Showing papers by "P. B. Armentrout published in 2019"
TL;DR: 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 N dO+ with CO, O 2, and Xe.
Abstract: 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.
21 citations
TL;DR: Calculations for R,R'-BhPy+ ions predict that these ions fragment by the loss of pyridine via loose transition states, and the computed threshold energies of these fragmentations are significantly lower than those of the dissociation of the benzylpyridinium ions.
Abstract: Previous attempts to characterize the internal energies of ions produced by electrospray ionization (ESI) have chiefly relied upon benzylpyridinium ions, R-BnPy+, as thermometer ions. However, thes...
19 citations
TL;DR: In this article, a combination of experiments under both single-collision conditions using a guided ion beam tandem mass spectrometer (GIBMS) apparatus and at higher pressures using a selected-ion flow tube (SIFT) apparatus is investigated through density functional calculations.
15 citations
TL;DR: The results indicate that consideration of angular momentum conservation (as in PST) and spin-orbit corrected energies are needed to reproduce experimental results quantitatively.
14 citations
TL;DR: In this paper, the sequential activation of up to 4 CH_4 molecules by Ir^+ is investigated through a gas-phase infrared multiple photon dissociation (IRMPD) experiment and theoretical calculations.
14 citations
TL;DR: The binding interactions between Thr and biologically relevant metals in a prototypical environment is explored and comparison of current work with previous analyses allows for the elucidation of important metal dependent trends associated with physiologically important metal-amino acid binding.
Abstract: Complexes of threonine (Thr) cationized with Zn2+ and Cd2+ were examined by infrared multiple photon dissociation action spectroscopy using light generated from a free electron laser. Low-energy co...
12 citations
TL;DR: The kinetic energy dependences of the reactions of ThO+, ThO 2+, and OThOD+ with D2O, ThO2-D, OTh+-O, and Oth+-OD bond dissociation energies are experimentally determined for the first time and agree reasonably well with values calculated at the B3LYP, B3PW91, and PBE0 levels of theory with cc-pVQZ basis sets.
Abstract: The kinetic energy dependences of the reactions of ThO+, ThO2+, and OThOD+ with D2O, ThO2+ with D2, and OThOD+ with Xe were studied using guided ion beam tandem mass spectrometry. Exothermic formation of OThOD+ is the dominant process observed in reactions of both ThO+ and ThO2+ with D2O. Minor products formed in endothermic reactions include ThO2+, DThO+, and ThO2D2+. OThOD+ is also formed in the reaction of ThO2+ with D2 but in an endothermic process. Collision-induced dissociation (CID) of OThOD+ with Xe leads to endothermic loss of the hydroxide ligand. OThOD+ reacts further with D2O to form the associative complex ThO3D3+, which is long-lived before dissociating back to the reactants. The OThOD+-D2O bond energy of the associative complex is measured to be 2.96 ± 0.05 eV by modeling the kinetic energy-dependent cross section for association using a phase space theory model that rigorously conserves angular momentum. By comparison with theory, this bond energy identifies the ThO3D3+ species as the trihydroxide cation, Th(OD)3+. From the endothermic reactions and CID of OThOD+ with Xe, the OTh+-D, OTh+-O, and OTh+-OD bond dissociation energies (BDEs) are measured to be 2.33 ± 0.24, 4.66 ± 0.15, and 6.00 ± 0.17 eV, respectively. All four of these BDEs are experimentally determined for the first time and agree reasonably well with values calculated at the B3LYP, B3PW91, and PBE0 levels of theory with cc-pVQZ basis sets. Complete potential energy surfaces for all reactions were calculated at the B3LYP/cc-pVTZ level and elucidate the mechanisms for all processes observed.
12 citations
TL;DR: Computational results for predicted ground structures of M+(Lys) complexes yielded computed BDEs in reasonable agreement with experiment, which better explains recent infrared multiple photon dissociation action spectroscopy results.
Abstract: The kinetic energy dependence of the collision-induced dissociation (CID) of Group 1 metal cations (M+ = Li+, Na+, K+, Rb+, and Cs+) chelated to the amino acid lysine (Lys) was measured by threshol...
11 citations
TL;DR: The gas-phase structures of zinc and cadmium complexes of lysine (Lys) are investigated via a combination of infrared multiple photon dissociation action spectroscopy and ab initio quantum chemical calculations and identification of the experimentally formed isomers is possible.
Abstract: The gas-phase structures of zinc and cadmium complexes of lysine (Lys) are investigated via a combination of infrared multiple photon dissociation action spectroscopy and ab initio quantum chemical...
10 citations
TL;DR: Results predict a 2Σg + electronic ground state for Au2 + with BDEs calculated at the B3LYP and both CCSD(T) levels of theory in agreement with the experiment within the uncertainty.
Abstract: Guided ion beam tandem mass spectrometry was employed to measure the kinetic energy-dependent product ion cross sections for the collision induced dissociation of Au2+ with Xe. Gold dimer cations were formed in a glow discharge flow tube source that should create ions in their ground electronic state with thermal internal energies. Analysis of the endothermic kinetic energy dependent cross section accounts for multiple collisions, lifetime effects, and the internal energy of the reactant ion. The value obtained for the bond dissociation energy (BDE) of Au2+ is the first direct measurement and is reported here as 2.20 ± 0.21 eV. For comparison with experimental results, theoretical calculations were also completed at the B3LYP, M06-2X, and coupled cluster singles, doubles, and perturbative triples [CCSD(T,full)] levels of theory using the def2-TZVPPD basis set and at the CCSD(T)-F12/correlation-consistent polarized valence triple zeta basis with pseudopotential level. These results predict a 2Σg+ electronic ground state for Au2+ with BDEs calculated at the B3LYP and both CCSD(T) levels of theory in agreement with the experiment within the uncertainty. Several electronically excited states are also evaluated theoretically.
9 citations
TL;DR: Comparison of the experimental spectrum, obtained by monitoring the appearance of AuC+, and DFT calculated spectra leads to identification of the ground state carbene, AuCH2+ (1A1) as the species formed, as previously postulated theoretically.
Abstract: The present work explores the structure of the gold carbene cation, AuCH2+, using infrared multiple photon dissociation action spectroscopy and density functional theory (DFT). Unlike several other...
TL;DR: In this article, the authors present a thorough characterization of fragmentations observed in threshold collision-induced dissociation (TCID) experiments of protonated glycylalanylglycine (H+GAG) with Xe using a guided ion beam tandem mass spectrometer.
TL;DR: Comparisons between the IRMPD and theoretical IR spectra indicate that 18C6 binds to Gly and His via the protonated backbone amino group, whereas protonation Lys prefers binding via the Protonated side-chain amino group.
Abstract: Complexes of 18-crown-6 ether (18C6) with four protonated amino acids (AAs) are examined using infrared multiple photon dissociation (IRMPD) action spectroscopy utilizing light generated by the infrared free electron laser at the Centre Laser Infrarouge d'Orsay (CLIO). The AAs examined in this work include glycine (Gly) and the three basic AAs: histidine (His), lysine (Lys), and arginine (Arg). To identify the (AA)H+(18C6) conformations present in the experimental studies, the measured IRMPD spectra are compared to spectra calculated at the B3LYP/6-311+G(d,p) level of theory. Relative energies of various conformers and isomers are provided by single point energy calculations carried out at the B3LYP, B3P86, M06, and MP2(full) levels using the 6-311+G(2p,2d) basis set. The comparisons between the IRMPD and theoretical IR spectra indicate that 18C6 binds to Gly and His via the protonated backbone amino group, whereas protonated Lys prefers binding via the protonated side-chain amino group. Results for Arg are less definitive with strong evidence for binding to the protonated guanidino side chain (the calculated ground conformer at most levels of theory), but contributions from backbone binding to a zwitterionic structure are likely.
TL;DR: In this paper, the authors present a full description of the deamidation reaction (as well as other key dissociation processes) of protonated asparaginyl-threonine, [AsnThr+H]+, via complementary infrared multiple photon dissociation (IRMPD) ion spectroscopy, threshold collision-induced dissociation, and theoretical studies.
TL;DR: The slightly altered structures help explain the stabilization induced by 2′-O-methylation of the pyrimidine nucleosides.
TL;DR: In this article, species formed in the reactions of Ta+ and TaO+ with ethene were examined spectroscopically using infrared multiple photon dissociation (IRMPD) action spectroscopy.
TL;DR: Experimental collision-induced dissociation (CID) cross sections are presented as a function of kinetic energy for FeOH+(H2O) n, where n = 1-4, with xenon (Xe) obtained using a guided ion beam tandem mass spectrometer.
Abstract: We present experimental collision-induced dissociation (CID) cross sections as a function of kinetic energy for FeOH+(H2O)n, where n = 1–4, with xenon (Xe) obtained using a guided ion beam tandem mass spectrometer. Complexes with n = 2–4 are observed to undergo water loss, followed by sequential water loss at higher collision energies. In addition, we find that loss of the neutral hydroxide group is competitive with the primary water loss for n = 1. Bond dissociation energies (BDEs) at 0 K are derived through modeling of the experimental cross sections after accounting for multiple collisions, kinetic shifts, and reactant internal and kinetic energy distributions. Quantum chemical calculations include geometry optimizations performed at the B3LYP/6-311+G(d,p) level of theory and then used for single point calculations at B3LYP, B3P86, MP2, and CCSD(T) levels with a 6-311+G(2d,2p) basis set. Additional geometry optimizations at the cam-B3LYP/def2-TZVP were also performed as well as empirical dispersion cor...
TL;DR: In this article, the reaction of ground-state Ce+ (5d24f1) with deuterium in a reaction cell at a pressure of 1.5-4.0"Torr and temperatures ranging from approximately 265-515"K is studied.