore, this study suggests that molecular docking is a powerful tool for identifying novel therapeutics against tropical diseases such as typhoid fever.

Electrochemical, Characterization, and Quantum Chemical Studies of Two Newly Synthesized Aromatic Aldehydes-Based Xanthene Diones as Corrosion Inhibitors for Mild Steel in 1 M Hydrochloric Acid

Electrochemical, Characterization, and Quantum Chemical Studies of Two Newly Synthesized Aromatic Aldehydes-Based Xanthene Diones as Corrosion Inhibitors for Mild Steel in 1 M Hydrochloric Acid

Synthesis, Spectroscopic and Quantum Chemical Studies of N-Pentylhydrazinylthiazole Derivatives

Herein, a series of N-pentylhydrazinylthiazole based compounds (EP1–EP7) were synthesized via three step synthetic strategy. The intermediates (TH1–TH7) were prepared with Hantzsch’s approach followed by N-pentylation through substitution reaction to obtain targeted N-pentylhydrazinylthiazoles (EP1–EP7). The proposed structures were established with different spectroscopic methods like FTIR, 1H-, 13C-NMR, and HRMS. Further, the non-linear optical (NLO) effect of established structures was explored via quantum chemical investigations. NLO, ultraviolet–visible (UV–Vis), natural population analysis (NPA), global reactivity parameters (GRPs), and natural bond orbital (NBO) investigations were executed at M06/6-311G(d,p) level of density functional theory (DFT). UV–Vis analysis revealed that the yielded systems (EP1–EP7) exhibited absorption wavelength in UV–Vis spectrum in the range of 328.61–389.58 nm. EP1 exhibited the highest λ max value (389.58 nm) among all examined compounds due to its minimal E gap of 4.028 eV. The widening of the energy gap was observed from EP1 to EP7 (4.028–4.492 eV) as elucidated by Frontier molecular orbital (FMO) investigation. The GRPs were correlated with the results of energy gap. As EP1 depicted the minimum band gap (4.028 eV), so it exhibited the highest value of softness (0.248 eV−1) along with lower-most value of hardness (2.014 eV). NBO analysis revealed valuable insights into the charge delocalization and stability of the compounds (EP1–EP7). The dipole moment ( μ tot ) , average linear polarizability <α>, first and second order hyperpolarizabilities ( β to t and γ tot ) were also executed for EP1–EP7 at the above-mentioned level. Consequently, the maximum β tot (2.10 × 10−29 esu) and γ tot (9.31 × 10−35 esu) values were depicted by EP1 and EP3, respectively. Thus, all these outcomes unveiled that EP1 depicted robust response and proved to be the best NLO candidate for various hi-tech applications such as signal processing, fiber optics and data storage.

Novel ultra-sensitive and highly selective cyanine sensors based on solvent-free microwave synthesis for the detection of trace hypochlorite ions in drinking water

The adoption of chlorine in drinking water disinfection with the determination of residual chlorine in the form of hypochlorite ion (ClO-) is in widespread demand. Several sensors including colorimetric, fluorometric, and electrochemical methods are currently in use, but detection limits and ease of application remain a challenge. In this work, two new cyanine derivatives-based ClO- sensors, that were prepared by solvent-free microwave synthesis, are reported. The two sensors are highly sensitive and selective to ClO-, exhibiting a noticeable color change visible to the naked eye. Additionally, the sensors can detect ClO- without interference from other potential water pollutants, with low detection limits of 7.43 ppb and 0.917 ppb based on absorption performance. When using fluorometric methods, the sensors' detection limits are pushed down to 0.025 ppb and 0.598 ppb for sensors I and II, respectively. The sensors can be loaded with paper strips for field and domestic detection of ClO- in tap water treatment installations. Using the quartz crystal microbalance (QCM) technique, these sensors showed strong detection sensitivity to ClO-, with detection limits of 0.256 ppm and 0.09 ppm for sensors I and II, respectively. Quantum chemical studies using density functional theory (DFT) calculations, natural bond orbital (NBO) analysis, molecular electrostatic potential (MESP), and time-dependent density functional theory (TD-DFT) supported the findings. The sensing mechanism is rationalized in terms of radical cation formation upon ClO- oxidation of cyanine sensors I and II.

Corrosion inhibition performance of Punica granatum L extract on Q235 steel in H2SO4 environment: Electrochemical, morphological, and quantum chemical studies

The corrosion inhibitor used in this experiment was the extract of Punica granatum L (PGLE), which was obtained using the pure water extraction method. The inhibition performance of PGLE on Q235 steel in H2SO4 environmental was investigated using electrochemical methods, morphology studies and quantum chemical calculation. The corrosion inhibition properties of PGLE were found to be excellent, with a corrosion inhibition efficiency of approximately 95% at 200 mg/L, and it exhibits characteristics of a mixed-type corrosion inhibitor. The electrochemical impedance (EIS) test revealed a remarkable increase in the charge transfer resistance with the increment of PGLE concentration, and the surface of Q235 steel was covered by a tight and well-organized protective layer of PGLE. The surface morphology test indicates a noticeable decrease in the average surface roughness upon the adsorption of PGLE extract onto the Q235 steel. According to the adsorption isotherm analysis, the adsorption behavior of PGLE on Q235 steel conformed to the Langmuir adsorption. Additionally, adsorption might be physical or chemical. Quantum chemical calculations also showed that PGLE has excellent corrosion inhibition properties.

Quantum-Chemical Study of C–H Bond Activation in Methane on Ni–Cu Oxide and Sulphide Clusters

Density functional theory (DFT) (PBE) was used for modeling of C–H bond breaking in methane on Ni–Cu clusters enriched in copper as the first stage of catalytic dry reforming of methane. Nanosized clusters NiCu11S6(PH3)8, NiCu11S6, NiCu11O6(PH3)8, NiCu11O6 are considered as catalyst models. The binding energy for methane with clusters was calculated and the activation energy of the \({\text{CH}}_{4}^{*}\) → \({\text{CH}}_{3}^{*}\) + H* step was determined. Based on the data obtained, it was found that the NiCu11O6 catalytic system is the most promising for CH4 activation both in kinetic (activation energy is 99 kJ/mol) and thermodynamic (step energy change is –29 kJ/mol) aspects. To assess the stability of the NiCu11O6 cluster towards coke formation, CH adsorption followed by dissociation (CH* → C* + H*) was modeled. The calculated value of the activation energy of this step is rather high, 159 kJ/mol.

A quantum chemical and kinetics study on the unimolecular reactions of fuel radicals formed during the oxidation of n‐propylamine

AbstractThe major intermediate product under co‐combustion conditions of hydrocarbon fuels with ammonia are amines. Herein, we have theoretically investigated the unimolecular reactions of fuel radicals formed during the oxidation of n‐propylamine. Quantum chemical calculations were performed to obtain the optimized structures and vibrational frequencies of reactants, products, and transition states at the B3LYP/aug‐cc‐pVTZ theory level. CCSD(T) single point energy calculations with the basis sets of aug‐cc‐pVDZ and aug‐cc‐pVTZ were further performed against the optimized structures, and the energies were extrapolated into infinite basis limit. Pressure‐dependent rate constants were calculated using Rice–Ramsperger–Kassel–Marcus/master equation analysis. The major reaction pathways for the fuel radicals were found to be β‐scission reactions at CC or CN bonds, and minor pathways were internal hydrogen shift and β‐scission reactions at CH or NH bonds. The calculated reaction rate constant trends were attributed to the decrease in CC and CN bond dissociation energies due to substitution effects from the amino group.