Cycloparaphenylene Lemniscates and Trefoils

A number of variants of the recently synthesized cycloparaphenylene lemniscates G have been explored at ωB97X-D/6-311G(d). Lemniscates with four to eight phenyl rings in each loop having the N-N, C═C, or B-N bond as the linkage all exhibit the figure-eight shape. Their ring strain energies (RSEs) are relatively independent of the nature of the linkage bond, but the RSE does systematically decrease with the increasing size of the loop. Selective nitrogen substitution into the ortho positions of the aromatic rings allows for the rings to become coplanar; this manifests in a more ribbon-like structure of the lemniscates. It also reduces the RSE of the lemniscates. Similarly, nitrogen substitution into the recently synthesized cycloparaphenylene trefoil E creates a more ribbon-like structure with reduced RSEs.