Isomers of Small Carbon Cluster Anions: Linear Chains with up to 20 Atoms

Helden, Gert von; Kemper, Paul R.; Gotts, Nigel G.; Bowers, Michael T.

doi:10.1126/science.259.5099.1300

Cited by 173 publications

(130 citation statements)

References 20 publications

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“…For example, molecular mechanics calculations are essential for interpreting data from ion mobility measurements of large biopolymers. [6][7][8] In these experiments, ion cross sections are determined by measuring ion flight times in a drift tube. Information about the ion structure can be obtained by comparing the measured cross sections to those determined from calculated low-energy structures.…”

Section: Introductionmentioning

confidence: 99%

Structures of Protonated Arginine Dimer and Bradykinin Investigated by Density Functional Theory: Further Support for Stable Gas-Phase Salt Bridges

Strittmatter

Williams

2000

J. Phys. Chem. A

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The gas-phase structures and energetics of both protonated arginine dimer and protonated bradykinin were investigated using a combination of molecular mechanics with conformational searching to identify candidate low-energy structures, and density functional theory for subsequent minimization and energy calculations. For protonated arginine dimer, a good correlation (R = 0.88) was obtained between the molecular mechanics and EDF1 6-31+G* energies, indicating that mechanics with MMFF is suitable for finding low-energy conformers. For this ion, the salt-bridge or ion-zwitterion form was found to be 5.7 and 7.2 kcal/mol more stable than the simple protonated or ion-molecule form at the EDF1 6-31++G** and B3LYP 6-311++G** levels. For bradykinin, the correlation between the molecular mechanics and DFT energies was poor (R = 0.28), indicating that many lowenergy structures are likely passed over in the mechanics conformational searching. This result suggests that structures of this larger peptide ion obtained using mechanics calculations alone are not necessarily reliable. The lowest energy structure of the salt-bridge form of bradykinin is 10.6 kcal/mol lower in energy (EDF1) than the lowest energy simple protonated form at the 6-311G* level. Similarly, the average energy of all salt-bridge structures investigated is 13.6 kcal/mol lower than the average of all the protonated forms investigated. To the extent that a sufficient number of structures are investigated, these results provide some additional support for the salt-bridge form of bradykinin in the gas phase.

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Section: Introductionmentioning

confidence: 99%

Structures of Protonated Arginine Dimer and Bradykinin Investigated by Density Functional Theory: Further Support for Stable Gas-Phase Salt Bridges

Strittmatter

Williams

2000

J. Phys. Chem. A

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“…For example, the stagnation pressure and the O 2 concentration in He were 4 atm and 5% for production of titanium oxide cluster ions and 3 atm and 2.5% for iron oxide cluster ions. On the other hand, sodium uoride cluster ions were produced by laser vaporization of a Na rod and subsequent reaction with uorine-containing molecules such as C 6 F 6 or SF 6 . Cluster ions thus produced were then injected into the ion dri cell by a pulsed electric eld, which is herea er denoted as an "ion gate" pulse.…”

Section: Methodsmentioning

confidence: 99%

“…Ion structures of several atomic and molecular clusters, such as semiconductor clusters, [6][7][8][9] metal clusters, [10][11][12][13][14] ionic bond clusters 15,16) and so on, were already investigated by IM-MS.…”

Section: Introductionmentioning

confidence: 99%

Application of Ion Mobility-Mass Spectrometry to the Study of Ionic Clusters

et al. 2014

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Stable cluster sizes and compositions have been investigated for cations and anions of ionic bond clusters such as alkali halides and transition metal oxides by ion mobility-mass spectrometry (IM-MS). Usually structural information of ions can be obtained from collision cross sections determined in IM-MS. In addition, we have found that stable ion sizes or compositions were predominantly produced in a total ion mass spectrum, which was constructed from the IM-MS measurement. ese stable species were produced as a result of collision induced dissociations of the ions in a dri cell. We have con rmed this result in the sodium uoride cluster ions, in which cuboid magic number cluster ions were predominantly observed. Next the stable compositions, which were obtained for the oxide systems of the rst row transition metals, Ti, Fe, and Co, are characteristic for each of the metal oxide cluster ions.

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“…3 With advances in molecular beam apparatus and quantum calculations, anion clusters have been extensively studied. [4][5][6] Benzene does not form a stable dimer anion in the gas phase, and naphthalene forms a dimer anion which may have T-shaped geometry due to the strong repulsion from the π-electron. 7 Dimer anions larger than naphthalene all have parallel-displaced (PD) geometries with charge resonance.…”

mentioning

confidence: 99%

Photoelectron Spectroscopy of 4-Bromochlorobenzene Dimer and Trimer Anions

Kim¹

2013

Bulletin of the Korean Chemical Society

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Clusters are the aggregates of molecules or ions which have intrinsic properties that are not found in their monomer unit.1 Their structure and charge distribution greatly affect the properties of the clusters. Charge resonance is the key factor that determines the structure of the cation clusters of aromatic hydrocarbons.2 T. Shida and S. Iwata also calculated the charge resonance band and observed it experimentally.3 With advances in molecular beam apparatus and quantum calculations, anion clusters have been extensively studied.4-6 Benzene does not form a stable dimer anion in the gas phase, and naphthalene forms a dimer anion which may have T-shaped geometry due to the strong repulsion from the π-electron.7 Dimer anions larger than naphthalene all have parallel-displaced (PD) geometries with charge resonance. 8-10Sometimes homocluster anions show ion core switching with the increase of the cluster size. 8For the heterodimer anions, the geometry is determined by the differences in electronegativity of the molecules. Dimer anions with a large electronegativity difference have T-shaped geometries and those with a small electronegativity difference have PD geometries. 11Bromochlorobenzene (BCB) is able to accept an extra electron even though benzene monomer cannot. We found that an excess electron entered the anti-bonding orbital formed between C and Br atoms in bromochlorobenzene monomer anion that has the character of atomic Br.12 Thus, the electron binding energy (EBE) is exceedingly large compared to that of other large aromatic hydrocarbon monomers. In this article, I report the photoelectron spectra and quantum calculation results for the dimer and trimer anions of 4-BCB, which are much different from those of the monomer anion.The details of our experimental scheme have been described elsewhere.13 Briefly, thermally evaporated 4-BCB molecules were co-expanded with 5 bar of Ar carrier gas through a pulsed solenoid valve to generate molecular clusters. Low energy secondary electrons were generated from the ionization of Ar with high energy electron from an electron gun (400 eV, 200 μA), which attached to the neutral molecules and turned them into anions. A Wiley-McLaren type timeof-flight mass spectrometer with a mass gate was used to select anions by their mass. The anions then entered a magnetic-bottle-type photoelectron spectrometer and were irradiated by the second harmonic output (532 nm) of a pulsed Nd:YAG laser. The kinetic energy of the ejected photoelectron was measured to yield the photoelectron spectrum by subtracting it from the incident photon energy.In the mass spectrum of 4BCB cluster anions, the monomer anion has the largest peak intensity with the exception of the Br − that comes from the dissociative electron attachment. The dimer anion has a significant intensity while the trimer and larger clusters have a very low intensity under our experimental conditions. − is quite different from that of [4-BCB] 1 − in our previous study. It seems that there is only one broad peak that stands for the ...

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Isomers of Small Carbon Cluster Anions: Linear Chains with up to 20 Atoms

Abstract: The structure of small carbon cluster anions, Cn(-) (4 Show more

Cited by 173 publications

References 20 publications

Structures of Protonated Arginine Dimer and Bradykinin Investigated by Density Functional Theory: Further Support for Stable Gas-Phase Salt Bridges

Structures of Protonated Arginine Dimer and Bradykinin Investigated by Density Functional Theory: Further Support for Stable Gas-Phase Salt Bridges

Application of Ion Mobility-Mass Spectrometry to the Study of Ionic Clusters

Photoelectron Spectroscopy of 4-Bromochlorobenzene Dimer and Trimer Anions

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