Towards Tetraradicaloid: The Effect of Fusion Mode on Radical Character and Chemical Reactivity

Pan Hu, Sangsu Lee, Tun Seng Herng, Naoki Aratani, Theo Goncalves, Qingbiao Qi, Xueliang Shi, Hiroko Yamada, Kuo-Wei Huang, Jun Ding, Dongho Kim, Jishan Wu

Research output: Contribution to journalArticlepeer-review

62 Scopus citations

Abstract

Open-shell singlet diradicaloids display unique electronic, non-linear optical and magnetic activity and could become novel molecular materials for organic electronics, photonics and spintronics. However, design and synthesis of diradicaloids with a significant polyradical character is a challenging task for chemists. In this article, we report our efforts toward tetraradicaloid system. A series of potential tetraradicaloids by fusion of two p-quinodimethane (p-QDM) units with naphthalene or benzene rings in different modes were synthesized. Their model compounds containing one p-QDM moiety were also prepared and compared. Their ground-state structures, physical properties and chemical reactivity were systematically investigated by various exper-imental methods such as steady-state and transient absorption, two-photon absorption, X-ray crystallographic analysis, electron spin resonance, superconducting quantum interference device and electrochemistry, assisted by density functional theory calculations. It was found that their diradical and tetraradical characters show a clear dependence on the fusion mode. Upon the introducing of more five-membered rings, the diradical characters greatly decrease. This difference can be explained by the pro-aromaticity/anti-aromaticity of the molecules as well as the intramolecular charge transfer. Our comprehensive studies provide a guideline for the design and synthesis of stable open-shell singlet polycyclic hydrocarbons with significant polyradical characters.
Original languageEnglish (US)
Pages (from-to)1065-1077
Number of pages13
JournalJournal of the American Chemical Society
Volume138
Issue number3
DOIs
StatePublished - Jan 12 2016

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