PFI-ZEKE SPECTROSCOPY OF METAL-POLYCYCLIC AROMATIC HYDROCARBONS: Sc-PYRENE and Sc-NAPHTHALENE

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2004

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Ohio State University

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Gas-phase complexes of scandium with pyrene $(C_{16}H_{20})$ and naphthalene $(C_{10}H_{8})$ are produced by using laser ablation and a polycyclic aromatic hydrocarbon (PAH) oven in a pulsed molecular beam source. The resulting Sc-PAH complexes are characterized with pulsed field ionization-zero electron kinetic energy (PFI-ZEKE) photoelectron spectroscopy. The PFI-ZEKE spectrum of Sc-Pyrene exhibits vibrational progressions of 361 and $154 cm^{-1}$ and a vibrational spacing of $144 cm^{-1}$, with the band origin at $40937 cm^{-1}$. Through comparison with ab initio and Franck-Condon factor calculations, it is determined that this spectral profile arises from a Sc-pyrene complex in which the scandium atom is bound to the ``outer'' ring in an $\eta^{4}$ configuration. The $361 cm^{-1}$ progression is assigned to the $Sc^{+}$ -ring stretch and 154 and $144 cm^{-1}$ features are assigned to pyrene ``flying'' modes in the cation and neutral, respectively. For Sc-naphthalene, the spectrum shows four vibrational intervals of 389, 347, 298 and $112 cm^{-1}$, with the adiabatic ionization energy of $41192 cm^{-1}$. A preliminary analysis indicated the Sc atom is in an $\eta^{2}$ bonding mode in this complex. However, a detailed analysis is still in progress.

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Author Institution: Department of Chemistry, University of Kentucky

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