A combined experimental and theoretical DFT (B3LYP, CAM-B3LYP and M06-2X) study on electronic structure, hydrogen bonding, solvent effects and spectral features of methyl 1H-indol-5-carboxylate

Deconstructing 1H NMR Chemical Shifts in Strong Hydrogen Bonds: A Computational Investigation of Solvation, Dynamics, and Nuclear Delocalization Effects

This study provides the first quantitative dissection of the factors influencing 1H NMR chemical shifts δH in strong hydrogen-bonded systems, focusing on solvation, nuclear dynamics, and nuclear delocalization. A novel computational framework was developed, combining static quantum chemical calculations (nonrelativistic and relativistic), ab initio molecular dynamics (AIMD), and three-dimensional numerical solutions of the Schrödinger equation. This multiscale approach was applied to three model systems: the bifluoride anion (FHF)-, the Zundel cation (H5O2)+, and the pyridine-pyridinium cation (PyHPy)+. Our results reveal that nuclear dynamics and delocalization are the dominant factors determining δH in complexes with short, strong hydrogen bonds. Solvation effects, while critical for defining the hydrogen-bonding environment, play a secondary role. By isolating the contributions of each factor, we demonstrate that traditional methods often underestimate the quantum mechanical nature of the proton. The application of three-dimensional Schrödinger equation solutions represents a significant methodological advancement, enabling deeper insights into proton behavior in hydrogen bonds. This work not only enhances our understanding of NMR parameters in challenging systems but also establishes a robust framework for modeling complex interactions in chemical and biological environments.

Comprehensive assessment of 3-benzyloxyflavones as β-glucosidase inhibitors: in vitro, in vivo, kinetic, SAR and computational studies

In this study, a series of 3-benzyloxyflavone derivatives (1-10) was designed and, for the first time, evaluated for both in vitro and in vivo inhibitory activity against the β-glucosidase enzyme. The enzyme inhibitory potential of these derivatives was further assessed in an antihyperglycemic context using in vivo mechanism-based assays on p-nitrophenyl-β-d-glucopyranoside (PGLT) induced diabetic models. Additionally, structure-activity relationship (SAR) was employed to identify structural features crucial for activity. Molecular docking analyses revealed that both the potent compounds and co-crystallized ligands shared similar binding orientations within the active sites of β-glucosidase (PDB IDs: 3AJ7; 66K1). Molecular dynamics (MD) simulations validated the stability of the inhibitor-enzyme complexes under physiological conditions, while density functional theory (DFT) calculations helped elucidate electronic properties critical for activity. Drug-likeness analysis was also conducted to assess the pharmacokinetic potential of the derivatives. The results highlighted several derivatives with significant inhibitory activity, desirable pharmacokinetic profiles, and promising drug-like properties, making them potential candidates for therapeutic development. The target derivatives (1-10) demonstrated strong potential as lead compounds for developing new anti-diabetic agents with effective anti-hyperglycemic properties.

Pharmacological evaluation of 3-benzyloxyflavones for β-glucosidase inhibition: Experimental, kinetic and computational approaches

β-Glucosidase is a crucial enzyme involved in carbohydrate metabolism, playing a key role in the hydrolysis of glycosidic bonds in dietary polysaccharides. Inhibition of β-glucosidase has emerged as a promising therapeutic strategy for managing postprandial hyperglycemia in diabetes by delaying/slowing glucose absorption and moderating blood sugar levels. In this study, a series of 3-benzyloxyflavone derivatives (1-10) was designed and, for the first time, evaluated for both in vitro and in vivo inhibitory activity against the β-glucosidase enzyme. The enzyme inhibitory potential of these derivatives was further assessed in an antihyperglycemic context using in vivo mechanism-based assays on p-nitrophenyl-β-D-glucopyranoside (PGLT) induced diabetic models. Additionally, structure-activity relationship (SAR) was employed to identify structural features crucial for activity. Molecular docking analyses revealed that both the potent compounds and co-crystallized ligands shared similar binding orientations within the active sites of β-glucosidase (PDB IDs: 3AJ7; 66K1). Molecular dynamics (MD) simulations validated the stability of the inhibitor-enzyme complexes under physiological conditions. Drug-likeness analysis was also conducted to assess the pharmacokinetic potential of the derivatives. We have also conducted Density Functional Theory (DFT) studies on the lead compounds to gain deeper insights into their electronic properties, structural stability, and interaction mechanisms with the target enzyme. The results highlighted several derivatives with significant inhibitory activity, desirable pharmacokinetic profiles, and promising drug-like properties, making them potential candidates for therapeutic development. The target derivatives (1-10) demonstrated strong potential as lead compounds for developing new anti-diabetic agents with effective anti-hyperglycemic properties.

Computational Insights into the Antioxidant Activity of Luteolin: Density Functional Theory Analysis and Docking in Cytochrome P450 17A1

Background: Luteolin, a flavonoid with well-documented antioxidant properties, has garnered significant attention for its potential therapeutic effects. Objectives: This study aims to investigate the antioxidant properties of luteolin under the influence of solvents, utilizing computational techniques to elucidate its interactions and its potential role as a modulator of enzymatic activities, particularly with Cytochrome 17A1. Methods: Density Functional Theory (DFT) calculations were employed to determine luteolin's electronic and structural characteristics. Key aspects analyzed included electron density distribution and the energies of the frontier molecular orbitals (HOMO and LUMO). Free radical scavenging mechanisms were explored by comparing the dissociation enthalpy of the O-H bond in the absence and presence of water molecules. Additionally, molecular docking simulations were performed to assess the interactions of luteolin with Cytochrome 17A1, identifying preferred binding sites and interaction energies. Results: The findings indicate that luteolin possesses distinct structural and electronic features that contribute to its effectiveness in protecting against oxidative stress. However, hydrogen bonding interactions with water molecules were found to influence the dissociation enthalpy of the O-H bond. Docking simulations revealed significant interaction profiles between luteolin and Cytochrome 17A1, suggesting its potential role as a modulator of this protein. Conclusions: This study underscores the therapeutic potential of luteolin and highlights the importance of computational techniques in predicting and understanding the molecular interactions of bioactive compounds with biological targets. The results provide valuable insights that may aid in developing new therapeutic strategies for diseases associated with oxidative stress.

T- and pH-Dependent Hydroxyl-Radical Reaction Kinetics of Lactic Acid, Glyceric Acid, and Methylmalonic Acid in the Aqueous Phase

Carboxylic acids are a common class of compounds found in atmospheric aerosols and cloud droplets. In this study, the oxidation kinetics of several carboxylic acids in the aqueous phase by the atmospherically relevant •OH radical were investigated to better understand the loss processes for this class of compounds. The rate constants for the reactions of the •OH radical were determined using the thiocyanate competition kinetics method for lactic acid, glyceric acid, and methylmalonic acid as a function of temperature and pH. The Arrhenius equations for oxidation by the •OH radical are as follows (unit in L mol-1 s-1): For lactic acid: k(T, HA) = (1.3 ± 0.1) × 1010 × exp[(-910 ± 160 K)/T] and k(T, A-) = (1.3 ± 0.1) × 1010 × exp[(-800 ± 80 K)/T]; for glyceric acid: k(T, HA) = (6.0 ± 0.2) × 1010 × exp[(-1100 ± 170 K)/T] and k(T, HA±) = (3.6 ± 0.1) × 1010 × exp[(-1500 ± 100 K)/T]; and for methylmalonic acid: k(T, H2A) = (5.5 ± 0.1) × 1010 × exp[(-1760 ± 100 K)/T], k(T, HA-) = (1.4 ± 0.1) × 109 × exp[(-530 ± 80 K)/T] and k(T, A2-) = (9.6 ± 0.4) × 1010 × exp[(-1530 ± 270 K)/T]. The general trend of the •OH rate constant was observed kA2- > kHA- > kH2A. The energy barriers of the •OH radical reaction and thus the most probable site of H atom abstraction were calculated using density functional theory simulations in Gaussian with the M06-2X method and the 6-311++G(3df,2p) basis set. Kinetic data predicted from structure-activity relationships were compared to the measured •OH radical rate constants. •OH radical oxidation in the aqueous phase could serve as an important sink for carboxylic acids, and the pH- and T-dependent rate constants of •OH radical reactions provide a better description of the aqueous-phase sink processes. Hence, the atmospheric lifetime as well as the partitioning of the investigated carboxylic acids was calculated.

The Optical Properties, UV-Vis. Absorption and Fluorescence Spectra of 4-Pentylphenyl 4-n-benzoate Derivatives in Different Solvents

In this paper, electronic absorbance and fluorescence spectra of 4-Pentylphenyl 4-n-benzoate derivatives have been measured in 29 solvents, which are non-polar, polar protic and polar aprotic solvents, and electronic transitions that vary depending on the solvent are identified. As the solvent polarity increases, the forbidden energy difference between the frontier orbitals decreases. The statistical models in order to describe the solvent effect were derived using different solvent parameters. Quite complex and multiple absorbance transitions were observed in different solvent environments. Local fluorescence transition and intramolecular charge transfer occurred in the fluorescence spectra. Absorbance transitions are global transitions, and π*←π is the absorbance electronic transition. The frontier molecular orbitals and electrostatic potential surface were founded using quantum chemical calculations. Refractive indices were found with five different methods and forbidden energy gaps were found with the Tauc method. The forbidden energy ranges were found around 4.1 and 4.5, and the forbidden energy gap decreased as the alkyl chain became longer. All compounds can be defined as insulation materials according to the forbidden energy range. Refractive index values close to the E7 liquid crystal mixture used in liquid crystal display panels were found in the investigated liquid crystals.

Effect of structure and interaction on physicochemical properties of new [Emim][BF3X] complex anion ionic liquids studied by quantum chemistry

CONTEXT

One of the key challenges in the industrial application of ionic liquids (ILs) is their extreme characteristics, such as viscosity, glass transition temperatures, and conductivity. Understanding the relationship between ILs structure and physicochemical property is a crucial aspect of the directed design of ILs with good properties, which is a prerequisite for their successful implementation in industrial processes. In this work, high-level quantum-chemical research with for four pairs ionic liquids, [Emim][X] and [Emim][BF3X] (X = CH3SO3, EtSO4, HSO4, Tos), was performed, to analyze the stable structure, interionic interaction, and charge transfer and provide a new insight into the property variances at the molecular level. The result shows that the overall structural stability of ionic liquids is contributed with hydrogen bonding network between the protons in the C-H and N-H of the cation and oxygen atoms of the anion, as well as fluorine atoms. The nature and strength of the interionic interaction were measured via atoms in molecule analysis and sobEDAw method and results suggested that BF3 could waning interionic interaction of ion pairs. Moreover, a close relation between the binding energies of ion pairs and physicochemical properties was established: the weaker the interionic interaction, the lower is the viscosity and glass transition, and the higher is the conductivity.

METHODS

Quantum chemistry calculations were performed under B3LYP-D3/aug-cc-pVTZ level of DFT functional using the Gaussian 16 package (version C01). The Multiwfn 3.7 program was used to calculate the electrostatic potential, interaction region indicator, the information of bond critical points, core-valence bifurcation index, and ADCH charge. Visualization of structure and the region of interaction were achieved using VESTA and VMD.

Single-atom infrared emission in doped silicon nanocrystals

Silicon luminescence, due to silicon being abundant, non-toxic and harmless, is a topic of pivotal importance in optoelectronics and biological imaging. However, a major challenge in developing high-efficiency silicon light sources is the relatively weak allowable transitions. This study focuses on single atom-doped silicon nanocrystals (Si NCs) and theoretically investigates the emission behavior of single atoms within a tetrahedral coordination field. Doping a single atom in Si NCs can result in a ∼102 times improvement at least in the squared transition dipole moment (TDM2), and induce a spectral shift towards near- and mid-infrared wavelengths. These findings offer a strong foundation for designing Si NCs for on-chip optical communication and single photon emitters.

Graphene Amination towards Its Grafting by Antibodies for Biosensing Applications

The facile synthesis of biografted 2D derivatives complemented by a nuanced understanding of their properties are keystones for advancements in biosensing technologies. Herein, we thoroughly examine the feasibility of aminated graphene as a platform for the covalent conjugation of monoclonal antibodies towards human IgG immunoglobulins. Applying core-level spectroscopy methods, namely X-ray photoelectron and absorption spectroscopies, we delve into the chemistry and its effect on the electronic structure of the aminated graphene prior to and after the immobilization of monoclonal antibodies. Furthermore, the alterations in the morphology of the graphene layers upon the applied derivatization protocols are assessed by electron microscopy techniques. Chemiresistive biosensors composed of the aerosol-deposited layers of the aminated graphene with the conjugated antibodies are fabricated and tested, demonstrating a selective response towards IgM immunoglobulins with a limit of detection as low as 10 pg/mL. Taken together, these findings advance and outline graphene derivatives' application in biosensing as well as hint at the features of the alterations of graphene morphology and physics upon its functionalization and further covalent grafting by biomolecules.

Molecular structure and spectroscopic properties of two radicals of C4H2N: a DFT study

CONTEXT

The cyano propargyl radical (CH₂C₃N and HC₃HCN) is important reaction intermediate in both combustion flames and extraterrestrial environments such as cold molecular clouds and circumstellar envelopes of carbon stars. The acquisition of spectroscopic constants and anharmonic effect facilitates a more in-depth study of this radical. However, the data available in the literature do not allow the precise predictions for it in the interstellar medium. In this work, complete spectroscopic parameters as well as anharmonic constants of two radicals of C₄H₂N have been evaluated by different DFT methods. The calculated results show that it is reasonable to study the molecular spectroscopic properties of C₄H₂N by wB97XD/6-311++G theoretical level. On this basis, the sextic centrifugal distortion constants, anharmonic constants, vibration-rotation interaction constants, and so on are predicted for the study of high-precision rovibrational spectrum. In addition, the relationship between the anharmonic effect and vibration mode of CH₂C₃N and HC₃HCN and their infrared spectroscopic characteristics are discussed.

METHODS

The calculation of the anharmonic force fields and spectroscopy properties was performed using B3LYP, B3PW91, CAM-B3LYP, and wB97XD methods combined with the 6-311++G and aug-ccpVTZ basis sets, respectively, by the Gaussian16 program suite. The IR spectra were performed with Multiwfn3.8.

Manifesting Epoxide and Hydroxyl Groups in XPS Spectra and Valence Band of Graphene Derivatives

The derivatization of graphene to engineer its band structure is a subject of significant attention nowadays, extending the frames of graphene material applications in the fields of catalysis, sensing, and energy harvesting. Yet, the accurate identification of a certain group and its effect on graphene's electronic structure is an intricate question. Herein, we propose the advanced fingerprinting of the epoxide and hydroxyl groups on the graphene layers via core-level methods and reveal the modification of their valence band (VB) upon the introduction of these oxygen functionalities. The distinctive contribution of epoxide and hydroxyl groups to the C 1s X-ray photoelectron spectra was indicated experimentally, allowing the quantitative characterization of each group, not just their sum. The appearance of a set of localized states in graphene's VB related to the molecular orbitals of the introduced functionalities was signified both experimentally and theoretically. Applying the density functional theory calculations, the impact of the localized states corresponding to the molecular orbitals of the hydroxyl and epoxide groups was decomposed. Altogether, these findings unveiled the particular contribution of the epoxide and hydroxyl groups to the core-level spectra and band structure of graphene derivatives, advancing graphene functionalization as a tool to engineer its physical properties.

Synergistic effect of Si-doping and Fe2O3-encapsulation on drug delivery and sensor applications of γ-graphyne nanotube toward favipiravir as an antiviral for COVID-19: A DFT study

In this work, the behavior of favipiravir (FAV) adsorption on the pristine (2,2) graphyne-based γ-nanotube (GYNT) was theoretically studied. Also, the Si-doped form (Si-GYNT) and its composite with encapsulated Fe₂O₃ (Fe₂O₃@Si-GYNT) were investigated within density functional theory (DFT) calculations, using M05 functionals and B3LYP. It was found that FAV is weakly to moderately adsorb on the bare GYNT and Si-GYNT tube, releasing the energy of 2.2 to 19.8 kcal/mol. After FAV adsorption, the bare tube's electronic properties are changed. Localized impurity is induced at the valence and conduction levels by encapsulating a tiny Fe₂O₃ cluster. As such, the target composite becomes a magnetic material. The binding energy between the Fe₂O₃@Si-GYNT and the FAV molecule becomes substantially stronger (E_ad = -25.2 kcal/mol). We developed a drug release system in target parts of body, during protonation in the low pH of injured cells, detaching the FAV from the tube surface. The drug's reaction mechanism with Fe₂O₃@Si-GYNT shifts from covalence in the normal environment to hydrogen bonding in an acidic matrix. The optimized structure's natural bond orbital, quantum molecular descriptors, LUMO, HOMO and energy gap were also investigated. The recovery time can be reduced to less than 10 s by increasing the working temperature properly during the experimental test.

Computational Investigation of the Monomer Ratio and Solvent Environment for the Complex Formed between Sulfamethoxazole and Functional Monomer Methacrylic Acid

In this study, the molecularly imprinted polymers (MIPs) that will be formed by the sulfamethoxazole (SMX) molecule and methacrylic acid (MAA) molecule were examined theoretically. The most stable interaction region between the two molecules was determined in solvent environments (ethanol, acetonitrile, and dimethylsulfoxide), and monomer ratios (SMX/MAA; 1:1, 1:2, and 1:3) were examined to form the most stable geometry. The number and length of the hydrogen bonds formed between the template molecule and the functional monomer and the interaction between the atoms were determined. Geometry optimizations of the molecules were calculated by the DFT method at the M06-2X/ccpVTZ level, and single-point energy calculations were carried out at the B2PLYP-D3/ccpVDZ level. In addition to the theoretical studies, the experimental Fourier-transform infrared spectroscopy (FTIR) spectrum of the complex formed between SMX and MAA was compared with the theoretical FTIR spectrum. As a result of the studies, the monomer ratio and solvent environment in which the stable complex was formed were determined in the MIP studies carried out with the SMX template molecule and MAA monomer. The most stable template molecule-monomer ratio of the complex between SMX and MAA was determined to be 1:3, and the solvent medium in which the most stable geometry was formed was acetonitrile.

T- and pH-dependent OH radical reaction kinetics with glycine, alanine, serine, and threonine in the aqueous phase

Glycine, alanine, serine, and threonine are essential amino acids originating from biological activities. These substances can be emitted into the atmosphere directly. In the present study, the aqueous phase reaction kinetics of hydroxyl radicals (˙OH) with the four amino acids is investigated using the competition kinetics method under controlled temperature and pH conditions. The following T-dependent Arrhenius expressions are derived for the ˙OH reactions with glycine, k(T, H₂A⁺) = (9.1 ± 0.3) × 10⁹ × exp[(-2360 ± 230 K)/T], k(T, HA^±) = (1.3 ± 0.1) × 10¹⁰ × exp[(-2040 ± 240 K)/T]; alanine, k(T, H₂A⁺) = (1.4 ± 0.1) × 10⁹ × exp[(-1120 ± 320 K)/T], k(T, HA^±) = (5.5 ± 0.2) × 10⁹ × exp[(-1300 ± 200 K)/T]; serine, k(T, H₂A⁺) = (1.1 ± 0.1) × 10⁹ × exp[(-470 ± 150 K)/T], k(T, HA^±) = (3.9 ± 0.1) × 10⁹ × exp[(-720 ± 130 K)/T]; and threonine, k(T, H₂A⁺) = (5.0 ± 0.1) × 10¹⁰ × exp[(-1500 ± 100 K)/T], k(T, HA^±) = (3.3 ± 0.1) × 10¹⁰ × exp[(-1320 ± 90 K)/T] (in units of L mol^-1 s^-1). The energy barriers of the ˙OH-induced H atom abstractions were simulated by the density functional theory (DFT) calculation performed with GAUSSIAN using the method of M06-2X and the basis set of 6-311++G(3df,2p). According to the calculation results, the -COOH and -NH₃⁺ groups with strong negative inductive effects increase the energy barriers and thus decrease the ˙OH reaction rate constants. In contrast, the presence of a -OH or -CH₃ group with weak negative or positive inductive effects can reduce energy barriers and hence increase the ˙OH reaction rate constants. To improve the previous structure-activity relationship, the contribution factors of -NH₃⁺ at C_α-atom and C_β-atom are determined as 0.07 and 0.15, respectively. Aqueous phase ˙OH oxidation acts as an important sink of the amino acids in the atmosphere, and can be accurately described by the obtained Arrhenius expressions under atmospheric conditions.

The molecular structure and spectroscopic properties of C3H2O and its isomers: An ab initio study

The spectroscopic parameters and anharmonic force fields of three isomers (c-H₂C₃O, HCCCHO and CH₂CCO) of C₃H₂O have been calculated by Density Functional Theory (B3LYP, CAM-B3LYP, wB97XD) and second-order Møller-Plesset perturbation theory (MP2) combining with 6-311++G (3df, 3pd) and aug-cc-pVTZ basis sets. The equilibrium geometries, energies, rotational constants, harmonic and fundamental frequencies, and centrifugal distortion constants of three isomers of C₃H₂O are calculated and compared with the existed results. The anharmonic constants, vibration-rotation interaction constants, Coriolis coupling constants and force constants of three isomers of C₃H₂O are firstly predicted. The ingredients of complex vibration modes, and infrared spectral characteristics of three isomers as well as the relationship between structure and spectroscopic properties are detailedly discussed.

Effect of tunable π bridge on two-photon absorption property and intramolecular charge transfer process of polycyclic aromatic hydrocarbons

The influences of the conjugation effect on the charge transfer and nonlinear optical (NLO) properties of polycyclic aromatic hydrocarbons (PAHs) are comprehensively investigated at the microscopic molecular level. We found that the conjugation effect of π bridge is negatively correlated with molecular planarity, excitation energy, two-photon absorption (TPA) cross-section, and the second hyperpolarizability. For the first time, the charge transfer matrix (CTM) is applied to the molecular two-photon transition process. Combining the charge difference density (CDD) diagram with CTM heat map to visually quantitative investigate the characteristics of excited states, the charge transfer path and transfer amount between atoms. During the two-photon transition of all molecules, the electronic excited state is locally excited. Compared with the first process, the range of intramolecular charge transfer in the second process of the two-photon transition is expanded. Comprehensive results prove that the π bridge with large conjugation effect distorts the molecular structure, which is not conducive to the intramolecular charge transfer. Therefore, the molecule DBP-1 with a carbon-carbon double bond as the π bridge has the largest transition dipole moments, TPA cross-section, and second static hyperpolarizability. Our research method can provide effective guidance for the design and optimization of nonlinear organic conjugated molecular materials.

Thermal Stability and Decomposition Kinetics of 1-Alkyl-2,3-Dimethylimidazolium Nitrate Ionic Liquids: TGA and DFT Study

The thermal stability and decomposition kinetics analysis of 1-alkyl-2,3-dimethylimidazole nitrate ionic liquids with different alkyl chains (ethyl, butyl, hexyl, octyl and decyl) were investigated by using isothermal and nonisothermal thermogravimetric analysis combined with thermoanalytical kinetics calculations (Kissinger, Friedman and Flynn-Wall-Ozawa) and density functional theory (DFT) calculations. Isothermal experiments were performed in a nitrogen atmosphere at 240, 250, 260 and 270 °C. In addition, the nonisothermal experiments were carried out in nitrogen and air atmospheres from 30 to 600 °C with heating rates of 5, 10, 15, 20 and 25 °C/min. The results of two heating modes, three activation energy calculations and density functional theory calculations consistently showed that the thermal stability of 1-alkyl-2,3-dimethylimidazolium nitrate ionic liquids decreases with the increasing length of the alkyl chain of the substituent on the cation, and then the thermal hazard increases. This study could provide some guidance for the safety design and use of imidazolium nitrate ionic liquids for engineering.

Quantum chemical computations and photophysical spectral features studies of two coumarin compounds

An attempt was made to determine the ground state and excited state dipole moments and quantum chemical computations of two coumarin compounds, namely 3-hydroxy-3-[2-oxo-2-(2-oxo-2H-chromen-3-yl)-ethyl]-1,3-dihydro-indol-2-one (3HOCE) and 3-[2-(8-methoxy-2-oxo-2H-chromen-3-yl)-2-oxo-ethylidene]-1,3-dihydro-indol-2-one (3MOCE). Both compounds displayed a red shift with enhancement in solvent polarity. The larger excited state dipole moment indicated the more polar nature of the selected compounds in the excited state than in the ground state. Kinetic stability and chemical reactivity of the selected compounds were studied with help of the quantum chemical properties of the compounds such as frontier molecular orbital analysis using density functional theory calculations with B3LYP/6-311+G (d, p) basis sets. Molecular electrostatic potential, Mulliken charges, natural bond orbital, and nonlinear optical properties were further studied. NBO analysis showed proton transfer within the selected donor-acceptor, depicting the large energy of stabilization for the compounds. The calculated Fukui function inferred the local softness and electrophilicity indices of used solute compounds.

Theoretical insights into the hydrogen bonding interaction in the complexation of epinephrine with uracil

The present study is aimed at probing the hydrogen bonding interaction between epinephrine and uracil by means of density functional theory calculations concerning their complexation's geometries, interaction energies, and vibrational frequencies. Geometry optimization was carried out giving 19 stable geometries of epinephrine-uracil complex with interaction energies in a range of - 21.51 to - 62.37 kJ mol^-1 using the basis set superposition error (BSSE) correction. The analysis of structure and vibration shows that the hydrogen bonding elongates the length of corresponding bond O(N)-H and decreases the symmetric stretching vibrational frequency, which indicates red-shifted H-bonding interactions in all the geometries. Additionally, the analysis with theories of natural bond orbital (NBO), atoms in molecules (AIM), and the reduced density gradient (RDG) of hydrogen bonding properties and characteristics of the 19 geometries suggests that the hydrogen bonding in all the optimized structures of epinephrine-uracil complex is kind of a closed-shell interaction and mainly electrostatic dominant.