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

The recently discovered family of metal-carbon clusters, designated me tallo-carbohedrenes or ''met-cars'' by Castleman and co-workers, are r einvestigated with a focus on titanium and vanadium systems. In additi on to the stable M8C12+ Clusters reported previously, a family of larg er metal-carbon systems are observed. Mass spectroscopy and mass-selec ted laser photodissociation measurements are used to investigate the s tructures and stabilities of these systems, which contain up to 60 ato ms 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 t o those of the M8C12 Species. Photodissociation of larger nanocrystals produces both the 8/12 and 14/13 stoichiometries as abundant photofra gments. Evidence is also presented for the formation of endohedral met -car clusters containing a central carbon atom, which are formed as ph otodissociation products from larger systems.