Reductive O-triflylation of naphthalene diimide: access to alkyne- and amine-functionalized 2,7-diazapyrenes

Herein we report the facile reductive O-triflylation and O-silylation of naphthalene diimide as a scalable one-step approach. The resulting highly reactive 1,3,6,8-tetratriflato-2,7-diazapyrene was prepared at the 3 gram scale and serves as a versatile platform for further functionalizations via Sonogashira cross coupling or nucleophilic aromatic substitution by piperidine or iodide leading to tetrasubstituted diazapyrenes with tunable optoelectronic properties. Fine tuning is demonstrated by means of absorption and emission maxima varying within a range of more than 100 nm. The different diazapyrenes are characterized by means of XRD diffraction, UV-Vis and photoluminescence spectroscopy as well as cyclic voltammetry and TD-DFT calculations. The applicability of so far unaccessible tetra-1-alkynyl diazapyrenes for organic molecular beam epitaxy (OMBE) is demonstrated by characterization of a sub-monolayer on Cu(111) using scanning tunneling microscopy (STM).