Tuning Aromaticity, Stability and Radicaloid Character of Periacenes by Chemical BN Doping

ABSTRACT In this work, the stability, aromaticity and radical character of pristine and eleven BN‐doped armchair 5 and zigzag 5, 6, and 7 periacenes, were chosen for studying the effect of different doping schemes to stabilize the periacene, and to direct the open‐shell density into specific regions of the PAH sheets. Ab initio multireference methods and different DFT functionals were used to analyze the singlet triplet (ST) energy. Moreover, a range of descriptors were used to characterize the open‐shell character and aromaticity of the different doped structures. The overall results provide a good overview of the efficiency of the different doping topologies. In general, because of the closed‐shell character of the borazine doping units, the role of the doping is to reduce the strong open‐shell character of the pristine periacenes. Substitutions along the zigzag edges has a significant effect while doping along the armchair edges is not significant. Borazine doping at the center row (BN‐center) stabilizes the pristine periacene by reducing the density of strongly correlated electrons (FOD), besides facilitating a shift in the active site within the structure. ACID plots reveal that the insertion of borazine rings disrupts electron delocalization, which, instead of being evenly distributed throughout the structure, becomes concentrated in the uppermost and lowest regions of the BN‐center structure. Such disruption affects the overall aromaticity of structures.