Detection of OH stretching mode of CH3OH chemisorbed on Ni 3+ and Ni4+ by infrared photodissociation spectroscopy

Shinichi Hirabayashi, Ryuji Okawa, Masahiko Ichihashi, Tamotsu Kondow, Yoshiyuki Kawazoe

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Structures of nickel cluster ions adsorbed with methanol, Ni 3+(CH3OH)m (m = 1-3) and Ni 4+(CH3OH)m (m = 1-4) were investigated by using infrared photodissociation (IR-PD) spectroscopy based on a tandem-type mass spectrometer, where they were produced by passing Ni 3,4+ through methanol vapor under a multiple collision condition. The IR-PD spectra were measured in the wavenumber region between 3100 and 3900 cm-1. In each IR-PD spectrum, a single peak was observed at a wavenumber lower by ∼40 cm1 than that of the OH stretching vibration of a free methanol molecule and was assigned to the OH stretching vibrations of the methanol molecules in Ni3,4+(CH 3OH)m. The photodissociation was analyzed by assuming that Ni3,4 +(CH3-OH)m dissociate unimolecularly after the photon energy absorbed by them is statistically distributed among the accessible modes of Ni3,4+(CH 3OH)m. In comparison with the calculations performed by the density functional theory, it is concluded that (1) the oxygen atom of each methanol molecule is bound to one of the nickel atoms in Ni3,4 + (defined as molecular chemisorption), (2) the methanol molecules in Ni3,4+(CH3OH)m do not form any hydrogen bonds, and (3) the cross section for demethanation [CH4 detachment from Nin+(CH3-OH)] is related to the electron density distribution inside the methanol molecule.

Original languageEnglish
Pages (from-to)7664-7669
Number of pages6
JournalJournal of Physical Chemistry A
Issue number31
Publication statusPublished - 2007 Aug 9


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