EVIDENCE FROM ION CHROMATOGRAPHY EXPERIMENTS THAT MET-CARS ARE HOLLOW CAGE CLUSTERS

Ion chromatography studies were performed to assess various models proposed for the structure of M(8)C(12) species, the met-cars. A laser desorption source was used to make a sequence of titanium-carbon clusters centered around Ti8C12+. The Ti8C12+ was determined to be a hollow cage cluster, with the dodecahedron structure originally proposed giving the best fit to experiment; cubic structures could be excluded. Collisional breakup of Ti8C12+ yielded only Ti7C12+ under the experimental conditions described herein, and modeling indicated that the cage structure was retained. Both Ti8C11+ and Ti8C13+ were made by the cluster source, and again, dodecahedral-type cage structures were consistent with experiment. The extra carbon atom in Ti8C13+ was attached exohedrally to a single titanium atom. No evidence for an endohedral species was found.