Search

The study examined the interactions between a deep eutectic solvent (DES) containing choline chloride (ChCl) along with ethylene glycol (EG) in a molar ratio of 1:3, and three carboxylic acids: acetic acid, propanoic acid and butanoic acid. The structural stability, electrical characteristics and dynamic behavior of these DES-carboxylic acid systems were investigated utilizing techniques like density functional theory (DFT), natural bond orbital (NBO) analysis and molecular dynamics (MD) simulations. The results showed that the addition of carboxylic acids in the DES framework had a substantial impact on the distribution of electrons and the interactions between molecules in the system. More specifically, the presence of longer alkyl chains in the acids caused a more significant disturbance in the hydrogen-bond network of the DES. This was observed through alterations in the electron localization function (ELF) and noncovalent interaction (NCI) investigations. The results yielded useful insights into the design and implementation of DESs, including improving their stability and reactivity through targeted acid interactions. [ABSTRACT FROM AUTHOR]

The intramolecular [3 + 2] cycloaddition (IM32CA) reactions of azides and diazoalkanes leading to fused tricyclic 1,2,3-triazolines and 1-pyrazolines have been studied at the MPWB1K/6-311G(d,p) computational level within the molecular electron density theory (MEDT). The IM32CA reactions of azides are classified as zw- type following non-concerted one-step mechanism with earlier N1-C5 bond formation implied from the bonding evolution theory (BET) study with the Gibbs free activation energies between 26.3–30.0 kcal mol−1 at 298 K in benzene while that of the diazoalkanes are classified as pmr- type with the earlier C3-C5 bond formation and Gibbs free activation energies between 24.7–29.1 kcal mol−1 at 298 K in n-pentane. The influence of substituent effects on these IM32CA reactions is studied. Azide reactions with minimal global electron density transfer (GEDT) are classified as the null electron density flux (NEDF) while that of the diazoalkanes are classified as forward electron density flux (FEDF). QTAIM analysis and ELF study allow revealing the non-covalent interactions at the TSs. [ABSTRACT FROM AUTHOR]

Electrides, in which anionic electrons are localized independently of the atoms in the compound, have shown promise, especially as catalysts and optoelectronic materials. Here, we present a new computationally designed molecular electride, Li@calix[3]pyrrole (Li@C3P). Electron density and electron localization function analyses unequivocally confirm the existence of localized electride electron density, outside the system, independent of any specific atoms. Non‐covalent interaction plots further validate the character of the isolated localized electron, suggesting that the system can be accurately represented by Li+@calix[3]pyrrole ⋅ e−, denoting its distinct charge separation. The remarkable non‐linear optical properties of Li@C3P, including average polarizability, α‾ ${\bar{\alpha }}$ =412.4 au, first hyperpolarizability, β=4.46×104 au, and second hyperpolarizability, γ∥ ${{\gamma }_{\parallel }}$ =18.40×106 au, are unparalleled in the previously reported and similar Li@C4P molecular electride. Furthermore, energy decomposition analysis in combination with natural orbital for chemical valence theory sheds light on the mechanism of electron density transfer from Li to the C3P cage, yielding the charge‐separated Li@C3P complex. In addition to the electron transfer, a key factor to its electride nature is the electronic structure of the CnP cage, which has its lowest unoccupied molecular orbital located in the void adjacent to the N−H groups at the back of the bowl‐shaped CnP cage. [ABSTRACT FROM AUTHOR]

The study explores the application of molecular electron density theory, focusing on the [2 + 3] cycloaddition mechanisms between nitrile-imine and chalcone or thiochalcone. Density Functional Theory (DFT) calculations employing the B3LYP/6–311(d,p) methodology are utilized to determine activation and reaction energies, as well as reactivity indices. Through investigation of conceptual DFT indices, nitrile-imine is identified as a nucleophile, while chalcone and thiochalcone act as electrophiles in the reaction. The reactions exhibit both chemo- and regiospecifics, as confirmed by Parr functions, Electron Localization Function (ELF) survey, and energetic analysis, consistent with experimental results. ELF analysis suggests a two-phase mechanism for these [2 + 3] cycloadditions. Furthermore, docking studies on the resultant products reveal enhanced interaction energies with proteins due to the presence of oxygen and sulfur atoms, in their interaction with the crystal structure of COVID-19 main protease (PDB ID: 6LU7) and paves a ways for manufacturing innovation. [ABSTRACT FROM AUTHOR]

Purposes In order to obtain additional microstructural information on the ConMoS(n＝1-5) cluster and establish a theoretical foundation for subsequent investigations of its electronic properties and catalytic performance, the atomic interaction relationships and frontier orbital compositions of the cluster are investigated. Methods To accomplish this, density functional theory with the B3LYP functional and def2-TZVP basis set is adopted to optimize the cluster configuration and perform theoretical analysis under various spin multiplicities with the Gaussian09 software package. Findings The results demonstrate the existence of 21 stable configurations. AIM theory, electron localization function, and deformation density are analyzed to obtain information on the degree of internal interaction and electron density transfer trends of the cluster. The findings indicate that covalent bonding interactions between Co, Mo, and S atoms are strong in the internal atom interactions of the cluster, with S atoms exhibiting high localization and low probability of electron escape from the domain. In contrast, Co and Mo atoms exhibit strong delocalization and are likely to exchange electrons with the outside electrons. Through Hirshfeld analysis of atomic contribution rates, it can be observed that metal atoms are the primary contributors to the HOMO and LUMO orbitals, with Mo and Co atoms dominating the frontier orbitals. Overall, covalent bonding is the primary atomic interaction within the cluster, but the strength of these interactions varies. Mo and Co atoms should be the focus in chemical reactions of the cluster.

This work provides a detailed multi‐component analysis of aromaticity in monosubstituted (X = CH3, CH2−, CH2+, NH2, NH−, NH+, OH, O−, and O+) and para‐homodisubstituted (X = CH3, CH2, NH2, NH, OH, and O) benzene derivatives. We investigate the effects of substituents using single‐reference (B3LYP/DFT) and multireference (CASSCF/MRCI) methods, focusing on structural (HOMA), vibrational (AI(vib)), topological (ELFπ), electronic (MCI), magnetic (NICS), and stability (S0–T1 splitting) properties. The findings reveal that appropriate π‐electron‐donating and π‐electron‐accepting substituents with suitable size and symmetry can interact with the π‐system of the ring, significantly influencing π‐electron delocalization. While the charge factor has a minimal impact on π‐electron delocalization, the presence of a pz orbital capable of interacting with the π‐electron delocalization is the primary factor leading to a deviation from the typical aromaticity characteristics observed in benzene. [ABSTRACT FROM AUTHOR]

The mechanism and regioselectivity of [3 + 2] cycloaddition (32CA) reactions of N-methyl-1-phenylmethanimine oxide nitrone 1 and bicyclopropylidene 2 are analyzed using molecular electron density theory (MEDT) at the B3LYP/6–311 + + G(d,p) level. A study of the electron localisation function (ELF) predicts the zwitter-ionic nature of the nitrone, allowing its participation in zw-type 32CA reactions with a high energy barrier that must be surmounted by suitable electrophilic–nucleophilic interactions. The global electronic flux from the strong nucleophilic bicyclopropylidene 2 to the electrophilic nitrone 1 is predicted by an analysis of the CDFT indices. In this 32CA reaction, no new covalent bonds are generated at the TSs, and the mechanism is one-step and kinetically controlled with low asynchronicity in bond formation. The Gibbs free energy of this 32CA reaction in the gas phase is −9.88 and −15.01 kcal.mol−1 for exo and endo path, respectively. The increased thermodynamic stability of the cycloadducts 4 favors the endo regiochemical route. The ELF topological examination at the transition states is in agreement with the predictions of bonding evolution theory (BET) for the endo and exo routes, which point to a one-step process including early transition states. [ABSTRACT FROM AUTHOR]

The [3 + 2] cycloaddition (32CA) reactions of a series of pyridinium bis(methoxycarbonyl)methylides (PMYs) and pyridinium dicyanomethylides (PCYs) with cyclooctyne to generate indolizines have been studied within the Molecular Electron Density Theory (MEDT). Interestingly, the electronic structure of these azomethine ylides (AYs) revealed from the topological analysis of the electron localization function (ELF) differs considerably from that of the simplest AY and accordingly, the molecular reactivity is changed. Consequently, the corresponding 32CA reactions of PCYs and PMYs require refluxing toluene conditions to overcome the high activation barrier contrary to the unappreciable energy cost demanded by the simplest AY. This is explained by the analysis of conceptual DFT indices characterizing the ambiphilic character of the PMYs and PCYs classified as strong electrophiles and strong nucleophiles within the standard reactivity scales. The 32CA reactions of PCYs are more facile relative to the PMYs in agreement with the experimental outcome. These polar 32CA reactions show the global electron density transfer (GEDT) higher than 0.2 e and proceed through one-step mechanism with highly asynchronous TSs in which the new covalent bond formation has not been started. Herein, we report the first MEDT study to comprehend the reactivity of pyridinium methylides towards 32CA reactions leading to indolizines. [ABSTRACT FROM AUTHOR]

The intramolecular [3 + 2] cycloaddition (32CA) reactions of allenic nitrones have been studied within the molecular electron density theory (MEDT) at the MPWB1K/6-311G(d,p) computational level. These zwitter-ionic type 32CA reactions show high activation free energies between 22.2 and 34.9 kcal mol−1 in ethanol consistent with their predicted non-polar character and follow one-step mechanism with highly asynchronous transition states. Interestingly, when the nitrone and the allene moieties are separated by two methylene units, the [3 + 2] addition is energetically feasible along the C5-C6 terminal double bond of the allene, while the presence of four methylene units change the cyclization selectivity towards the internal C4-C5 double bond of the allene. This is in complete agreement with the experimental outcomes. The molecular mechanism study in terms of bonding evolution theory (BET) shows varied electron density changes along these two reaction paths. Finally, the topological analysis of AIM (atoms-in-molecules) reveals the presence of non-covalent interactions at the interatomic bonding regions of the transition states, which agrees well with the electron localization function analysis and the forming C–C and C-O bond distances. [ABSTRACT FROM AUTHOR]

The influence of ethylene substitution and the tether length between the two reacting counterparts on the selectivity and reactivity of the intramolecular [3 + 2] cycloaddition (IM32CA) reactions of cyclic nitrones leading to tricyclic isoxazolidines have been studied within the Molecular Electron Density theory at the MPWB1K/6‐311G(d,p) computational level. These zw‐type IM32CA reactions follow one‐step mechanism, and the activation barrier decreases with the introduction of electron withdrawing (EW) substituent at the alkene moiety in both the intramolecular and intermolecular versions. The IM32CA reactions involving unsubstituted alkene have non‐polar character with minimal electron density flux classified as null electron density flux type, while that involving the EW nitro substituted ethylene is more facile with a strong electron density flux from the nitrone to the ethylene moiety, classified as forward electron density flux type. The increase in the polar character of the IM32CA reaction decreases the activation Gibbs free energies associated with these intramolecular processes, while the highly polar IM32CA reactions are disfavored with respect to the intermolecular ones. Interestingly, the preferred regioselectivity observed in low polar IM32CA reactions having three methylene units between the nitrone and ethylene frameworks is reversed to that in nitrones separated with four methylene units, in conformity with the experimental outcome. Finally, electron localization function and quantum theory of atoms‐in‐molecules studies reveal that, in general, these IM32CA reactions involve early transition state structures in which the formation of new C‐C and C‐O single bonds have not yet started. [ABSTRACT FROM AUTHOR]

The pharmaceutical proprieties of the 2,6-dimethylpiperazine-1,4-diium oxalate oxalic acid compound have been studied and the relevant drug design has been considered. The investigated organic compound with formula (2,6-(CH3)C4H10N2)2(C2O4)2·H2C2O4 (2DPOA) has been synthesized by slow evaporation technique at room temperature of a molar ratio 3:2 mix of oxalic acid and 2,6-dimethylpiperazine. Then 2DPOA has been characterized by IR, 13C NMR, UV–visible and the DFT calculation at the B3LYP level of theory has been made. The molecular structure and parameters (bond angles and lengths) of the molecule have been optimized using the Gaussian 09 software and compared with the XRD data. The atoms-in-molecules (AIM), electron localization function (ELF), and localized orbital locator (LOL) methods have been utilized to determine the types and nature of noncovalent interactions present within the 2DPOA molecule. These methods offer insights into the characteristics and behavior of these interactions. Furthermore, the presence of these interactions has been confirmed through the Hirshfeld Surface (HS) and reduced density gradient (RDG) analysis. The NBO analysis is employed to assess the charge exchange occurring within the studied compound. The molecular reactive sites have been examined using the molecular potential surface and Mulliken atomic charges. The energy gap between HOMO–LUMO and chemical properties of 2DPOA have been determined within the frontier molecular orbital theory. The UV–Vis spectrum of the 2DPOA molecule has been recorded and examined. The calculated and experimental infrared absorption and nuclear magnetic resonance spectra of 2DPOA molecule have been investigated. Finally, the molecular docking simulation has been used to find novel inhibitors and drugs for the cancer and epilepsy disease treatment. [ABSTRACT FROM AUTHOR]

The [3+2] cycloaddition (32CA) reaction between cyclic azomethine ylide (generated from N-phenacylquinolinium bromide) and N-arylmaleimide, leading to pyrrolo[1,2-a]quinolone, has been investigated using the Molecular Electron Density Theory at the B3LYP/6-311++G(d,p) computational level with D3 correction. This study focuses on the zwitter-ionic type 32CA reaction, highlighting its polar character with the electronic flux from the azomethine ylide to the alkene. The reaction proceeds with complete endo-stereoselectivity, and the activation parameters show minimal variations in different solvents, consistent with experimental observations. The activation energy is associated with the depopulation of the N2–C1 and C4–C5 bonding regions, formation of non-bonding electron density at N2 nitrogen and creation of pseudoradical centers at C3, C4 and C5. These findings suggest that the formation of new covalent bonds does not occur at the transition states, in line with the presence of non-covalent interactions at the interatomic bonding regions, as revealed by the topological analysis of the Quantum Theory of Atoms-in-Molecules. [ABSTRACT FROM AUTHOR]

The nature of chemical bonding in BeF− anion is investigated quantum mechanically. Topological analyses within the realm of quantum theory of atoms in molecules (QTAIM) and electron localization function (ELF) clearly establish the bonds as having "Charge shift" character. The laplacian of electron density is significantly positive and the basin population is lower with a large covariance, indicating significant charge shift character. Detailed analysis reveals no multiple bonding character in this anion and its heavier analogues. [ABSTRACT FROM AUTHOR]

Development of novel self-cleaning technologies, especially those based on semiconductor photocatalysis system, is one of the most important research problems in environmental cleanup. Titanium dioxide (TiO2) is a well-known semiconductor photocatalyst that has a strong photocatalytic activity in the ultra-violet part of the spectrum while its photocatalytic efficiency is very limited within the visible range due to its large band gap. In the field of photocatalytic materials, doping is an efficient method to increase the spectral response and promote charge separation. However, the type of dopant is not the only important factor, but also its position in the material lattice. In the present study, we have carried out first-principle calculations based on density functional theory to explore how particular doping configuration, such as Br or Cl doping at an O site, may influence the electronic structure and the charge density distribution within rutile TiO2. Furthermore, optical properties such as the absorption coefficient, the transmittance, and reflectance spectra have also been derived from the calculated complex dielectric function and examined to see whether this doping configuration has any effect on the use of the material as a self-cleaning coating on photovoltaic panels. [ABSTRACT FROM AUTHOR]

[3+2] cycloaddition reactions play a crucial role in synthesizing complex organic molecules and have significant applications in drug discovery and materials science. In this study, the [3+2] cycloaddition (32CA) reactions of N-methyl-C-4-methyl phenyl-nitrone 1 and 2-propynamide 2, which have not been extensively studied before, were investigated using molecular electron density theory (MEDT) at the B3LYP/6–311++G(d,p) level of theory. According to an electron localization function (ELF) study, N-methyl-C-4-methyl phenyl-nitrone 1 is a zwitterionic species with no pseudoradical or carbenoid centers. Conceptual density functional theory (CDFT) indices were used to predict the global electronic flux from the strong nucleophilic N-methyl-C-4-methyl phenylnitrone 1 to the electrophilic 2-propynamide 2 functions. The 32CA reactions proceeded through two pairs of stereo- and regioisomeric reaction pathways to generate four different products: 3, 4, 5, and 6. The reaction pathways were irreversible owing to their exothermic characters: −136.48, −130.08, −130.99, and −140.81 kJ mol−1, respectively. The enthalpy of the 32CA reaction leading to the formation of cycloadduct 6 was lower compared with the other path owing to a slight increase in its polar character, observed through the global electron density transfer (GEDT) during the transition states and along the reaction path. A bonding evolution theory (BET) analysis showed that these 32CA reactions proceed through the coupling of pseudoradical centers, and the formation of new C-C and C-O covalent bonds did not begin in the transition states. [ABSTRACT FROM AUTHOR]

This theoretical study, performed using density functional theory at the B3LYP/6-311+G(d,p) level, shows that the most likely route to obtain 3-phenyl[1,2,4]oxadiazolo[4,5-a]benzimidazole from the reaction of 2-chlorobenzimidazole with benzonitrile oxide implies the presence of anionic species. A concerted [3+2] cycloaddition reaction on the imidoyl group of 2-chlorobenzimidazole is not possible. The presence of a polar protic solvent (MeOH) favors the reaction. The analysis of the Wiberg indices shows that the transition states are earlier in MeOH than in THF or gas phase. Finally, topological analysis of the electron localization function indicates that the formation of the N4–C3 and C5–O bonds and the breaking of the C5–Cl bond in the preparation of 3-phenyl[1,2,4]oxadiazolo[4,5-a]benzimidazole are marked for each by the presence of an asynaptic basin V(Asyn) and proceed through tetrahedral intermediates, indicating the nonconcerted nature of the mechanism. These results are in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Context: [2,2′-Bi(1,3,4-oxadiazole)]-5,5′-dinitramide (ICM-101), 2,4,6-triamino-5-nitropyrimidine-1,3-dioxide (ICM-102), and 6-nitro-7-azido-pyrazol[3,4-d][1,2,3]triazine-2-oxide (ICM-103) are excellent China-made explosives, but their performance under external electric fields (EEF) has never been explored, especially sensitivity. To study the induction effect of EEF on it, the chemical reactivity, electron localization function (ELF), spectrum, and other parameters were calculated by density functional theory. The results show that the increasing EEF can weaken the △EHOMO-LUMO (△EHOMO-LUMO = EHOMO-ELUMO) materials, making the stability worse and the sensitivity higher. The proportion of the positive electrostatic surface potential area is also smaller under the increasing EEF, indicating that ICM molecules are becoming more and more unstable. The ELF and localized orbital locator (LOL) decrease with the increase of EEF strength, which suggests that the trigger bond length increases, the EBDE decreases, and the molecular sensitivity increases. When the intensity of EEF increases, the absorption peak of the molecular spectrum gradually redshifts, and even a weak new absorption peak appears, indicating that the color of the material may change. Finally, EEF strength affects electron density, nitro charge, and chemical reactivity parameters. Methods: Gaussian 16 software was used for calculation. The calculation levels are B3LYP/6-311G+ (d, p) and B3LYP/Def2-TZVPP. The optimized structure has a local true minimum energy on the potential energy surface and no imaginary frequency. Multiwfn 3.8 and VMD 1.9.3 were used in this work to analyze the ICM series of energetic material wave functions. The strength range of EEF is 0.000–0.016 a.u., and the increasing gradient is 0.002 a.u. [ABSTRACT FROM AUTHOR]

In this study, optical response, lithiation and charge transfer in existing M2SnC MAX phases with electron localization function (ELF) were investigated for the first time using the density functional theory (DFT). Calculations show that the non-zero value of ε1(0) is an indication of the large availability of free charge carriers in these metallic systems. High reflection of light at the low frequencies indicates the high conductivity and low absorption power of the studied materials. In the visible light region, the average reflectivity of M2SnC is more than 40%, making them potential coating materials for reducing solar heating with greater possibility for Nb2SnC. M2SnC phases are optically anisotropic. The static absorption coefficient represents the universal non-zero value for the hexagonal M2SnC phases. The Plasma frequency is found to be slightly larger for ⟨001⟩ polarization. Lithium (Li) incorporation into M2SnC show that the formation energy required for Li incorporation into Lu2SnC is low, and therefore, it should be suitable for use as an anode in battery. The chemical bonds (M–X) between transition metal ions and carbon are expected to be strong localized bonds as predicted from the ELF maps. The bonds (M–Sn) between transition metal M and A-group element Sn are less localized and more spread out, possibly pointing to a weaker bond. The magnitude of the Bader charges is significantly larger compared to the Mulliken and Hirshfeld charges. According to Bader analysis, maximum charge transfer occurs in Hf2SnC and minimum charge transfer occurs in V2SnC.

Recently, triboelectric nanogenerators (TENGs) have been widely used for energy harvesting and self-powered sensing due to their significant and unique advantages. However, the intrinsic mechanisms that contribute to tribo-electricification (TE) between two materials remain as a subject of rigorous debate. In addition to predicting the qualitative charge transfer in solid-solid contacts based on the difference in the work functions of the two moieties constituting the interface, we argue that it is essential to obtain atomic-level, first principles, insights into the bonding properties, quantitative charge transfer, and the possible presence of a electrostatic potential barrier at the interface to fully understand the TE mechanism of a system. We have utilized dispersion-corrected density functional theory (DFT) calculations in this study to systematically investigate the TE potential of bare surface Ti 3 C 2 and Ti 3 N 2 2D MXene monolayers and their surface functionalized modifications Ti 3 C 2 R 2 and Ti 3 N 2 R 2 (where R = -O, -OH, or -F) in contact with Al(111). For these heterostructures, we have analyzed the adhesive energy of the interfaces, the nature of interaction through the electron localization function (ELF), and the charge distribution, which have revealed distinct characteristics of MXene/Al contacts for these monolayer/metal interfaces at their equilibrium distance and the changes in their properties under uniaxial pressure. Among all the metallic 2D MXene variants investigated in this study, we have determined that Ti 3 C 2 F 2 /Al and Ti 3 N 2 F 2 /Al interfaces show exceptional potential for TE. [Display omitted] • A first-principles study on the mechanism of MXene-Al contact electrification is performed. • MXenes with different surface functionalizations are assessed for their role in the contact electrification process. • Crucial insights into different types of interface contacts and their potential in contact electrification are revealed. • A comprehensive assessment of interface barrier variations and their role in the dynamics of contact electrification is performed. [ABSTRACT FROM AUTHOR]

The regioselective synthesis of a potent antiviral sugar nucleoside isoxazole analogue in the [3+2] cycloaddition (32CA) reaction of acetonitrile- -N-oxide (ANO) and acetyl-protected 5-ethynyl-2’-deoxyuridine (EDU) has been studied at the MPWB1K/6-311G(d,p) level within perspective of the molecular electron density theory (MEDT). From an electron localization function (ELF) analysis, ANO is classified as a zwitterionic species devoid of any pseudoradical or carbenoid centre. The ortho regioisomer is energetically preferred over the meta one by the activation enthalpy of 21.7–24.3 kJ mol-1, suggesting complete regioselectivity in agreement with the experiment. The activation enthalpy increases from 53.9 kJ mol-1 in the gas phase to 71.5 kJ mol-1 in water, suggesting more facile reaction in low polar solvents. The minimal global electron density transfer (GEDT) at the TSs suggests non-polar character and the formation of new covalent bonds has not been started at the located TSs, showing non-covalent intermolecular interactions from an atoms-in- -molecules (AIM) study and in the independent gradient model (IGM) isosurfaces. The AIM analysis shows more accumulation of electron density at the C–C interacting region relative to the C–O one, and earlier C–C bond formation is predicted from a bonding evolution theory (BET) study.

The high-pressure structures and properties of MH2 (M = Nb, Ta) are explored through an ab initio evolutionary algorithm for crystal structure prediction and first-principles calculations. It is found that NbH2 undergoes a phase transition from a cubic Fm3¯m structure with regular NbH8 cubes to an orthorhombic Pnma structure with fascinating distorted NbH9 tetrakaidecahedrons at 48.8 GPa, while the phase transition pressure of TaH2 from a hexagonal P63mc phase with slightly distorted TaH7 decahedron to an orthorhombic Pnma phase with attractive distorted TaH9 tetrakaidecahedrons is about 90.0 GPa. Besides, the calculated electronic band structure and density of states demonstrate that all of these structures are metallic. The Poisson’s ratio, electron localization function, and Bader charge analysis suggest that these phases possess dominant ionic bonding character with the effective charges transferring from the metal atom to H. From our electron–phonon calculations, the calculated superconducting critical temperature Tc of the Pnma-NbH2 is 6.903 K at 50 GPa. Finally, via the quasi-harmonic approximation method, the phase diagrams at pressure up to 300 GPa and temperature up to 1000 K of MH2 (M = Nb, Ta) are established, where the transition pressure of Fm3¯m-NbH2 → Pnma-NbH2 and P63mc-TaH2 → Pnma-TaH2 were found to decrease with increasing temperature.

The [3+2] cycloaddition (32CA) reaction of N-methyl-C-(4-hydroxylphenyl) nitrone 1 and maleic anhydride 2 has been investigated using molecular electron density theory (MEDT) at the MPWB95/6-311++G(d,p) computational level. This 32CA reaction undergoes two stereo- and stereoisomeric reaction paths to form two different products 3 and 4. An electron localization function (ELF) study predicts that the N-methyl-C-(4-hydroxylphenyl) nitrone 1 has a zwitterionic character and it takes place through a one-step mechanism, with activation enthalpies in between 17.48 and 23.41 kJ mol−1 in the gas phase. The CDFT indices are used to forecast the global electron density flux from the strong nucleophilic N-methyl-C-(4-hydroxylphenyl) nitrone 1 to the electrophilic maleic anhydride 2. These exergonic 32CA reactions have negative Gibbs free energy along the endo and exo stereochemical routes. The endo stereochemical process is favored over the exo stereochemical pathway due to the increased thermodynamic stability of the cycloadduct. Bonding evolution theory (BET) predictions for the endo and exo routes indicate a one-step process with early transition states, which is consistent with the ELF topological investigation at the transition states. [ABSTRACT FROM AUTHOR]

[3+2] cycloaddition reactions play a crucial role in synthesizing complex organic molecules and have significant applications in drug discovery and materials science. In this study, the [3+2] cycloaddition (32CA) reactions of N-methyl-C-4-methyl phenyl-nitrone 1 and 2-propynamide 2, which have not been extensively studied before, were investigated using molecular electron density theory (MEDT) at the B3LYP/6–311++G(d,p) level of theory. According to an electron localization function (ELF) study, N-methyl-C-4-methyl phenyl-nitrone 1 is a zwitterionic species with no pseudoradical or carbenoid centers. Conceptual density functional theory (CDFT) indices were used to predict the global electronic flux from the strong nucleophilic N-methyl-C-4-methyl phenylnitrone 1 to the electrophilic 2-propynamide 2 functions. The 32CA reactions proceeded through two pairs of stereo- and regioisomeric reaction pathways to generate four different products: 3, 4, 5, and 6. The reaction pathways were irreversible owing to their exothermic characters: −136.48, −130.08, −130.99, and −140.81 kJ mol−1, respectively. The enthalpy of the 32CA reaction leading to the formation of cycloadduct 6 was lower compared with the other path owing to a slight increase in its polar character, observed through the global electron density transfer (GEDT) during the transition states and along the reaction path. A bonding evolution theory (BET) analysis showed that these 32CA reactions proceed through the coupling of pseudoradical centers, and the formation of new C-C and C-O covalent bonds did not begin in the transition states.

In the present work, the electronic structure and stability of acyclic nitronic acids were studied. Depending on the different substituents, the analyzed compounds can be classified as pseudo(mono)radical or zwitterionic nitronic acids. ELF topological analysis of the electron density of nitronic acids containing in their structure EWG substituent (-NO 2 (1); –COOCH 3 (2); –NO 2 , –CH 3 (5); –COOCH 3 , –OCH 3 (6); –NO 2 , –H (7); –COOH 3 , –H (8)) permits establishing a pseudo(mono)radical electronic structure with a pseudoradical centers at the C1 carbon atom. In turn, ELF analysis of the compounds 3 , 4, 9 and 10 containing substituent belonging to the EGD group (-CH 3 (3); –OCH 3 (4); –CH 3 , –H (9); –COH 3 , –H (10)) and based on the presence of C1–N2 double bond and absence of pseudoradical centre allows for the classification of these compounds as a zwitterionic nitronic acids. Nitronic acids containing EDG substituents in their structure are the most stable among the analyzed nitronic acids. In turn, nitronic acids containing EWG groups are characterized by higher reactivity in chemical reactions compared to other analyzed nitronic acids. [Display omitted] • The electronic structure and stability of acyclic nitronic acids were studied. • Depending on the different substituents, the analyzed compounds can be classified as pseudo(mono)radical or zwitterionic nitronic acids. • ELF topological analysis of the electron density of nitronic acids containing in their structure EWG substituent permits establishing a pseudo(mono)radical electronic structure. • ELF analysis of the compounds containing substituent belonging to the EGD group and based on the presence of C1–N2 double bond and absence of pseudoradical centre allows for the classification as a zwitterionic nitronic acids. [ABSTRACT FROM AUTHOR]

We investigated the flow of electron density along the cyclocondensation reaction between ethyl acetate 2‐oxo‐2‐(4‐oxo‐4H‐pyrido[1.2‐a]pyrimidin‐3‐yl) polyazaheterocycle (1) and ethylenediamine (2) at the ωB97XD/6–311++G(d,p)computational method within of bond evolution theory (BET). The exploration of potential energy surface shows that this reaction has three channels (1–3) with the formation of product 3 via channel‐2 (the most favorable one) as the main product and this is in good agreement with experimental observations. The BET analysis allows identifying unambiguously the main chemical events happening along channel‐2. The mechanism along first step (TS2‐a) is described by a series of four structural stability domains (SSDs), while five SSDs for the last two steps (TS2‐b and TS2‐c). The first and third steps can be summarized as follows, the formation of N1‐C6 bond (SSD‐II), then, the restoration of the nitrogen N1 lone pair (SSD‐III), and finally, the formation of the last O1‐H1 bond (SSD‐IV). For the second step, the formation of hydroxide ion is noted, as a result of the disappearance of V(C6,O7) basin and the transformation of C6‐N1 single bond into double one (SSD‐IV). Finally, the appearance of V(O7,H2) basin lead to the elimination of water molecule within the last domain is observed. [ABSTRACT FROM AUTHOR]

The [3+2] cycloaddition (32CA) reactions of strongly nucleophilic norbornadiene (NBD), with simplest diazoalkane (DAA) and three DAAs of increased electrophilicity, have been studied within the Molecular Electron Density Theory (MEDT) at the MPWB1K/6-311G (d,p) computational level. These pmr-type 32CA reactions follow an asynchronous one-step mechanism with activation enthalpies ranging from 17.7 to 27.9 kcal·mol−1 in acetonitrile. The high exergonic character of these reactions makes them irreversible. The presence of electron-withdrawing (EW) substituents in the DAA increases the activation enthalpies, in complete agreement with the experimental slowing-down of the reactions, but contrary to the Conceptual DFT prediction. Despite the nucleophilic and electrophilic character of the reagents, the global electron density transfer at the TSs indicates rather non-polar 32CA reactions. The present MEDT study establishes the depopulation of the N–N–C core in this series of DAAs with the increase of the EW character of the substituents present at the carbon center is responsible for the experimentally found deceleration.

[3+2] cycloaddition reaction of C-(pyridin-3-yl)-N-phenylnitrone and 2-propen-1-ol yields stereochemically defined potent antinociceptive isoxazolidine derivative. Computational quantum calculations (CQC) are performed for this synthesis to predict the polar character, mechanism and selectivity within the framework of molecular electron density theory (MEDT). Topological analysis of the electron localization function (ELF) classifies the nitrone as a zwitter-ionic(zw-) type three atom component (TAC) showing absence of any pseudoradical or carbenoid centre. Four reaction channels corresponding to the possible regio- and stereoselective pathways are studied at DFT/ /B3LYP/6-311G(d,p) level of theory. The reaction follows one-step mechanism with asynchronous transition states and the computed activation energies agree well with experimental data. The reaction can be differentiated into nine ELF topological phases, with faster C–C bond formation. Global electron density theory (GEDT) at the favoured transition state and conceptual density functional theory (CDFT) indices at the ground state of the reagents indicate non-polar character. Non-covalent interactions are predicted by atoms-in-molecules (AIM) analysis and non-covalent interaction (NCI) plots at the transition states.

In this study, we employ an evolutionary algorithm in conjunction with first-principles density functional theory (DFT) calculations to comprehensively investigate the structural transitions, electronic properties, and chemical bonding behaviors of XI 3 compounds, where X denotes phosphorus (P) and arsenic (As), across a range of elevated pressures. Our computational analyses reveal a distinctive phenomenon occurring under compression, wherein the initially trigonal structures of PI 3 (P 6 3 ) and AsI 3 (R-3) undergo an intriguing transformation, leading to the emergence of six-coordinated monoclinic phases (C2/m) at 6 GPa and 2 GPa for PI 3 and AsI 3 , respectively. These high-pressure phases exhibit their stability up to 10 GPa for PI 3 and 12 GPa for AsI 3 . Notably, the resulting structures at elevated pressures bear striking resemblance to the widely recognized six-coordinated octahedral BiI 3 crystal configuration observed at ambient conditions. Our investigation further underscores the pivotal role of pressure-induced reactivity of the lone-pair electrons in PI 3 and AsI 3 , facilitating their enhanced stereochemical reactivity and thereby enabling higher six-fold coordination. Complementary analyses employing electron localization function (ELF) and density of states (DOS) effectively delineate the progression towards augmented coordination in PI 3 and AsI 3 with increasing pressure. While the phenomenon of heightened coordination is conventionally associated with heavier pnictide iodides such as SbI 3 and BiI 3 under ambient conditions due to heightened ionic character and relativistic effects in bismuth (Bi) and antimony (Sb), our findings accentuate that analogous structural transformations can also be induced in lighter elements like phosphorus (P) and arsenic (As) under the influence of pressure., (© 2024 Wiley-VCH GmbH.)

The substituted arynes, an imine compound, and atmospheric CO2 have been considered as the starting materials in a theoretical study of a CO2 transformation to N‐containing heterocycles. Functional groups show substantial effects on the studied mechanisms. The obtained results show that Mechanism A, in which the imine compound is added to arynes, is the most probable mechanism. Kinetic studies are performed by the energetic span model. The transition stats of Step 1 and the corresponding intermediates are the turnover‐frequency determining transition state (TDTS) and turnover‐frequency determining intermediate (TDI), respectively. Also, electron localization function (ELF) analyses reveal that the electron densities of developing monosynaptic basins on the carbon atom (V[C]) at the transition state show a good linear correlation with the calculated energy values of TDTS. Electron‐withdrawing and electron‐releasing characters of the substituents affect the TDTS energy values. [ABSTRACT FROM AUTHOR]

In this present work, structural, spectral, and electronic properties of newly synthesized 1-phenyl-3(4-methoxyphenyl)-2-propenone compounds are examined by making the use of the density functional theory Gaussian 16 W tool. Optimized structural parameters, topological properties (Electron localization function and Localized orbital locators) are investigated in the aqueous phase. Experimental spectroscopic (Fourier transform infrared spectroscopy and Fourier transform Raman spectroscopy) investigation and quantum chemical analysis are performed on the title compound. Non-covalent interaction analysis is performed in different solutions. Bandgap energies are calculated from molecular orbital energies in various solvent atmospheres. Electrophilic site strength of headline compound is identified and analyzed from molecular electrostatic potential surface and Mulliken atomic charges analysis in different polar and non-polar liquids. Experimental and theoretical chemical shift values are recorded and predicted in a nonpolar solvent by Nuclear magnetic resonance spectral investigation. Hyperconjucative interactions are studied from the natural bond orbitals method. Drug likeness and mol inspiration properties are calculated. Moreover, a Molecular docking study is performed with breast cancer and anti-malarial receptors. [ABSTRACT FROM AUTHOR]

In this study, all electron relativistic calculations with 4-component Dirac–Coulomb–Breit (DCB), 4-component Dirac–Coulomb (DC), Dyall's spin-free Dirac–Coulomb (SFDC), exact two-component (X2C) and Levy–Leblond non-relativistic hamiltonians calculations were performed in polyatomic closed shell E121X3 (X = F, Cl, Br) within density functional theory (DFT) with hybrid functional B3LYP, where E121 is the superheavy element (SHE) with Z = 121. The aims of this study were to investigate relativistic effects in polyatomic E121X3 (X = F, Cl, Br) and verify the importance of Gaunt effects. The results demonstrate that although the effect of Gaunt interaction is small on change equilibrium bond lengths and bonding, it is important to obtain reliable vibrational frequencies. Moreover, it is possible to use the X2C spin-free hamiltonian to lower computational costs in a fully relativistic investigation of polyatomics including the SHE of the 8th period. Finally, a comparison between electron localization function (ELF) analysis and Mulliken population analysis suggests bonding similarity between LaBr3 and E121Br3. [ABSTRACT FROM AUTHOR]

Confinement and pressure have profound effects on the electronic structure of atoms and molecules. In this work, we study the effects of a harmonic confinement on the electronic structure of the lithium dimer. To do this, we use quantum chemistry methods that include much of the electronic correlation (Coupled Cluster and CASSCF). The confinement induces a change, with respect to the free molecule, in the electronic configuration of Li2. There is a critical confinement value for which the ground state stops being the singlet 1∑g+ and becomes the triplet 3∑g−. We also study changes in the bonding pattern. Li2 conserves the bonding pattern of the free molecule independently of the strength of confinement, as it is revealed by the electron localization function. [ABSTRACT FROM AUTHOR]

Based on the quantum chemical topology of the modified electron localization function ELFx, an efficient and robust mechanistic methodology designed to identify the favorable reaction pathway between two reactants is proposed. We first recall and reshape how the supermolecular interaction energy can be evaluated from only three distinct terms, namely the intermolecular coulomb energy, the intermolecular exchange‐correlation energy and the intramolecular energies of reactants. Thereafter, we show that the reactivity between the reactants is driven by the first‐order variation in the coulomb intermolecular energy defined in terms of the response to changes in the number of electrons. Illustrative examples with the formation of the dative bond B‐N involved in the BH3NH3 molecule and the typical formation of the hydrogen bond in the canonical water dimer are presented. For these selected systems, our approach unveils a noticeable mimicking of Edual onto the DFT intermolecular interaction energy surface calculated between the both reactants. An automated reaction‐path algorithm aimed to determine the most favorable relative orientations when the two molecules approach each other is also outlined. [ABSTRACT FROM AUTHOR]

Three novel isostructural equiatomic gold tetrel pnictides, AuSiAs, AuGeP, and AuGeAs, were synthesized and characterized. These phases crystallize in the noncentrosymmetric (NCS) monoclinic space group Cc (no. 9), featuring square‐planar Au within cis‐[AuTt2Pn2] units (Tt=tetrel, Si, Ge; Pn=pnictogen, P, As). This is in drastic contrast to the structure of previously reported AuSiP, which exhibits typical linear coordination of Au with Si and P. Chemical bonding analysis through the electron localization function suggests covalent two‐center two‐electron Tt−Pn bonds, and three‐center Au−Tt−Au and Au−Pn−Au bonds with 1.6 e− per bond. X‐ray photoelectron spectroscopy studies support the covalent and nonionic nature of Au−Pn and Au−Tt bonds. The title materials were found to be n‐type narrow‐gap semiconductors or semimetals, with nearly temperature‐independent electrical resistivities and low thermal conductivities. A combination of the semimetallic properties with tunable NCS structure provides opportunities for the development of materials based on gold tetrel pnictides. [ABSTRACT FROM AUTHOR]

The ground and lowest singlet excited state geometries of selected (para -C5H4X)Ir(PH3)3 iridabenzene complexes (para -substituent = NH2, OMe, Me, H, F, Cl, CCl3, CF3, NO2) are optimized using the MPW1PW91 procedure employing the LanL2DZ(Ir) and 6-311G(d, p) (C, H, N, O, P, F, Cl, P) basis sets. The excited state is generated using the time-dependent density function method. The effects of electron-donating groups and electron-withdrawing groups on the energy, atomization energy, rotational constants, and frontier orbital energies in the first singlet excited state (S1) of iridabenzene are investigated and compared to those of the ground state (S0). The Ir–C and Ir–P bonds in the studied molecules are analyzed by electron localization function and localized-orbital locator methods. The correlations between the Ir-C and Ir–P bond distances, electron localization function, and localized-orbital locator values Hammett constants (σp) and dual parameters (σI and σR) are given for the two studied states. The para -delocalization index is used for investigation of the aromaticity of the studied complexes. [ABSTRACT FROM AUTHOR]

The [3 + 2] cycloaddition (32CA) reactions of 1‐pyrroline‐1‐oxide with acetylene and with a series of four symmetrically disubstituted acetylenes (XC ≡ CX, X = CH3, NH2, OH, F), leading to 4,5‐disubstituted bicyclic 4‐isoxazolines, have been studied within molecular electron density theory at the B3LYP‐D3/6‐311++G(d,p) computational level. These 32CA reactions take place through a one‐step mechanism, with activation enthalpies in toluene between 24.4 (X = NH2) and 12.9 (X = F) kcal mol−1. Due to the strong exergonic character of these 32CA reactions, between −12.0 and −47.6 kcal mol−1, they are irreversible. The 32CA reaction of difluoroacetylene, involving fluorine as the most electronegative atom of this series attached to the acetylene carbons, presents the lowest activation enthalpy due to the increase of the polar character of this 32CA reaction, evidenced by the analysis of the global electron density transfer at the corresponding transition state structure. The topological analysis of the electron localization function along the reaction paths of these 32CA reactions allows us to characterize them as the zwitterionic‐type ones. The formation of the new CC and CO single bonds takes place at the end of the reactions through the coupling of pseudoradical centers. [ABSTRACT FROM AUTHOR]

Three tin oxide halides, Sn7O4Cl6, Sn7O4Br6, and Sn4OI6, were synthesized by solid‐state reactions of SnO and SnX2 (X=Cl, Br, I) at 300 °C. Crystal structures were solved and refined from single crystal X‐ray diffraction data, revealing the presence of cubane‐like [Sn4O4] units in the structures of Sn7O4Cl6 and Sn7O4Br6. The electronic structure of Sn7O4Cl6 was analyzed by DFT band structure calculations and the electron localization function (ELF). [ABSTRACT FROM AUTHOR]

The strain promoted [3+2] cycloaddition reaction of benzyl azide with cyclooctyne has been studied within the molecular electron density theory (MEDT) at the MPWB1K/6-311G(d,p) computational level. This reaction takes place through a one-step mechanism with activation free energy of 27.1 kcal mol-1 in gas phase and 30.2 kcal mol-1 in acetonitrile. The activation enthalpies are 13.8 and 16.5 kcal mol-1, respectively in gas phase and acetonitrile. Topological analysis of the electron localization function (ELF) of the reagents shows zwitter-ionic type character of this reaction. The calculated activation free energy is lowered by 5.0 kcal mol-1 in gas phase and 4.2 kcal mol-1 in acetonitrile relative to the analogues reaction with acetylene. The corresponding activation enthalpy is lowered by 6.4 kcal mol-1 in gas phase and 5.9 kcal mol-1 in acetonitrile. A comparative bonding evolution theory (BET) analysis of the two reactions reveals lower energy requirements for the depopulation of the alkyne framework and the formation of pseudoradical centers along the reaction path of the cyclooctyne reaction. Topological analysis of the ELF and the Quantum Theory of Atoms in Molecules (QTAIM) parameters reveal early transition states with no covalent bonding interactions between the reacting nuclei, which is consistent with the forming bond distances greater than 2 Å in each case. [ABSTRACT FROM AUTHOR]

This study aims to investigate the efficiency and effectiveness of some of the intramolecular boron‐nitrogen frustrated Lewis pairs (B/N‐FLPs) as metal‐free organocatalysts in CO2 conversion. A two‐step mechanism was considered for the catalytic reaction, including the hydrogen splitting by the FLPs (step 1) and reduction reaction by the hydrogenated FLPs (FLPH2s) (step 2). The boron atom in the studied FLPs is bonded to various substituents, which have substantial effects on the performance of the B atom as a Lewis acid. The studied FLPs are classified into two distinguished categories. The quantum theory of atoms in molecules method and natural bond orbital analyses showed that more occupation of the p orbital of boron by the substituted groups causes the reluctance of the boron atom in hydrogen splitting and acceptation of electron density of the hydride ion. However, molecular electrostatic potential at the nuclear positions was used as a novel descriptor in justification of the kinetic behavior of FLPs in hydrogen splitting and reduction reactions. Obtained ΔΔVn values in the donor‐acceptor interacting system, as an outcome of the electrostatic potential concept, show a remarkable linear correlation with the calculated barrier energies (∆G≠) of hydrogen splitting and reduction reactions. This linear correlation can be observed for ΔΔVn values vs electron localization function and localized orbital locator of the developing bond at transition states 1 and 2. Finally, it is concluded that similar activation energies for hydrogen splitting and reduction reactions can be an appropriate criterion for the performance and efficacy of the studied FLPs in the overall reaction. [ABSTRACT FROM AUTHOR]

The [3 + 2] cycloaddition (32CA) reactions of 1-pyrroline-1-oxide with N-vinyl nucleobases leading to bicyclic N,O nucleoside analogues have been studied within the molecular electron density theory (MEDT) at the MPWB1K/6-311G(d,p) computational level. These non-polar zwitterionic type 32CA reactions take place through a one-step mechanism with minimal global electron density transfer (GEDT) at the TSs and the exo/ortho approach mode as the energetically favoured reaction path. The 32CA reactions of N-vinyl nucleobases with thymine and cytosine substituents respectively show the activation enthalpies of 15.2 and 12.5 kcal mol−1 in toluene. The reactions are irreversible due to strong exothermic character of − 35.4–− 26.4 kcal mol−1 in toluene. The bonding evolution theory (BET) study suggests that these 32CA reactions take place through the coupling of pseudoradical centres with earlier C–C bond formation and the formation of new C–C and C–O covalent bonds has not been started in the TSs. Non-covalent interactions (NCI) are predicted at the TSs from the visualization of NCI gradient isosurfaces. [ABSTRACT FROM AUTHOR]

In this study, we theoretically investigated Methyl hydrazinecarbodithioate by quantum chemical calculations for geometry optimization, vibration frequencies, and electronic structure parameters. The geometry optimization by DFT, ab initio MP2 method and the frequency calculation by DFT method was performed at the highest available Pople style 6-311G++(3df,3pd) basis set level. The semi-empirical calculations were performed by the latest PM7 method. The theoretically obtained results were compared with the experimental data. Conformational behavior, frontier molecular orbitals, molecular electrostatic potential, electron localization function, and non-covalent interaction plots were also analyzed. The study explained the geometry, conformational flexibility and relative stability of different conformers.

Experimentally (G. Mlostoń et al. J. Fluor. Chem. 2016, 190, 56–60), it has been found that the type of the obtained cycloadduct of the [3+2] cycloaddition (32CA) reaction of thiocarbonyl S‐methanides with α,β‐unsaturated ketones depends strongly on the location of the trifluoromethyl group. In the case of enones containing the CF3CH=CH moiety, the 32CA reaction occurs chemo‐ and regioselectively onto the C=C double bond giving trifluoromethylated tetrahydrothiophene derivatives. On the other hand, enones containing the CF3−C=O fragment react as carbonyl heteroethylenes leading to trifluoromethylated 1,3‐oxathiolanes also in a chemo‐ and regioselective manner. Our aim in the present work is to perform a theoretical study of the all chemo‐, regio‐, and stereo‐isomeric reaction paths of these 32CA reactions within the Molecular Electron Density Theory. Activation Gibbs free energies, calculated at the B3LYP/6‐311G(d,p) level in tetrahydrofurane at −40 °C, show that the ortho/endo reaction path giving the trifluoromethylated tetrahydrothiophene is more favoured, while the meta/endo reaction path leading to trifluoromethylated 1,3‐oxathiolanes is more preferred in total agreement with experimental findings. The low activation barriers in combination of the Electron Localization Function topological analysis of the most relevant points along the Intrinsic Reaction Coordinate reveals the pseudomonoradical character of the studied 32CA reactions. [ABSTRACT FROM AUTHOR]

In this study, the MPW1PW91 method is applied to analyze the quantum theory of atoms in molecules, the electron localization function, and the localized-orbital locator in trans -(NHC)PtI2(para -NC5H4X) (X = H, F, COOH, CN, NO2, Me, OH, NH2) complexes. The substituent effect is assessed in the presence of electron-withdrawing groups and electron-donating groups and their influence on the Pt–C and Pt–N bonds of the molecules is analyzed using quantum theory of atoms in molecules, electron localization function, and localized-orbital locator methods. In addition, the eta index (η) is used to evaluate the Pt–C and Pt–N bonds in the studied complexes. The correlations between electron localization function, localized-orbital locator, and the η index values of Pt–C and Pt–N bonds with Hammett constants (σp) and dual parameters (σI and σR) are given. [ABSTRACT FROM AUTHOR]

The participation of the nitroethene and its α-substituted analogs as model nitrofunctionalized monomers, and (Z)-C,N-diphenylnitrone and methyl vinyl ether as initiators in the polymerization reactions, has been analyzed in the framework of the density functional theory calculations at the M06-2X(PCM)/6-311 + G(d) level. Our computational study suggests the zwitterionic mechanism of the polymerization process. The exploration of the nature of critical structures shows that the first reaction stage exhibits evidently polar nature, whereas additions of further nitroalkene molecules to the polynitroalkyl molecular system formed should be considered as moderate polar processes. The more detailed view on the molecular transformations gives analysis based on the bonding evolution theory. This study shows that the case of polymerization reaction between nitroethene and (Z)-C,N-diphenylnitrone allows for distinguishing eleven topologically different phases, while, in the case of polymerization reaction nitroethene and methyl vinyl ether, we can distinguish nine different phases. [ABSTRACT FROM AUTHOR]

Based on parametrized tight Gaussian functions, an efficient and robust methodology designed to restore the effective core potentials electron densities and the inner shells of the electron localization function is introduced and tested. Attention is focused on the underlying effects of augmented coreless electron densities on selected quantum topological descriptors computed for a test set of species containing heavy elements such as the emblematic uranyl cation. Also, this article shows how a proper topology of the electron density can be recovered from semi‐empirical Hückel calculations where core densities are missing. [ABSTRACT FROM AUTHOR]

The effects of the Lewis acid (LA) AlCl3 catalyst on the oxa‐Diels‐Alder (ODA) reaction of 2‐aryl‐butadiene 1 toward benzaldehyde 2 have been studied within the molecular electron density theory at the M06‐2X/6‐311G(d,p) computational level. Coordination of the LA AlCl3 to the carbonyl oxygen of benzaldehyde 2 not only considerably accelerates the reaction, but also facilitates the ODA reaction along a high polar two‐step mechanism. The complete regioselectivity and endo‐stereoselectivity experimentally observed are explained through Parr functions, respectively, non‐covalent interactions analyses. Electron localization function topological analysis along the most favorable meta/endo reaction path permits characterizing the C‐C and C‐O single bond formation along this two‐step mechanism. [ABSTRACT FROM AUTHOR]