BEYOND METALLO-CARBOHEDRENES - GROWTH AND DECOMPOSITION OF METAL-CARBON NANOCRYSTALS

The recently discovered family of metal-carbon clusters, designated metallo-carbohedrenes or ''met-cars'' by Castleman and co-workers, are reinvestigated with a focus on titanium and vanadium systems. In addition to the stable M8C12+ Clusters reported previously, a family of larger metal-carbon systems are observed. Mass spectroscopy and mass-selected laser photodissociation measurements are used to investigate the structures and stabilities of these systems, which contain up to 60 atoms in the cluster framework. The larger metal-carbon species exhibit 1/1 M/C stoichiometries characteristic of cubic lattice structures and arc therefore designated as ''nanocrystals'. The species Ti14C13+ and V14C13+, Which are proposed to have the 3 x 3 x 3 cubic structure, are especially abundant and are believed to have stabilities comparable to those of the M8C12 Species. Photodissociation of larger nanocrystals produces both the 8/12 and 14/13 stoichiometries as abundant photofragments. Evidence is also presented for the formation of endohedral met-car clusters containing a central carbon atom, which are formed as photodissociation products from larger systems.