Switchable Aromaticity in an Isostructural Mn Phthalocyanine Series Isolated in Five Separate Redox States.

The synthesis and characterization of a new phthalocyanine (Pc) Mn-nitride complex, (Pc)MnN (2; Pc = 1,4,8,11,15,18,22,25-octaethoxy-Pc), as well as its stable, readily accessible oxidized (2 and 2) and reduced (2, 2) congeners is reported. This unique isostructural series displays switchable aromatic character spanning the aromatic (2), nonaromatic (2), and antiaromatic (2) triad, in addition to the open-shell radical states (2, 2). All complexes were structurally characterized and displayed significant structural distortions at the redox extrema (2, 2) consistent with proposed [16 or 18]annulene π ring circuit models. Spectroscopic and computational studies further support these models. This isolated, fully characterized, isostructural series spanning five redox states (2, 2, 2, 2, 2) is unique in both the Pc and related macrocyclic (ex. porphyrinoids) literature and may offer direct insight into structural-electronic correlations driven by switchable aromaticity.