On-Surface Synthesis of Nanographenes Through Domino Cyclization Reactions

On-surface synthesis has emerged as a powerful method to synthesize nanographenes that are difficult to obtain through the solution chemistry, but the number of available reactions is still highly limited. In this study, we demonstrate an unprecedented on-surface domino cyclization of bis{2-(7-formylnaphthalen-2-yl)phenyl}diacetylene, leading to dibenzo[hi,st]ovalene and peryleno[2,1,12,11-fghij]pentaphene through a sequence of 1) cycloisomerization of diaryldiacetylene moieties, 2) oxidative cyclodehydrogenation, and 3) reductive cyclization of formyl groups. The structures of these nanographenes and other cyclized products were unambiguously elucidated by using scanning tunneling microscopy directly on Au(111). Moreover, their electronic properties were investigated by scanning tunneling spectroscopy combined with density functional theory calculations. Our findings offer new insights into the on-surface cyclization reactions, providing an effective strategy for synthesizing a wider variety of carbon nanostructures.