MULTIPHOTON DISSOCIATION AND IONIZATION OF ORGANOMETALLICS: THE CORRELATION BETWEEN MOLECULAR STRUCTURE AND A METAL ATOM PRODUCT.

One-color multiphoton dissociation/ionization (MPD/MPI) spectra have been measured for a series of arene chromium tricarbonyls (ACTs). These experiments are part of a program to determine whether unimolecular bond-selective photochemistry is feasible using isolated gas-phase organometallic molecules. Bond-selective chemistry must involve a means of activating a molecule so that when dissociation occurs, the weakest bond does not break first. If it is possible to induce unimolecular photodissociation on selected excited electronic potential surfaces, it will be possible to remove selectively different ligands from a metal atom, regardless of their relative bonding energies. If excitation can be thought of as initially localized, for bond selective chemistry to occur the dissociation must occur on a time scale competitive with the radiationless transitions associated with intramolecular energy redistribution (IER). The experiment described focus on the relative time scales of these two processes compared with that of multiphoton absorption in isolated organometallic molecules.