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An Open‐Shell Coronoid with Hybrid Chichibabin–Schlenk Conjugation
Author(s) -
Prajapati Bibek,
Dang DuyKhoi,
Chmielewski Piotr J.,
Majewski Marcin A.,
Lis Tadeusz,
GómezGarcía Carlos J.,
Zimmerman Paul M.,
Stępień Marcin
Publication year - 2021
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.202109273
Subject(s) - singlet state , chemistry , cationic polymerization , open shell , molecule , band gap , photochemistry , crystallography , polymer chemistry , materials science , atomic physics , optoelectronics , organic chemistry , physics , excited state
A hexaradicaloid molecule with alternating Kekulé and non‐Kekulé connectivities between adjacent spin centers was obtained by fusing two conjugation motifs in Chichibabin and Schlenk hydrocarbons into a coronoid structure. 1 H NMR, ESR, and SQUID experiments and computational analyses show that the system has a singlet ground state with a significant hexaradicaloid character ( γ 0 =0.826, γ 1 = γ 2 =0.773). It has multiple thermally accessible high‐spin states (up to the septet), with uniform energy gaps of ca 1.0 kcal mol −1 between consecutive multiplicities. In line with its open‐shell character, the coronoid has a small electronic band gap (ca. 0.8 eV) and undergoes two consecutive one‐electron oxidations at low potentials, yielding cationic forms with extended near‐infrared absorption. The hexaradicaloid, which combines open‐shell and macrocyclic contributions to its π conjugation, is an example of a design strategy for multistate spin switches and redox‐amphoteric NIR dyes.