Pyridinic Nitrogen Doping: A Versatile Approach for Precise Structure–Property Manipulations of Nanographenes

The electronic structure of nanographene fragments (NGs) is closely related to heteroatom-doping, which is a continuous research hotspot in the fields of organic electronics and spintronics materials. Without altering the number of π-electrons and aromaticity, "pyridinic" nitrogen-doping can finely tune the π-electronic structure of NGs, thus manipulating the optical, electronic, and magnetic properties as well as assembly patterns. However, the exact influence of pyridinic N-doping on these features has been still ambiguous due to the lack of a systematic summary and analysis. Meanwhile, pyridinic N-incorporation might also give rise to certain exotic characteristics for NGs, such as symmetry breaking, stabilization of the edge states, and manipulation of potential topological phases, which have long been obscured. While considerable N-embedded NGs with various edge topologies have been developed over the past decades, this review aims to summarize the representative pyridinic nanographenes (PNGs) recently reported and present a comprehensive understanding on the impact of pyridinic N-incorporation on materials properties, which might provide future perspectives for the PNG development and facilitate their practical applications.