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Unformatted text preview: Photoelectron Spectroscopy of V x (Coronene) y and Ti x (Coronene) y Anions M. A. Duncan* and A. M. Knight Department of Chemistry, Uni V ersity of Georgia, Athens, Georgia 30602 Y. Negishi, S. Nagao, K. Judai, A. Nakajima, and K. Kaya Department of Chemistry, Faculty of Science and Technology, Keio Uni V ersity, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan Recei V ed: June 13, 2001; In Final Form: August 23, 2001 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 (C 24 H 12 ). 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 (EAs) are observed to be greater for the organometallic complexes than they are for the isolated metal clusters or the isolated coronene molecule. EAs 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- C 60 , suggesting that the metal binds as a 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. Introduction Metal complexes with aromatic molecular ligands exhibit unusual bonding which has fascinated organometallic chemists for many years. 1 Ferrocene 2 and dibenzene chromium 3 were early examples of these systems, but this is now a rather large subfield of organometallic chemistry. The diversity of metal complexes has increased dramatically in recent years with the development of gas-phase experiments in which metal vapor can be combined directly with unusual ligands in nontraditional synthetic schemes. There are many experimental and theoretical studies of metal benzene complexes. 4- 12 Kaya and co-workers have described multimetal/multibenzene complexes that are proposed to have multidecker sandwich structures, and other ligands 13 also are found to follow this structural pattern. Exohedral metallofullerenes 14- 19 and metals bound to polycyclic aromatic hydrocarbons (PAHs) 20- 29 have been described recently in molecular beam experiments and in mass spectrom- etry. Multidecker sandwiches and other network structures have also been proposed for some of these systems. These new complex clusters have never been isolated, but their structure and bonding properties are nonetheless interesting. Although metal- PAH complexes have attracted considerable attention, there has so far been no spectroscopy on these systems. We report here the first investigation of spectroscopy for a metal...
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