Structure and stability of palladium-carbon cations
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abstract
A theoretical study has been carried out to explore various isomers of palladium-carbon cations, PdCx+. By using the B3LYP density functional method, the geometries have been optimized for linear PdCx+ as well as several classes of cyclic, bicyclic, and graphitic isomers. Linear clusters are shown to be the most stable isomers for x < 10, which is contrary to the previously studied behavior of lanthanum, an early transition metal. For larger systems, several classes of ring-containing structures are more stable than the linear isomers. Experimental ion mobility studies of the PdCx+ clustering process reveal monocyclic rings for x > 10, a result consistent with the B3LYP prediction of rings as the most stable isomer. The ion mobility experiments did not produce any results for x < 10, which may be due to the reactivity of the linear PdCx+, which are predicted by B3LYP to be the most stable isomers at those sizes. Bicyclic PdC20+ is shown to be less stable than the monocyclic rings, but the appearance of bicyclic PdC20+ in the ion mobility experiments is explained as the result of binary collisions since it is stable with respect to PdC10+ and C10 rings. Graphitic PdC20+ is shown to be more stable than either monocyclic or bicyclic rings, although the graphitic sheets do not appear in the ion mobility experiments until PdC26+.
