A theoretical study of large planar [N]phenylenes.

Ab initio studies of 14 [N]phenylenes containing 12-membered rings furnish geometries, energies, standard heats of formation, NICS(1) values, and proton chemical shifts. The extent of double-bond localization, DeltaR (in A), for each type of the 58 unique six-membered rings-angular, branched, and terminal-varies linearly with both their NICS(1) values and proton resonances. Values of these parameters depend upon the number and type of neighboring rings. DeltaRtot, the molecular sum of the bond localizations, correlates linearly with the ab initio energy and heat of formation. Reactions that conserve the numbers of angular, branched, terminal, and 12-membered rings are thermoneutral, and their net DeltaRtot and DeltaNICS(1) are also nearly zero.