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, (OEtPc)­MnN (2; OEtPc = 1,4,8,11,15,18,22,25-octaethoxy-Pc), as well as its stable,
readily accessible oxidized (2+ and 22+) and reduced (2–, 22–) congeners is reported. This unique isostructural
series displays switchable aromatic character spanning the aromatic
(2), nonaromatic (22+), and antiaromatic (22–) 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 (22+, 22–) 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 (22+, 2+, 2, 2–, 22–) 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.

本文报道了一种新型酞菁（phthalocyanine, Pc）锰氮化物配合物(OEtPc)­MnN（2；其中OEtPc为1,4,8,11,15,18,22,25-八乙氧基酞菁）的合成与表征，同时还报道了其稳定且易于获取的氧化态（2+与22+）及还原态（2–、22–）同系物。该独特的同构系列展现出可切换的芳香特性，覆盖芳香态（2）、非芳香态（22+）与反芳香态（22–）三重体系，同时包含开壳层自由基态（2+、2–）。所有配合物均完成了结构表征，且在氧化还原极值点（22+、22–）处呈现出显著的结构畸变，与所提出的[16或18]轮烯π环环流模型相符。光谱学与计算研究进一步佐证了上述模型。这一分离得到、完全表征的同构系列涵盖五种氧化还原态（22+、2+、2、2–、22–），在酞菁及相关大环（例如卟啉类）研究文献中均属罕见，可为由可切换芳香性驱动的结构-电子相关性研究提供直接的参考依据。