Atoms In Molecules Research Articles

Computational analysis of substituent effects on proton affinity and gas-phase basicity of TEMPO derivatives and their hydrogen bonding interactions with water molecules

The study investigates the molecular structure of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and its derivatives in the gas phase using B3LYP and M06-2X functional methods. Intermolecular interactions are analyzed using natural bond orbital (NBO) and atoms in molecules (AIM) techniques. NO2-substituted TEMPO displays high reactivity, less stability, and softer properties. The study reveals that the stability of TEMPO derivatives is mainly influenced by LP(e) → σ∗ electronic delocalization effects, with the highest stabilization observed on the oxygen atom of the nitroxide moiety. This work also considers electron density, atomic charges, and energetic and thermodynamic properties of the studied NO radicals, and their relative stability. The proton affinity and gas-phase basicity of the studied compounds were computed at T = 298 K for O-protonation and N-protonation, respectively. The studied DFT method calculations show that O-protonation is more stable than N-protonation, with an energy difference of 16.64–20.77 kcal/mol (22.80–25.68 kcal/mol) at the B3LYP (M06-2X) method. The AIM analysis reveals that the N–O…H interaction in H2O complexes has the most favorable hydrogen bond energy computed at bond critical points (3, − 1), and the planar configurations of TEMPO derivatives exhibit the highest EHB values. This indicates stronger hydrogen bonding interactions between the N–O group and water molecules.

Synthesis, Structure, and Antimicrobial Properties of New Cobalt(II) Complexes with 1-Propargylimidazoles

Abstract: Complexes of cobalt(II) chloride with 1-propargylimidazole, 1-propargyl-2-methylimidazole, and 1- propargylbenzimidazole ligands were synthesized and studied by FTIR spectroscopy and X-ray analysis. According to the X-ray analysis, the crystal molecules of compounds were connected by non-covalent interactions, such as halogen bonds and π-stacking. The nature and energy of coordination metal-ligand and noncovalent bonds for structures under study were estimated in the frame of QTAIM (Quantum Theory “Atoms In Molecules”). The antimicrobial activity of obtained cobalt(II) chloride complexes was evaluated in relation to microorganisms, E. durans, B. subtilis, and E. coli. Complexes of 1-propargyl-2-methylimidazole and 1- propargylbenzimidazole with cobalt(II) chloride demonstrated high activity against E. coli and E. durans relatively and could be recommended as antimicrobial drugs.

Ionic liquids and Graphene: The ultimate combination for High-Performance supercapacitors

Ionic liquids (ILs), due to their tunable propensities and properties, are discussed as a new class of solvents for scientific and industrial applications. Developing novel processes and applying ionic liquids further accelerate the growth of our fundamental and engineering understanding.In this work, the structure of four ILs, 1-ethyl-3-methylimidazolium tetrafluoroborate formate (Emim+BF4−)/chloride (Emim+Cl−)/Nitrate (Emim+NO3−), and thiocyanate (Emim+SCN−) is reported. Then via employing classical molecular dynamics and well-tempered metadynamics simulations their dynamics are investigated. The dynamics of ILs are represented by studying mean squared displacements. Additionally, the increased size and weight of anions interacting with the Emim+ cation cause the dynamics to become slow. Therefore, due to the higher molecular weight, the BF4− anion has lower diffusion than any other. Indeed, radial distribution functions between cations and anions reveal the structural arrangement in ILs. On the other hand, it is unexpectedly found that a certain amount of ILs are distributed near the electrode surface. Such phenomena occur because of the relatively strong ionic interactions between cations and anions; also, the π–π stacking between cations and graphene caused their interactions to become stronger. Furthermore, the atoms in molecules (AIM) analyses identified several interatomic interactions between the ILs and graphene. The free energy values for the ILs at their global minima are about ∼ -271.79, −267.93, −251.37 kJ mol−1 and ∼ -241.98 kJ mol−1 in systems Emim+/Cl−, Emim//NO3−, Emim+/SCN−, and Emim+/BF4−, respectively. Our findings represent a crucial step towards interpreting the complex interactions and nanostructures at the electrolyte–electrode interface, which could be beneficial for designing high-performance supercapacitors in energy storage using carbon electrodes and IL electrolytes in experiments.

Synthesis of 2-amino-5-methylpyridinium tetrachloridocadmate(II) (C6H9N2)2[CdCl4]: Structure, DFT-calculated descriptors and molecular docking study

In this research paper, (C6H9N2)2[CdCl4], was effectively synthesized using the slow solvent evaporation procedure. Single crystal X-ray diffraction (scXRD) analysis revealed that the compound crystallizes in the triclinic system, specifically in the space group P1¯. Powder XRD (PXRD) of the bulk material showed some minor impurities. The atomic arrangement of the title structure comprises discrete tetrahedral groups [CdCl4]2− linked to the organic entities through weak N(C)H…Cl hydrogen bonds. Solid-state contacts were further studied through Hirshfeld surface analyses, complemented by 2D fingerprint plots. Computational results, obtained using the B3LYP tool with 6-311++G(d,p) + LANL2DZ mixed basis set, demonstrated consistent geometrical, vibrational, and electronic features to the experimental data. Non-covalent interactions were explored in depth using Atoms-In-Molecule (AIM) and Reduced Density Gradient (RDG) analyses. Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC) analyses showed melting at 378 K and decomposition at around 540 K. Furthermore, the inhibition activity of the examined compound was explored in-silico through molecular docking studies targeting the inducible Nitric Oxide Synthase (iNOS) enzymes.

New heteroleptic l-argininato copper(II) complex with bromide and N, N’– heterocyclic ligands – synthesis, supramolecular, spectroscopic, magnetic and theoretical investigations

A new heteroleptic [CuBr(l−Arg)(bpy)]Br·2H2O (1) (l−Arg=l−Arginine, bpy=2,2’−bipyridine) complex has been synthesized and its molecular and supramolecular structure aspects have been discussed based on the X−ray single crystal structure and Hirshfeld analyses. In addition, the properties of complex 1 have been elucidated using different spectroscopic methods (FT−IR / FIR, Raman, NIR−Vis−UV, Q− / X− band EPR) and magnetic measurements. In this complex, the bromide anion occupies the apex of a slightly distorted square pyramid (τ = 0.12). The [CuBr(l−Arg)(bpy)]+ complex units exhibit a ribbon−like organization, with Cu(II) metal centers located at the corners of triangles where the shortest Cu∙∙∙Cu distance is 5.579 Å. The aromatic moieties of bpy are aligned nearly parallel leading to π···π interactions. Both, non−bonded and coordinated, Br− ions act as hydrogen−bond acceptors for guanidinium groups. Hirshfeld analysis indicated the importance of the Br∙∙∙H (17.9 − 18.4 %), O∙∙∙H (14.9−15.2 %), and H∙∙∙H (42.3−43.1 %) interactions in the molecular packing of the studied complex. Atoms in molecules (AIM) calculations indicated mainly the closed shell character for the Cu−N, Cu−O and Cu−Br coordination interactions. The G value calculated using the Q−band EPR spectra parameters g|| = 2.235 and g⊥= 2.05 is 4.7, what indicating negligible coupling and that local tetragonal axes are aligned parallel. A negative value of Weiss temperature θCW = -0.32 K indicates the presence of weak antiferromagnetic coupling between the neighboring Cu(II) ions mediated through hydrogen bonds and π-π stacking of aromatic moieties of bpy. The value of gav= 2.113 obtained from Q−band EPR spectra is consistent with that corresponding to the Curie constant (C = 0.4138 emu K mol−1), i.e.g = 2.101, and that obtained from the best fitting to the Brillouin function: g = 2.139.

Theoretical investigation of formaldehyde recognition by aluminum nitride nanoclusters(Al12N12): a DFT approach

This study analyses how formaldehyde molecules (H2CO and (H2CO)2) interact with a Al12N12 nanocluster with a specific theoretical approach (B3LYP/6-311++G(d,p)). We use the GAMESS software package for all calculations. Scientists have used the Atoms in Molecules (AIM) theory to better grasp how gases stick to and interact with Al12N12 nanoclusters The Al12N12 nanocluster electronic properties change significantly when exposed to formaldehyde adsorption. Furthermore, the pure Al12N12 cluster can capture up to four single molecules and three pairs of formaldehyde, leading to a decrease in the HOMO–LUMO gap by around 37–54%. The Al12N12 nanocluster can detect formaldehyde because its conductivity changes when formaldehyde molecules are present. The Bader theory of atoms in molecules (AIM) is used to study how formaldehyde interacts with a nanocluster. The pure Al12N12 nanocluster may be a good choice for finding formaldehyde molecules. The results show that Al12N12 could be a good chemical sensor for detecting formaldehyde.

Spectroscopic and computational study of Favipiravir-Adenine cocrystallization biomolecular complex

The research focuses on the structural investigation of biomolecules and biomolecular complexes using the DFT method, spectroscopic techniques, and determining cocrystal formation. The significant difficulties in making new drug products are low oral bioavailability and poor aqueous solubility. However, the co-crystallization of biomolecules can enhance their solubility without changing their pharmacological properties. The optimized structure of the molecules is obtained using the B3LYP/6–311++G(d,p) basis set within the framework of Density Functional Theory (DFT). Various vibrational techniques such as Fourier Transform Infrared (FTIR), Raman, and Surface-Enhanced Raman Spectroscopy (SERS) are employed to characterize the monomers and their interacting system. Possible vibrational assignments along with Potential energy distribution (PED) analysis are carried out using Vibrational Energy Distribution Analysis (VEDA). Natural Bond Orbital (NBO), Non-Linear Optical (NLO), Non-Covalent Interaction (NCI), and Atoms in Molecule (AIM) study are carried out to understand the interacting mechanism in the Favipiravir-Adenine biomolecular complex. The study shows that there is charge transfer through inter and intramolecular interaction in the complex. The binding energy of protein and Ligand is investigated using the Autodock tool for the molecular docking method and the negative value of binding energy – 4.36 kcal/mol of Favipiravir-Adenine biomolecular complex exclaims good binding affinity with the chosen protein 6LU7. Lipinski's criteria for druglikeness also claim that monomers and synthesized biomolecular complexes have the potential to influence drugs with good oral bioavailability. Cocrystal formation is confirmed by the X-ray diffraction pattern. The Protox II software claims that the toxicity of the drug and synthesized biomolecular complex is class IV.

Application of density function theory (DFT) to study the microstructure property of ethyleneglycoldiacetate + 1-alcohols (C3-C8) systems from experimental point of view

For a more discussion of non-covalent interactions of binary mixtures of ethyleneglycoldiacetate (EGDA) with 1-alcohols (C3-C8), the density functional theory (DFT) calculation is applied at the ωB97XD/cc-PVDZ level of theory. The adsorption and interaction energy, thermodynamic parameters, the highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbital (LUMO), the reduced density gradient, the localized orbital locator (LOL), and the atom in molecule (AIM) and topological parameters are also calculated for all binary mixtures at T = 298.15 K. The quantum computational reveals that the interaction of EGDA with1-alcohols is van der Walls type and all adoption process are exothermic. The computational results confirm the behavior of experimental results in the form of excess molar volumes VmEatT=298.15K and ambient pressure (81.5 kPa). The results were correlated with Redlich-Kister relation.

Theoretical investigation of the nature of hydrogen bonds and cooperativity effect in methanol-water and ethanol-water clusters

ABSTRACT This study aims to cast light on the nature of hydrogen bonds and their cooperativity that exists in alcohol-water ( ROH ( H 2 O ) n ) ( R = − C H 3   ( − Me ) ,   − C H 2 C H 3   ( − Et ) ) (n = 1–10) clusters using atoms in molecules (AIM) theory and symmetry-adapted perturbation theory (SAPT). The investigation of optimum structures suggests that alcohol ( ROH ) forms two hydrogen bonds, one primary hydrogen bond ( O − H ⋅ ⋅ ⋅ O ) , and one secondary hydrogen bond ( C − H ⋅ ⋅ ⋅ O ) Two types of hydrogen bonds are addressed in these studies, where alcohol works as the hydrogen bond donor ( ROH ⋅ ⋅ ⋅ O H 2 ) and hydrogen bond acceptor ( RHO ⋅ ⋅ ⋅ HOH ) . The AIM results reveal that RHO ⋅ ⋅ ⋅ HOH and ROH ⋅ ⋅ ⋅ O H 2 hydrogen bonds are partially covalent. The SAPT study demonstrates that in all the clusters studied herein, the electrostatic interaction between alcohol and water is the main attractive force, and its contribution may be two times larger than the separate corresponding contributions from the dispersion and the induction terms. The electron density (ρ) at the bond critical point (BCP) is a suitable parameter to assess the strength of the interaction. The current study shows the strength and nature of ROH ⋅ ⋅ ⋅ O H 2 and RHO ⋅ ⋅ ⋅ HOH hydrogen bond, and cooperative effect in ( ROH ( H 2 O ) n ) ( R = − C H 3   ( − Me ) ,   − C H 2 C H 3   ( − Et ) .) (n = 1–10).

Study on separation of acetonitrile and methanol azeotropic system using tetraethylammonium chloride-based deep eutectic solvents

Large quantities of waste streams containing mixed acetonitrile (ACN) and methanol (MeOH) are generated during pharmaceutical and chemical production. The polarity of these two substances is extremely similar, resulting in the formation of an azeotrope at room temperature and atmospheric pressure. In this study, deep eutectic solvents (DESs) were selected as extractants for the separation of ACN-MeOH binary azeotrope. To obtain suitable DESs, the σ-profiles of ACN, MeOH, DESs were calculated using the COSMO-SAC model, and the results demonstrated that the DESs synthesized when tetraethylammonium chloride (TEAC) was chosen as the hydrogen bond acceptor (HBA) and acetamide as the hydrogen bond donor (HBD) could effectively break the azeotropy of ACN and MeOH. Therefore, four DESs were synthesized with molar ratios of TEAC: acetamide = 1: n (n = 1, 2, 3, 4) for subsequent ACN-MeOH-DESs ternary vapor–liquid phase equilibrium (VLE) experiments at 101.3 kPa to determine the optimal extractant. The measured VLE data revealed the higher separation of DES TEAC-2acetamide on the ACN-MeOH binary azeotrope compared with other DESs. Afterward, the NRTL model was adopted to calculate the binary interaction parameters between ACN/MeOH and DESs. The results of the fitting indicated agreement with the experimental data. Finally, the separation mechanism was further analyzed using the interaction energy analysis, improved independent gradient model (IGMH), and the theory of atoms in molecules (AIM). The results indicated that the strong interaction between DESs and MeOH is the primary factor in the ability of DESs to break the azeotrope of the system.

Exploring the bonding and aromaticity of [Au3{C2H2N2E(L)2}3]+ (E = Si, Ge and L = –CH3, -H, -CF3, –NO2): Trinuclear gold superalkali complexes

Coinage metal [Cu, Ag, Au] complexes, with carbene analogous ligands, especially silylene, and germylene, have been getting attention in recent years for their potential applications, either in homogeneous catalysis or in photophysical properties. In this study, we have designed trinuclear gold complexes with different substituted silylene and germylene and observed that these trinuclear gold complexes are stable in cationic form and behave like a superalkali. Conceptual density functional theory (CDFT) based descriptors like electrophilicity give the idea about the reactivity of these superalkali complexes. Negative NICS values determine the aromatic nature of the trinuclear core of these complexes. Atom in molecules (AIM) study has been performed to gain a clear idea about the bonding nature of complexes. Energy decomposition analysis (EDA) suggests that electrostatic interaction stabilizes the complex. First-order hyperpolarizability calculation confirms their high nonlinear optical (NLO) properties.

Study on separation of methanol and dimethyl carbonate azeotropic system with deep eutectic solvents

Dimethyl carbonate (DMC) is an important diesel and gasoline additive that is also a low-toxic and environmentally friendly chemical raw material. However, it will form an azeotrope with methanol (MeOH) during the actual chemical production process. Therefore, separating high-purity DMC from the azeotrope is of significance. In extractive distillation, deep eutectic solvents (DESs) have demonstrated superior separation performance as green extractants. This study calculated the σ-profiles of DMC, MeOH, and DESs by the COSMO-SAC model to examine the most appropriate DES for the MeOH and DMC separation. Eventually, DES1(1:2 choline chloride (ChCl): malonic acid (MA)), DES2(1:2 ChCl: urea), DES3(1:2 ChCl: glycerol (G)), DES4(1:2 ChCl: ethylene glycol (EG)), DES5(1:2 ChCl: pyruvic acid (PA)) were designated as preferred extractants. The vapor pressures of five DESs at different temperatures were determined using a thermogravimetric analyzer, while their critical properties, normal boiling points, and acentric factors were predicted. The vapor–liquid equilibrium (VLE) data measured for DMC + MeOH + DESs ternary systems at 101.3 kPa showed that the addition of 15 mol % of any of the five DESs could successfully break the azeotrope and DES2 achieved a higher degree of separation in the MeOH-DMC binary azeotrope compared to the other DESs evaluated. The binary interaction parameters between MeOH/DMC and DESs were calculated through the NRTL (Non-Random Two-Liquid) model, and the fitting results were found to be consistent with the experimental data. The mechanism of the MeOH-DMC separation by DES2 was elucidated through quantum chemical (QC) calculations. The improved independent gradient model (IGMH) and the theory of atoms in molecules (AIM) demonstrated that the stronger interaction between DES2 and MeOH molecules is the key for DES2 to break the azeotrope of the system.

Unveiling the unique properties of carbon nitride (C6N8) monolayer as a novel flexible sensor for hydrogen cyanide and hydrogen fluoride: A DFT study

Surge for the advancement of sensor that accurately and selectively detect toxic materials particularly cyanides and fluorides, is expanding every day. Herein, we analyze the sensing ability of carbon nitride (C6N8) monolayer for precise detection of hydrogen cyanide (HCN) and hydrogen fluoride (HF) using DFT approach. Interaction energy analysis reveals that HF binds strongly to C6N8 monolayer which is probably due to chemical bond formation whereas, HCN adsorbed to the surface by weak van der Waals forces. The atom in molecules (AIM), the density of states (DOS), non-covalent interaction (NCI), molecular electrostatic potential (MEP), electron localization function (ELF), frontier molecular orbitals (FMO), and QNBO were used to gain a thorough understanding of the complexation of HCN and HF with monolayer. HCN and HF analytes with C6N8 monolayer exhibit slight variations in band gap energy in FMO analysis (4.206 to 4.267 eV) indicating weak NCIs. Furthermore, MEP map demonstrate that more charge transfer is occurred from the C6N8 monolayer towards HF@C6N8 resulting in a strong ionic bonding. In addition, the existence of non-covalent interactions among complexes confirmed by NCI-RDG and QTAIM analysis. A short recovery period for HCN@C6N8 (1.677 × 10−7 s) makes desorption process simpler. Appreciable selectivity of monolayer towards analytes and prospects of all findings will provide an experimentalist with practical suggestions to build highly sensitive sensors for HCN and HF using C6N8 monolayer.

Size Matters: Computational Insights into the Crowning of Noble Gas Trioxides.

In pursuit of enhancing the stability of the highly explosive and shock-sensitive compound XeO3, we performed quantum chemical calculations to investigate its possible complexation with electron-rich crown ethers, including 9-crown-3, 12-crown-4, 15-crown-5, 18-crown-6, and 21-crown-7, as well as their thio analogues. Furthermore, we expanded our study to other noble gas trioxides (NgO3), namely, KrO3 and ArO3. The basis set superposition error (BSSE) corrected interaction energies for these adducts range from -13.0 kcal/mol to -48.2 kcal/mol, which is notably high for σ-hole-mediated noncovalent interactions. The formation of these adducts was observed to be more favorable with the increase in the ring size of the crowns and less favorable while going from XeO3 to ArO3. A comprehensive analysis by various computational tools such as the mapping of the electrostatic potential (ESP), Wiberg bond indices (WBIs), Bader's theory of atoms-in-molecules (AIM), natural bond orbital (NBO) analysis, noncovalent interaction (NCI) plots, and energy decomposition analysis (EDA) revealed that the C-H···O interactions, as well as dispersion interactions, play a pivotal role in stabilizing adducts involving larger crowns. A noteworthy outcome of our study is the revelation of a coordination number of 9 for xenon in the complex formed between XeO3 and the thio analogue of 18-crown-6, which is higher than the largest number reported to date.

Investigation of the adsorption and sensor properties of resorcinol (RSL) on X9N9 (X = Al, B, Ga, In) nanorings by DFT and QTAIM analysis with solvent effects

De-aromative oxygenation of resorcinol is recognized as an important process that produces a variety of bioactive chemicals. Hence, we evaluated the sensing application by utilizing density functional theory to study the resorcinol (RSL)-X9N9 (X = Al, B, Ga, and In) nanoring interaction. We saw that RSL had a strong interaction with every ring. A charge transfer occurs between nanorings and RSL, causing dipole moment to be induced. The band gap energies of all complexes are less than that of RSL. In vacuum the band gap energies of the complexes are less than that of pristine rings while in water, RSL-Ga/In-N complexes, the band gap energies are higher than that of pristine rings. In vacuum all the complexes, except B9N9-RSL have higher adsorption energies. In water phase, Al9N9/Ga9N9-RSL complexes have higher adsorption energies. These values suggest they are good dopants for RSL. The electrical conductivity and work function are significantly altered as a result of the alteration in the Frontier Molecular Orbitals (FMOs) energies of the nanorings following interaction. It is possible to use the X9N9 nanorings for RSL as both an electronic sensor and a work function-based sensor. The extended recovery time of RSL with X9N9, however, indicates that it can be used to store RSL or remove it from a specific environment. Atom in Molecules (AIM) analysis predicts the comprehension reactivity, chemical bonding, and the creation of compounds. The present work can be extended to investigate the effect of coinage metal doping with nanorings to study doping effects and drug delivery carrier properties.

Screening of toluene absorbents based on molecular simulation and experimental investigation on novel compound solvents

This work aims to screen out absorbents with excellent performance to control toluene pollution. Based on density functional theory (DFT), this article calculated the binding energy between toluene and organic solvents molecules with specific functional groups, and comprehensively examined the physical and chemical properties of the solvents to screen out suitable toluene absorbents. The computational binding energy and the experimental absorption efficiency have the same change tendency, that is, the value of the binding energy determines the ability of the solvents to absorb toluene. Pentaethylene glycol dimethyl ether (PGDE), 1-methyl-2-pyrrolidinone (NMP), dioctyl phthalate (DOP) and sulfolane (SUL) were initially selected as toluene absorbents. Atoms in molecules (AIM) analysis, reduced density gradient (RDG) analysis and symmetry-adapted perturbation theory (SAPT) analysis were used to explore the microscopic mechanism of toluene absorption by four organic solvents. The results show that the interactions between organic solvents and toluene are weak interactions dominated by dispersion attraction. The experiment used polyethylene glycol dimethyl ether (NHD) with very low volatility as the main solvent, which is a polymer containing the main component PGDE, and compounded it with NMP, DOP, and SUL respectively. The absorption experiment investigated the efficiency of compound solvents with different mass fractions of compound components on toluene under the conditions of normal pressure, liquid-to-gas ratio 2.5 L/m3, gas flow rate 4 L/min, temperature 30°C, inlet concentration approximately 6000 mg/m3, and packing height 60 cm. The results show that the toluene absorption efficiency of the three compound solvents is more than 91%. Considering the absorption performance, consumption and stability of the solvent, NHD-SUL solvent (20 wt.% SUL) was finally selected as the new compound solvent. The new compound solvent regenerated lean solution still maintains a good absorption efficiency of 90% after 13 desorption cycles. Theoretical and experimental research are of great significance for the future treatment of exhaust gas pollution.

Exploring Unconventional σ-Hole Interactions: Computational Insights into the Interaction of XeO3 with Non-Aromatic Coordinating Solvents.

In order to control the explosiveness and shock sensitivity of XeO3 , we have investigated its plausible interaction with various non-aromatic coordinating solvents, serving as potential Lewis base donors, through density functional theory (DFT) calculations. Out of twenty six such solvents, the top ten were thus identified and then thoroughly examined by employing various computational tools such as the mapping of the electrostatic potential surface (MESP), Wiberg bond indices (WBIs), non-covalent interaction (NCI) plots, Bader's theory of atoms-in-molecules (AIM), natural bond orbital (NBO) analysis, and the energy decomposition analysis (EDA). The amphoteric nature of XeO3 was also explored by investigating the extent of back donation from the lone pair of Xe to the antibonding orbital of the donating atom/group of the solvent molecules. The C-H…O interactions were also found to be a contributing factor in the stabilization of these adducts. Although these aerogen-bonding interactions were found to be predominantly electrostatic, significant contributions from the orbital contributions, as well as dispersion interactions, were observed. The top three non-aromatic solvents (among the twenty six studied) which form the strongest adducts with XeO3 are proposed to be hexamethylphosphoramide (HMPA), N,N'-dimethylpropyleneurea (DMPU) and tetramethylethylenediamine (TMEDA).

Computational study on the characteristics of the complexes resulting from the interaction of carbonyl selenide and hypohalous acids

This study computationally investigates the properties and competition of complexes formed by the interaction between hypohalous acids (HOX, where X = F, Cl, Br, and I) and carbonyl selenide (COSe) at the MP2/aug-cc-pVTZ computational level. Three distinct groups of complexes were obtained. The first group, consisting of complexes with a cyclic structure (HB-TB), exhibited the highest stability. remaining two groups formed less stable linear structures with different characteristics (ChB and XB). In the first group, the electronegativity of the halogen atom significantly influenced the stability of the complexes. Conversely, the stability of complexes in groups II and III was primarily determined by the acid and base strengths of the interacting monomers. To comprehensively evaluate the obtained results, various analyses were employed, including Molecular electrostatic potential (MEP), geometry Optimization, Spectroscopic, Interaction energy (SE), Natural bond orbital (NBO) analysis, Atoms in molecules (AIM) analysis, Non-covalent interaction (NCI) index, Energy decomposition analysis (EDA), and Electron density difference(EDD) analysis.

Novel Pharmaceutical Cocrystals of Tegafur: Synthesis, Performance, and Theoretical Studies.

Tegafur (TF) is one of the most important clinical antitumor drugs with poor water solubility, severely reducing its bioavailability. This work develops new cocrystals to improve the solubility of TF and systematically investigates the intermolecular interactions to provide new insights into the formation of cocrystal and changes in physicochemical properties. In this paper, two new 1:1 cocrystals of TF with 2,4 dihydroxybenzoic acid (2,4HBA) and p-nitrophenol (PNP) were synthesized. The cocrystal products were identified and characterized by various solid state analysis techniques. And the high performance liquid chromatography (HPLC) was conducted to determine the solubility and dissolution rate of TF and cocrystals. Moreover, the quantum chemistry calculations of crystal structure provided theoretical support for the results. Compared with pure TF, the solubility and dissolution rate of TF-2,4HBA is significantly increased in a pH 6.8 buffer at 37°C. Under accelerated storage conditions (40°C, 75% RH), all cocrystal exhibits excellent stability over 8weeks. Hirshfeld surface (HS) analysis, atoms in molecules (AIM) analysis, interaction region indicator (IRI) analysis, molecular electrostatic potential surface (MEPS) analysis and frontier molecular orbital (HOMO-LUMO) analysis were integrated to understand the hydrogen bonding interaction more comprehensively. The simulation results are in good agreement with the experimental data. The results show that the analysis of physical and chemical properties of TF-PNP cocrystal and TF crystal by quantum chemistry method is reliable at molecular level. These results are helpful to provide guiding methods in the cocrystal development and theoretical study of tegafur.

Theoretical study on formation mechanism of acetic acid associating configurations and their distributions under saturated conditions.

The vapor-liquid equilibrium (VLE) properties of acetic acid systems generally behave strong non-ideality due to the associating interaction among acetic acid molecules. Theoretical study of the associating mechanism will provide guidance for the VLE property prediction, which is crucial for the designing on the separation process of the acetic acid systems. In this work, the association conformers and their distribution on acetic acid molecules in saturated gas and liquid phase were firstly studied. The proportions of the acetic acid monomer and multimers were obtained, which will contribute to the foundation for the vapor-liquid equilibrium simulations. The association mechanism on acetic acid molecules was then investigated by comparing among the structures and non-bonded interaction energies of different dimers. The structure of the cyclic dimer containing two OC-HO hydrogen bonds, may be found probably when acetic acid molecules approached. Electronic properties of different acetic acid dimers showed that the electrons around carbonyl oxygen atoms were deflected by the attraction of hydrogen atoms in the other molecule, which polarized the acetic acid molecules when the hydrogen bonds between acetic acid molecules were formed, providing theoretical basis for the polarized acetic acid molecular model. In this work, the molecular dynamics (MD) simulations and DFT calculations were conducted through the software GROMACS and Gaussian 09, respectively. For the MD simulations, the OPLS-AA force field was used as the atomic force field, with the cubic simulation cells constructed by Packmol program. For the DFT calculations, the M06-2X functional was employed for the optimization of the associating structures with the 6-311G** basis sets. Hydrogen bonding energies of dimers were corrected for the basis set superposition error (BSSE) and the deformation energies of monomers. Furthermore, the energy decomposition analysis was conducted at DFT/M06-2X/def-tzp level by the ADF software, and the wave function analysis was conducted by the Multiwfn software including the atom in molecule (AIM) topology analysis, the electronic potential analysis, and the electron density difference analysis.