Photoelectron spectroscopy of V_x(coronene)_y and Ti_x(coronene)_y anions

Gas-phase anion complexes are produced containing one or more vanadium or titanium atoms bound to one or more molecules of the polycyclic aromatic hydrocarbon (PAH) coronene (C₂₄H₁₂). These species are prepared with coincident laser vaporization of a metal rod and a pressed pellet of coronene in a pulsed-nozzle cluster source. The anion complexes produced are mass-selected with a time-of-flight spectrometer and photoexcited with various Nd:YAG laser harmonics. A magnetic bottle instrument is employed for time-of-flight photoelectron spectroscopy measurements on these complexes. Electron affinities (EA's) are observed to be greater for the organometallic complexes than they are for the isolated metal clusters or the isolated coronene molecule. EA's increase with the number of metal atoms in the complex. The spectra observed for V-coronene complexes are similar in appearance to those seen previously for V-benzene and V-C₆₀, suggesting that the metal binds as a π complex in a symmetric ring site. V-(coronene)₂ complexes exhibit different spectra under different conditions attributed to the formation of sandwich and external-metal isomers.