Highly regioselective cyclodehydrogenation reactions of tetraphenyldibenzoperiflanthene (DBP) on metal substrates

Abstract

Regioselective cyclodehydrogenation reactions enable the direct, high-efficiency construction of complex multi-ring structures. Tetraphenyldibenzoperiflanthene (DBP), an exceptional organic semiconductor, exhibits promising applications predominantly for high-performance organic optoelectronic devices. Although significant progress has been made in DBP research, the cyclodehydrogenation behavior of DBP on metal surfaces has, to our knowledge, not been reported. Here, we reported the high regioselectivity of DBP molecules during cyclodehydrogenation reaction process on both Au(111) and Ag(111) substrates. In particular, DBP molecules initially form two highly regioselective intermediates after the first-stage annealing. During the second-stage annealing, these intermediates convert to four final products, exhibiting yields exceeding 96% on Au(111) substrates and over 98% on Ag(111) substrates, respectively. Using high-resolution scanning tunneling microscopy and density functional theory calculations, we clearly resolved the atomic structural characteristics of the resulting cyclodehydrogenation products. The calculated total energies of these four main products are substantially lower than those of the other rare products, and this energy trend is in qualitative agreement with our experimental observations. Furthermore, using scanning tunneling spectroscopy, we provided insights into the differences in the electronic properties of DBP before and after selective cyclodehydrogenation. Our work elucidates the selective cyclodehydrogenation of a model single-reaction system on metal surfaces at the atomic scale, which may provide a framework for understanding the surface chemical processes undergone by other reactants.