Quantum Chemical Investigation Research Articles

Spectrophotometric, quantum chemical and molecular docking investigations of 4H-1-benzopyran-derived Pd(II) complexes

Spectrophotometric, quantum chemical and molecular docking investigations of 4H-1-benzopyran-derived Pd(II) complexes

Deep eutectic solvents: Quantum chemical investigation, thermal stability and physicochemical properties

The current quantum-based research focuses on the eutectic mixtures formulated by combining hydrogen bond donors (Urea, Lactic acid, Xylitol, Proline Xylitol) and acceptor (Betaine, Choline chloride, Proline) molecules. The quantum chemical investigation reveals that DESs Choline chloride-Proline and Choline chloride-Xylitol are the best solvents with the lowest energy gap, highest chemical softness, and the least chemical hardness. FTIR spectroscopy spectra provided evidence of the production of new hydrogen bonds between the two DES components, illuminating the mechanisms behind the impact of the components on the physicochemical characteristics of the DESs. The thermal stability, viscosity, electrical conductivity of DESs under the effect of type of HBAs/HBDs was studied. The influence of the water on the electrical conductivity, density and viscosity are discussed. The initiation of decomposition temperatures for DESs was derived from dynamic thermogravimetric analysis (TGA). DESs have the second level of thermal stability, which means they can be used in technological processes with a range of operating temperatures within ∼ 100–150 °C.

Kinetic Isotope Effects and the Mechanism of CO2 Insertion into the Metal-Hydride Bond of fac-(bpy)Re(CO)3H.

The 1,2-insertion reaction of CO2 into metal-hydride bonds of d6-octahedral complexes to give κ1-O-metal-formate products is the key step in various CO2 reduction schemes and as a result has attracted extensive mechanistic investigations. For many octahedral catalysts, CO2 insertion follows an associative mechanism in which CO2 interacts directly with the coordinated hydride ligand instead of the more classical dissociative mechanism that opens an empty coordination site to bind the substrate to the metal prior to a hydride migration step. To better understand the associative mechanism, we conducted a systematic quantum chemical investigation on the reaction between CO2 and fac-(bpy)Re(CO)3H (1-Re-H; bpy = 2,2'-bipyridine) starting with the gas phase and then moving to THF and other solvents with increased dielectric constants. Detailed analyses of the potential energy surfaces (PESs) and intrinsic reaction coordinates (IRCs) reveal that the reaction is enabled in all media by an initial stage of making a 3c-2e bond between the carbon of CO2 and the metal-hydride bond that is most consistent with an organometallic bridging hydride Re-H-CO2 species. Once CO2 is bent and anchored to the metal-hydride bond, the reaction proceeds by a rotation motion via a cyclic transition state TS2 that interchanges Re-H-CO2 and Re-O-CHO coordination. The combined stages provide an asynchronous-concerted pathway for CO2 insertion on the Gibbs free energy surface with TS2 as the highest energy point. Consideration of TS2 as a rate-determining TS gives activation barriers, inverse KIEs, substituent effects, and solvent effects that agree with the experimental data available in this system. An important new insight revealed by the analyses of the results is that the initial stage of the reaction is not a hydride transfer step as has been assumed in some studies. In fact, the loose vibration of the TS that can be identified for the first stage of the reaction in solution (TS1) does not involve the Re-H stretching vibrational mode. Accordingly, the imaginary frequency of TS1 is insensitive to deuteration, and therefore, TS1 leads to no significant KIE.

Quantum Chemical Investigation into the Structural Analysis and Calculated Raman Spectra of Amylose Modeled with Linked Glucose Molecules.

This study presents a quantum chemical investigation into the structural analysis and calculated Raman spectra of modeled amylose with varying units of linked glucose molecules. We systematically examined the rotation of hydroxymethyl groups and intramolecular hydrogen bonds within these amylose models. Our study found that as the number of linked glucose units increases, the linear structure becomes more complex, resulting in curled, cyclic, or helical structures facilitated by establishing various intramolecular interactions. The hydroxymethyl groups were confirmed to form interactions with oxygen atoms and with hydroxymethyl and hydroxyl groups from adjacent rings in the molecular structures. We identified distinct peaks and selected specific bands applicable in various analytical contexts by comparing their calculated Raman spectra. Representative vibrational modes within selected regions were identified across the different lengths of amylose models, serving as characteristic signatures for linear and more coiled structural conformations. Our findings contribute to a deeper understanding of amylose structures and spectroscopic signatures, with implications for theoretical studies and potential applications. This work provides valuable reference points for the detailed assignment of Raman peaks of amylose structure, facilitating their application in broader research on carbohydrate structures and their associated spectroscopic properties.

Azide Assisted Corrosion Inhibition of Mild Steel by Bioactive Metallic Complexes – A Quantum Chemical Investigation

Azide Assisted Corrosion Inhibition of Mild Steel by Bioactive Metallic Complexes – A Quantum Chemical Investigation

Theoretical Investigation of Transient Species Following Photodissociation of Ironpentacarbonyl in Ethanol Solution.

Photodissociation of ironpentacarbonyl [1Fe(CO)5] in solution generates transient species in different electronic states, which we studied theoretically. From ab initio molecular dynamics simulations in ethanol solution, the closed-shell parent compound 1Fe(CO)5 is found to interact weakly with the solvent, whereas the irontetracarbonyl [Fe(CO)4] species, formed after photodissociation, has a strongly spin-dependent behavior. It coordinates a solvent molecule tightly in the singlet state [1Fe(CO)4] and weakly in the triplet state [3Fe(CO)4]. From the simulations, we have gained insights into intersystem crossing in solvated irontetracarbonyl based on the distinct structural differences induced by the change in multiplicity. Alternative forms of coordination between 1Fe(CO)4 and functional groups of the ethanol molecule are simulated, and a quantum chemical investigation of the energy landscape for the coordinated irontetracarbonyl gives information about the interconversion of different transient species in solution. Furthermore, insights from the simulations, in which we find evidence of a solvent exchange mechanism, challenge the previously proposed mechanism of chain walking for under-coordinated metal carbonyls in solution.

Relativistic Quantum Chemical Investigation of Actinide Covalency Measured by Electron Paramagnetic Resonance Spectroscopy.

We investigate actinide covalency effects in two [AnCptt3] (An = Th, U) complexes recently studied with pulsed electron paramagnetic resonance spectroscopy, using the Hyperion package to obtain relativistic hyperfine coupling constants from relativistic multiconfigurational wave functions. 1H and 13C HYSCORE simulations using the computed parameters show excellent agreement with the experimental data, highlighting the accuracy of modern relativistic ab initio methods. The extent of covalency indicated from the calculations on [ThCptt3] is in agreement with the original report based on traditional spectral fitting methods, while the covalency in [UCptt3] is found to be previously overestimated. The latter is due to the paramagnetic spin-orbit effect that arises naturally in a relativistic theory of hyperfine coupling and yet was not accounted for in the original study, thus highlighting the necessity of relativistic approaches for the interpretation of magnetic resonance data pertaining to actinides.

Cyсlopentadienone and Pyrone Derivatives as Precursors of Electron-Deficient Cycloheptatrienes: Quantum Chemical Investigation and Synthesis

AbstractUnstable tetra(methoxycarbonyl)cyclopentadienone was investigated in the synthesis of electron-deficient cycloheptatrienes via [4+2]-cycloaddition/cycloelimination reaction with cyclopropenes. The use of its stable dimer did not afford the product although similar reactions with alkynes have been reported. Quantum chemical calculation revealed that cyclopentadienone is not generated from the dimer and the reaction with alkynes proceeds via a more complicated cycloelimination/cycloaddition/cycloelimination cascade. However, the formation of cycloheptatrienes was found favorable over the formation of the dimer. Therefore, the trapping of tetra(methoxycarbonyl)cyclopentadienone upon formation was successful to give cycloheptatrienes with five ester groups. The use of methyl coumalate as a four-electron component was successful with cyclopropenes containing only one ester group to afford only two ester groups in the product.

Systematic Study of Different Types of Interactions in α-, β- and γ-Cyclodextrin: Quantum Chemical Investigation.

In this work, comprehensive ab initio quantum chemical calculations using the DFT level of theory were performed to characterize the stabilization interactions (H-bonding and hyperconjugation effects) of two stable symmetrical conformations of α-, β-, and γ-cyclodextrins (CDs). For this purpose, we analyzed the electron density using "Atom in molecules" (AIM), "Natural Bond Orbital" (NBO), and energy decomposition method (CECA) in 3D and in Hilbert space. We also calculated the H-bond lengths and OH vibrational frequencies. In every investigated CD, the quantum chemical descriptors characterizing the strength of the interactions between the H-bonds of the primary OH (or hydroxymethyl) and secondary OH groups are examined by comparing the same quantity calculated for ethylene glycol, α-d-glucose (α-d-Glcp) and a water cluster as reference systems. By using these external standards, we can characterize more quantitatively the properties of these bonds (e.g., strength). We have demonstrated that bond critical points (BCP) of intra-unit H-bonds are absent in cyclodextrins, similar to α-d-Glcp and ethylene glycol. In contrast, the CECA analysis showed the existence of an exchange (bond-like) interaction between the interacting O…H atoms. Consequently, the exchange interaction refers to a chemical bond, namely the H-bond between two atoms, unlike BCP, which is not suitable for its detection.

Thermodynamic and quantum chemical investigation of MIBK as a liquid phase extraction solvent for separating pyridine compounds from water

Pyridine compounds play a crucial role in the synthesis of fine chemicals and pharmaceuticals; however, the generation of a large amount of wastewater may pose a threat to the ecological environment and human health. Considering environmental factors and economic benefits, it is essential to explore efficient methods for separating pyridine compounds from water. In this study, pyridine compounds were separated from water by liquid–liquid extraction using MIBK as solvent. Liquid-liquid equilibrium (LLE) data for the ternary system water + pyridine compounds(pyridine, 2-methylpyridine, 3-methylpyridine, 2,6-dimethylpyridine, and 2,4,6-trimethylpyridine) + MIBK were measured at 303.2 K and 101.3 kPa. Subsequently, the distribution coefficient (D) and separation factor (S) were calculated based on the obtained data, serving as indicators to evaluate the performance of the extractant. The LLE data were then correlated with NRTL and UNIQUAC models to obtain binary interaction parameters. The accuracy of the regressed binary interaction parameters was assessed through Gibbs energy topology analysis. To explore the intrinsic mechanism of extraction between MIBK and pyridine or alkylpyridines, the σ-profile was used to investigate the interaction form between MIBK and pyridine or alkylpyridines. Based on this, quantum chemical calculations and wave function analysis were used to reveal the molecular-level separation mechanism. The interaction behavior of the MIBK and pyridine or alkylpyridines systems was systematically investigated. The results indicate that van der Waals forces are the main intermolecular interactions, and it is through these strong forces that MIBK can efficiently separate pyridine and alkylpyridines from water.

Electrochemical and Quantum Chemical Investigations of novel pyrazole derivatives as a Corrosion Inhibitor for Stainless Steel in 2M H2SO4 medium

Stainless steels play a crucial role in diverse industrial domains. However, due to their exposure to acidic environments, stainless steels undergo the corrosion phenomenon, leading to the deterioration of the material and its properties. Thus, the objective of this work is to study the corrosion inhibition of stainless steel in an H2SO4 2M medium by using two organic compounds, namely Py-3:{1-amino-5,10-dioxo-3-(p-tolyl)-5,10-dihydro-1H-pyrazolo[1,2-b] phthalazine-2-carbonitrile} and Py-4:{1-amino-3-(2-chlorophenyl)-5,10-dioxo-5,10-dihydro-1H-pyrazolo[1,2-b]phthalazine-2carbonitrile}. This study was conducted using transient electrochemical methods in conjunction with a theoretical approach. The obtained results demonstrate that the addition of pyrazole compounds in the corrosive medium H2SO4 exhibits excellent inhibitory power against steel corrosion, with an inhibitory efficiency reaching 98%. The tested inhibitors are adsorbed into the surface of the metal by chemical bonds, Moreover, the adsorption of these compounds follows the Langmuir adsorption model. Theoretical calculations based on the Density Functional Theory (DFT) provide a better understanding of the reactivity of tested inhibitor towards stainless steel which they are in good agreement with the experimental findings.

Combined experimental and quantum computational studies on 5-Fluorouracil salicylic acid cocrystal: Assessment on anti-breast cancer potential through docking simulation

5-fluorouracil salicylic acid (5FUSA) cocrystal was synthesised via mechanochemical and solution evaporation technique and spectroscopic experiments and theoretical research were conducted. Methods for the experiments included XRD, FTIR, and UV spectroscopy. Following that, 5FUSA was the subject of quantum chemistry investigations employing the DFT/B3LYP/6–311++G (d, p) basis level. First, the resultant simulated XRD pattern was compared to the relevant experimental pattern. The estimated FT-IR frequencies were gathered from the same level of theory and compared to the experimental data. To learn more about the reactive properties of the 5FUSA, the molecular electrostatic potential plot was generated, and Fukui function calculations were also performed. In order to examine intramolecular interactions and verify the bioactivity of the 5FUSA molecule, the natural bond orbital study was also carried out. We examined the UV–Vis absorption wavelengths (λ) via theoretical (TD-DFT) and experimental methods. The non-linear optical properties were identified, and it was discovered that it had three times the NLO activity of urea. The inter- and intramolecular interactions of the 5FUSA were explored using the Hirshfeld surface and finger print approaches. At various temperatures thermodynamic parameters were calculated and topological analyses were conducted using the (ELF, LOL, and RDG). The anticancer activity of 5FUSA cocrystal was studied using molecular docking and the docking scores ranges between -8.1 to -9.0 Kcal/mol against breast tumor proteins.

Solvation effects on the excitation dynamics, structural and photorelaxation, quantum chemical investigation, and photophysical properties of 2D p-expanded quinoidal terthiophene (2DQTTs): Outlook from Ab-initio calculations

All dyes have different degrees of absorption. The present study delves into the intricate interplay between solvation and the photophysical behaviors of 2D p-expanded quinoidal terthiophene (2DQTT) dye compounds represented as A3, A4, and A5. In this study, a comprehensive investigation is presented, elucidating how solvation impacts excitation dynamics, ground and excited state geometry, photophysical characteristics. and photorelaxation dynamics of 2DQTTs. The energy gap data shows that the energies of the compounds increased in polar mediums and were greater for compound A3 which had ΔE values of 3.5227 eV in water, and 3.5225 eV in DMSO while compound A5 had the highest ΔE in all phases, with a ΔE value of 3.5453 eV in EtOH. Relaxation of the compounds leads to changes in the bonds and structural conformation of the 2D P-expanded quinoidal terthiophene (2DQTT) compounds as the compounds de-excite back to a lower energy level, and the photon causes a change in structural bonding (Stokes shift) in the heteroatoms which was taken into consideration. This manuscript not only advances our fundamental understanding of the interactions between solvation and molecular structure but also provides valuable insights into optimizing the performance of 2DQTT in optoelectronic devices as the compounds display a high absorption band in all phases, especially in water medial with compound A3, A4 and A5 recording absorbances of 785.32 nm, 787.13 nm, and 786.78 nm respectively, a high light harvesting efficiency LHE, great electron exciton energy and an injecting capacity (ΔGinject) greater than 0.20 eV in all phases. This work contributes significantly to the design and application of novel materials for next-generation optoelectronic technologies hence we hope that experimental research tests the studied compound towards the mentioned application.

Electrochemical, gravimetric, quantum chemical and computational investigations on an effective synthetic chlorinated cyclic imide derivative as a corrosion inhibitor for carbon steel in sulfuric acid solution

Although many different human activities such as the oil and gas sector, mineral production, utilities, transportation, etc. depend on the utilization of steel and its alloys, they are highly susceptible to corrosion, especially in acidic media. Hence, processing entails substantial material expenditures due to metal losses. In this regard, the inhibitory characteristics of the synthetic heterocyclic derivative (3aR,7S,7aS)-4,5,6,7,8,8-hexachloro-1,3-dioxo-1,3,3a,4,7,7a-hexahydro-2H-4,7-methanoisoindol-2-yl)benzenesulfonamide (MBSI) was studied against corrosion of C-steel in 0.5 M H2SO4 at 25-55 °C. The structure of the synthesized molecule was confirmed by FTIR, 1H-NMR, 13C-NMR, and MS. Weight-loss, potentiodynamic polarization, electrochemical impedance spectroscopy, electrochemical frequency modulation measurements as well as theoretical analyses were employed in this investigation. The results showed that the investigated MBSI compound functions as an efficient inhibitor with a physical adsorption nature on the surface of carbon steel. MBSI concentration causes the inhibition efficiency to rise, reaching a maximum of 94% for the steel alloy corrosion at 37 × 10−6 M and 25°C. The synthesized compound was suggested to act as a mixed-type inhibitor. SEM surface analysis showed the construction of a protective layer at the carbon steel surface. DFT-based quantum chemical indices provided more insight into the inhibitory mechanism. Molecular dynamics (MD) simulations were also applied to predict the conformational adsorption change of the inhibitor on the iron surface. In addition, thermodynamic and kinetic parameters were calculated. The experimental results are largely consistent with the theoretical results.

Synthesis, crystal structure, spectroscopy and quantum chemical investigations of hexahydroquinoline molecule

The synthesis and crystal structure of benzyl 4-([1,1'-biphenyl]-4-yl)-2-methyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate are described. Single crystal X-ray diffraction of title molecule was used to investigate the crystal structure. The most stable optimised structure was identified using the B3LYP/6-31 + G(d) method. IR, 1H-NMR and elemental analysis of the title compound were performed. Besides, frontier molecular orbitals, molecular electrostatic potential, and thermodynamic properties were investigated by theoretically. In order to explore the nonlinear optical properties were performed theoretically. Hirshfeld analysis was also performed to determine the interactions of the molecule.

Spectroscopic characterization, quantum chemical and molecular docking investigations on methyl indole-3-carboxylate: A potent cervical cancer drug

Bioactive indole derivatives had great importance in recent years due to their numerous biological and pharmaceutical applications. In the present work, the vibrational, electronic, physicochemical, and inhibitory properties of the Methyl Indole-3-Carboxylate (MIC) molecule were predicted and analyzed. Initially, the molecular structure of the title molecule was optimized and its structural parameters were calculated, which were highly correlated with the previous reports. The simulated infrared and Raman spectra of the molecule were in good agreement with the FT-IR and FT-Raman spectra that were observed via the experiment. The observed UV–Visible spectrum validates the MIC molecule's π→π* electronic transition, which was also well matched with the simulated UV–Visible spectrum. The investigation of frontier molecular orbitals highlights intramolecular charge transfer across the molecule, establishing the bioactivity of the MIC molecule. The electron transport from the methyl group hydrogen atom H22 to the oxygen atom O11 is confirmed by Mulliken atomic charge distribution analysis and molecular electrostatic potential surface analysis. The calculated Fukui functions values validated the FMOs and Mulliken atomic charge distribution results. The natural bond orbital study further confirms the MIC molecule's intramolecular charge transfer and bioactivity. Molecular docking investigation results that the MIC molecule hinders the function of an enzyme known as Mitogen-activated protein kinase 14, which has been linked to cervical cancer. As a result, the present study provides the possibility towards the development of innovative to treat cervical cancer.

Chelating Effect of Siderophore Desferrioxamine-B on Uranyl Biomineralization Mediated by Shewanella putrefaciens.

In contaminated water and soil, little is known about the role and mechanism of the biometabolic molecule siderophore desferrioxamine-B (DFO) in the biogeochemical cycle of uranium due to complicated coordination and reaction networks. Here, a joint experimental and quantum chemical investigation is carried out to probe the biomineralization of uranyl (UO22+, referred to as U(VI) hereafter) induced by Shewanella putrefaciens (abbreviated as S. putrefaciens) in the presence of DFO and Fe3+ ion. The results show that the production of mineralized solids {hydrogen-uranium mica [H2(UO2)2(PO4)2·8H2O]} via S. putrefaciens binding with UO22+ is inhibited by DFO, which can both chelate preferentially UO22+ to form a U(VI)-DFO complex in solution and seize it from U(VI)-biominerals upon solvation. However, with Fe3+ ion introduced, the strong specificity of DFO binding with Fe3+ causes re-emergence of biomineralization of UO22+ {bassetite [Fe(UO2)2(PO4)2·8(H2O)]} by S. putrefaciens, owing to competitive complexation between Fe3+ and UO22+ for DFO. As DFO possesses three hydroxamic functional groups, it forms hexadentate coordination with Fe3+ and UO22+ ions via these functional groups. The stability of the Fe3+-DFO complex is much higher than that of U(VI)-DFO, resulting in some DFO-released UO22+ to be remobilized by S. putrefaciens. Our finding not only adds to the understanding of the fate of toxic U(VI)-containing substances in the environment and biogeochemical cycles in the future but also suggests the promising potential of utilizing functionalized DFO ligands for uranium processing.

Comprehensive Evaluation of Models for Ammonia Binding to the Oxygen Evolving Complex of Photosystem II.

The identity and insertion pathway of the substrate oxygen atoms that are coupled to dioxygen by the oxygen-evolving complex (OEC) remains a central question toward understanding Nature's water oxidation mechanism. In several studies, ammonia has been used as a small "water analogue" to elucidate the pathway of substrate access to the OEC and to aid in determining which of the oxygen ligands of the tetramanganese cluster are substrates for O-O bond formation. On the basis of structural and spectroscopic investigations, five first-sphere binding modes of ammonia have been suggested, involving either substitution of an existing H2O/OH-/O2- group or addition as an extra ligand to a metal ion of the Mn4CaO5 cluster. Some of these modes, specifically the ones involving substitution, have already been subject to spectroscopy-oriented quantum chemical investigations, whereas more recent suggestions that postulate the addition of ammonia have not been examined so far with quantum chemistry for their agreement with spectroscopic data. Herein, we use a common structural framework and theoretical methodology to evaluate structural models of the OEC that represent all proposed modes of first-sphere ammonia interaction with the OEC in its S2 state. Criteria include energetic, magnetic, kinetic, and spectroscopic properties compared against available experimental EPR, ENDOR, ESEEM, and EDNMR data. Our results show that models featuring ammonia replacing one of the two terminal water ligands on Mn4 align best with experimental data, while they definitively exclude substitution of a bridging μ-oxo ligand as well as incorporation of ammonia as a sixth ligand on Mn1 or Mn4.

Comparative study of experimental and DFT calculations for 3-cinnamoyl 4-hydroxycoumarin derivatives.

Computational research plays an important role in predicting the chemical and physical properties of biologically active compounds important in future structural modifications to improve or modify biological activity. This research focuses on quantum chemical and spectroscopic investigations properties of synthesized 4-hydroxycoumarin derivatives. Quantum chemical calculations were obtained using B3LYP, HF, and M06-2x level methods with the 6-31++G (d,p) basis set. Afterward, IR, 1H, 13C, UV-Visible experimentally parameters were compared with the results obtained using the B3LYP/6-31+G*(d) basis set of the molecules to be able to characterize the structures. Based on the quantum chemical calculations compound with acetamido group on the phenyl ring is the most reactive, and compound with nitro substituent is the least reactive and the the strongest electrophile among tested compounds. With the exception of compounds with dimethylamino group, all other compounds have a pronounced tautomer between between OH and C = O group. The calculated and experimental values are in agreement with each other. The molecular structure in the ground state of six 3-cinnamoyl 4-hydroxycoumarin derivatives was optimized using density functional theory. The observed and computed values were compared and it can be concluded that the theoretical results were in good linear agreement with the experimental data.

Quantum chemical, spectroscopic and third order nonlinear optical investigations on 3-(3-Bromo-phenyl)-1-imidazol-1-yl-propenone

Quantum chemical, spectroscopic and third order nonlinear optical investigations on 3-(3-Bromo-phenyl)-1-imidazol-1-yl-propenone