NaCl has been successfully used as a template for the
synthesis
of 2D nanomaterials, but it is seldom used for the construction of
flat small organic molecules. Herein, a simple, low-cost, and highly
efficient synthesis of phenazines with planar main frames, such as
5-phenyl-5,14-dihydro-5,7,12,14-tetraazapentacene, in the presence
of NaCl micro-crystal as a kind of molecular mold is described. The
reactants were mixed with NaCl powder and heated to 320 °C for
5 min. Yields >90% were readily achieved after a simple precipitation
in water. The effectiveness of NaCl crystal as a mold with HCl was
confirmed by comparison with common inorganic salts, SiO2, and γ-Al2O3 with HCl together with
combinations including NaNO3 + HNO3, Na2SO4 + H2SO4, NaH2PO4 + H3PO4, and NaH2PO4 + polyphosphoric acid. The mechanism was deduced with
the aid of computer simulation, which confirms the stabilization of
5,14-dihydro-5,7,12,14-tetraazapentacene by the NaCl surface. DMSO
solution of a product, 1,3-dihydro-imidazo[4,5-b]phenazin-2-one,
showed enhanced fluorescence in H2O, and it was used as
a fluorescent probe for pH and Hg2+. A full-color material
was prepared by mixing precursors of epoxy resin and phenazines, and
its fluorescent color could be adjusted by the ratio of phenazines.
