Insights into the intermolecular interactions between stacked antiaromatic 24-π hexaphyrin macrocycles: variation of...

The understanding of antiaromatic characteristics and their variations requires the study of medium-sized species, towards a generalization of their behavior. In this work, we account for a medium-sized hexaphyrin macrocycle, namely naphthorosarin, which features an antiaromatic 24-π electron kernel. The structure exhibits a large deshielding cone behavior, inducing an increased magnetic anisotropy in the center of the structure, confirmed by ¹H-NMR experiments and calculated data. Furthermore, naphthorosarin is prone to form π-π stacked dimers promoted by dispersion-type interactions, contributed by electrostatic and orbital interactions, which largely reduces the central deshielding region and the related anisotropy, suggesting that medium-sized stacks are able to build-up a lesser magnetic anisotropic central region, in relation to the parent isolated rings. Thus, the establishment of π-π interactions between medium-sized antiaromatic rings impacts the characteristics observed for the isolated units, offering valuable guidance and insights into the expected changes in molecular properties when larger aggregates are formed.