Deciphering aromaticity in porphyrinoids via adaptive natural density partitioning.

The adaptive natural density partitioning (AdNDP) method has been applied for the first time to porphyrinoids in order to describe their aromaticity. The analysis of π-electron system reveals that aromaticity of annulene originates from 6-π-electron delocalization, while aromaticity of porphyrin can be better described in terms of local aromaticities of the appended 6-π-electron pyrrolic heterocycles and 6-π-electron central fragment. The patterns of chemical bonding for porphyrinoids obtained by AdNDP are consistent with chemical intuition and lead to unique and compact graphic formulas.