Methanol production from methane in lithium-doped argon matrices by photoassisted, dissociative electron attachment to N2O

Article abstract of DOI:10.1021/j100036a033

Photolytic generation of methanol from methane in Ar matrices containing Li and N₂O is proposed to occur via a UV-light-induced electron transfer from Li to N₂O to form N₂O^-. A weak ground-state interaction between Li and N₂O is suggested by the observation of a Li-N₂O complex which decays rapidly during the initial stages of the reaction. N₂O^- is believed to decompose spontaneously or, following photo-excitation, to form N₂ and O^-. The O^- thus formed, or O(¹D) produced via photodetachment from O^-, then reacts with methane to form methanol. An electron is believed to be transferred to a nearby Li⁺ ion in the process, thereby regenerating the initial electron donor and allowing significant amounts of N₂O to be consumed, despite the limited amount of Li available in the matrix. Formation of the formaldehyde/water complex during the latter stages of the reaction occurs as a result of secondary reactions of methanol with O^- or O(¹D). The wavelength cutoff of 350-400 nm for the process is in reasonable accord with the predicted threshold for formation of a Li⁺/N₂O^- ion pair in an Ar matrix. The unusual dependence of the rate of methanol production, in irradiation time, with N₂O concentration in the matrix is interpreted as arising from a reversible, redundant electron transfer from Li to N₂O. This is believed to occur when there is an absence of significant stabilization from Ar polarization interactions, due to the ions being formed in too close proximity.