EMSL: Bert deJong's Publications

Aubriet F, JJ Gaumet, WA De Jong, GS Groenewold, AK Gianotto, ME McIIwain, MJ Van Stipdonk, and CM Leavitt. 2009. "Cerium Oxyhydroxide Clusters: Formation, Structure and Reactivity." Journal of Physical Chemistry A 113(22):6239-6252. doi:10.1021/jp9015432 Abstract Cerium oxyhydroxide cluster anions were produced by irradiating ceric oxide particles using 355 nm laser pulses that were synchronized with pulses of nitrogen gas admitted to the irradiation chamber. The gas pulse stabilized the nascent clusters that are largely anhydrous [CexOy] ions and neutrals. These initially-formed species react with water, principally forming closed-shell (c-s) oxohydroxy species that are described by the general formula [CexOy(OH)z]-. In general, the extent of hydroxylation varies from a value of 3 OH per Ce atom when x = 1 to a value slightly greater than 1 for x > 8. The Ce3 and Ce6 species deviate significantly from this trend: the x = 3 cluster accommodates more hydroxyl moieties compared to neighboring congeners at x = 2 and x = 4. Conversely, the x = 6 cluster is significantly less hydroxylated. Density functional theory (DFT) modeling of the cluster structures show that the hydrated clusters are hydrolyzed, and contain one-to-multiple hydroxide moieties, but not datively bound water. DFT also predicts an energetic preference for formation of highly symmetric structures as the size of the clusters increases. The calculated structures indicate that the ability of the Ce3 oxyhydroxide to accommodate more extensive hydroxylation is due to a more open, hexagonal structure in which the Ce atoms can participate in multiple hydrolysis reactions. Conversely the Ce6 oxyhydroxide has an octahedral structure that is not conducive to hydrolysis. In addition to the c-s clusters, open-shell (o-s) oxyhydroxides and superoxides are also formed, and they become more prominent as the size of the clusters increases, suggesting that the larger ceria clusters have an increased ability to stabilize a non-bonding electron. The overall intensity of the clusters tends to monotonically decrease as the cluster size increases, however this trend is interrupted at Ce13, which is significantly more stable compared to neighboring congeners, suggesting formation of a dehydrated Keggin-type structure.

Leavitt CM, VS Bryantsev, WA De Jong, MS Diallo, WA Goddard III, GS Groenewold, and MJ Van Stipdonk. 2009. "Addition of H2O and O-2 to Acetone and Dimethylsulfoxide Ligated Uranyl(V) Dioxocations." Journal of Physical Chemistry A 113(11):2350-2358. doi:10.1021/jp807651c Abstract Gas-phase complexes of the formula [UO2(lig)]+ (lig=acetone (aco) or dimethylsulfoxide (dmso)) were generated by electrospray ionization (ESI) and studied by tandem ion-trap mass spectrometry to determine the general effect of ligand charge donation on the reactivity of UO2+ with respect to water and dioxygen. The original hypothesis that addition of O2 is enhanced by strong σ-donor ligands bound to UO2+ is supported by results from competitive collision-induced dissociation (CID) experiments, which show near exclusive loss of H2O from [UO2(dmso)(H2O)(O2)]+, while both H2O and O2 are eliminated from the corresponding [UO2(aco)(H2O)(O2)]+ species. Ligand-addition reaction rates were investigated by monitoring precursor and product ion intensities as a function of ion storage time in the ion-trap mass spectrometer: these experiments suggest that the association of dioxygen to the UO2+ complex is enhanced when the more basic dmso ligand was coordinated to the metal complex. Conversely, addition of H2O is favored for the analogous complex ion that contains an aco ligand. Experimental rate measurements are supported by density function theory calculations of relative energies, which show stronger bonds between UO2+ and O2 when dmso is the coordinating ligand, while bonds to H2O are stronger for the aco complex.

Nichols PJ, N Govind, EJ Bylaska, and WA De Jong. 2009. "Gaussian Basis Set and Planewave Relativistic Spin-Orbit Methods in NWChem." Journal of Chemical Theory and Computation 5(3):491-499. doi:10.1021/ct8002892 Abstract Relativistic spin-orbit density functional theory (DFT) methods have been implemented in the molecular Gaussian DFT and pseudopotential plane-wave DFT modules of the NWChem electronic-structure program. The Gaussian basis set implementation is based upon the zeroth-order regular approximation (ZORA) while the planewave implementation uses spin-orbit pseudopotentials that are directly generated from the atomic Dirac-Kohn-Sham wavefunctions or atomic ZORA-Kohn-Sham wavefunctions. Compared to solving the full Dirac equation these methods are computationally efficient, but robust enough for a realistic description of relativistic effects such as spin-orbit splitting, molecular orbital hybridization, and core effects. Both methods have been applied to a variety of small molecules, including I$_{\text{2}}$, IF, HI, Br$_{\text{2}}$, Bi$_{\text{2}}$, AuH, and Au$_{\text{2}}$, using various exchange-correlation functionals. Our results are in good agreement with experiment and previously reported calculations.

Bryantsev V, WA De Jong, KC Cossel, MS Diallo, WA Goddard III, GS Groenewold, W Chien, and MJ Van Stipdonk. 2008. "Two-Electron Three-Centered Bond in Side-On (η2) Uranyl(V) Superoxo Complexes." Journal of Physical Chemistry A 112(26):5777-5780. doi:10.1021/jp804202q Abstract Mononuclear dioxygen-metal compounds, such as FeO2 complexes with Schiff base and porphyrin ligands, play an essential role in chemistry ranging from oxyhemoglobin to cytochrome P-450 and cytochrome oxidase. It is well known that the superoxo complexes involved in these systems have end-on (η1) coordination geometries with O–O bond lengths of ~1.30 Å, Fe–O–O bond angles of ~135o, and vibrational frequencies of ~1150 cm-1,1 which reflects a formal change of the oxidation state from Mn+ to Mn+1. In addition, there are side-on (η2) peroxospecies, such as [Fe(porphyrin)(O2)]–, in which the O–O bond lengths is ~1.46 Å and vibrational frequencies of ~820 cm-1.1 These reflect a formal change of the oxidation state from Mn+ to Mn+2.

De Macedo LGM, and WA De Jong. 2008. "Fully Relativistic Calculations on the Potential Energy Surfaces of the Lowest 23 States of Molecular Chlorine." Journal of Chemical Physics 128(4):Art. No. 041101. doi:10.1063/1.2827457 Abstract The electronic structure and spectroscopic properties (Re, ωeϰe, βe, Te ) of the ground state and the 22 lowest excited states of chlorine molecule were studied within a four component relativistic framework using the MOLFDIR program package. The potential energy curves of all possible 23 covalent states were calculated using relativistic complete open shell configuration interaction (COSCI) approach. In addition, four component multi-reference configuration interaction with singles and doubles excitations (MRCISD) calculations were performed in order to infer the effects due to dynamical correlation in vertical excitations. The calculated properties are in good agreement with the available experimental data.

Groenewold GS, AK Gianotto, ME McIIwain, MJ Van Stipdonk, M Kullman, DT Moore, N Polfer, J Oomens, IA Infante, L Visscher, B Siboulet, and WA De Jong. 2008. "Infared Spectroscopy of Discrete Uranyl Anion Complexes." Journal of Physical Chemistry A 112(3):508-521. doi:10.1021/jp077309q Abstract The Free-Electron Laser for Infrared Experiments (FELIX) w 1 as used to study the wavelength-resolved multiple photon photodissociation of discrete, gas phase uranyl (UO2 2 2+) complexes containing a single anionic ligand (A), with or without ligated solvent molecules (S). The uranyl antisymmetric and symmetric stretching frequencies were measured for complexes with general formula [UO2A(S)n]+, where A was either hydroxide, methoxide, or acetate; S was water, ammonia, acetone, or acetonitrile; and n = 0-3. The values for the antisymmetric stretching frequency for uranyl ligated with only an anion ([UO2A]+) were as low or lower than measurements for [UO2]2+ ligated with as many as five strong neutral donor ligands, and are comparable to solution phase values. This result was surprising because initial DFT calculations predicted values that were 30–40 cm-1 higher, consistent with intuition but not with the data. Modification of the basis sets and use of alternative functionals improved computational accuracy for the methoxide and acetate complexes, but calculated values for the hydroxide were greater than the measurement regardless of the computational method used. Attachment of a neutral donor ligand S to [UO2A]+ produced [UO2AS]+, which produced only very modest changes to the uranyl antisymmetric stretch frequency, and did not universally shift the frequency to lower values. DFT calculations for [UO2AS]+ were in accord with trends in the data, and showed that attachment of the solvent was accommodated by weakening of the U-anion bond as well as the uranyl. When uranyl frequencies were compared for [UO2AS]+ species having different solvent neutrals, values decreased with increasing neutral nucleophilicity.

Groenewold GS, MJ Van Stipdonk, WA De Jong, J Oomens, GL Gresham, ME McIIwain, D Gao, B Siboulet, L Visscher, M Kullman, and N Polfer. 2008. "Infrared Spectroscopy of Dioxouranium (V) Complexes with Solvent Molecules: Effect of Reduction." Chemphyschem 9(9):1278-1285. doi:10.1002/cphc.200800034 Abstract UO2+-solvent complexes having the general formula [UO₂ (ROH)]+ (R = H, CH₃, C₂H₅, and n-C₃H₇) were formed using electrospray ionization and stored in a Fourier transform ion cyclotron resonance mass spectrometer, where they were isolated by mass-to-charge ratio, and then photofragmented using a free electron laser scanning through the 10 μm region of the infrared spectrum. Antisymmetric O=U=O stretching frequencies (ν3) were measured for all four complexes, which ranged from ~ 953 cm¯¹ for H₂O to ~ 944 cm¯¹ for n- PrOH, with the value for the EtOH-containing complex intermediate, systematically decreasing with increasing nucleophilicity of the solvent. The value for the MeOH-containing did not follow the trend, and had a measured ν3 value equal to that of the n-PrOH-containing complex. The ν3 frequency values for these U(V) complexes are comparable to those for the anionic [UO₂ (NO₃)₃]- complex, and lower than previously reported values for ligated uranyl (VI) dication complexes by 40 – 70 cm¯¹, and cationic uranyl (VI) ion-pair complexes by 10 – 40 cm¯¹. The lower frequency is attributed to weakening of the O=U=O bonds by repulsion related to reduction of the U metal center, which increases electron density in the antibonding π* orbitals of the uranyl moiety. Computational modelling of the ν3 frequencies of these species using PBE, B3LYP and LDA functionals showed good agreement with the IRMPD measurements. In general, expected trend in ν3 frequencies expected for the H₂O – MeOH – EtOH – n-PrOH series was produced by all three computational methods, however the three alcohols produced very similar values. The inverted order of MeOH and EtOH was not directly accounted for by the models, but is probably the result of overlapping C-H wagging modes that shift the apparent maxima of the O=U=O ν3 absorptions in the MeOH and EtOH complexes.

Groenewold GS, J Oomens, WA De Jong, GL Gresham, ME McIIwain, and MJ Van Stipdonk. 2008. "Vibrational Spectroscopy of Anionic Nitrate Complexes of UO₂2+ and Eu³+ Isolated in the Gas Phase." Physical Chemistry Chemical Physics. PCCP 10(8):1192-1202. doi:10.1039/b715337f Abstract Wavelength-selective infrared multiple photon photo-dissociation (IRMPD) was used to generate infrared spectra of anionic nitrate complexes of UO₂²+ and Eu3+ in the mid-infrared region. A pattern of absorptions were observed for both species, including splitting of the antisymmetric O-N-O stretch into high and low frequency components with the magnitude of the splitting consistent with attachment of nitrate to a strong Lewis acid center. The frequencies measured for [UO2(NO3)3]- were within a few cm-1 of those measured in the condensed phase, the best agreement yet achieved for a comparison of IRMPD with condensed phase absorption spectra. In addition, experimentally-determined values were in good general agreement with those predicted by DFT calculations, especially for the antisymmetric UO₂ stretch. The spectrum from the [UO₂ (NO₃)₃]- was compared with that of [Eu(NO3)4]-, which showed that nitrate was bound more strongly to the Eu3+ metal center, consistent with its higher charge. The spectrum of a unique uranyl-oxo species having an elemental composition [UO9N₃]- was also acquired, for which calculations suggested a [UO₂(NO₃)₂(O)]- structure.

Hammond JR, WA De Jong, and K Kowalski. 2008. "Coupled-Cluster Dynamic Polarizabilities Including Triple Excitations." Journal of Chemical Physics 128:224102-1 - 224102-11. doi:10.1063/1.2929840 Abstract Dynamic polarizabilities for open- and closed-shell molecules were obtained using coupled-cluster (CC) linear response theory with full treatment of singles, doubles and triples (CCSDT-LR) with large basis sets utilizing the NWChem software suite. Using four approximate CC methods in conjunction with augmented cc-pVNZ basis sets, we are able to evaluate the convergence in both many-electron and one-electron spaces. For systems with primarily dynamic correlation, the results for CC3 and CCSDT are almost indistinguishable. For systems with more static correlation, the PS(T) approximation [J. Chem. Phs. 127, 164105 (2007) performs better that CC3. Additionally, the PS(T) approach separates the triples contribution to the poles of the response function from the triples amplitudes themselves, and demonstrates that the latter are less important than originally thought Lastly, our results show that the choice of reference (ROHF versus UHF) can have a significant impact on the accuracy of polarizabilities for open-shell systems.

Jackson VE, RN Craciun, DA Dixon, KA Peterson, and WA De Jong. 2008. "Prediction of the Vibrational Frequencies of UO₂²+ at the CCSD(T) Level." Journal of Physical Chemistry A 112(17):4095-4099. doi:10.1021/jp710334b Abstract Electronic structure calculations at the coupled cluster (CCSD(T)) and density functional theory levels with various relative effective core potentials and basis sets have been used to predict the isolated uranyl ion frequencies. The effects of anharmonicity and spin-orbit corrections on the harmonic frequencies have been calculated. The anharmonic effects are larger than the spin orbit corrections and both are small. The anharmonic effects decrease the frequencies and the spin orbit corrections increase the stretches and decrease the bend. Overall, these corrections decrease the harmonic asymmetric stretch frequency by 6 cm-¹, the symmetric stretch by 3 cm-1 and the bend by 3 cm-¹. The splitting between the asymmetric and symmetric stretch is predicted to be 86 cm-¹, which is consistent with experimental trends for substituted uranyls in solution and in the solid state.