Density functional theory study of adamantanediyl dications C10H142+ and protio-adamantyl dications C10H162+.

Structures of the isomeric adamantanediyl dications C(10)H(14)(2+) and protio-1- and protio-2-adamantyl dications C(10)H(16)(2+) were investigated by using the density functional theory (DFT) method at the B3LYP/6-31G** level. Four structures, 1 b-e, were found to be minima on the potential energy surface of C(10)H(14)(2+). The 1,3-adamantanediyl dication 1b with two bridgehead tertiary carbocationic centers was found to be the most stable structure. On the potential energy surface of C(10)H(16)(2+) (protonated adamantly cation), five structures, 2 b-f, were found to be minima. Each of the structure contains a two-electron, three-center bond. The C-C protonated 1-adamantyl dication, 2f, was characterized as the most stable structure. (13)C NMR chemical shifts of the structures were also calculated by using gauge-including atomic orbital-density functional theory and gauge-including atomic orbital-self-consistent field methods.