Strain in [n]triangulanes

The molecular structures and strain energies of some [n]triangulanes have been studied by high-level ab initio calculations and compared with results for [n]ladderanes. The calculations provided several unexpected results. We show that the strain energies in triangulanes are smaller than previously suggested. The estimated strain energies in individual rings reveal that those with a larger number of proximal C-C bonds (inner rings) are more strained than peripheral rings with distal bonds. The total electron energies of branched and isomeric unbranched triangulanes are virtually identical. The strain energies of cyclotriangulanes are much smaller than previously estimated which makes them more easily achievable synthetic targets than earlier thought.