Isomeric Structural Characterization of Polyhedral Oligomeric Silsesquioxanes (POSS) with Styryl and Epoxy Phenyl Capping Agents

Ion mobility and molecular modeling methods were used to examine the gas-phase structures of sodiated POSS capped with styryl and epoxy phenyl substituents (Na+StyxEp8-xT8). Results were obtained for x = 5−7 and indicated that three distinct isomers with different collision cross-sections were present for each value of x. Theoretical modeling also yielded three different families of structures for each POSS system, and their calculated cross-sections agreed very well with experimental values (<1% difference). For Na+Sty7EpT8, the three families differ in the number of “paired” Sty groups. For Na+Sty6Ep2T8 and Na+Sty5Ep3T8, the three isomers correspond to the three different ways the Ep groups can be positioned on the POSS cage.