Novel Synthesis of Down-/Up-Conversion Fluorescent Oligo(2-pyrazoline)s

The polycondensation of 2-pyrazolines is presented. The products are oligomers with the five-membered rings of the 2-pyrazoline as the backbone and the reaction is a polycondensation reaction by decomposition of ROH from the hydrogen atom in the −NH– group and the −OR in the ester group. Metal catalysts, reaction periods, and the addition amounts of the catalyst are investigated to optimize the reaction conditions. The products are down-/up-conversion fluorescence molecules that can significantly enhance cell imaging through the synchronized excitation of visible and near-infrared light and may be widely used in other optical fields.