title: Fully Fused Quinoidal/Aromatic Carbazole Macrocycles with Poly-radical Characters.
abstract: While the chemistry of open-shell singlet diradicaloids has been successfully developed in recent years, the synthesis of π-conjugated systems with poly-radical characters (i.e., beyond diradical) in the singlet ground state has been mostly unsuccessful. In this study, we report the synthesis and isolation of two fully fused macrocycles containing four (4MC) and six (6MC) alternatingly arranged quinoidal/aromatic carbazole units. Ab initio electronic structure calculations and various experimental measurements indicate that both 4MC and 6MC have an open-shell singlet ground state with moderate tetraradical and hexaradical characters, respectively. Both compounds can be thermally populated to high-spin excited states, resulting in weak magnetization at room temperature. Our study represents the first demonstration of singlet π-conjugated molecules with poly-radical characters and also gives some insights into molecular magnetism in neutral π-conjugated polycyclic heteroarenes.
authors.affiliation: Department of Chemistry, National University of Singapore , 3 Science Drive 3, 117543 Singapore.
authors.forename: Soumyajit
authors.initials: S
authors.lastname: Das
authors.affiliation: Department of Materials Science & Engineering, National University of Singapore , 119260 Singapore.
authors.forename: Tun Seng
authors.initials: TS
authors.lastname: Herng
authors.affiliation: Department of Physical Chemistry, University of Malaga , Campus de Teatinos s/n, 29071 Malaga, Spain.
authors.forename: José L
authors.initials: JL
authors.lastname: Zafra
authors.affiliation: Department of Physical Chemistry, University of Malaga , Campus de Teatinos s/n, 29071 Malaga, Spain.
authors.forename: Paula Mayorga
authors.initials: PM
authors.lastname: Burrezo
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University , Sakyo-ku, Kyoto 606-8502, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Kitano
authors.affiliation: Department of Chemistry and Biochemistry, Graduate School of Engineering and Center for Molecular Systems, Kyushu University , 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Ishida
authors.affiliation: Department of Chemistry, National University of Singapore , 3 Science Drive 3, 117543 Singapore.
authors.forename: Tullimilli Y
authors.initials: TY
authors.lastname: Gopalakrishna
authors.affiliation: Department of Chemistry, National University of Singapore , 3 Science Drive 3, 117543 Singapore.
authors.forename: Pan
authors.initials: P
authors.lastname: Hu
authors.affiliation: Department of Chemistry, Graduate School of Science, Kyoto University , Sakyo-ku, Kyoto 606-8502, Japan.
authors.forename: Atsuhiro
authors.initials: A
authors.lastname: Osuka
authors.affiliation: Department of Physical Chemistry, University of Malaga , Campus de Teatinos s/n, 29071 Malaga, Spain.
authors.forename: Juan
authors.initials: J
authors.lastname: Casado
authors.affiliation: Department of Materials Science & Engineering, National University of Singapore , 119260 Singapore.
authors.forename: Jun
authors.initials: J
authors.lastname: Ding
authors.affiliation: IKERBASQUE - Basque Foundation for Science & Donostia International Physics Center & Kimika Fakultatea, Euskal Herriko Unibertsitatea , Paseo Manuel de Lardizabal, 4, 20018 Donostia-San Sebastián, Euskadi, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Casanova
authors.affiliation: Department of Chemistry, National University of Singapore , 3 Science Drive 3, 117543 Singapore.
authors.forename: Jishan
authors.initials: J
authors.lastname: Wu