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, Delta R (in angstrom), 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. Delta R-tot, 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 Delta R-tot and ANICS(1) are also nearly zero.