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-OEt)MnN (2; Pc-OEt = 1,4,8,11,15,18,22,25-octaethoxy-Pc), as well as its stable, readily accessible oxidized (2(+) and 2(2+)) and reduced (2(-), 2(2-)) congeners is reported. This unique isostructural series displays switchable aromatic character spanning the aromatic (2), nonaromatic (2"), and antiaromatic (2(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+), 2(2-)) consistent with proposed [16 or 18]annulene pi 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(-), 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.