Ab inito study and NBO analysis of the enantiomerization energy profile of tetra-peri-substituted overcrowded naphthalenes

Further, NBO analysis, based on the HF/3-21G* optimized ground state geometries, revealed that in compounds 1-4, the resonance energy associated with σCaryl-M to σC9-C10* delocalization is 1.43, 3.53, 3.96 and 4.62 kcal mol−1, respectively. These resonance energy values could explain the easiness of ring flipping processes from compound 4 to 1. The NBO results are in good agreement with the calculated energy barriers for ring flipping in compounds 1-4, as calculated by MP2, B3LYP and HF methods, using all electron (3-21G*) and pseudopotential (LANL2DZ*) basis sets.