Figure 2.

Reaction energy profile for the triplet pathway (solid blue lines) of the cyclization of the octa-1,7-diyne dication (Scheme 3, bottom). Energies of all species were computed relative to adiabatic triplet reactant 8a at the UCCSD/cc-pVDZ level of theory, and geometries (structures inset) were optimized at these same levels of theory. For convenience, we provide geometric parameters for interatomic distances R(5,6) and R(7,8) (Å) for all species; atom numbering is superimposed over the inset structure for species 8a.