Atoms In Molecules Theory Research Articles

Skeletal Editing of Energetic Materials: Acid-Catalyzed One-Step Synthesis of Bridged Triazoles as High-Energy-Density Materials via the Nef Reaction.

Thermally stable insensitive energetic materials have captivated significant attention from the global research community due to their potential impact. In this study, a series of symmetric and asymmetric nitromethyl-bridged triazole compounds were synthesized from pyrimidine moieties via a skeletal editing approach. Additionally, carbonyl-bridged compounds were synthesized in a single step by using acid-catalyzed Nef reactions from their nitromethyl precursors. Peripheral modifications of pyrimidine resulted in fused energetic moieties. All synthesized compounds were fully characterized by using infrared spectroscopy, high-resolution mass spectrometry, multinuclear magnetic resonance spectroscopy, elemental analysis, and differential scanning calorimetry. Single-crystal X-ray diffraction analysis confirmed the structures of compounds 4 and 10. The newly synthesized moieties exhibit densities ranging from 1.75 to 1.86 g cm-3, detonation velocities between 8044 and 8608 m s-1, and detonation pressures between 23.10 and 30.31 GPa. Notably, compounds 9 and 10 demonstrate exceptional heat resistance, with decomposition temperatures of 315 and 335 °C, respectively. Computational studies, including density functional theory, quantum theory of atoms in molecules, noncovalent interactions, and electrostatic surface potential analysis, account for hydrogen-bonding and noncovalent interactions. This work highlights the potential of skeletal editing in the development of high-performing, thermally stable energetic materials.

Machine learning-based prediction of bioactivity in HIV-1 protease: insights from electron density analysis.

Aim: To develop a model for predicting the biological activity of compounds targeting the HIV-1 protease and to establish factors influencing enzyme inhibition.Materials & methods: Machine learning models were built based on a combination of Richard Bader's theory of Atoms in Molecules and topological analysis of electron density using experimental x-ray 'protein-ligand' complexes and inhibition constants data.Results & conclusion: Among all the models tested, logistic regression achieved the highest accuracy of 0.76 on the test set. The model's ability to differentiate between less active and highly active classes was relatively good, as indicated by an AUC-ROC score of 0.77. The analysis identified several critical factors affecting the biological activity of HIV-1 protease inhibitors, including the electron density contribution of hydrogen atoms, bond-critical points and particular amino acid residues. These findings provide new insights into how these molecular factors influence HIV-1 protease inhibition, emphasizing the importance of hydrogen bonding, glycine's flexibility and hydrophobic interactions in ligand binding.

Interactions involved in the adsorption of ethylene glycol and 2-hydroxyethoxide on the Au(111) surface: a Density Functional Theory study.

The monolayers of ethylene glycol and 2-hydroxyethoxide on gold surfaces have been used in hybrid materials as biosensors. In this article, the adsorption of ethylene glycol and 2-hydroxyethoxide on the Au(111) surface was analyzed. For the first system, ethylene glycol on Au(111), there are Au O and Au H interactions. To the best of our knowledge, the Au H interaction has been overlooked until now. However, in this work, there is strong evidence that this interaction is important to stabilize the system. For the second system, the atomic interactions mentioned previously are also predicted, although there is an additional interaction between 2-hydroxyethoxide molecules. Such an interaction induces the link -O-H-O-, with high values of the electron density at the critical points of the corresponding bond path of the O-H interaction. These links suggest the forming of ethylene glycol chains. The calculations were performed using two exchange-correlation functionals: BEEF-vdW and C09 -vdW; both functionals incorporate dispersion effects within the Kohn-Sham approach in Density Functional Theory as implemented in GPAW code and ASE computational packages. The contacts between the molecules considered in this article and the Au(111) surface were analyzed through the Quantum Theory of Atoms in Molecules implemented in GPUAM code.

Aluminum Fluorides as Noncovalent Lewis Acids in Proteins: The Case of Phosphoryl Transfer Enzymes.

The Protein Data Bank (PDB) was scrutinized for the presence of noncovalent O ⋅ ⋅ ⋅ Al Triel Bonding (TrB) interactions, involving protein residues (e. g. GLU and GLN), adenosine/guanine diphosphate moieties (ADP and GDP), water molecules and two aluminum fluorides (AlF3 and AlF4 -). The results were statistically analyzed, revealing a vast number of O ⋅ ⋅ ⋅ Al contacts in the active sites of phosphoryl transfer enzymes, with a marked directionality towards the Al σ-/π-hole. The physical nature of the TrBs studied herein was analyzed using Molecular Electrostatic Potential (MEP) maps, the Quantum Theory of Atoms in Molecules (QTAIM), the Non Covalent Interaction plot (NCIplot) visual index and Natural Bonding Orbital (NBO) studies. As far as our knowledge extends, it is the first time that O ⋅ ⋅ ⋅ Al TrBs are analyzed within a biological context, participating in protein trapping mechanisms related to phosphoryl transfer enzymes. Moreover, since they are involved in the stabilization of aluminum fluorides inside the protein's active site, we believe the results reported herein will be valuable for those scientists working in supramolecular chemistry, catalysis and rational drug design.

Cs3LiGe4, One Compound with Two Complementary Structural Descriptions: Isolated [Ge4]4- Tetrahedral Clusters Coordinated by Li+ and Cs+ Cations or One-Dimensional [LiGe4]3- Polyanions Packed within a Matrix of Cs+ Cations?

Reported are the synthesis and structural characterization of Cs3LiGe4, the first structurally characterized lithium-containing cesium germanide. Single-crystal X-ray diffraction data indicate that Cs3LiGe4 crystallizes in an orthorhombic crystal system with the space group Cmcm (no. 63, Person symbol oS32) with unit cell parameters a = 6.950(2) Å, b = 15.503(3) Å, and c = 9.919(2) Å and V = 1068.65(4) Å3. The structure consists of [Ge]44- tetrahedral clusters with the Li atoms positioned in such a way that polyanionic [LiGe]43- chains could be considered as well. Electronic structure calculations indicate an intrinsic semiconductor with a band gap of 0.76 eV. To understand the nuances of the chemical bonding, position-space techniques based on the quantum theory of atoms in molecules, the electron localizability indicator, and their basin intersections were employed confirming the covalent character of the Ge-Ge bonding. The strong polarity of the interactions between [Ge]44- and the surrounding lithium and cesium cations suggests to interpret these as mainly ionic, further supporting the most basic structure rationalization [Cs+]3[Li+][Ge]44-, following the Zintl-Klemm concept. The electron localizability indicator topology affirms the striking similarities between [Ge]44- and molecular As4 tetrahedra in yellow arsenic, further supporting Klemm's pseudoatom concept on a quantum chemical basis.

Noncovalent Interactions in Palladium(II)-Catalyzed Meta-Selective C-H Functionalization: Mechanistic Insights and Origins of Regioselectivity.

The use of noncovalent interactions to control the regioselectivity of transition metal-catalyzed C-H functionalization of arenes has received significant attention in recent years. Herein, we present a mechanistic study based on Density Functional Theory (DFT) of palladium(II)-catalyzed meta-selective C-H olefination employing a noncovalent directing template. We analyze the key steps of the mechanism and discuss the origins of reaction selectivity. The role of the directing template was elucidated, demonstrating its essential function in lowering reaction barriers and controlling selectivity. Our results reveal a competition in activation between ortho- and meta-C-H bonds. Contrary to the previous proposal in the literature, hydrogen bonds between the N-H bonds of the urea moiety and the carbonyl oxygen of the substrate predominantly favor ortho-selectivity over meta-selectivity. DFT results, alongside Quantum Theory of Atoms in Molecules (QTAIM) and Non-Covalent Interaction Index analysis, suggest that secondary interactions between the R group linked to the urea moiety and the catalyst exert a more pronounced influence compared to the aforementioned hydrogen bonds, directing the selectivity towards the meta C-H bond.

Behaviour of 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimdazolium thiocyanate and 1-butyl-1-methypyrrolidium chloride in dimethyl sulfoxide: Experimental, NCI and QTAIM analysis

The aim of this study is to examine the cation and anion influence on intermolecular interactions of mixtures comprising ionic liquids (ILs): 1-butyl-3-methylimidazolium chloride [Bmim][Cl], 1-butyl-3-methylimdazolium thiocyanate [Bmim][SCN] and 1-butyl-1-methylpyrrolidium chloride [Bmpym][Cl] with dimethyl sulfoxide (DMSO) at various temperatures. To understand the influence of cation and anion as well as temperature on interactions between the mixtures, thermodynamics parameters: apparent molar properties were calculated from the measured density (ρ) and sound velocity (u) data and fitted to the Redlich-Mayer type equation in order to obtained limiting apparent molar properties of the studied mixtures. A detailed non-covalent interaction (NCI) and quantum theory of atoms in molecules (QTAIM) analysis was done using density functional theory calculations. These calculations provided information on the electrostatic interactions between the anion, cation, and solvent. The experimental and computational results show that there is hydrogen bonding and strong ionic interactions in the studied systems.

Structural, Antioxidant, and Protein/DNA-Binding Properties of Sulfate-Coordinated Ni(II) Complex with Pyridoxal-Semicarbazone (PLSC) Ligand

The pyridoxal-semicarbazone (PLSC) ligand and its transition metal complexes have shown significant biological activity. In this contribution, a novel nickel(II)-PLSC complex, [Ni(PLSC)(SO4)(H2O)2], was obtained, and its structure was determined by X-ray crystallographic analysis, FTIR, and UV-VIS spectroscopy. The sulfate ion is directly coordinated to the central metal ion. The intermolecular stabilization interactions were examined using Hirshfeld surface analysis. The crystal structure was optimized by a B3LYP functional using two pseudopotentials for nickel(II) (LanL2DZ and def2-TZVP) together with a 6-311++G(d,p) basis set for non-metallic atoms. The experimental and theoretical bond lengths and angles were compared, and the appropriate level of theory was determined. The stabilization interactions within the coordination sphere were investigated by the Quantum Theory of Atoms in Molecules (QTAIM). The antioxidant activity towards hydroxyl and ascorbyl radicals was measured by EPR spectroscopy. The interactions between Human Serum Albumin (HSA) and the complex were examined by spectrofluorimetric titration and a molecular docking study. The mechanism of binding to DNA was analyzed by complex fluorescence quenching, potassium iodide quenching, and ethidium bromide displacement studies in conjunction with molecular docking simulations.

A comparative study of X-ray structural analysis, supramolecular investigation by Hirshfeld surface analysis and DFT computations for tricyclic 1,4-benzodiazepines

The tricyclic 1,4-benzodiazepines - seven-membered heterocyclic compounds were synthesized derived from the three-component reaction involving o-phenylenediamine, 5,5-dimethyl-1,3-cyclohexanedione and various aromatic aldehydes under the influence of HCl. The crystal structure of 11-(3-nitrophenyl)-3,3-dimethyl-2,3,4,5,10,11-hexahydro-1H-dibenzo[b,e][1,4]diazepin-1-one (NDDD) and 11-(2-chlorophenyl)-3,3-dimethyl-2,3,4,5,10,11-hexahydro-1H-dibenzo[b,e][1,4]diazepin-1-one (CDDD) corroborated through single crystal X-ray diffraction method. The Hirshfeld surface analysis indicates crystal packing along with role of intermolecular forces in stabilizing supramolecular assembly of NDDD and CDDD. 2D fingerprint analysis is carried out to envisage to the elemental interactions in the assumption of a single crystal containing molecular fragments. DFT investigations have been carried out to understand the reactivity of NDDD and CDDD at the m062x/def2tzvp method. The obtained geometric parameters from theoretical study are well consistent with experimentally reported XRD analysis. Bonding analysis and charge transfer were examined by performing quantum theory of atoms in molecules (QTAIM) and natural bonding orbital (NBO) analysis. The synthesized NDDD and CDDD exhibit excellent electronic and nonlinear optical properties. The NLO response is justified through computed hyperpolarizability values.

Elucidating the E‐Cadherin⋯ADTC5 Interactions: A Theoretical Examination of Amino Acid Active Site Binding on the Electronic Level via Density Functional Theory

AbstractThe presence of E‐cadherin⋯E‐cadherin interactions in the intercellular space (paracellular pathway) poses a notable limitation in drug delivery across the blood‐brain barrier (BBB). ADTC5 peptide has shown promising results in improving drug delivery across the BBB by modulating E‐cadherin⋯E‐cadherin interactions. However, the study of E‐cadherin⋯ADTC5 amino acid interactions using quantum mechanics approach has not been observed clearly. Herein, we observed the interaction between E‐cadherin⋯ADTC5 amino acids using density functional theory (DFT). Natural bond orbital (NBO), quantum theory of atoms in molecules (QTAIM), and reduced density gradient (RDG) analysis are performed to study the non‐covalent interaction in detail. The Arg55⋯Asp2 shows the strongest interaction between E‐cadherin⋯ADTC5 modulation, indicated by the highest stabilization energy (E(2)), and hydrogen bonding energy (EHB) about 22.04 and −6.90 kcal/mol, respectively. This interaction is dominated by hydrogen bonding. Such advancements could lead to significant improvements in therapeutic strategies for neurodegenerative diseases, where effective drug delivery across the BBB remains a major challenge.

On the Versatility of the sp-, sp 2-, and sp 3-Hybridized Chalcogen-Bearing Molecules To Engage in Type I Chalcogen···Chalcogen Interactions: A Quantum Mechanical Investigation of Like···Like and Unlike Complexes.

The predilection of sp-, sp 2-, and sp 3-hybridized chalcogen-bearing molecules to engage in type I chalcogen···chalcogen interactions was comparatively unveiled in like···like/unlike CY···YC, YCY···YCY, and F2Y···YF2 (where Y = O, S, and Se) complexes, respectively. Upon the optimized monomers, a potential energy surface (PES) scan was conducted to pinpoint the most favorable complexes. The energetic findings unveiled the ability of the investigated systems to engage in the interactions under study with binding energy values ranging from -0.36 to -2.33 kcal/mol. Notably, binding energies were disclosed to align in the posterior sequence; sp 2- (i.e., YCY···YCY) > sp- (i.e., CY···YC) > sp 3- (i.e., F2Y···YF2) hybridized complexes, except the like···like oxygen-bearing complexes. Instead, the highest negative binding energy values were detected for the OCO···OCO followed by those of the F2O···OF2 and CO···OC complexes. Furthermore, the like···like selenium-bearing complexes demonstrated the most considerable binding energies compared to the other investigated complexes. Remarkably, the quantum theory of atoms in molecules and noncovalent interaction index analyses revealed the highly directional and closed-shell nature of the investigated chalcogen···chalcogen interactions. Symmetry adapted-perturbation theory findings outlined the dispersion forces as the commanding forces for all the studied complexes. These observations will provide convincing justifications for the nature of chalcogens within type I chalcogen···chalcogen interactions, leading to increased progress in various domains regarding drug design and materials science.

Consequences of the Pb-S Bond Formation for Lead Halide Perovskites.

Lead halide perovskites are structurally not stable due to their ionic bonds. Using sulfur agents in the crystal growth improves the stability and performance of the photovoltaic and light-emitting devices. In this theoretical work, we use a small toy S-radical in place of A cation in the bulk of lead iodide perovskite, and highlight the significance of the Pb-S covalent-double-bond formation for: the charge redistribution on the neighboring bonds that also turn to be covalent, phase transformation to a stable non-perovskite structure, and superior optoelectronic properties. The chemical analysis was performed with the Quantum Theory of Atoms In Molecules (QTAIM) and Non-Covalent Interactions (NCI) index. Excitonic properties were obtained from the solution of ab initio Bethe-Salpeter equation. Presence of the spin-orbit coupling triggers an interplay between the Frenkel and charge-transfer multiexcitons, switching between the photovoltaic and laser applications. Multiexcitons obey the exciton-fission preconditions.

Conformations of α-cyclodextrin and its role on the stability of inclusion complexes in aqueous solution

α-Cyclodextrin (αCD), a cyclic carbohydrate polymer, presents a wealth of opportunities for drug delivery and various industrial applications. Its high affinity and selectivity in encapsulating target molecules have been well-documented. However, the influence of αCD's conformational variations on its encapsulation capacity remains a promising area for further exploration. This study explores the conformational dynamics of αCD and its relationship with the formation of inclusion complexes (ICs) in aqueous solutions, focusing on understanding the forces driving these dynamics and the formation of stable ICs. Classical molecular dynamics (CMD) demonstrate that αCD solvated in water can adopt two conformations: a truncated cone shape with a suitable cavity for encapsulation and a distorted cone shape with a collapsed cavity. The predominant conformation observed in the CMD trajectory of pristine αCD is the distorted cone. However, under complexation conditions with aliphatic molecules, the guest molecule's size dictates the ICs' stability, forcing αCD to maintain the truncated cone conformation. Quantum chemistry methods and electron density analyses (Quantum Theory of Atoms in Molecules and Non-Covalent Interactions index) support CMD observations by characterizing and quantifying non-covalent interactions. Findings indicate that the shift from the truncated to the distorted cone conformation in αCD is primarily driven by intramolecular non-covalent interactions and the reconfiguration of water molecules surrounding αCD. The ICs' analysis displays a significant correlation between the size of the aliphatic chain and the intensity of intermolecular interactions. The strength of these interactions can effectively disrupt the αCD intramolecular non-covalent interactions that lead to a conformational change and, consequently, the loss of the inclusion complex. In conclusion, although αCD's conformational change can affect encapsulation, guest molecules can manipulate the conformational preference. The systematic analysis of non-covalent interactions offers a way to characterize and quantify these forces, enhancing our ability to understand and predict the stability of inclusion complexes.

Catalytic behavior, electronic structure and spectroscopic (FT-IR, Raman, UV–vis) properties for the new ionic liquid imidazolium hydrogen sulfate

Catalytic performance, chemical reactivity, vibrational modes and electronic transitions of the ion pair [H–Im]+[HSO4]– were investigated in the current paper. Hence, a combined experimental (Hammett acidity function, infrared, Raman and ultraviolet-visible spectroscopies) and theoretical (molecular electrostatic potential surface, reduced density gradient, frontier molecular orbital analysis, quantum theory of atoms in molecules, net atomic charges, global and local reactivity descriptors) study was conducted. In terms of the catalytic performance, the acetic acid esterification with butanol was evaluated. Important kinetic (rate constant, activation energy, pre-exponential factor) and thermodynamic (enthalpy, entropy, Gibbs free energy barrier) factors for ester production as a function of the temperature and catalyst loading have been determined. Results revealed intensive electron density distribution in [H–Im]+[HSO4]– due to chemical interactions between the cationic and anionic moieties. These bonds were established as electrostatic in nature. The pronounced charge transfers within [H–Im]+[HSO4]– managed the title compound acidity (H0) and its catalytic behavior towards butyl acetate synthesis. Using the thermodynamic and kinetic measurements, a mechanism for acetic acid esterification with butanol in the presence of imidazolium hydrogen sulfate ionic liquid was offered.

In-Depth Theoretical Investigations of Borazine’s Aromaticity: Tailoring Electron Delocalization through Substituent Effects

The current study investigates the influence of several R substituents (e.g., Me, SiH3, F, Cl, Br, OH, NH2, etc.) on the aromaticity of borazine, also known as the “inorganic benzene”. By performing hybrid DFT methods, blended with several computational techniques, e.g., Natural Bond Orbital (NBO), Quantum Theory of Atoms in Molecules (QTAIM), Gauge-Including Magnetically Induced Current (GIMIC), Nucleus-Independent Chemical Shift (NICS), and following a simultaneous evaluation of four different aromaticity indices (para-delocalization index (PDI), multi-centre bond order (MCBO), ring current strength (RCS), and NICS parameters), it is emphasized that the aromatic character of B-substituted (B3R3N3H3) and N-substituted (B3H3N3R3) borazine derivatives can be tailored by modulating the electronic effects of R groups. It is also highlighted that the position of R substituents on the ring structure is crucial in tuning the aromaticity. Systematic comparisons of calculated aromaticity index values (i.e., via regression analyses and correlation matrices) ensure that the reported trends in aromaticity variation are accurately described, while the influence of different R groups on electron delocalization and related aromaticity phenomena is quantitatively assessed based on NBO analyses. The most relevant interactions impacting the aromatic character of investigated systems are (i) the electron conjugations occurring between the p lone pair electrons (LP) on the F, Cl, Br, O or N atoms, of R groups, and the π*(B=N) orbitals on the borazine ring (i.e., LP(R)→π*(B=N) donations), and (ii) the steric-exchange (Pauli) interactions between the same LP and the π(B=N) bonds (i.e., LP(R)↔π(B=N) repulsions), while inductive/field effects influence the aromaticity of the investigated trisubstituted borazine systems to a much lesser extent. This work highlights that although the aromatic character of borazine can be enhanced by grafting electron-donor substituents (F, OH, NH2, O−, NH−) on the N atoms, the stabilization due to aromaticity has only a moderate impact on these systems. By replacing the H substituents on the B atoms with similar R groups, the aromatic character of borazine is decreased due to strong exocyclic LP(R)→π*(B=N) donations affecting the delocalization of π-electrons on the borazine ring.

Equilibrium Structures of Propane and 2,2-Difluoropropane and Comparison with Other Two-Top Molecules

The Born–Oppenheimer ab initio equilibrium structures of propane (CH3)2CH2 and 2,2-difluoropropane (CH3)2CF2 were computed at the CCSD(T) level of theory using a basis set of quadruple zeta quality. The semiexperimental structure of propane was also determined from the ground state rotational constants corrected for rovibrational corrections calculated at the MP2 level of theory. Structural comparisons are made with other molecules and are discussed in terms of the quantum theory of atoms in molecules.

Unusual Metal–organic Multicomponent Ni(II) and Mononuclear Zn(II) Compounds Involving Pyridine dicarboxylates: Supramolecular Assemblies and Theoretical Studies

In the present work, we reported the synthesis and characterization [single crystal X-ray diffraction technique, spectroscopic, etc.] of two new Ni(II) and Zn(II) coordination compounds, viz. [Ni(2,6-PDC)2]2[Ni(en)2(H2O)2]2[Ni(en)(H2O)4]·4H2O (1) and [Zn(2,6-PDC)(Hdmpz)2] (2) (where 2,6-PDC = 2,6-pyridinedicarboxylate, en = ethylene-1,2-diamine, and Hdmpz = 3,5-dimethyl pyrazole). Compound 1 is found to crystallize as a multicomponent Ni(II) compound with five discrete complex moieties, whereas compound 2 is isolated as a mononuclear Zn(II) compound. A deep analysis of the crystal structure of 1 unfolds unusual dual enclathration of guest complex cationic moieties within the supramolecular host cavity stabilized by anion–π, π-stacking, N–H⋯O, C–H⋯O, and O–H⋯O hydrogen bonding interactions. Again, the crystal structure of compound 2 is stabilized by the presence of unconventional C–H⋯π(chelate ring) interactions along with C–H⋯O, C–H⋯N hydrogen bonding, π-stacking, and C–H⋯π(pyridyl) interactions. These non-covalent interactions were further studied theoretically using density functional theory (DFT) calculations, molecular electrostatic potential (MEP) surfaces, non-covalent interaction (NCI) plot index, and quantum theory of atoms in molecules (QTAIM) computational tools. The computational study displays that π-stacking or H bonds greatly tune the directionality of compound 1, although non-directional electrostatic forces dominate energetically. For compound 2, a combined QTAIM/NCI plot analysis confirms the presence of unconventional C–H⋯π(chelate ring) interactions along with other weak interactions obtained from the crystal structure analysis. Further, the individual energy contributions of these weak yet significant non-covalent interactions have also been determined computationally.

Incrimination and impact on recovery times and effects of BN nanostructures on antineoplastic drug-electronic density study.

By delivering the drug to the intended cell location, the use of nanomaterials in the drug delivery system may influence how the patient receives the medication and may assist in mitigating severe side effects. Density functional theory was used to assess the use of boron carbon nitride nanocages (BNCNCs), boron nitride (BNNSs), and boron carbon nitride nanosheets (BNCNSs) as melphalan (Mln) drug carriers in both the gaseous and fluid phases. We systematically examined the dipole moment, density of states, frontier molecular orbital, and optimal adsorption energy to understand the targeted drug delivery potential of these nanostructures. Adsorption energy analysis revealed that in both gas and water media, Mln drug adsorption takes place spontaneously on all the conjugated structures. The occurrence of adsorption energy as physisorbed energy suggests that the process is reversible, and desorption can take place with a much lower energy input. This physical contact is appropriate for the unquestionable unloading of Mln medications to the intended location. The reactivity is higher in BNNSs and BNCNSs, while the stability is higher in BNCNCs. The recovery time shows a shorter time for BNNSs and BNCNSs, while BNCNC shows a potential desorption time in higher temperature. These conclusions are corroborated by the results of the quantum theory of atoms in molecules (QTAIM). After the interaction analysis, it was observed that the BNCNCs can act as potential carriers for the melphalan. From dipole moment analysis, all three nanostructures show a high hydrophilic nature but quite higher in BNCNCs after doping in both media. Overall, all the structures show the potential carrier for melphalan drug. The quantum mechanical approach, or DFT, has been used to study the fundamental structural, electrical, thermodynamic, and other aspects of proposed structures to develop an acceptable Mln drug detector. The adsorbate and all adsorbents were optimized via the hybrid B3LYP functional and the 6-311G + + (2d, p) basis set approach prior to the adsorption process. The Gaussian 09 package was used at 298K as the constant temperature and 1 atm as the constant pressure. The structures are examined using the same functional models for solvation analysis-6-311 G + + (2d, p) and B3LYP-as well as the polarized continuum model (PCM) model as the foundation set. Density of states was studied using GaussSum 3.0 software. The interaction studies QTAIM and RDG were studied using VMD and Multiwfn software.

Charge-Assisted Anion-π Interaction and Hydrogen Bonding Involving Alkylpyridinium Cations.

Competition and cooperation of charge-assisted anion-π interactions and hydrogen bonding were explored in the solid state and in solutions of 1-ethyl-4-carbomethoxypyridinium iodide, the compound utilized by Kosower to calculate solvent polarity Z-indices. X-ray structural analysis of this salt revealed multiple short contacts of iodide anions with hydrogen atoms and aromatic rings of pyridinium cations. Geometric characteristics, quantum theory of atoms in molecules (QTAIM), and noncovalent interaction (NCI) analysis of these contacts indicated comparable interaction energies of the anion-π and hydrogen bonding between iodide and pyridinium cation. 1H NMR (indicating the presence of the hydrogen-bonded complexes) and UV-vis measurements (which were consistent with the formation of anion-π associations) pointed out that both these supramolecular interactions also coexist in solutions. The comparable interaction energies (ΔE) of these modes were confirmed by the DFT computations. Also, while the variations of ΔE with the dielectric constant of the solvents for the complexes of iodide with the neutral π-acceptors were related to the increase of the effective radii of hydrogen- or anion-π bonded iodides, the changes in ΔE for the complexes with pyridinium followed interaction energies between two unit charges. However, the distinction of the bonding in hydrogen-bonded and anion-π complexes of iodide with pyridinium led to a switch of their relative energies with an increase of the polarity of the medium.

Study of the Torquoselectivity of a Set of Unusual Ring‐Opening Electrocyclic Reactions: Determination of the Electronic Bonding Structure Through the Methodologies of Natural Bond Orbital Analysis and Quantum Theory of Atoms in Molecules, and Analysis of the Electronic Reaction Mechanism Through Bond Reactivity Descriptors

ABSTRACTIn this work, we have studied the torquoselectivity of a set of unusual ring‐opening electrocyclic reactions that have not been successfully rationalized using models based on orbital symmetry nor have they been explained by steric hindrance. Firstly, the corresponding transition states have been obtained, and it has been verified that the intrinsic reaction coordinates associated with these transition states are consistent with the reactants and products of the reactions studied. This has allowed us to theoretically calculate the reaction barriers (with their corresponding thermal corrections) and compare them with the corresponding experimental values. In a second step, we have analyzed the electronic bonding structure using the methodologies of Natural Bond Orbital Analysis and Quantum Theory of Atoms in Molecules, searching for interactions that may significantly stabilize the transition states. Finally, we have analyzed the reactivity using a recent model that has allowed us to calculate the corresponding bond reactivity descriptors.