Electron localization in nonplanar conjugated macrocycles: Failure of electron buffers to delocalize electrons

We investigate the distribution of the unpaired electron generated by the homolysis of the axial metal–ligand bond in some aromatic metallomacrocycles. For one group of the compounds, the unpaired electron is delocalized in the conjugated ring. This is an expected feature for planar macrocycles. Consequently, the conjugated ring is significantly affected. In contrast, the unpaired electron localizes around the central metal and leaves the aromatic ring almost unaffected in the other group of the compounds. These two different distribution patterns are revealed by different structural features, spin densities, electron localization functions (ELF), and nucleus-independent chemical shifts (NICS).