Investigations of small carbon cluster-ion structures by reactions with hydrogen cyanide

Unimolecular gas-phase laser-photodissociation reaction mechanisms of open-shell lanthanide cyclopentadienyl complexes, Ln(Cp)3 and Ln(TMCp)3, are analyzed from experimental and computational perspectives. The most probable pathways for the photoreactions are inferred from photoionization time-of-flight mass spectrometry (PI-TOF-MS), which provides the sequence of reaction intermediates and the distribution of final products. Time-dependent excited-state molecular dynamics (TDESMD) calculations provide insight into the electronic mechanisms for the individual steps of the laser-driven photoreactions for Ln(Cp)3. Computational analysis correctly predicts several key reaction products as well as the observed branching between two reaction pathways: (1) ligand ejection and (2) ligand cracking. Simulations support our previous assertion that both reaction pathways are initiated via a ligand-to-metal charge-transfer (LMCT) process. For the more complex chemistry of the tetramethylcyclopentadienyl complexes Ln(TMCp)3, TMESMD is less tractable, but computational geometry optimization reveals the structures of intermediates deduced from PI-TOF-MS, including several classic “tuck-in” structures and products of Cp ring expansion. The results have important implications for metal–organic catalysis and laser-assisted metal–organic chemical vapor deposition (LCVD) of insulators with high dielectric constants.

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“…Dehydrogenation, invoked above in the formation of n ′ and n ″ from n , is also commonly observed. 43 …”

Section: Resultsmentioning

confidence: 99%

Photofragmentation of Gas-Phase Lanthanide Cyclopentadienyl Complexes: Experimental and Time-Dependent Excited-State Molecular Dynamics

et al. 2014

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“…For small clusters containing less than 10 atoms information on their structure were available from spectroscopic data and reactivity patterns. The latter indicated unambiguously [36] the presence of different isomeric forms of C n + (n = 6-8) and the photoelectron studies [37] suggested a structural "phase" transition near C 10 À . Using ion mobility experiments Bowers and coworkers [38] systematically studied the structure of carbon cluster ions from 3 to 60 atoms and demonstrated a transition from linear to ring to fullerene structures.…”

Section: And Simentioning

confidence: 91%

Mass spectrometry and its role in advancing cluster science

Jena

Castleman

2015

International Journal of Mass Spectrometry

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“…Direct laser vaporization (DLV) experiments were performed on a Fourier transform ion cyclotron resonance (ICR) mass spectrometer (FTMS), which has been described in detail [8]. Pressed pellets containing various combinations of yttrium oxide (Y 2 0 3 ), graphite and bulk fullerenes were placed on a solids probe located flush with one of the trapping plates and irradiated with the frequency-doubled output (532 nm) of a Quanta Ray DCR-2 Nd:YAG laser.…”

Section: Methodsmentioning

confidence: 99%

Mass Spectrometry of Metallofullerenes

et al. 1992

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Fullerenes with a metal atom inside of the cage, metallofulierenes, were produced by either laser vaporization or a graphite arc and characterized using a variety of mass spectrometric methods. First, yttrium-fullerene adducts were formed by direct laser vaporization of samples consisting of graphite, yttrium oxide and fullerenes. Fragmentation and oxidation ion/molecule reactions showed that the laser-generated adducts are endohedral complexes (Y,@Cj), in contrast to externally-bound Y(C,)+ species formed by gas-phase reactions. In addition, evidence was obtained for laserinduced bulk coalescence reactions yielding the metallofullerenes. Second, negative ion/desorption chemical ionization mass spectrometry was used to characterize metallofullerenes in arc-generated soot, pyridine extracts and the extract residue. The pyridine extracts of La 2 0 3 /graphite soot contain mostly La@Cs 2 and La 2 @Cs 0 , in addition to (empty) fullerenes. However, the raw soot and the extract residue contain a broader range of metallofullerenes with relative abundances different than those observed from the extract (e.g. abundant La@C6 0 , La@C 7 ) 0 and La@C 7 4 ). The thermal desorption behavior of the doped and undoped fullerenes indicate an interaction between the C. and LaQ@C, species. Analysis of aqueous solutions of dried pyridine extracts of LaO 3 /graphite soot show C. and La•@C,, which is consistent with the possible presence of metallofullerene/ fullerene ionic complexes, (La,@C)+C,-.

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Investigations of small carbon cluster-ion structures by reactions with hydrogen cyanide

Cited by 109 publications

References 10 publications

Photofragmentation of Gas-Phase Lanthanide Cyclopentadienyl Complexes: Experimental and Time-Dependent Excited-State Molecular Dynamics

Photofragmentation of Gas-Phase Lanthanide Cyclopentadienyl Complexes: Experimental and Time-Dependent Excited-State Molecular Dynamics

Mass spectrometry and its role in advancing cluster science

Mass Spectrometry of Metallofullerenes

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