Sequential activation of methane by Ir+: An IRMPD and theoretical investigation

Oscar W. Wheeler, Michelle Salem, Amanda Gao, Joost M. Bakker, Peter B Armentrout

Research output: Contribution to journalArticle

Abstract

The sequential activation of up to 4 CH4 molecules by Ir+ is investigated through a gas-phase infrared multiple photon dissociation (IRMPD) experiment and theoretical calculations. A molecular beam apparatus was used to generate Ir+ by laser ablation and expose it to controlled amounts of CH4. Product ions were irradiated with IR light from a free electron laser over the 500–1800 cm−1 spectral range and photodissociation was monitored using a time-of-flight mass spectrometer. Experimental spectra were obtained for five distinct species: [Ir,3C,8 H]+, [Ir,3C,10 H]+, [Ir,4C,10 H]+, [Ir,4C,12 H]+, and [Ir,O,3C,12 H]+. To identify these species, B3LYP/def2-TZVPPD geometry optimizations were performed on a variety of possible structures, with computed IR spectra compared to the experimental IRMPD spectra. This has led to the following assignments: [Ir,3C,8 H]+ = IrCH2(CH3)2 +, [Ir,3C,10 H]+ = HIr(CH3)3 +, [Ir,4C,10 H]+ = Ir(CH3)2(C2H4)+, [Ir,4C,12 H]+ = a mixture of HIr(CH3)(C2H4)+(CH4), HIr(CH3)2(C2H5)+, Ir(CH3)4 +, and (H2)Ir(CH3)2(C2H4)+, and [Ir,O,3C,12 H]+ = (H2O)HIr(CH3)3 +. Notably, evidence for C–C coupling is observed upon reaction with a fourth methane. Mechanisms for the formation of the observed products were also explored computationally by examining the reaction coordinate pathways for the reactions of methane with HIrCH+, IrCH2 +, Ir(CH3)2 +, HIrCH2(CH3)+, HIr(CH3)3 +, and IrCH2(CH3)2 +.

LanguageEnglish (US)
Pages78-92
Number of pages15
JournalInternational Journal of Mass Spectrometry
Volume435
DOIs
StatePublished - Jan 1 2019

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Iridium
Methane
Dehydrogenation
methane
Photons
Chemical activation
activation
dissociation
Infrared radiation
photons
Photodissociation
Molecular beams
Free electron lasers
Mass spectrometers
Laser ablation
products
free electron lasers
photodissociation
molecular beams
mass spectrometers

Keywords

  • Carbon-carbon coupling
  • Dehydrogenation
  • Infrared multiple photon dissociation
  • Iridium
  • Methane activation
  • Reaction coordinate pathway

ASJC Scopus subject areas

  • Instrumentation
  • Condensed Matter Physics
  • Spectroscopy
  • Physical and Theoretical Chemistry

Cite this

Sequential activation of methane by Ir+ : An IRMPD and theoretical investigation. / Wheeler, Oscar W.; Salem, Michelle; Gao, Amanda; Bakker, Joost M.; Armentrout, Peter B.

In: International Journal of Mass Spectrometry, Vol. 435, 01.01.2019, p. 78-92.

Research output: Contribution to journalArticle

Wheeler, Oscar W. ; Salem, Michelle ; Gao, Amanda ; Bakker, Joost M. ; Armentrout, Peter B. / Sequential activation of methane by Ir+ : An IRMPD and theoretical investigation. In: International Journal of Mass Spectrometry. 2019 ; Vol. 435. pp. 78-92.
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abstract = "The sequential activation of up to 4 CH4 molecules by Ir+ is investigated through a gas-phase infrared multiple photon dissociation (IRMPD) experiment and theoretical calculations. A molecular beam apparatus was used to generate Ir+ by laser ablation and expose it to controlled amounts of CH4. Product ions were irradiated with IR light from a free electron laser over the 500–1800 cm−1 spectral range and photodissociation was monitored using a time-of-flight mass spectrometer. Experimental spectra were obtained for five distinct species: [Ir,3C,8 H]+, [Ir,3C,10 H]+, [Ir,4C,10 H]+, [Ir,4C,12 H]+, and [Ir,O,3C,12 H]+. To identify these species, B3LYP/def2-TZVPPD geometry optimizations were performed on a variety of possible structures, with computed IR spectra compared to the experimental IRMPD spectra. This has led to the following assignments: [Ir,3C,8 H]+ = IrCH2(CH3)2 +, [Ir,3C,10 H]+ = HIr(CH3)3 +, [Ir,4C,10 H]+ = Ir(CH3)2(C2H4)+, [Ir,4C,12 H]+ = a mixture of HIr(CH3)(C2H4)+(CH4), HIr(CH3)2(C2H5)+, Ir(CH3)4 +, and (H2)Ir(CH3)2(C2H4)+, and [Ir,O,3C,12 H]+ = (H2O)HIr(CH3)3 +. Notably, evidence for C–C coupling is observed upon reaction with a fourth methane. Mechanisms for the formation of the observed products were also explored computationally by examining the reaction coordinate pathways for the reactions of methane with HIrCH+, IrCH2 +, Ir(CH3)2 +, HIrCH2(CH3)+, HIr(CH3)3 +, and IrCH2(CH3)2 +.",
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N2 - The sequential activation of up to 4 CH4 molecules by Ir+ is investigated through a gas-phase infrared multiple photon dissociation (IRMPD) experiment and theoretical calculations. A molecular beam apparatus was used to generate Ir+ by laser ablation and expose it to controlled amounts of CH4. Product ions were irradiated with IR light from a free electron laser over the 500–1800 cm−1 spectral range and photodissociation was monitored using a time-of-flight mass spectrometer. Experimental spectra were obtained for five distinct species: [Ir,3C,8 H]+, [Ir,3C,10 H]+, [Ir,4C,10 H]+, [Ir,4C,12 H]+, and [Ir,O,3C,12 H]+. To identify these species, B3LYP/def2-TZVPPD geometry optimizations were performed on a variety of possible structures, with computed IR spectra compared to the experimental IRMPD spectra. This has led to the following assignments: [Ir,3C,8 H]+ = IrCH2(CH3)2 +, [Ir,3C,10 H]+ = HIr(CH3)3 +, [Ir,4C,10 H]+ = Ir(CH3)2(C2H4)+, [Ir,4C,12 H]+ = a mixture of HIr(CH3)(C2H4)+(CH4), HIr(CH3)2(C2H5)+, Ir(CH3)4 +, and (H2)Ir(CH3)2(C2H4)+, and [Ir,O,3C,12 H]+ = (H2O)HIr(CH3)3 +. Notably, evidence for C–C coupling is observed upon reaction with a fourth methane. Mechanisms for the formation of the observed products were also explored computationally by examining the reaction coordinate pathways for the reactions of methane with HIrCH+, IrCH2 +, Ir(CH3)2 +, HIrCH2(CH3)+, HIr(CH3)3 +, and IrCH2(CH3)2 +.

AB - The sequential activation of up to 4 CH4 molecules by Ir+ is investigated through a gas-phase infrared multiple photon dissociation (IRMPD) experiment and theoretical calculations. A molecular beam apparatus was used to generate Ir+ by laser ablation and expose it to controlled amounts of CH4. Product ions were irradiated with IR light from a free electron laser over the 500–1800 cm−1 spectral range and photodissociation was monitored using a time-of-flight mass spectrometer. Experimental spectra were obtained for five distinct species: [Ir,3C,8 H]+, [Ir,3C,10 H]+, [Ir,4C,10 H]+, [Ir,4C,12 H]+, and [Ir,O,3C,12 H]+. To identify these species, B3LYP/def2-TZVPPD geometry optimizations were performed on a variety of possible structures, with computed IR spectra compared to the experimental IRMPD spectra. This has led to the following assignments: [Ir,3C,8 H]+ = IrCH2(CH3)2 +, [Ir,3C,10 H]+ = HIr(CH3)3 +, [Ir,4C,10 H]+ = Ir(CH3)2(C2H4)+, [Ir,4C,12 H]+ = a mixture of HIr(CH3)(C2H4)+(CH4), HIr(CH3)2(C2H5)+, Ir(CH3)4 +, and (H2)Ir(CH3)2(C2H4)+, and [Ir,O,3C,12 H]+ = (H2O)HIr(CH3)3 +. Notably, evidence for C–C coupling is observed upon reaction with a fourth methane. Mechanisms for the formation of the observed products were also explored computationally by examining the reaction coordinate pathways for the reactions of methane with HIrCH+, IrCH2 +, Ir(CH3)2 +, HIrCH2(CH3)+, HIr(CH3)3 +, and IrCH2(CH3)2 +.

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