Global Aromaticity in Macrocyclic Cyclopenta‐Fused Tetraphenanthrenylene Tetraradicaloid and Its Charged Species
2018; Wiley; Volume: 130; Issue: 40 Linguagem: Inglês
10.1002/ange.201807185
ISSN1521-3757
AutoresXuefeng Lu, Tullimilli Y. Gopalakrishna, Hoa Phan, Tun Seng Herng, Qing Jiang, Chunchen Liu, Guangwu Li, Jun Ding, Jishan Wu,
Tópico(s)Luminescence and Fluorescent Materials
ResumoAbstract A stable cyclopenta‐fused tetraphenanthrenylene macrocycle, CPTP‐M , was synthesized, and the structure was confirmed by X‐ray crystallographic analysis. It exhibits a large radical character (number of unpaired electron, N U =3.52) and a small singlet–triplet energy gap (Δ E S‐T =−2.8 kcal mol −1 by SQUID). Its backbone contains 60 ([4 n ]) conjugated π electrons and is globally antiaromatic. NMR measurements and theoretical calculations revealed that its dication/dianion is globally aromatic owing to the existence of [4 n −2]/[4 n +2] π‐conjugated electrons. Remarkably, the ring‐current map of the tetraanion shows a unique ring‐in‐ring structure, with a diamagnetic outer ring and a paramagnetic inner ring. Accordingly, both the inner‐rim and outer‐rim protons are deshielded in its 1 H NMR spectrum. The tetraanion can be regarded as an isoelectronic structure of the known octulene, which shows similar electronic properties.
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