Laser plasma production of metal and metal compound complexes with polycyclic aromatic hydrocarbons

Gas-phase complexes of metals and/or metal compounds with polycyclic aromatic hydrocarbons (PAHs) are produced by covaporization of materials in a laser plasma source and detected using a time-of-flight mass spectrometer. Mixtures of metal powder, metal salts, metal oxides, or other materials with the PAH of interest are ablated and ionized with a pulsed Nd:YAG laser. Mass spectroscopy reveals that transition and rare earth metals efficiently produce both monoligand and sandwich complexes of the form M+(PAH)(x), with x = 1, 2. Surprisingly, both iron and cobalt resist the formation of complexes when pure metal powder is employed, but produce them efficiently when salts, oxides, or organometallics are employed. Covaporization of the organometallic-pi complexes iron cyclopentadienyl and dibenzene chromium with PAHs yields both homoligand and heteroligand complexes. Transition metal oxides and chlorides produce monoligand complexes exclusively. In contrast, rare earth oxides produce both monoligand and sandwich complexes, presumably due to the increased ionic radius of the metal center.