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Guided ion beam tandem mass spectrometry (GIBMS) was used to measure the kinetic energy dependent product ion cross sections for reactions of the lanthanide metal dysprosium cation (Dy

Sodiated complexes of the aliphatic amino acids, Gly, Ala, Val, Leu, and Ile, were examined with infrared multiple-photon dissociation action spectroscopy utilizing light from a free-electron laser. To identify structures, the experimental spectra were compared to linear spectra calculated at the B3LYP/6-311+G(d,p) level of theory. Relative energetics of all complexes were calculated at B3LYP, B3P86, MP2(full), B3LYP-GD3BJ, and M06-2X levels using a 6-311+G(2d,2p) basis set. Spectral comparison for all complexes indicates that the dominant conformation, [N, CO], binds to the amino nitrogen and carbonyl oxygen. For all complexes except Gly, contributions are observed from [CO2-] structures, where the sodium cation binds to both oxygens of the carboxylate group in the zwitterionic form of the amino acid. The semiquantitative distribution between these two structures appears to be best-predicted by the B3LYP and MP2(full) levels of theory, with predictions from the other three levels inconsistent with the experiment.

The kinetic-energy-dependent cross section for the reaction of Nd+ with D2 was studied by using a guided ion beam tandem mass spectrometer. The formation of NdD+ is endothermic, and analysis of the reaction cross section gave an NdH+ 0 K bond dissociation energy (BDE) of 1.99 ± 0.06 eV. Theoretical calculations for the NdH+ BDE were performed for comparison with the experimental thermochemistry and generally gave accurate results. Additionally, relaxed potential energy surfaces for NdH2+ were performed, and no strongly bound dihydride intermediate was located. The Nd+ + D2 reactivity and BDE of NdH+ are compared with analogous results for the lanthanide cations La+, Ce+, Pr+, Sm+, Gd+, and Lu+ to establish periodic trends and insight into the role of the electronic configurations on this reactivity and the lanthanide hydride cation bond strengths.

Guided ion beam tandem mass spectrometry (GIBMS) was used to measure the kinetic energy dependent product ion cross sections for reactions of the lanthanide metal praseodymium cation (Pr+) with O2, CO2, and CO and reactions of PrO+ with CO, O2, and Xe. PrO+ is formed through barrierless exothermic processes when the atomic metal cation reacts with O2 and CO2, whereas all other reactions are observed to be endothermic. Analyses of the kinetic energy dependences of these cross sections yield 0 K bond dissociation energies (BDEs) for PrO+, PrC+, PrCO+, and PrO2+. The 0 K BDE for PrO+ is determined to be 7.62 ± 0.09 eV from the weighted average of five independent thresholds. This value is combined with the well-established ionization energy (IE) of Pr to indicate an exothermicity of the chemi-ionization reaction, Pr + O → PrO+ + e−, of 2.15 ± 0.09 eV. Additionally, BDEs of Pr+–C, OPr+–O, and Pr+–CO are determined to be 2.97 ± 0.10. 2.47 ± 0.11, and 0.31 ± 0.07 eV. Theoretical Pr+–O, Pr+–C, OPr+–O, and Pr+–CO BDEs are calculated for comparison with experimental values. The Pr+–O BDE is underestimated at the B3LYP and PBE0 level of theory but better agreement is obtained using the coupled-cluster with single, double, and perturbative triple excitations, CCSD(T), level. Density functional theory approaches yield better agreement for the BDEs of Pr+–C, OPr+–O, and Pr+–CO.

Reactions of the atomic lanthanide cerium cation (Ce+) with H2, D2, and HD were studied by using guided ion beam tandem mass spectrometry. Analysis of the kinetic-energy-dependent endothermic reactions to form CeH+ (CeD+) led to a 0 K bond dissociation energy (BDE) for CeH+ of 2.19 ± 0.09 eV. Theoretical calculations for CeH+ were performed at the B3LYP, BHLYP, and PBE0 levels of theory and overestimate the experimental BDE. In contrast, extrapolation to the complete basis set limit using coupled-cluster with single, double, and perturbative triple excitations, CCSD(T), gave a value (2.33 eV) in reasonable agreement with the experimental BDE. The branching ratio of the CeH+ and CeD+ products in the HD reaction suggests that the reaction occurs via a statistical mechanism involving a long-lived intermediate. Relaxed potential energy surfaces for CeH2+ were computed and are consistent with the availability of such an intermediate, but the crossing point between quartet and doublet surfaces helps explain the inefficiency of the association reaction observed in the literature. The reactivity and CeH+ BDE are compared with previous results for group 4 transition metal cations (Ti+, Zr+, and Hf+), other lanthanides (La+, Sm+, Gd+, and Lu+), and the isovalent actinide Th+. Periodic trends and insight into the role of the electronic configuration on metal-hydride bond strength are discussed.

The gas-phase structures of cationized glycine (Gly), including complexes with Li+, Na+, K+, Rb+, and Cs+, are examined using infrared multiple-photon dissociation (IRMPD) spectroscopy utilizing light generated by a free electron laser, in conjunction with ab initio calculations. To identify the structures present in the experimental studies, measured IRMPD spectra are compared to spectra calculated at B3LYP/6-311+G(d,p) for the Li+, Na+, and K+ complexes and at B3LYP/def2TZVP for the Rb+ and Cs+ complexes. Single-point energy calculations were carried out at the B3LYP, B3P86, and MP2(full) levels using the 6-311+G(2d,2p) basis set for Li+, Na+, K+ and the def2TZVPP basis set for Rb+ and Cs+. The Li+ and Na+ complexes are identified as metal cation coordination to the amino nitrogen and carbonyl oxygen, [N,CO]-tt, although Na+(Gly) may have contributions from additional structures. The heavier metal cations coordinate to either the carbonyl oxygen, [CO]-cc, or the carbonyl oxygen and hydroxy oxygen, [CO,OH]-cc, with the former apparently preferred for Rb+ and Cs+ and the latter for K+. These two structures reside in a double-well potential and different levels of theory predict very different relative stabilities. Some experimental evidence is provided that MP2(full) theory provides the most accurate relative energies.

The kinetic-energy-dependent cross section for the reaction of Nd

Guided ion beam tandem mass spectrometry (GIBMS) was used to measure the kinetic energy dependent product ion cross sections for reactions of the lanthanide metal praseodymium cation (Pr+) with O2, CO2, and CO and reactions of PrO+ with CO, O2, and Xe. PrO+ is formed through barrierless exothermic processes when the atomic metal cation reacts with O2 and CO2, whereas all other reactions are observed to be endothermic. Analyses of the kinetic energy dependences of these cross sections yield 0 K bond dissociation energies (BDEs) for PrO+, PrC+, PrCO+, and PrO2+. The 0 K BDE for PrO+ is determined to be 7.62 ± 0.09 eV from the weighted average of five independent thresholds. This value is combined with the well-established ionization energy (IE) of Pr to indicate an exothermicity of the chemi-ionization reaction, Pr + O → PrO+ + e-, of 2.15 ± 0.09 eV. Additionally, BDEs of Pr+-C, OPr+-O, and Pr+-CO are determined to be 2.97 ± 0.10. 2.47 ± 0.11, and 0.31 ± 0.07 eV. Theoretical Pr+-O, Pr+-C, OPr+-O, and Pr+-CO BDEs are calculated for comparison with experimental values. The Pr+-O BDE is underestimated at the B3LYP and PBE0 level of theory but better agreement is obtained using the coupled-cluster with single, double, and perturbative triple excitations, CCSD(T), level. Density functional theory approaches yield better agreement for the BDEs of Pr+-C, OPr+-O, and Pr+-CO.

Guided ion beam tandem mass spectrometry was used to study the reactions of the atomic lanthanide praseodymium cation (Pr

Reactions of the atomic lanthanide cerium cation (Ce

The exothermicity of the chemi-ionization reaction, Nd + O → NdO

The exothermicity of the chemi-ionization reaction, Nd + O → NdO+ + e−, has been indirectly determined by measuring the thermochemistry for reactions of the lanthanide metal neodymium cation (Nd+) with O2, CO2, and CO and reactions of NdO+ with CO, O2, and Xe. Guided ion beam tandem mass spectrometry was used to measure the kinetic energy dependent product ion cross sections for these reactions. NdO+ is formed through a barrierless exothermic process when the atomic metal cation reacts with O2 and CO2. All other reactions are observed to be endothermic. Analyses of the kinetic energy dependences of these cross sections yield 0 K bond dissociation energies (BDEs) for several species. The 0 K BDE for Nd+–O is determined to be 7.28 ± 0.10 eV from the average of four independent thresholds. This value is combined with the well-established Nd ionization energy to indicate an exothermicity of the title reaction of 1.76 ± 0.10 eV, which is lower and more precise than literature values. In addition, the Nd+–C, ONd+–O, and Nd+–CO BDEs are determined to be 2.61 ± 0.30, 2.12 ± 0.30, and 0.30 ± 0.21 eV. Additionally, theoretical BDEs of Nd+–O, Nd+–C, ONd+–O, and Nd+–CO are calculated at several levels for comparison with the experimental values. B3LYP calculations seriously underestimate the Nd+–O BDE, whereas MP2 and coupled-cluster with single, double-and perturbative triple excitations values are in reasonable agreement. Good agreement is generally obtained for Nd+–C, ONd+–O, and Nd+–CO BDEs as well.