Hirshfeld Charge Research Articles

Catalyst-free formal [3 + 2] cycloaddition of stabilized N,N-cyclic azomethine imines to 3-nitrobenzofurans and 3-nitro-4H-chromenes: access to heteroannulated pyrazolo[1,2-a]pyrazoles.

We have studied the [3 + 2]-cycloaddition of various N,N-cyclic azomethine imines to 3-nitrobenzofurans. This process is a rare example of their dearomatization. We have also extended this process to the related 3-nitro-4H-chromenes as dipolarophiles. Both reactions provide access to benzofuro- and chromeno-condensed pyrazolo[1,2-a]pyrazoles with 100% atom economy in a diastereoselective manner under mild eco-friendly conditions. Finally, on the basis of DFT calculations, the mechanistic insights into the mentioned [3 + 2]-cycloadditions and explanations of the experimentally determined limitations of the method are given. Hirshfeld atomic charge values of push-pull heterocycles were suggested as a criterion for a priori assessment of the possibility of their dipolar cycloaddition with N,N-cyclic azomethine imines.

Solvation effect on the ESIPT mechanism of nitrile-substituted ortho-hydroxy-2-phenyl-oxazolines.

In this study, density functional theory (DFT) and time-dependent density functional theory (TD-DFT) were used to unveil the solvation effects on the excited-state intramolecular proton transfer (ESIPT) of nitrile-substituted ortho-hydroxy-2-phenyl-oxazoline (NOHPO) molecules in three different solvents. According to the functional analysis of the reduced density gradient, hydrogen bond in low-polar solvents is stronger compared to that in high-polar solvents, indicating that proton transfer (PT) can be influenced by the polarity of the solvent. Moreover, the geometric parameters and infrared vibration spectrum of NOHPO in different types of solvents in the S0 and S1 state were compared, which confirmed the above results. By analyzing electronic spectra and frontier molecular orbitals, it was found that the spectral properties were affected by different polar solvents. Molecular electrostatic potential surface calculations proved that PT took place between the H2 atom and N3 atom, and the natural population analysis and Hirshfeld charge reveal the charge distribution after photoexcitation. To investigate the ESIPT progress intensively, the potential energy curves of NOHPO in three types of solvents were established. The findings revealed that NOHPO could transform from enol to keto form in the S1 state spontaneously, and ESIPT progress was promoted with the decrease in polarity.

Evaluation of the performances of different atomic charge and nonelectrostatic models in the finite‐difference Poisson–Boltzmann approach

AbstractIn this work, we investigate the effects of different atomic charge and nonelectrostatic models on the hydration energies of neutral molecules, using an implicit solvation model. The solvation free energy is divided into two main components, the first resulting from a self‐consistent reaction field treatment of the bulk electrostatics obtained by solving the Poisson equation in a finite‐difference (FD) approach where the solute charge density is approximated by atomic charges, the second corresponding to short‐range interactions between the solute and the solvent in the first solvation shell. Five different atomic charge models (Mulliken, Hirshfeld, Hirshfeld‐I, CM5 and its iterative version, CM5‐I) have been considered, both at the Hartree–Fock (HF) and B3LYP levels, with three different basis sets, alongside two nonelectrostatic models including the cavity, dispersion, and solvent structural effects (CDS) model. Averaging over the three considered basis sets, Hirshfeld charges combined to the CDS model led to the lowest mean unsigned error (MUE), with a value of 0.92 kcal/mol with respect to the experimental data. On the other hand, a MUE of 2.02 kcal/mol was obtained with CM5 charges combined to the CDS model, highlighting the low transferability of the original CDS parameters developed for the generalized Born electrostatics to a different electrostatics model. By scaling down the CM5 charges to better balance with the original CDS model, a MUE of 0.68 kcal/mol was however obtained, outlining the delicate balance existing between the electrostatic and nonelectrostatic contributions to the solvation free energy in implicit solvation models.

Structural features of nickel(II) mixed ligand complexes with mefenamic acid and nitrogen donor ligands

The reaction between Ni(NO3)2.6H2O and the non-steroidal anti-inflammatory mefenamic acid (2-[(2,3-dimethylphenyl)amino]benzoic acid), in the presence of various nitrogen donor ligands (imidazole, 2-methylimidazole, pyridine, and nicotinamide) have resulted in the formation of four novel mixed ligand mononuclear Ni(II) complexes. A direct one step metal-ligand complexation method was adopted in synthesizing the complexes under similar conditions using a solvent mixture of EtOH: H2O (2:1). The synthesized complexes have the general formula; [Ni(mef)2(L)2(EtOH)2] or [Ni(mef)2(L)2(H2O)2]·2H2O, where mef is mefenamato, L is the corresponding nitrogen donor ligand. The complexes were characterized by analytical and spectroscopic methods. FTIR studies supported the complex formation and indicated that the mefenamato ligand was coordinated as monodentate through the deprotonated carboxylate oxygen atom. Single-crystal X-ray diffraction studies show that all the complexes crystallize in the triclinic space group P-1. The complexes are isostructural, and Ni(II) lies in an octahedral geometry with NiN2O4 chromophore. Parallel stacking arrangement of the ligands, similar intramolecular N-H···O, and intermolecular O-H···O interactions between the mefenamato ligand and coordinated solvent dominated the connectivity pattern in the complexes. Also, intermolecular interactions depending on the coordinated nitrogen donor ligand further stabilized the structures of the complexes. Furthermore, density functional theory (DFT) study was done to obtain the Hirshfeld charges on different atoms.

A cocrystal of L-ascorbic acid with picolinic acid: the role of O-H...O, N-H...O and C-H...O hydrogen bonds and L-ascorbic acid conformation in structure stabilization.

A new 1:1 cocrystal (L-Asc-Pic) of L-ascorbic acid (vitamin C) with picolinic acid was prepared as a powder and as single crystals. The crystal structure was solved and refined from single-crystal X-ray diffraction (SCXRD) data collected at 293 (2) and 100 (2) K. The samples of the L-Asc-Pic cocrystal were characterized by elemental (HCNS) analysis and titrimetric methods, TG/DTG/DSC, and IR and Raman spectroscopy. The asymmetric unit comprises a picolinic acid zwitterion and an L-ascorbic acid molecule. The stabilization energy of intermolecular interactions involving hydrogen bonds, the vibrational spectrum and the energies of the frontier molecular orbitals were calculated using the GAUSSIAN09 and the CrystalExplorer17 programs. The charge distribution on the atoms of the L-Asc-Pic cocrystal, L-ascorbic acid itself and its 12 known cocrystals (structures from Version 5.40 of the Cambridge Structural Database) were calculated by the methods of Mulliken, Voronoi and Hirshfeld charge analyses (ADF) at the bp86/TZ2P+ level of theory. The total effective charges and conformations of the L-ascorbic acid molecules in the new and previously reported cocrystals were compared with those of the two symmetry-independent molecules in the crystals of L-ascorbic acid. A correlation between molecular conformation and its effective charge is discussed.

Regeneration of [Bmim]BF4 ionic liquid by ozonation: hydrogen bond roles, synergistic effect, and DFT calculation.

Ionic liquids (ILs) are a kind of promising extractants for removing undesirable organics from industrial wastewater and crude oil, etc. Herein, IL regeneration by ozonation was proposed for its recycling. 1-Butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4) and phenol were used as the representative IL and organic matter, respectively. The regeneration performance, stability of [Bmim]BF4, and roles of hydrogen bonds between O3 and [Bmim]BF4 in the phenol removal were studied. The experimental results showed that 90.2% of phenol was degraded in [Bmim]BF4 after ozonation treatment for 30 min with the O3 concentration of 1.2 mg/L. The nonvolatility of [Bmim]BF4-made phenol was adequately degraded, while the concentration of phenol increased during ozone treatment in the conventional extractants (ethanol, ethyl acetate, and dichloromethane) due to their high volatility. The reuse experiments, spectra of Fourier transform infrared spectroscopy and 1H nuclear magnetic resonance spectroscopy indicated that [Bmim]BF4 was steady under the ozonation process. Density functional theory simulation confirmed that hydrogen bonds between [Bmim]+ and O3 could be formed, and calculational results of Hirshfeld charges indicated that the nucleophilicity of O3 was enhanced by the hydrogen bonds. The enhanced nucleophilicity resulted in the increase of phenol degradation efficiency by ozonation, and the synergistic effect between O3 and ILs was proportional to the hydrogen bond donor ability of ILs.

Hirshfeld surface, charge density and site selectivity studies of 1-(2-Methyl-5-nitro-1H-imidazol-1-yl)-acetone

Extensive quantum chemical calculations were carried out for the molecule with B3LYP/6311G++(d,p) level of theory. The molecular packing of the crystal is stabilized by CH…N and CH…O interactions and those interactions were investigated through Hirshfeld surface analysis. Aspherical distribution of charges was estimated using Hansen-Coppens multipole formalism and the effect of temperature on charge density was analyzed. Bader’s AIM theory was used to perform the topological analysis of electron density which disclose the strength and nature of atom-atom interaction. Stability of the molecule arising from hyper conjugative interactions and charge delocalization was examined using Natural Bond Orbital analysis and it also confirms the existence of CH…N and CH…O hydrogen bonds. Frontier Molecular Orbital analysis was carried out and the molecule is found to be a good electrophile with the electrophilicity index of 9.7349 eV. Molecular Electrostatic Potential was used to identify the possible reactive locations of the molecule.

A new bifunctional C3N nanosheet of NO2, SO2 gas sensor and CO2 separation: A first-principles study

A new-style two-dimensional C 3 N monolayer, unlike the honeycomb C 3 N monolayer, is proposed as a gas sensor, capture and separation. By using the first-principles method, the adsorption behaviors of gas molecules (NH 3 , H 2 S, SO 2 , CO, CO 2 , NO, NO 2 , CH 4 , HCN, N 2 , H 2 and O 2 ) on the C 3 N monolayer were investigated, and the charge density difference, density of state and Hirshfeld charge of those adsorption systems were also discussed. The results show that the SO 2 and NO 2 are chemisorbed on the C 3 N nanosheet with large adsorption strength, while the other gases are adsorbed by weak physisorption. The analysis of charge density difference and density of state suggests that SO 2 and NO 2 gain much charge from C 3 N sheet, and the hybridizations between C 3 N sheet and SO 2 /NO 2 -p orbitals lead to strong gas-adsorbent interactions. The recovery time of SO 2 and NO 2 is predicted to be 7.47 × 10 −4 s and 15.91 s at room temperature. Additionally, the CO 2 can be captured and separated from the mixtures of CO 2 , NH 3 , H 2 S, CO, CH 4 , H 2 through injecting two electrons into C 3 N sheet. Therefore, the new C 3 N nanosheet can be a promising bifunctional material as SO 2 , NO 2 sensor and CO 2 separation.

Adsorption of acid Blue 25 dye by CPAA coated on SBA-15 in aqueous solution: A density functional theory study

In this research, the geometric and electronic structure of the Acid Blue 25 dye as adsorbate and SBA-15 mesoporous silica functionalized with cross-linked polyacrylic acid (CPAA) polymer (SBA-15/CPAA) as adsorbent are studied using density functional theory (DFT) in the aqueous phase. In order to determine the best site of the dye for interacting with adsorbent, the atomic Hirshfeld charges and frontier orbitals are investigated. The result of this investigation confirms that the sulfonate group of the dye is the best nucleophilic site. The adsorbent has two protonated sites (–NH2+ and = OH+) to attract dye anion. The evaluation of calculated adsorption energy, quantum descriptors such as electronic chemical potential (μ) and chemical hardness (η), dipole momentum and solvent effect are shown that the (–NH2+) group in comparison with (=OH+) group attracts the sulfonate group of the dye with more potent force and forms more stable complex. The adsorbent and adsorbate species have the full charge before adsorption. The results of computed transferred charge and the bond order determined that the interaction is mainly electrostatic. In this work, thermodynamic parameters such as enthalpy, entropy, and Gibbs free energy changes are calculated. The results of these parameters showed that the adsorption is an exothermic and spontaneous process. Besides, the obtained values of thermodynamic parameters are in the range of electrostatic interaction.

Molecular structure and quantum descriptors of cefradine by using vibrational spectroscopy (IR and Raman), NBO, AIM, chemical reactivity and molecular docking.

This study aims to investigate the structural and vibrational features of cefradine (the first-generation cephalosporin antibiotic) based on spectroscopic experiments and theoretical quantum chemical approach. The fundamental structural aspects of cefradine have been examined based on optimized geometry, spectroscopic behavior, intermolecular interaction, chemical reactivity, intramolecular hydrogen bonding, and molecular docking analysis. The most stable minimum energy conformer of the title molecule was identified by performing a one-dimensional potential energy surface scan along the rotational bonds at B3LYP/6-311++G (d,p) level of theory. The vibrational features of the molecule and information about the coupled modes were predicted. The chemical reactivity and stability of all the possible conformers of cefradine were estimated based on the HOMO-LUMO energy gap and NBO approach. The overall picture of accumulation of charges on individual atoms of the molecule was predicted by molecular electrostatic potential (MEP) surface map which in turn identifies the nucleophilic and electrophilic region or sites. The quantitative analysis of electrophilicity and nucleophilicity indices was done by Hirshfeld charge analysis and it was found that N8 atom is the most prominent site for nucleophilic attack while C14 atom is feasible for electrophilic attack. QTAIM study has also been performed to investigate the nature and strength of hydrogen bonding interactions. Besides, molecular docking studies were performed to examine the active binding residues of the target.

Anomalous Melting Point of Multicharge Ionic Liquids: Structural, Electrostatic, and Orbital Properties of [Ln(NO3)6]3- (Ln = Ce, Pr) Anions.

Salts composed of multicharged cations/anions usually exhibit a large lattice energy and strong Coulomb force, which results in high melting points. However, an increasing number of highly charged ionic liquids exceed expectations based on conventional experience; even their melting points are much lower than those found for simple ionic liquids composed of monovalent ions. To further study this phenomenon, we studied a group of stable ionic liquids containing tricharged [Ce(NO3)6]3- and [Pr(NO3)6]3- anions. The structures for [C6mim]3[Ce(NO3)6] and [C6mim]3[Pr(NO3)6] were determined by single-crystal X-ray diffraction with triclinic and P1̅ space groups. The electrostatic potential density per unit ion surface and volume was proposed and calculated. Additionally, theoretical analysis based on Hirshfeld surface and charge decomposition was carried out to explore the intermolecular interaction and electronic structure of the lanthanide anions. The electrostatic and orbital properties were found to be more useful for understanding the melting points of highly charged salts compared with the sole use of lattice energy. The electrostatic potential density per unit ion surface and volume showed a linear relationship with the melting point of ionic liquids composed of monovalent to trivalent ions. These structure-melting point relationships will be beneficial for expounding new low-melting-point ionic liquids with a wide liquidus range.

Adsorption mechanism of toxic heavy metal ions on oxygen-passivated nanopores in graphene nanoflakes

In this work, using density functional theory, we investigate the adsorption process of toxic metal ions (Hg2+, Cd2+, and Pb2+) on graphene nanoflakes (GNF) comprised of various sized oxygen-passivated nanopores to gain molecular insights into the ability of such surfaces in effectively removing the metal ions from contaminated environments. Thermodynamically, the adsorption of these ions on the oxygen-passivated nanopores is shown to be more energetically favorable than that on the pristine surface. The dispersion corrected adsorption energy calculations indicate Hg2+ ion to have the highest and Pb2+ ion the lowest affinities for interaction with such surfaces (Hg2+ > Cd2+ > Pb2+). The highest adsorption of Hg2+ and Cd2+ ions on the surfaces is seen in the 12-crown-3…Hg2+ (− 382.9 kcal/mol) and 12-crown-3…Cd2+ (− 314.7 kcal/mol) complexes, while Pb2+ ion shows the highest adsorption energy for the 18-crown-6 surface (− 195.0 kcal/mol). Noncovalent interaction plots, Hirshfeld charge analysis and energy decomposition analysis conclude that the role of charge transfer in formation of surface…ion complexes is more important than noncovalent interactions and therefore plays a key role in the adsorption of these ions on the surfaces. The magnitude of charge transfer in the complexes follows the order: surface…Hg2+ > surface…Cd2+ > surface…Pb2+, which is consistent with the adsorption energetic order of these metal ions on the surfaces. We also found that Pb2+ ion is mainly adsorbed on the surfaces via electrostatic interactions, while Hg2+ and Cd2+ ions are adsorbed through van der Waals (vdW) interactions. This could be attributed to the presence of vacant p orbitals on Pb2+ ion, which interact with the π bonds on the GNF and oxygen atoms in the nanopores through electrostatic interactions. No such vacant orbitals are available for Hg2+ and Cd2+ ions thus resulting in such ions adsorbing via vdW interactions. The contribution of ΔEorb, induction energy component of total energy, for the surface…Hg2+ complexes is more than that for the surface…Cd2+ and surface…Pb2+ complexes, following the order: surface…Hg2+ > surface…Cd2+ > surface…Pb2+ again, consistent with the calculated adsorption energy order suggesting that charge transfer indeed plays a major role in formation of such surface…ion complexes. Finally, time-dependent density functional theory calculations show that the absorption spectra of the surfaces undergo significant changes, including peak shifts, peak quenching and appearance of new peaks, upon interaction with Hg2+, Cd2+, and Pb2+ ions, such changes being consistent with binding energetics rank order of ions on these surfaces. These complexes would have potential applications in near-infra-red photonics in addition to their service of effectively remediating of toxic heavy elements from contaminated environments.

Quantum Chemical Calculation and DFT Study of Sitagliptin: Insight from Computational Evaluation and Docking Approach

This study aims to explore the structural and chemical behavior of sitagliptin using density functional theory (DFT). The chemical reactivity has been studied in terms of MEP, HOMO-LUMO energy gap, Hirshfeld charge, and global and local reactivity descriptors. Thermodynamic parameters like entropy, enthalpy and specific heat capacity and, nonlinear optical (NLO) properties have been analysed. Higher value of the first hyperpolarizability than that of urea show its potential use as NLO material. Intra-molecular Hydrogen bonding and topological parameters at the bond critical point (BCP) of title molecule have been studied by using the quantum theory of atoms in molecules (QTAIM) approach. The bond of 2.3777 Å between H42…N11 is noticed to be strongest one. The pharmacological behavior and protein-ligand interaction of the title molecule have been investigated in terms of drug-likeness and molecular docking which motivates that the amine and carbonyl group bind with the amino acid of the protein.

Theoretical insights into the electronic structure of nickel(0)-diphosphine-carbon dioxide complexes

The coordination properties of carbon dioxide bound to Ni(0) with various phosphines have been investigated by means of DFT calculations. Reasonable linear correlation has been found between Tolman’s electronic parameters (TEPs) and the asymmetric stretching frequency of the coordinated CO2. Two descriptors from EDA-NOCV calculations, namely the interaction energy and the Hirshfeld charge associated with the back donation component gave acceptable linear correlation as well with the TEPs. The coordination strength, as well as the CO bond order in coordinated carbon dioxide can be tuned by varying the substituents on phosphorus: in the presence of electron withdrawing groups the CO bond remains stronger and Ni-C interaction is weaker, moreover, a new Ni-O bond path is formed; whereas for more basic diphosphines the NiC bond order is higher and the coordinated carbon dioxide possess a weaker CO bond.

Cyclic Carbonate Formation from Epoxides and CO2 Catalyzed by Sustainable Alkali Halide-Glycol Complexes: A DFT Study to Elucidate Reaction Mechanism and Catalytic Activity.

We provide a comprehensive DFT investigation of the mechanistic details of CO2 fixation into styrene oxide to form styrene carbonate, catalyzed by potassium iodide–tetraethylene glycol complex. A detailed view on the intermediate steps of the overall reaction clarifies the role of hydroxyl substances as co-catalysts for the alkali halide-catalyzed cycloaddition. The increase of iodide nucleophilicity in presence of tetraethylene glycol is examined and rationalized by NBO and Hirshfeld charge analysis, and bond distances. We explore how different alkali metal salts and glycols affect the catalytic performance. Our results provide important hints on the synthesis of cyclic carbonates from CO2 and epoxides promoted by alkali halides and glycol complexes, allowing the development of more efficient catalysts.

Investigation of excited state proton transfer mechanism for 2-(benzo[d]thiazol-2-yl)naphthalene-1,3-diol in different solvents

This work systematically investigates solvent effects on hydrogen bond strength and excited-state intramolecular proton transfer (ESIPT) behaviour of 2-(benzo[d]thiazol-2-yl)naphthalene-1,3-diol (DHT) chromophore. The calculated electronic spectra accord with experimental observation. Our work confirms hydrogen bond is enhanced in excited state, which facilitates ESIPT behaviour. The Hirshfeld charges analysis reveal that effect of different solvents on electronegativity of proton donor and acceptor results in change of hydrogen bond strength. It follows that strength of hydrogen bond is gradually weakened with the increase of solvent polarity in excited state. The constructing potential energy profiles show that with the decreased solvent polarity, ESIPT is more likely to occur.

Calculating and Characterizing the Charge Distributions in Solids.

Accurate estimation of the partial atomic charges on metal centers is useful for understanding electronic and catalytic properties of materials. However, different methods of calculating these charges may give quite different results; this issue has been more widely studied for molecules than for solids. Here we study the charges on the metal centers of a test set of 18 solids containing transition metals by using density functional theory with several density functionals (PBE, PBE+U, TPSS, revTPSS, HLE17, revM06-L, B3LYP, B3LYP*, and other exchange-modified B3LYP functionals) and four charge models (Bader, Hirshfeld, CM5, and DDEC6). The test set contains 12 systems with nonmagnetic metal centers (eight metal oxides (MO2), two metal sulfides (MS2), and two metal selenides (MSe2)) and six ferromagnetic transition metal complexes. Our study shows that, among the four types of charges, Bader charges are the highest and Hirshfeld charges are the lowest for all the systems, regardless of the functional being used. The CM5 charges are bigger than DDEC6 charges for MX2 with M = Ti or Mo and X = S or Se, but for the other 14 cases they are lower. We found that the most of the systems are sensitive to the Hubbard U parameters in PBE+U and to the percentage X of Hartree-Fock exchange in exchange-modified B3LYP; as we increase U or X, the charges on the metal atoms in MX2 increase steadily. Testing different density functionals shows charges calculated with higher Hubbard U parameters in PBE+U are comparable to B3LYP (with 20% Hartree-Fock exchange). Among four meta-GGA functionals studied, the charges with HLE17 have the closest agreement with B3LYP. The variation of charges with choice of charge model is greater than the variation with choice of density functional.

Identifying the active sites of carbonaceous surface for the adsorption of gaseous arsenic trioxide: A theoretical study

Arsenic pollutants released from coal-fired power plant caused great harm to human health and the environment due to its high toxicity and bioaccumulation. Gaseous As2O3 is one of the main arsenic pollutants in coal power plant flue gas. The literature suggests that As2O3 can be effectively removed by the unburned carbon. However, the active sites of the unburned carbon for As2O3 adsorption has not been clearly identified, which greatly hinders the development of effective adsorbents. To reveal the active sites of As2O3 adsorption, the adsorption characteristic of As2O3 on different carbonaceous surfaces were systematically investigated through density functional theory calculations. In this work, the adsorption mechanism of As2O3 was studied through Mayer bond order, overlap population Density-of-states (OPDOS), and Atomic Dipole Moment Corrected Hirshfeld (ADCH) charge analysis. The adsorption of As2O3 on defective surfaces is associated with stable chemisorption, and surface defects can significantly improve the adsorption energy of As2O3. This theoretical study clarifies the adsorption active sites in carbonaceous surfaces and provide theoretical guidance for the development of efficient adsorbents for As2O3.

Photodegradation of seven bisphenol analogues by Bi5O7I/UiO-67 heterojunction: Relationship between the chemical structures and removal efficiency

Bisphenol analogues have been widely used and displayed adverse effects on human beings. Although many photocatalysts displayed remarkable performance in degrading bisphenol A (BPA) or bisphenol F (BPF), it is not clear if they may also efficiently decompose other bisphenol analogues. In this study, Bi5O7I with satisfactory photocatalytic activity was doped with metal-organic framework (UiO-67) to build up Bi5O7I/UiO-67 heterojunctions. The heterojunction enhanced the charge mobility and separation of the electron-hole pairs, which was conducive for improving the photocatalytic activity. Consequently, 4:1-Bi5O7I/UiO-67 realized highly effective degradation of seven bisphenol analogues in one hour. Density functional theory (DFT) calculations uncovered that the reaction rate constant k displayed a positive correlation with the Hirshfeld charge q (N) of tertiary butyl carbon attached with different substituent groups. This provides a prospective heterojunction catalyst to degrade a group of pollutants with similar structures, and sheds light on the structural relationship of degradation efficiency.

Ab initio predictions for the reaction mechanism and orbital topological properties of the formation of Neptunimine, Plutonimine, and its side products.

Exploring the different mechanisms involved in the application of actinide is necessary to obtain a more comprehensive understanding of actinide science. In this study, the mechanisms of gas-phase Np and Pu atoms dissociating NH3 molecules forming Neptunimine and Plutonimine complexes were systematically investigated using different approaches of density functional theory. A new dehydrogenation channel was discovered. The results reveal that the intermediates HAn-NH2 are the lowest energy in the overall reaction, and the direct planar evolution dehydrogenations are the lowest energy reaction path. Besides, the mechanism of the initial complexation process is discussed on the electron localization function, atoms-in-molecules, atomic dipole moment corrected Hirshfeld atomic charges, and electron density difference analysis. The results indicate that An-N in complex I exhibits a very weak covalent interaction, and it comes down to pulling the original dipole moment of the NH3 molecule and stretched between An atom and three H atoms. Graphical abstract.