NaCl Micro-Crystal as a Molecular Mold for Enhanced Synthesis of Planar Phenazines and Their Applications on Chemosensing and a Full-Color Fluorescent Material.

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, SiO 2 , and γ-Al 2 O 3 with HCl together with combinations including NaNO 3 + HNO 3 , Na 2 SO 4 + H 2 SO 4 , NaH 2 PO 4 + H 3 PO 4 , and NaH 2 PO 4 + 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 H 2 O, and it was used as a fluorescent probe for pH and Hg 2+ . 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.