Mechanochemical Synthesis, Photophysical Properties, and X‐ray Structures of N‐Heteroacenes

The described mechanochemical methodology is an example of a proof‐of‐concept in which solution‐based tedious, poor yielding, and difficult syntheses of pyrazaacenes are achieved under solvent‐free ball‐milling conditions; the method is easy, high yielding, time‐efficient, and environmentally benign. The synthesized compounds also include pyrazaacenes (N‐heteroacenes) that are octacene analogues containing pyrene building blocks. The compounds were sparingly soluble in common solvents, and column chromatographic purifications could be avoided after the solvent‐free syntheses. The UV/Vis absorption spectra of the pyrazaacenes show intense absorption bands in the near‐IR region. The single‐crystal X‐ray analyses of selected pyrazaacene derivatives showed pairwise π–π interactions and some C–H ··· π interactions, which could account for some of the photophysical features of the compounds in the solid state.