On‐Surface Bottom‐Up Synthesis of Azine Derivatives Displaying Strong Acceptor Behavior

Abstract

On‐surface synthesis is an emerging approach to obtain, in a single step, precisely defined chemical species that cannot be obtained by other synthetic routes. The control of the electronic structure of organic/metal interfaces is crucial for defining the performance of many optoelectronic devices. A facile on‐surface chemistry route has now been used to synthesize the strong electron‐acceptor organic molecule quinoneazine directly on a Cu(110) surface, via thermally activated covalent coupling of para‐aminophenol precursors. The mechanism is described using a combination of in situ surface characterization techniques and theoretical methods. Owing to a strong surface‐molecule interaction, the quinoneazine molecule accommodates 1.2 electrons at its carbonyl ends, inducing an intramolecular charge redistribution and leading to partial conjugation of the rings, conferring azo‐character at the nitrogen sites.

Azo bond formation on metal surfaces

“…During the last decade,on-surface chemistry has attracted extensive attention as ab ottom-up strategy for the synthesis of materials with interesting properties and functions.V arious organic reactions have been successfully realized on metal surfaces [1][2][3][4] and most of them aim for carbonÀcarbon bond formation. Only af ew carbonÀnitrogen and nitrogenÀnitrogen bond forming processes have been reported, such as imine, [5][6][7] imide, [8] azo group formation [9][10][11] and azide-alkyne cycloaddition. [12,13] Among these N-based functional groups, the azo group shows valuable properties in photo switching.…”

“…Various organic reactions have been successfully realized on metal surfaces [1–4] and most of them aim for carbon−carbon bond formation. Only a few carbon−nitrogen and nitrogen−nitrogen bond forming processes have been reported, such as imine, [5–7] imide, [8] azo group formation [9–11] and azide–alkyne cycloaddition [12, 13] . Among these N‐based functional groups, the azo group shows valuable properties in photo switching [14–16] .…”

On‐Surface Driven Formal Michael Addition Produces m‐Polyaniline Oligomers on Pt(111)

“…[38][39][40] On the other hand, most of the amine groups remain intact (BE of 399.35 eV for N1s) while aminority of the molecules present partially and fully dehydrogenated nitrogen species (peaks with BE of 399.9 eV and 397.6 eV, respectively). [41] Finally,a tt emperatures around 475 K( range C), linear chains are formed through covalent coupling between the activated molecules,ascan be observed in the STM images of Figure 1. XPS reveals that oxygen is fully removed from the surface,leaving an insignificant contribution at 533 eV,due to adventitious oxygen (note that XPS measurements are carried out at 120 K).…”

On‐Surface Driven Formal Michael Addition Produces m‐Polyaniline Oligomers on Pt(111)

“…Most of the species present a strong interaction with the Pt surface (new component at 530.3 eV for O 1s) through activated site 6 (see Scheme 1), while the rest adopt a quinone form as suggested by the binding energy of the related peak (532.3 eV) [38–40] . On the other hand, most of the amine groups remain intact (BE of 399.35 eV for N 1s) while a minority of the molecules present partially and fully dehydrogenated nitrogen species (peaks with BE of 399.9 eV and 397.6 eV, respectively) [41] …”