Stable Nitrogen‐Centered Bis(imino)rylene Diradicaloids

• Published in: Chemistry : a European journal Vol. 24; no. 19; pp. 4944 - 4951
• Main Authors: Zeng, Wangdong, Hong, Yongseok, Medina Rivero, Samara, Kim, Jinseok, Zafra, José L., Phan, Hoa, Gopalakrishna, Tullimilli Y., Herng, Tun Seng, Ding, Jun, Casado, Juan, Kim, Dongho, Wu, Jishan
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 03.04.2018; Wiley Subscription Services, Inc
• Subjects: Absorption; Chemistry; Chemistry, Multidisciplinary; diradicaloids; Electrochemical analysis; electrochemical properties; Electrochemistry; electronic structure; Intermediates; Nitrogen; Photon absorption; Physical Sciences; radicals; Science & Technology; TUNABLE GROUND-STATES; POLYCYCLIC AROMATIC-HYDROCARBON; radicals; absorption; 2-PHOTON ABSORPTION; electrochemical properties; SINGLET BIRADICAL CHARACTER; OPEN-SHELL; EXTENDED P-QUINODIMETHANES; QUINOIDAL OLIGOTHIOPHENES; NEAR-INFRARED ABSORPTION; electronic structure; 2ND HYPERPOLARIZABILITIES; diradicaloids; CLOSED-SHELL
• ISSN: 0947-6539; 1521-3765; 1521-3765
• DOI: 10.1002/chem.201706041

The synthesis of stable open‐shell singlet diradicaloids is critical for their practical material application. So far, most reported examples are based on carbon‐centered radicals, which are intrinsically reactive, and there are very few examples of stable nitrogen‐centered diradicaloids. In this full paper, a series of soluble and stable bis(imino)rylenes up to octarylene were synthesized on the basis of newly developed dibromorylene intermediates. It was found that from hexarylene onward, these quinoidal rylenes showed open‐shell singlet ground states and could be thermally populated to paramagnetic triplet aminyl diradicals. They are stable due to efficient spin delocalization onto the rylene backbone as well as kinetic blocking of the aminyl sites by the bulky and electron‐deficient 2,4,6‐trichlorophenyl groups. They exhibited very different electronic structures, diradical character, excited‐state dynamics, one‐photon absorption, two‐photon absorption, and electrochemical properties from their respective aromatic rylene counterparts. These bis(imino)rylenes represent a rare class of stable, neutral, nitrogen‐centered aminyl diradicaloids. Long rylene‐bridged aminyl diradicaloids! We report the successful synthesis of a series of bis(imino)rylenes up to octarylene. The long quinoidal rylenes from hexarylene onward show an open‐shell singlet ground state. Their electronic structures and physical properties are very different from those of their aromatic rylene counterparts.