Conjugate Fluorescent Compound Based on Pyrene-imidazole: Design, Synthesis, Crystal Structure and Fluorescence Property

Pyrenes are an important group of polycyclic aromatic hydrocarbons（PAHs）. In order to expand the diversity of conjugate compounds based on pyrene, two new isomeric compounds anti-PyDTPAI and syn-PyDTPAI containing pyrene, imidazole and triphenylamine are synthesized via a one-pot cyclization reaction and characterized. The anti-PyDTPAI is characterized by single-crystal X-ray diffraction which crystallizes in monoclinic, space group P2;/n with a = 10.132（4）, b = 14.997（7）, c = 18.968（9） ?, β = 95.543（19）o, V = 2869（2） ?;, Z = 2, F（000） = 1092, Dc = 1.196 Mg/m;, Mr = 1033.28 and μ（Mo Kα） = 0.070 mm;. The presence of intermolecular C–H···π interactions results in the stability of the compound. The crystal structure shows a centrosymmetric, coplanar configuration towards pyrene-imidazole segment and a slip-stacked packing mode across the longer molecular axis which is similar to the J-type aggregation. The investigation of UV-vis absorption and fluorescence in solution indicates a strong blue emission under the ultraviolet light excitation. The two isomers also display high thermal stability which is proved by differential scanning calorimetry（DSC） and thermogravimetric analysis（TGA）. Additionally, the molecular structure and HOMO and LUMO levels are calculated by density functional theory（DFT） at the B3 LYP/6-31 G（d） level.