Bond Order Calculations Research Articles

Spontaneous Formation of Strained Anti-Bredt Bridgehead Alkenes upon Computational GeometryOptimization of Bicyclic β-Halo Carbanions

Bridgehead alkenes are polycyclic molecules bearing at least one C=C bond that includes a bridgehead carbon atom. For small bicyclic systems, these bonds are highly strained due to geometric constraints placed on the sp2 hybridized carbon atoms. These small, strained molecules have been termed “anti-Bredt” alkenes. β-halo carbanions have served as convenient precursors to bridgehead alkenes in experimental studies. We observed that upon attempted computational geometric optimizations (ωB97X-D/aug-cc-pVDZ) of the precursors, spontaneous elimination of the halide occurs along with formation of the anti-Bredt alkene in many cases. Such computational eliminations were shown to faithfully mimic experimentally obtained results. Computational elimination was not observed for [1.1.1] or [2.1.1] frameworks, in agreement with predictions that these bridgehead alkenes are too strained to be formed. However, computational elimination from the [2.2.1] framework was observed to form 1-norbornene, a compound suggested in experimental work to be a reactive intermediate. Similarly, [3.1.1] frameworks and higher led to eliminations upon computational geometric optimization, in agreement with experimental findings. Natural bond order (NBO) calculations of the starting geometries proved to be excellent predictors as to whether elimination would take place. Those precursor compounds exhibiting delocalization energies in the order of 10 kcal/mol between the lone-pair electrons of the carbon atom and σ*C-Br were generally found to undergo elimination. Thus, computational optimization of β-halo substituted bicyclic precursor anions can be used to predict whether strained anti-Bredt alkenes are likely to be formed, thereby saving valuable time and costs in the experimental lab.

Dissociation Constant of Di‐ and Tri‐Basic Solvents Based on Piperazine and Its Derivatives for Post‐Combustion CO2 Capture

AbstractAmine solvents remain popular in the industries for post combustion carbon dioxide (CO2) capture. Dissociation constant of basic amine solvents plays significant role to influence the CO2 absorption. It is thus important to study the dissociation of new amine solvents for assessing their viability for CO2 capture. In the present work, potentiometric titration method is employed to determine the dissociation constants of dibasic (e. g., Piperazine (PZ), 1‐methyl piperazine (1‐MPZ) and tribasic amines (1‐(2‐aminoethyl‐piperazine) (AEPZ) which could be promising for formulating blended solvent system towards enhancing the rate of CO2 absorption. The estimated dissociation constants for the PZ and 1‐MPZ while match well with reported results, the dissociation constants for AEPZ has been determined newly here within the temperature range 298—318 K. In addition, the structural geometric parameters and Natural Bond Order (NBO) calculations of the amine solvents are performed based on Density Functional Theory (DFT). The NBO calculations predict charge distribution on the nitrogen and other elements, and envisage its effect on the pKa values of the amines. Further, potential energy surface (PES) scanning calculations are performed for AEPZ to explain it's ring inversion which is responsible for obtaining a single pKa value in experimental studies.

Insights into ThB40: Stability, Electronic Structure, and Interaction.

The interaction between nonmetal and metal atoms has attracted great interest in the development of organometallic compounds and their promising applications. In this study, we explored the interaction between boron and thorium atoms, based on the stable B40Th coordination compound, by employing density functional theory calculations. We elucidated the stability and geometries of the B40Th coordination compound and revealed the electron transfer from the metal atom Th to B40, which is evidenced by the natural bond orbital calculations. This electron transfer is attributed to the electron-withdrawing character of the boron atom and results in clear electrostatic interaction. Additionally, bond critical analysis and bond order calculations show obvious covalent characters between the metal and nonmetal atoms. The IR spectrum was simulated to give detailed information to identify this targeted compound in future experiments. This study is expected to enhance the understanding of metal-nonmetal interactions and provides useful information for constructing new organometallic compounds based on actinium metal atoms.

Electronic and topological analyses of C–O bonds in carbohydrates and lignin-carbohydrate complexes: An atomistic understanding of refractory molecules in agro-industrial waste

Theoretical calculations were employed to investigate carbohydrates and model molecules representing lignin-carbohydrate complexes (LCCs). These complexes exhibit resistance to chemical transformation due to specific C–O chemical bonds, being a part of certain agro-industrial waste. Enthalpy values for C–O bonds at different positions in carbohydrates unveiled distinct stabilities. Calculations of bond orders and topological properties were performed to better understand the properties of carbohydrates. Model molecules of LCCs were also analyzed to explore primary lignin-carbohydrate (LC) linkages. The enthalpy values of C–O bonds were found to be closely tied to the functional group nature in LCCs—ether, ester, or aromatic bonding. Bond orders revealed crucial features influencing the stability of these complexes. Particularly noteworthy, topological properties unveiled the covalency inherent in the C–O bond within specific LC linkages, contributing to the refractory nature of these complexes. This study provides analytical insights into the recalcitrant characteristics of LCCs.

Towards structurally versatile mesoionic N-heterocyclic olefin ligands and their coordination to palladium, gold, and boron hydride.

We have developed an efficient and versatile approach for the synthesis of a family of 1,2,3-triazole-based mesoionic N-heterocyclic olefin (mNHO) ligands and investigated their coordination to palladium, gold, and boron hydride experimentally and computationally. We reacted mNHOs obtained through deprotonation of the corresponding methylated and ethylated 1,3,4-triaryl-1,2,3-triazolium salts with [Pd(allyl)Cl]2 to give the corresponding [Pd(η3-allyl)Cl(mNHO)] coordination complexes. 13C NMR data revealed the strong σ-donor character of the mNHO ligands, consistent with the calculated bond orders and atom-condensed charges. Furthermore, we also synthesized [AuCl(mNHO)] and a BH3-mNHO adduct by reacting the triazolium salts with AuCl(SMe2) and BH3·THF, respectively. The BH3-mNHO adduct was tested in the reduction of select aldehydes and ketones to alcohols.

Ab initio study of electronic structure, bonding and optical properties of ternary A2B2In (A = Ca, Eu and B = Pd, Pt) indides

Crystal structure, optical and electronic properties of metal rich intermetallic Ca2Pd2In, Ca2Pt2In, Eu2Pd2In and Eu2Pt2In compounds have been explored using density functional theory based orthogonalized linear combination of atomic orbitals (OLCAO) method and code. The local density approximation scheme has been employed to probe all the properties. The outcomes of the electronic structure revealed the conducting nature of ternary indides. Density of states plots of ternary indides exhibited an increased number of energy states moving from Ca2Pd2In, Ca2Pt2In, Eu2Pd2In to Eu2Pt2In at Fermi level which substantiate the metallic nature of these compounds. The localization index calculations reflected the highly delocalized states in the vicinity of Fermi level. The cationic behavior of Ca- and Eu-atoms and anionic character of Pd-, Pt-, In-atoms has been evaluated through the effective charge (Qα*) calculations. Bond order calculations indicated highest strength of Ca2Pt2In among the studied indides. Optical features in the form of complex dielectric function, optical conductivity and electron energy loss function have been thoroughly discoursed. Two eminent peaks in electron energy loss L(ω) spectra have been observed at 29.77 and 27.83 eV which are associated to the plasmonic resonance.

Bonding Analysis of the Ge‐Ge Bonds in the Octagermacubane Ge8(Sit‐butyl2methyl)6

AbstractQuantum chemical calculations have been carried out at the BP86/def2‐SVP level on Ge8(Sit‐butyl2methyl)6(1) and the bonding situation has been analyzed with a variety of methods. The calculated equilibrium geometry of1is in good agreement with the reported x‐ray structure analysis. The D3 correction for dispersion interactions as a sum of pairwise attractions leads to an overestimate of the effect of dispersion forces. Calculations at BP86‐D3(BJ)/def2‐SVP give shorter bonds for Ge(I)−Ge(I) than for Ge(0)−Ge(I), which is in contrast to the experimental values and the BP86/def2‐SVP results. The NBO analysis suggests that the best Lewis structure of1has lone‐pair orbitals at the Ge(0) atoms with occupation numbers of 1.70 e. A lone‐pair character at Ge(0) albeit with less weight is also suggested by the shape of the HOMO, which is an antibonding orbital between the Ge(0) atoms with small contributions from the Ge(I) atoms. The LUMO of1is the corresponding bonding combination of the Ge(0) AOs, which can be explained with the reluctance of the heavier main‐group atoms to s/p hybridization of the valence orbitals. The calculated bond order values suggest significant direct Ge(0)−Ge(0) interactions. This is supported by the shape of the HOMO and by the results of EDA‐NOCV calculations. The deformation densities and the orbitals associated with the pairwise orbital interaction show that there is a direct charge flow between the Ge(0) atoms of the two fragments, but it is not completely separated from the Ge(0)−Ge(I) and Ge(I)−Ge(I) bond formation. The QTAIM calculations suggest that1has a cubic structure with a cage critical point but not a bond critical point for the Ge(0)−Ge(0) interactions. The dispersion interactions of the large substituents in1have a significant influence on the stability of the compound.

Theoretically Revealing the Response of Intermolecular Vibration Energy Transfer and Decomposition Process of the DNTF System to Electric Fields Using Two-Dimensional Infrared Spectra.

The external electric field (E-field), which is an important stimulus, can change the decomposition mechanism and sensitivity of energetic materials. As a result, understanding the response of energetic materials to external E-fields is critical for their safe use. Motivated by recent experiments and theories, the two-dimensional infrared (2D IR) spectra of 3,4-bis (3-nitrofurazan-4-yl) furoxan (DNTF), which has a high energy, a low melting point, and comprehensive properties, were theoretically investigated. Cross-peaks were observed in 2D IR spectra under different E-fields, which demonstrated an intermolecular vibration energy transfer; the furazan ring vibration was found to play an important role in the analysis of vibration energy distribution and was extended over several DNTF molecules. Measurements of the non-covalent interactions, with the support of the 2D IR spectra, indicated that there were obvious non-covalent interactions among different DNTF molecules, which resulted from the conjugation of the furoxan ring and the furazan ring; the direction of the E-field also had a significant influence on the strength of the weak interactions. Furthermore, the calculation of the Laplacian bond order, which characterized the C-NO2 bonds as trigger bonds, predicted that the E-fields could change the thermal decomposition process of DNTF while the positive E-field facilitates the breakdown of the C-NO2 in DNTFⅣ molecules. Our work provides new insights into the relationship between the E-field and the intermolecular vibration energy transfer and decomposition mechanism of the DNTF system.

Bandgap modification in 0D tellurium iodide perovskite derivatives via incorporation of polyiodide species.

Halide perovskites provide a versatile platform for exploring the effect of non-covalent interactions, including halogen bonding, on material properties such as band gap, luminescence, and frontier orbital landscape. Herein we report six new zero-dimensional tellurium iodide perovskite derivatives, consisting of [TeI6]2- octahedra charge balanced by one of several X-Py cations (X = H, Cl, Br, I, and Py = pyridinium). These compounds also feature robust halogen bonding between [TeI6]2- octahedra and polyiodides in the form of I2 (1-4), I3 - (5), or adjacent octahedra (4 and 6). These relatively strong non-covalent interactions (NCIs) are modeled by natural bond order (NBO) and second order perturbation theory (SOPT) calculations. NCIs are responsible for reducing the bandgap of these materials (measured via diffuse reflectance spectroscopy) relative to those without polyiodide species. They also affect inner sphere bonding in the metal halide, exacerbating [TeI6]2- octahedron asymmetry as compared to previously published compounds, with greater asymmetry correlating with higher van der Waals overlap of halogen-halogen contacts. We also demonstrate the ability of hydrogen and carbon bonding (which dominates in the absence of polyiodides) to affect inner sphere tellurium iodide bonding and octahedral symmetry.

Effect of pH and Cl- concentration on the electrochemical oxidation of pyridine in low-salinity reverse osmosis concentrate: Kinetics, mechanism, and toxicity assessment

To reduce the pressure of salt separation crystallization and contaminants removal, we systematically investigated the electrochemical oxidation of pyridine (Pyr) in low-salinity reverse osmosis concentrate (ROC) using a Ti/RuO2-IrO2 anode with a high-performance chlorine evolution reaction. We mainly focused on the pH- and Cl- concentration-dependent reaction kinetics, degradation mechanisms, and toxicity assessment. Specifically, the Pyr degradation followed a pseudo-first-order kinetic model. A pH-dependent reaction kinetics study showed that reactive chlorine species (RCS) and ·OH were the dominant species that reacted with Pyr. Furthermore, the degradation efficiency of Pyr reached its maximum value at pH 2, owing to the formation of more RCS. Additionally, Pyr degradation depends on the contribution of RCS in the presence of Cl-. Under low and high Cl- concentrations, the secondary effects were free available chlorine (FAC) and ·OH, respectively. The concentration of trichloromethane (TCM) increased to 9.96 μM first and then decreased to 5.42 μM within 90 min. The variation trend in its concentration is consistent with that of the RCS contribution under different pH and Cl- concentration. The active sites of Pyr were calculated using frontier electron density (FED) and Laplacian bond order (LBO) calculations. The degradation performance and mechanisms of Pyr, wherein ring cleavage on the 6 N atom of Pyr was the main mechanism by electrochemical treatment, were explored through theoretical calculations and gas chromatography-mass spectrometry (GC–MS) analysis. The generation of transformation products (TPs) increased the toxicity of the Pyr water after electrochemical treatment. The overall findings provide new insights into the treatment of ROC, offering significant reference information for improving water utilization and near-zero liquid discharge (near-ZLD) of real wastewater.

Zr-MOFs–catalyzed transfer hydrogenation of furfural to furfuryl alcohol: Unveiled performance of DUT-52

Catalytic transfer hydrogenation (CTH) of 2-furfuraldehyde (FALD) at 1 atm has potential industrial applications to produce furfuryl alcohol (FOL) and its derivatives mildly. The process was explored using alcohols in the absence of H2. Solvothermally prepared zirconium(IV) metal organic frameworks (Zr-MOFs) of DUT-52 (DUT: Dresden University of Technology) and UiO-66 (UiO: University of Oslo) were employed in the CTH. Energetic studies (GFN2-xTB level) revealed a similar Gibbs free energy of DUT-52 and UiO-66 when they were reacted by 2-propanol. Electrostatic potential (ESP) charges and Wiberg bond order (WBO) calculations showed that two Zr atoms available for FALD coordination had higher Lewis acidity in DUT-52 than UiO-66. DUT-52 successfully gave >99% of FOL in 3 h at 160 °C under 2-propanol with Ea of 61 kJ/mol and an equal turnover frequency (TOF) to UiO-66 (5.4 h−1). DUT-52 was also easily recyclable up to the 4th run with no significant performance loss.

Mutations of Omicron Variant at the Interface of the Receptor Domain Motif and Human Angiotensin-Converting Enzyme-2.

The most recent Omicron variant of SARS-CoV-2 has caused global concern and anxiety. The only thing certain about this strain, with a large number of mutations in the spike protein, is that it spreads quickly, seems to evade immune defense, and mitigates the benefits of existing vaccines. Based on the ultra-large-scale ab initio computational modeling of the receptor binding motif (RBM) and the human angiotensin-converting enzyme-2 (ACE2) interface, we provide the details of the effect of Omicron mutations at the fundamental atomic scale level. In-depth analysis anchored in the novel concept of amino acid-amino acid bond pair units (AABPU) indicates that mutations in the Omicron variant are connected with (i) significant changes in the shape and structure of AABPU components, together with (ii) significant increase in the positive partial charge, which facilitates the interaction with ACE2. We have identified changes in bonding due to mutations in the RBM. The calculated bond order, based on AABPU, reveals that the Omicron mutations increase the binding strength of RBM to ACE2. Our findings correlate with and are instrumental to explain the current observations and can contribute to the prediction of next potential new variant of concern.

Covalency in actinide(iv) hexachlorides in relation to the chlorine K-edge X-ray absorption structure.

Chlorine K-edge X-ray absorption near edge structure (XANES) in actinideIV hexachlorides, [AnCl6]2− (An = Th–Pu), is calculated with relativistic multiconfiguration wavefunction theory (WFT). Of particular focus is a 3-peak feature emerging from U toward Pu, and its assignment in terms of donation bonding to the An 5f vs. 6d shells. With or without spin–orbit coupling, the calculated and previously measured XANES spectra are in excellent agreement with respect to relative peak positions, relative peak intensities, and peak assignments. Metal–ligand bonding analyses from WFT and Kohn–Sham theory (KST) predict comparable An 5f and 6d covalency from U to Np and Pu. Although some frontier molecular orbitals in the KST calculations display increasing An 5f–Cl 3p mixing from Th to Pu, because of energetic stabilization of 5f relative to the Cl 3p combinations of the matching symmetry, increasing hybridization is neither seen in the WFT natural orbitals, nor is it reflected in the calculated bond orders. The appearance of the pre-edge peaks from U to Pu and their relative intensities are rationalized simply by the energetic separation of transitions to 6d t2gversus transitions to weakly-bonded and strongly stabilized a2u, t2u and t1u orbitals with 5f character. The study highlights potential pitfalls when interpreting XANES spectra based on ground state Kohn–Sham molecular orbitals.

Acceleration of FeIII/FeII cycle enhanced by Pd/MOF‐808(Zr) composite in hydrogen promotion Fenton system for sulfamethazine elimination

AbstractUnder normal temperature and pressure, a novel improved Fenton system that was named MHACF‐MOF‐808(Zr) was constructed after the introduction of Pd/MOF‐808(Zr) and H2 to solve the inherent problem of the production of iron sludge in the classic Fenton system. Only trace amount of FeII was required during the whole reaction because FeIII could be rapidly reduced by the active hydrogen derived from the adsorption and activation of H2 on the surface of Pd/MOF‐808(Zr) composite. The concentration of FeII could be maintained more than 10 μM. The removal of target pollutant sulfamethazine in this system was mainly relied on the degradation of ·OH verified by both of the direct detection and indirect inhibition (using methanol). By using the calculation of Laplacian bond order, the degradation pathway of sulfamethazine followed by the cleavage of NS bond. This prediction was verified by the detection of intermediate products. Only 21% sulfamethazine could be degraded after 3‐h reaction in the classic Fenton reaction system, while it could be thoroughly degraded in 1.5 h in the MHACF‐MOF‐808(Zr) system. The influence of main parameters on the degradation effect of sulfamethazine, such as initial pH, the flow of H2, dosage of Pd/MOF‐808(Zr), concentration of sulfamethazine, ferrous, and hydrogen peroxide, were systematically studied. Based on the relative stability of Pd/MOF‐808(Zr) confirmed by the morphological characterization, sulfamethazine could be efficiently degraded in the MHACF‐MOF‐808(Zr) system.

Structural stability, electronic structure, mechanical and optical properties of MAX phase ternary Mo2Ga2C, Mo2GaC and Mo3GaC2 carbides

In this article, structural, mechanical, optical and electronic properties of MAX phase ternary Mo2Ga2C, Mo2GaC and Mo3GaC2 carbides are reported. Theoretical calculations are performed by applying OLCAO method within the density functional theory. All three carbides fulfill the structural stability criteria mechanically. The calculated formation energies of all three ternary carbides indicate the structural stability of these carbides. The Mo2GaC and Mo3GaC2 carbides are found less resistant to thermal shock as compared to Mo2Ga2C carbide. Band structure plots reveal conducting behavior of Mo2Ga2C, Mo2GaC and Mo3GaC2 carbides. DOS spectra of Mo2Ga2C, Mo2GaC and Mo3GaC2 carbides show an increasing number of energy states at Fermi level. The calculations of localization index reveal highly delocalized energy states near Fermi level, EF. Effective charge (Q∗) calculations reveal that the Mo atoms have charge losing trend in these carbides. Bond order (BO) calculations show dominant role of covalent nature of Mo–C bonds in the stability and cohesion of all three carbides. Optical behavior of carbides shows anisotropic characteristics up to energy ≤9.0 eV. Above 9.0 eV, carbides exhibit isotropic behavior. Theoretical results suggest that these carbides can of interest for electronic and optical applications.

Revisiting UF6, NpF6 and PuF6 for bonding and molecular surface analysis within density functional theory: Comparative study at the different theory levels with the same basis set

UF6, NpF6 and PuF6 have been reexamined for their bonding characteristics and molecular surfaces. The bonding properties of these compounds were analyzed by calculating bond orders, partial charges, dipole moments, localized molecular orbitals, and topological properties. The bond orders increase with the atomic number (Z) of actinide as the bond lengths decrease. The partial charges, calculated by Atoms in Molecules (AIM) and Mulliken methods, and the bond dipole moment decrease with increasing Z. There is a fluctuation in the partial charge value for Np according to other charge models. The f character of the localized molecular orbital increases with Z. In general, the parameters obtained from topological analysis show an increase in the covalency across the period for U, Np and Pu. The molecular volume and surface obtained from surface analysis decrease with Z, which is consistent with the bond lengths. The molecular surface electrostatic potentials for intermolecular interactions decrease with Z according to surface analysis. The mass density and heat of sublimation data are interpreted based on molecular surface analysis results. All the density functionals and HERDB with the same basis set give consistent results for almost all the quantities calculated.

Luminescence of Mn4+ in the orthorhombic perovskites, AZrO3 (A=Ca, Sr)

The spectroscopic properties of the Mn 4+ (3 d 3 ) ion in the orthorhombic perovskites A B O 3 (A = Ca, Sr; B Zr 4+ ) is the subject of this investigation. The optical properties of the Mn 4+ ion in CaZrO 3 is sensitive to oxygen stoichiometry. Comparison with the reported optical properties of oxygen-stoichiometric CaZrO 3 :Mn 4+ obtained by synthesizing in oxygen atmosphere indicates that the air sintered sample represents Mn 4+ luminescence in an oxygen deficient perovskite lattice. The luminescence of SrZrO 3 :Mn 4+ suggests that this perovskite is less prone to the formation of oxygen vacancies. The difference between the energies of the zero-phonon line ( 2 E→ 4 A 2 transition; R-line) in CaZrO 3 and SrZrO 3 is related to the deviation of the octahedral O–Mn–O bond angle from the ideal 90° value. Comparison with isostructural perovskites ASnO 3 (A = Ca, Sr) shows that the energy of the 2 E level depends on the covalent character of B –O bonding. The stronger covalence of Zr 4+ 4d 0 - O 2− 2p bonding compared to that of Sn 4+ 4d 10 - O 2− 2p bonding is responsible for the higher energy position of the Mn 4+ 2 E level in the zirconate perovskite. Mulliken population analysis and bond order calculations are made to understand the nature of chemical bonding in the perovskites A B O 3 (A = Ca, Sr; B = Zr 4+ , Sn 4+ ). • Luminescence of Mn 4+ in perovskites AZrO 3 are discussed. • Comparative study with Mn 4+ luminescence in perovskite ASnO 3 is provided. • Influence of covalent bonding on R-line energy is discussed. • Calculations of the Mulliken charges are used to interpret optical data.

DFT Study on the Chemical Absorption Mechanism of CO2 in Diamino Protic Ionic Liquids.

Diamino protic ionic liquids (DPILs) possess a wide application prospect in the field of acid gas absorption. In this work, two representative DPILs, that is, dimethylethylenediamine 4-fluorophenolate ([DMEDAH][4-F-PhO]) and dimethylethylenediamine acetate ([DMEDAH][OAc]), which had been proved to display favorable CO2 absorption performance in experiments, were selected. Based on the solvation model, the different mechanisms of CO2 absorption by [DMEDAH]+ cations combined with different anions were investigated using the dispersion-corrected density functional theory method. Above all, the possible active sites of the reaction between DPILs and CO2 were analyzed by electrostatic potential (ESP) and electronegativity, and the transition states in each path were searched and verified by frequency calculation and intrinsic reaction coordinate calculation. Furthermore, the Gibbs free energy and reaction heat of each path were calculated, and the free energy barrier and enthalpy barrier diagrams were shown. It was found that the absorption path by the anion of [DMEDAH][4-F-PhO] was favorable in kinetics, while the absorption path by the cation was thermodynamically beneficial. In addition, [DMEDAH][OAc] only showed the possibility of cation absorption, and the mechanism of the transfer of active protons to weak acid anions and the formation of acetic acid molecules was more favorable. Moreover, through the structural analysis, bond order and bond energy calculation, ESP analysis of the ion pair absorption configuration, and comparison with the products of CO2 absorbed by isolated ions, it was found that the interaction between anions/cations and CO2 could weaken or enhance the interaction between anions and cations in different reaction steps. Hopefully, this study is helpful to understand the absorption mechanism of CO2 by DPILs and provides a theoretical basis for the R&D of multi-active site functionalized ILs.

Bis-(1,2,4-triazin-3-yl) ligand structure driven selectivity reversal between Am3+ and Cm3+: solvent extraction and DFT studies.

Selectivity between Am3+ and Cm3+ was investigated after their aqueous complexation with three structurally tailored hydrophilic bis-(1,2,4-triazin-3-yl) ligands followed by their extraction with N,N,N'N'-tetraoctyl diglycolamide (TODGA) dissolved in an ionic liquid (C4mim·Tf2N). The three hydrophilic ligands used were SO3PhBTP, SO3PhBTBP, and SO3PhBTPhen. It was evident from the solvent extraction studies that SO3PhBTP formed a stronger complex with Cm3+ than with Am3+, but SO3PhBTPhen showed better complexation ability for Am3+ than for Cm3+, and SO3PhBTBP showed no selectivity for the two actinide ions. DFT calculations indicated that the coordinating 'N' atoms in BTP were more co-planar in the complex and this co-planarity was higher in the Cm3+ complex as compared to that in Am3+. In the case of BTBP and BTPhen ligands, on the other hand, the co-planarity was more pronounced in the Am3+ complexes. Mayer's bond order calculations of M-N bonds in the complexes also indicated a reversal of the complexation ability of the BTP and BTPhen ligands for Am3+ and Cm3+. Calculations of the complexation energies further supported the higher selectivity of the BTP ligand for Am3+ by -52.0 kJ mol-1, and better selectivity of the BTPhen ligand for Cm3+ by -24.7 kJ mol-1.

Polynitro-acetone, dimethyl ether, and dimethylamine: a series of potential green and powerful oxidants for propellants.

With the purpose of searching novel, green and energetic oxidants, polynitro-acetone, polynitro-dimethyl ether, and polynitro-dimethylamine are designed as potential powerful oxidants and energetic materials in this work. Their optimized molecular geometries and electronic structures are calculated using density functional theory at m062x/6-311G++(d,p) level. Based on these results, heat of formation (HOF), detonation energy (Q), detonation velocity (D), and detonation pressure (P) are further evaluated. It is found that the oxygen-rich and chlorine-free compounds with 5 to 6 NO2 groups in molecule can be used as the potential energetic oxidants with high oxygen balance, while those with 3 to 4 NO2 groups are suitable for high-density energetic materials. Furthermore, stability correlations of all the compounds are established according to calculated bond order, natural bond orbital (NBO), bond dissociation enthalpies (BDE), and energy gaps (ΔELUMO-HOMO). Finally, burning rate is also calculated to show their potential application as oxidants in propellants. Graphical abstract.