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Synthesis and Characterization of 16π Antiaromatic 2,7‐Dihydrodiazapyrenes: Antiaromatic Polycyclic Hydrocarbons with Embedded Nitrogen
Author(s) -
Nakazato Takumi,
Takekoshi Haruka,
Sakurai Takahiro,
Shinokubo Hiroshi,
Miyake Yoshihiro
Publication year - 2021
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.202103667
Subject(s) - antiaromaticity , chemistry , ring (chemistry) , crystallography , nitrogen , aromaticity , molecule , organic chemistry
We describe the two‐electron reduction of N,N′‐dimethyl‐2,7‐diazapyrenium dications ( MDAP 2+ ), which afforded the corresponding reduced form ( MDAP 0 ) as a highly electron‐rich 16π antiaromatic system. A single‐crystal X‐ray diffraction analysis of MDAP 0 revealed a distorted quinoidal structure with high bond‐length alternation. The 1 H NMR spectrum of MDAP 0 exhibited a diagnostic proton signal (4.6 ppm) that is distinctly upfield shifted compared to that of aromatic diazapyrene (8.3 ppm). Theoretical calculations supported the existence of a paratropic ring current. These results indicate that MDAP 0 exhibits antiaromatic character derived from its peripheral 16π‐electron conjugation.