NBN-doped nanographene embedded with five- and seven-membered rings on Au(111) surface* *Project supported by the National Natural Science Foundation of China (Grant Nos. 51761135130 and 61888102), the National Key R&D Program of China (Grant Nos. 2018YFA0305800 and 2019YFA0308500), DFG EnhanceNano (Grant No. 391979941), the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB30000000), the International Partnership Program

Abstract

Nanographenes (NGs) can be embedded with predesigned dopants or nonhexagonal rings to tailor the electronic properties and provide ideal platforms to study the unique physical and chemical properties. Here, we report the on-surface synthesis of NBN-doped NG embedded with five- and seven-membered rings (NBN-575-NG) on Au(111) from a oligophenylene precursor preinstalled with a NBN unit and a heptagonal ring. Scanning tunneling microscopy and non-contact atomic force microscopy images elucidate the intramolecular cyclodehydrogenation and the existence of the five- and seven-membered rings. Scanning tunneling spectroscopy spectra reveal that the NBN-575-NG is a semiconductor, which agrees with the density functional theory calculation results on a freestanding NBN-575-NG with the same structure. This work provides a feasible approach for the on-surface synthesis of novel NGs containing non-hexagonal rings.