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Defective Nanographenes Containing Seven-Five-Seven (7–5–7)-Membered Rings

Fei, Y.; Fu, Y.; Bai, X.; Du, L.; Li, Z.; Komber, H.; Low, K.-H.; Zhou, S.; Lee Phillips, D.; Feng, X.; Liu, J.

Defects have been observed in graphene and are expected to playa key role in its optical, electronic, and magnetic properties. However, becausemost of the studies focused on the structural characterization, the implications oftopological defects on the physicochemical properties of graphene remain poorlyunderstood. Here, we demonstrate a bottom-up synthesis of three novelnanographenes (1−3) with well-defined defects in which seven-five-seven (7−5−7)-membered rings were introduced to their sp2carbon frameworks. From theX-ray crystallographic analysis, compound1adopts a nearly planar structure.Compound2, with an additionalfive-membered ring compared to1, possesses aslightly saddle-shaped geometry. Compound3, which can be regarded as the“head-to-head”fusion of1with two bonds, features two saddles connectedtogether. The resultant defective nanographenes1−3were well-investigated byUV−vis absorption, cyclic voltammetry, and time-resolved absorption spectra and further corroborated by density functional theory(DFT) calculations. Detailed experimental and theoretical investigations elucidate that these three nanographenes1−3exhibit ananti-aromatic character in their ground states and display a high stability under ambient conditions, which contrast with the reportedunstable biradicaloid nanographenes that contain heptagons. Our work reported herein offers insights into the understanding ofstructure-related properties and enables the control of the electronic structures of expanded nanographenes with atomically precise defects.

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  • Secondary publication expected from 27.01.2022

Permalink: https://www.hzdr.de/publications/Publ-32328
Publ.-Id: 32328