Designing the Backbone of Hexasilabenzene Derivatives with a High Unimolecular Kinetic Stability.

It is an important subject to theoretically predict the kinetic stability of transient species. In this study, we have studied the kinetic stability of hexasilabenzene Si6 H6 and its derivatives, that is, decasilanaphthalene Si10 H8 and Li-substituted hexasilabenzene Si6 Li6 , theoretically by the artificial force induced reaction (AFIR) method combined with the rate constant matrix contraction (RCMC) method. Molecular design was further conducted to extend the unimolecular lifetime of hexasilabenzene derivatives. Although both Si10 H8 and Si6 Li6 were shown to possess shorter lifetimes than Si6 H6 , we found that the lifetimes of Si6 Li6 changed depending on arrangements of Li atoms around the monocyclic Si6 backbone. Based on this knowledge, we found that a compound of an atomic composition Si6 H4 Li2 with a planar, monocyclic Si6 backbone has a relatively long unimolecular lifetime. Moreover, substitution of the two Li atoms by Na atoms further increased the lifetime.