Heats of formation, bond dissociation energies, proton affinities, gas phase acidities, and pKa values in water, dimethyl sulfoxide, acetonitrile, and tetrahydrofuran were calculated for all hydrogen-containing halomethanes and methane using composite correlated molecular orbital theory at the G3(MP2) and Feller-Peterson-Dixon (FPD) levels. Notably, the G3(MP2) method was extended to include iodine-containing compounds. The calculated gas phase acidities generally agree with available experimental data within experimental error limits, often within ±4 kJ/mol; however, CH2F2 is a significant exception where theory and experiment differ by nearly 40 kJ/mol for the acidity ΔG. Aqueous pKa values range from 53.6 for CH3F to 28.0 for CHF2I. The latter's unexpectedly high acidity results from the CF2I- anion resembling a CF2 carbene interacting with an iodide anion. These computed values rationalize literature base choices for anion generation: trihalomethanes (pKa 28.0-34.2) are deprotonated by nonorganometallic bases (KOH, DBU, KOtBu), whereas less acidic dihalomethanes (pKa ≳ 38), particularly fluorodihalomethanes (pKa 42-49), require strong metal amides (e.g., LTMP, LDA), with LHMDS proving inadequate. An experimental CHBrCl2 case study corroborates these predictions, showing clean deprotonation with lithium amides compared to diminished efficiency with weaker bases due to competitive hydroxide addition. This work provides the most comprehensive high-accuracy thermochemical data set for the complete set of hydrogen-containing halomethanes.

Stabilized radicals formed by irradiation of thin poly(vinylidene fluoride) films with high-energy accelerated 22Ne+4, 132Xe+26 and 209Bi+51 ions with respective energies of 24, 158 and 670 MeV were studied by EPR, Fourier transform infrared, and UV-visible spectroscopies. The bombarding ions cause significant excitation and ionization along the ion tracks throughout the thickness of the film. The reduction of crystallinity and the formation of unsaturated bonds in the irradiated polymer were explored spectroscopically The presence of alkyl, peroxide, and polyenyl radicals were identified in the spectra of the irradiated polymer; mechanisms for radical formation are proposed. Preliminary freezing of the irradiated films to dry ice temperature and subsequent study after storage at room temperature led to quantitative estimates of the loss of radicals during storage. Computational chemistry was used to predict the thermodynamics of the degradation processes and resulting peroxide radical reactions. Localized energy due to the ion bombardment enabled thermodynamically unfavorable reactions to proceed. The results of the study should be useful for optimization of processes for creating PVDF-based membranes for various applications.

ABSTRACT Copper–zeolite catalysts exhibit superior performance in selective catalytic reduction (SCR) of NO x and partial oxidation of methane (POM), but identification of their active sites remains elusive and is often controversial. Recent reports suggest that dimeric copper species are responsible for the active sites for these reactions. We demonstrate that infrared and UV‐resonance Raman spectroscopy (using 244 nm laser) combined with UV–vis spectroscopy can reveal the anchoring and speciation of copper in SSZ‐13 zeolite, particularly the dominant monomeric copper species that cannot be observed by Raman spectroscopy with commonly employed visible laser excitation (∼400–600 nm). Electronic structure modeling corroborates the spectroscopic features and reveals the vibrational coupling modes associated with the interfacial bonding between copper and the zeolite framework. The pseudo‐square‐planar monomeric Z 2 Cu species (“Z” represents the zeolite framework charge site) were found to be the active sites for both SCR and POM at ∼400°C, whereas monomeric ZCuOH species are responsible for SCR at lower temperatures.

The chemical and electronic properties of all diatomic 3d transition metal oxides are investigated to further understand their bonding and growing involvement in atmospheric science. High-level CCSD(T) and spin-orbit icMRCI+Q calculations were used to predict the potential energy curves (PECs) for the ground state and the low-lying states for TiO (3Δ), VO (4Σ-), CrO (5Π), MnO (6Σ+), FeO (5Δ), CoO (4Δ), CuO (2Π), and ZnO (1Σ+). The inclusion of spin-orbit effects is critical for the determination of the ground states in FeO and CoO. Vibrational frequencies of each transition metal oxide are also calculated with CCSD(T) and icMRCI+Q. For the vibrational frequency calculations, the performance of using Hartree-Fock and PW91 reference orbitals was evaluated. The use of PW91 reference orbitals was found to provide better agreement with literature values for the vibrational frequencies and aids in property prediction of highly multireference transition metal oxides. The calculated vibrational frequencies are found to be in reasonable agreement with prior experimental and computational results. Bond dissociation energies (BDEs) of these systems were calculated at the Feller-Peterson-Dixon (FPD) level and are 158.5 kcal/mol (ScO), 158.2 kcal/mol (TiO), 150.1 kcal/mol (VO), 106.2 kcal/mol (CrO), 83.6 kcal/mol (MnO), 97.0 kcal/mol (FeO), 91.4 kcal/mol (CoO), 90.8 kcal/mol (NiO), 65.9 kcal/mol (CuO), and 35.6 kcal/mol (ZnO).

Density functional theory (B3LYP) and correlated molecular orbital theory (CCSD(T)) calculations were used to predict the properties of novel actinide-fluoride complexes formed by the addition of a fluorine to AnFn compounds, with actinides in their normal maximum oxidation state (n), leading to the formation of an ion-pair complex [AnFn-1+][F2-] for the earlier actinides (Ac, Th, and Pa). UF7 prefers a structure with a weakly associated fluorine, forming a [UF6][F•] complex, likely due to steric hindrance. Ionization of [AnFn-1+][F2-] forms a weakly bound [AnFn-1+][F2] complex. Ionization of AnFn leads to the formation of [AnFn-22+][F2-] complex so that the electron is not removed from the actinide and maintains the An oxidation state. The ionization energies, An-F bond dissociation energies, and enthalpy for the loss of F20/- of these complexes are in agreement with the available experimental data. The fluoride affinities of AnFn and the electron affinities of AnFn+1 were calculated. The fluoride affinities are large and comparable to those of AsF5 and SbF5 so they are strong Lewis acids. The electron affinities are sizable, indicating that AnFn+1- will be powerful oxidizing agents and should be considered in models of molten salt reactors when fluoride is present.

1,2,4-Triazole is a ubiquitous heterocycle of significance for pharmaceuticals, materials, and ligand design. A convergent, atom-economical strategy for the construction of this important moiety has been developed, leveraging functionalized heteroaryl hydrazonimides and carbaldehydes via iodine-mediated oxidative annulation in an efficient, scalable, and metal-free manner, providing completely chemoselective 1H- or 2H-3,5-disubstituted-1,2,4-triazoles of relevance to separation science and medicinal chemistry. The twenty-nine-example substrate scope is highlighted by rapid access to sp2- and sp3-hybridized substituents through carbaldehyde selection. Diversely functionalized pyridyl- and heteroaryl components were incorporated through a hydrazonimide synthon with several examples having relevance to unsymmetric, soft-N-donor complexant scaffolds utilized in minor actinide extraction in support of improving the sustainability of the nuclear fuel cycle. Single-crystal X-ray diffraction experiments confirmed the presence of 1H- and 2H-tautomers. Density functional theory computations provided support of a proposed mechanistic hypothesis. Method optimization, substrate scope, scale-up experiments, and a preliminary reaction mechanism are reported herein.

The properties of the fundamental hydrogen species, proton (H+), hydrogen atom (H•), and hydride anion (H-) are critical to a vast range of chemical processes, yet their thermodynamic properties in nonaqueous solvents are not well established. A hybrid supermolecule-continuum approach is used to predict the Gibbs free energies of solvation (ΔG°solv) and standard redox potentials (E°) for the 2H+/H2 and H•/H- couples in acetonitrile (MeCN) and tetrahydrofuran (THF) following the approach previously used for water. Gas phase and solution phase structures were optimized with ωB97X-D/aug-cc-pVTZ. Solvation was treated with the SMD self-consistent reaction field model, and CCSD(T)/aug-cc-pVTZ gas phase calculations were used as a benchmark for method sensitivity. For H+, the ΔG°solv values are predicted to be -258.7 kcal/mol in MeCN and -259.2 kcal/mol in THF. The standard redox potentials for the 2H+/H2 couple are +0.21 V (±0.1 V) in MeCN and +0.18 V (±0.15 V) in THF relative to the aqueous SHE (E°SHE = 4.28 V on the absolute scale), consistent with the available experimental data. The ΔG°solv for H- is predicted to be -76.9 kcal/mol in MeCN and -67.8 kcal/mol in THF, and for H•, ΔG°solv is predicted to be 2.1 kcal/mol in both MeCN and THF. These solvation energies yield calculated redox potentials for the H•/H- couple of -0.12 V (±0.3 V) in MeCN and -0.52 V (±0.1 V) in THF relative to the aqueous SHE. H2 solvation is near thermoneutral in both solvents. The pKa(H2) is predicted to be 43.0 in MeCN and 49.3 in THF. The proton-coupled electron transfer (PCET) accounting term CG was evaluated on the ferrocene scale and deviates from the reported literature values by 7.5 kcal/mol in MeCN and 5 kcal/mol in THF. These results establish an internally consistent thermodynamic framework for hydrogen redox chemistry in MeCN and THF and improve consistency across E°, ΔG°solv, pKa, and CG.

A machine learning (ML) framework is developed to predict normalized clustering energies (NCE) of metal(II) oxides in order to extrapolate them to predict cohesive bulk energies. The NCE is the permonomer averaged energy difference between the cluster and the corresponding isolated monomers. A data set of DFT-optimized M(II)O containing four alkaline earth and predominantly 3d transition metals (M = Mg, Ca, Sr, Ba, Sc, Ti, V, Cr, Mn, Co, Cu, Zn, Cd) is encoded with Smooth Overlap of Atomic Positions (SOAP) descriptors and used to train kernel ridge regression (KRR), a feed-forward artificial neural network (ANN), and tree-based models (Random Forest, AdaBoost, XGBoost). On a held-out test set, KRR achieves the lowest error (MAE = 0.619 kcal/mol, R2 = 0.994), followed by ANN (MAE = 1.250 kcal/mol, R2 = 0.986), while tree ensembles perform less well. By fitting the NCEs, bulk cohesive energies for closed-shell oxides (MgO, CaO, SrO, BaO, ZnO, and CdO) are predicted to within ∼1.5 kcal/mol of the corresponding DFT values. Adding higher-oxidation-state structures (e.g., TiO2 with Ti(IV)) improves ANN generalization within the Ti subset, suggesting that geometry and oxidation-state diversity improve model transferability. These results demonstrate that ML trained on modest cluster data can deliver accurate predictions of NCEs and bulk thermochemistry at a fraction of the cost of electronic-structure calculations. Furthermore, the model's ability to replicate DFT accuracy suggests that the complex electronic structure of metal oxides can be encoded into a suitable input vector for a simple ML regimen without a substantial increase in error.

The functional group interconversion of heteroaryl carbonitriles and benzohydrazides via microwave-assisted organic synthesis presents an opportunity to construct (1H)-1,2,4-triazole, 1,3,4-oxadiazole, or 1,3,4-thiazoles contingent on the electronic environment of the heteroaryl carbonitrile and benzohydrazide. The developed reaction protocol is atom economical, involving only the carbonitrile and benzohydrazide synthons and producing only water, or ammonia, as byproducts. The reaction strategy is free of metals and external oxidants and scalable. Complete chemoselectivity is achievable. This synthetic approach affords entry into a new class of non-C2-symmetric, tridentate, soft-N-donor complexants with potential utility in the selective separation of minor actinides from lanthanides in spent nuclear fuel toward potential closure of the nuclear fuel cycle. Synthetic method development, complexant and heteroaryl substrate scope, competition, application, and scale-up experiments as well as DFT calculations are reported herein.

The bonding and spectroscopic properties of LaX and AcX (X = O and F) diatomic molecules were studied by high-level ab initio CCSD(T) and SO-CASPT2 electronic structure calculations. Bond dissociation energies (BDEs) were calculated at the Feller-Peterson-Dixon (FPD) level. Potential energy curves and spectroscopic constants for the lowest-lying spin-orbit Ω states were obtained at the SO-CASPT2/aQ-DK level. A dense manifold of excited states was described for the monofluorides with the ground states well separated from the excited states. The spectroscopic parameters were in good agreement with those reported experimentally for LaO and LaF. For the diatomic molecules containing actinides, no experimental data of these parameters was found, but the results were consistent with other high-level calculations. The BDEs calculated at the FPD level were 791.3 (LaO), 705.2 (AcO), 650.0 (LaF), and 678.6 (AcF) kJ/mol. The NBO analysis showed that the monofluorides are essentially ionic, which explains why the BDE(AcF) is higher than BDE(LaF); for the monoxides, covalent contributions involving the d orbitals of the metal and the p orbitals of the oxygen are stronger for LaO than AcO, which explains the higher BDE for LaO. The bond orders are predicted to be 2 for LaF and AcF, 3 for AcO, and higher than 3 for LaO.

The periodic table provides an intuitive framework for understanding chemical properties. However, its traditional patterns may break down for the heaviest elements occupying the bottom of the chart. The large nuclei of actinides (Z > 88) and superheavy elements (Z ≥ 104) give rise to relativistic effects that are expected to substantially alter their chemical behaviours, potentially indicating that we have reached the end of a predictive periodic table1. Relativistic effects have already been cited for the unusual chemistry of the actinides compared with those of their lanthanide counterparts2. Unfortunately, it is difficult to understand the full impact of relativistic effects, as research on the later actinides and superheavy elements is scarce. Beyond fermium (Z = 100), elements need to be produced and studied one atom at a time, using accelerated ion beams and state-of-the-art experimental approaches. So far, no experiments have been capable of directly identifying produced molecular species. Here ions of actinium (Ac, Z = 89) and nobelium (No, Z = 102) were synthesized through nuclear reactions at the 88-Inch Cyclotron facility at Lawrence Berkeley National Laboratory and then exposed to trace amounts of H2O and N2. The produced molecular species were directly identified by measuring their mass-to-charge ratios using FIONA (For the Identification Of Nuclide A)3. These results mark the first, to our knowledge, direct identification of heavy-element molecular species using an atom-at-a-time technique and highlight the importance of such identifications in future superheavy-element chemistry experiments to deepen understanding of their chemical properties.

The diatomics BO, AlO, and ScO play roles in the combustion of the parent atoms. Potential energy curves for the lowest-lying spin-free (ΛS) and spin-orbit (Ω) states of gas-phase BO, AlO, and ScO were calculated with the SA-CASSCF/SO-icMRCI+Q/aug-cc-pwCVnZ-DK method (n = Q for ScO and n = 5 for BO and AlO). The spectroscopic parameters obtained at the icMRCI+Q level are consistent with the available experimental data, and new data for the spin-orbit states are presented. At the CCSD(T) level, the use of reference PW91 orbitals resulted in a significant improvement of the spectroscopic parameters for AlO and small improvements for BO and ScO. The dissociation energies were predicted at the icMRCI+Q and Feller-Peterson-Dixon (FPD) levels, including CCSDT, CCSDTQ, and spin-orbit effects. For BO, AlO, and ScO, the FPD D0 (De) values are 192.4 (195.1), 120.2 (121.6), and 158.2 (159.6) kcal/mol, respectively. NBO analysis shows that the ionic character increases in going from BO to AlO and slightly decreases in going from AlO to ScO, with two highly polarized π bonds and one σ bond. A pronounced multireference character is predicted for AlO at the CCSD(T) and SA-CASSCF/icMRCI+Q levels. The lowest excited states of BO and AlO are mostly formed from excitations on the 1π orbitals. For ScO, excitations on the 2σ orbital are the most significant to form the lowest excited states.

Our previously developed computational method for calculating the aqueous redox potentials of the early actinides has been extended to the later elements in the actinide series: Cm, Bk, Cf, Es, Fm, Md, No, and Lr in multiple oxidation states. These calculations were performed using density functional theory with small-core pseudopotentials and their associated basis sets. Solvation effects were considered via a supermolecule-continuum approach, with 30 water molecules representing two solvation shells. Both the COSMO and SMD implicit solvation models were utilized. The structural parameters and hydration numbers for Cm(III), Bk(III), Bk(IV), and Cf(III) are in reasonable agreement with the available experimental data. For redox processes involving atomic cations in solution, the B3LYP/COSMO approach predicted redox potentials to within ±0.2 V of the experimental values for most redox couples, consistent with our prior work. Inclusion of spin-orbit corrections in specific redox pairs, especially those with the later actinides in high oxidation states, yields improved results relative to calculations including only scalar-relativistic corrections. The An+m/An(0) redox potentials were calculated using a Born-Haber cycle incorporating sublimation, ionization, and hydration energies. Due to a lack of experimental data, three sets of ionization energies were used for the Born-Haber cycle. The calculated An(III/0) potentials showed better agreement with experimental data when using the COSMO solvation model and the test set comprising the NIST recommended ionization energies. The Md(II/0) potential was better described with the SMD model, whereas No(II/0) was not well described by all methods. The computational approach was able to predict redox potentials that for most cases agreed with the current available experimental or estimated data.

Density functional theory benchmarked by correlated molecular orbital theory is used to develop a fundamental and predictive understanding of the interaction of thorium oxide nanoclusters with gas phase water to provide insight into nuclear-waste storage, production of thorium nuclear reactor fuels, and reprocessing of spent fuel. The structures of ThnO2n (n = 3-6) clusters and their interactions with water have been studied at the B3LYP, MP2, and CCSD(T) levels. Hydrolysis is initiated by the formation of Lewis acid-base adducts, with relative H2O binding energies (physisorption) ranging from -15 to -22 kcal/mol. The initial H2O physisorption energy is ca. -21 kcal/mol regardless of the cluster size and is consistent with the experimentally obtained initial adsorption energy on a thorium dioxide surface. The physisorption enthalpies for additional water molecules can be affected by the presence of terminal groups OH groups generated by proton transfer to a Th-O near the site of adsorption. The hydrolysis products (chemisorption) form either bridging or terminal hydroxides. More exothermic hydrolysis steps were predicted for the formation of terminal hydroxides as compared to the formation of bridging hydroxides. The calculated transition state barriers for transfer of protons from bound water complexes to form the chemisorption products are very low. Overall, water readily reacts with thorium oxide clusters preferring hydroxide products over hydrated complexes. First and second order fits were predicted for the combined physisorption and chemisorption energies for the hydrolysis of thorium oxide clusters. Ionization energies and electron affinities were calculated as were HOMO-LUMO gaps to provide additional insights into the properties of the thorium oxide and hydroxide clusters.

High-level ab initio CCSD(T) and spin-orbit icMRCI+Q calculations were used to predict potential energy curves (PECs) for the lowest-lying states of ZrO, ZrS, HfO, and HfS. The prediction of the ground state is basis set dependent at the icMRCI+Q level for ZrO and ZrS due to the small singlet-triplet splitting between the lowest 1Σ+ and 3Δ states. CCSD(T) with a spin orbit correction predicted the 1Σ+ ground state in agreement with experiment. New all-electron basis sets were developed for Hf to improve the results over those predicted by use of effective core potentials (ECPs) that subsume the 4f electrons into the definition of the core. The use of the new DK-4f basis sets rather than ECPs became more important for HfO and HfS where there is a lack of a good core-valence separation. icMRCI+Q, CCSD(T), and DFT calculations for the spectroscopic parameters of ZrO, ZrS, HfO, and HfS were benchmarked with available experimental data. Bond dissociation energies (BDEs) of these four systems were calculated at the Feller-Peterson-Dixon (FPD) level to be 762.1 (ZrO), 543.5 (ZrS), 803.8 (HfO), and 575.1 kJ/mol (HfS), in excellent agreement with experiment. The HfS BDE was remeasured using the R3PI method, providing an updated experimental measurement of D0(HfS) = 5.978 ± 0.002 eV = 576.8 ± 0.2 kJ/mol. This experimental value, combined with experimental measurements of the ionization energies of Hf and HfS, gives the cationic BDE of D0(Hf+-S) = 5.124 ± 0.002 eV = 494.4 ± 0.2 kJ/mol.

A family of 8- and 9- coordinate homoleptic dimethyl sulfoxide An(IV) complexes is used to evaluate the solvation properties of tetravalent actinide ions in dimethyl sulfoxide (DMSO) vs aqueous media. These compounds are prepared from aqueous mixtures of DMSO and yield crystalline solids, whose solid-state electronic absorption spectra are compared to solution phase spectra, providing insight into the solution speciation. The thermodynamics of the equilibria between the 8- and 9-coordinate compounds were determined experimentally and computationally, showing a trend that correlates with ionic radius. Cyclic voltammetry data for the +IV/+III couples of Np and Pu in the DMSO electrolyte indicate that the +IV ions are significantly stabilized compared to aqueous media due to the more donating nature of DMSO compared to water. Computational studies of these systems indicate that further reactivity may take place upon reduction to the +III oxidation state.

Methanol (CH3OH) synthesis from carbon dioxide (CO2) hydrogenation is an industrially viable approach to CO2 utilization. For the recently developed indium oxide (In2O3) catalyst, higher performance may be achieved by introducing transition metal promoters, although recent studies suggest that single atom sites favour CO formation. Here, by density functional theory-based microkinetic simulations, bulk-doped Pt/In2O3 single atom catalysts (SACs) with much higher CO2 reactivity than the In2O3 catalyst while maintaining CH3OH selectivity were designed. Several Pt/In2O3 SACs were synthesized to confirm our theoretical predictions. The synthesized Pt/In2O3 SAC in the predominantly bulk-doped form exhibits much higher CO2 reactivity than the In2O3 catalyst with high stability and similar CH3OH selectivity, yielding a CH3OH productivity of 1.25 g gcat-1 h-1. This study demonstrates the power of computational methods in designing oxide-based catalysts for industrial reactions and reveals a bulk-doped SAC with high performance.

The redox potentials for U, Np, Pu, and Am for oxidation states +III up to +VIII in alkaline aqueous solutions were predicted using density functional theory (DFT) and small-core pseudopotentials and their basis sets, with a hybrid explicit/implicit solvent model using SHE = 4.28 V. For each oxidation state, various oxo/hydroxo complexes were evaluated, resulting in a variety of one-electron redox pathways. For An(VIII/VII) couples, the predicted redox potentials for the [An(VIII)O5(OH)]-3/[An(VII)O4(OH)2]-3 or [An(VIII)O4(OH)2]-2/[An(VII)O4(OH)2]-3 couples are in good agreement with existing estimates. For An(VII/VI) redox couples, all couples, particularly [An(VII)O4(OH)2]-3/[An(VI)O2(OH)4]-2, were in agreement with experimental values for U, Np, and Pu, but the results for Am showed larger differences from the estimated potentials. The An(VI/V) couples were consistent with experiments for dioxo/tetrahydroxo couples, and the An(V/IV) couples showed acceptable agreement based on actinide-specific couples, with neutral hydroxides often favored in the +IV state. The An(IV/III) couples were consistent with the literature values when modeled as soluble neutral hydroxides. The use of our approach yielded calculated redox potentials that were within ±0.2 V of experimental or estimated values consistent with our prior calculations on redox potentials of actinides from Ac to Am in acidic aqueous solutions. This supports the robustness of our DFT-based methodology for predicting actinide redox potentials, offering valuable insights into actinide chemistry in aqueous solutions.

Potential energy curves (PECs) for the spin-free (Lambda S) and spin-orbit (Omega) states associated with the four lowest-lying dissociation channels of Na-2 and K-2 were calculated at the SA-CASSCF/SO-CASPT2/aug-cc-pwCVQZ-DK level. The PECs of Na-2 were consistent with the experimental data and with the FS-CCSD (2,0) calculations, reproducing the double-well and the "shelf" character for some of the potentials of the excited states. For K-2, the PECs behaved in a similar way and the spectroscopic parameters for the ground and the excited states are in good agreement with the available experimental values. The dissociation energy of K-2 was predicted to be D-e = 4454 cm(-1), within an agreement of 5 cm(-1) with the experiments. For Na-2, D-e = 5789 cm(-1) compared to the experimental value of 6022 cm(-1). The inclusion of spin-orbit coupling effects resulted in avoided crossings, which affect the PECs. Spin-orbit changes the predicted curves for some excited Omega states arising from Lambda S states that overlap each other, affecting their associated vibrational frequencies and bond distances. The current studies of the low-lying states in K-2 reveal a similar structure to those of Na-2, which suggests the accessibility of long-lived energy storing reservoir states and possible population inversions in K-2 following prior experimental work on the reaction of halogen atoms with Na-3 to produce excited states of Na-2.