Facile Redox‐Induced Aromatic–Antiaromatic Interconversion of a β‐Tetracyano‐21,23‐Dithiaporphyrin under Ambient Conditions

• Published in: Chemistry : a European journal Vol. 26; no. 16; pp. 3633 - 3640
• Main Authors: Yamashita, Ken‐ichi, Nakajima, Kana, Honda, Yusuke, Ogawa, Takuji
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 18.03.2020; Wiley Subscription Services, Inc
• Subjects: antiaromaticity; aromaticity; Chemistry; Chemistry, Multidisciplinary; Conformation; Conjugation; Cyano groups; Hydrazine; Hydrazines; isophlorins; Oxidation; Physical Sciences; porphyrinoids; redox chemistry; Reduction; Science & Technology; Solvents; porphyrinoids; ELECTRONIC-STRUCTURES; isophlorins; COMPLEXES; antiaromaticity; OPTICAL-PROPERTIES; CRYSTAL; PORPHYRIN; aromaticity; redox chemistry
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201905823

Facile redox‐induced aromatic–antiaromatic interconversions were accomplished by using β‐tetracyano‐21,23‐dithiaporphyrin (CN4S2Por). Introduced cyano groups not only increased the reduction potential of the porphyrin core but also stabilized the antiaromatic isophlorin (CN4S2Iph) by π conjugation. The reduction of CN4S2Por with hydrazine in polar solvents quantitatively affords CN4S2Iph, even under ambient conditions. CN4S2Iph retains a nearly planar conformation and exhibits considerable antiaromaticity. Aerobic oxidation of CN4S2Iph to CN4S2Por occurs in nonpolar solvents. This study was conducted to contribute to the understanding of the structure–antiaromaticity relationship. Facile redox‐induced aromatic–antiaromatic interconversion was accomplished with β‐tetracyano‐21,23‐dithiaporphyrin. The introduced cyano groups not only increased the reduction potentials of the porphyrin core, but also stabilized the antiaromatic state of isophlorin by conjugation.