Design, synthesis, and characterization of a new class of efficient dihydropyridazine-dibenzosuberenone derived fluorescent dyes and investigation of their some photophysical properties

A new series of dihydropyridazine-dibenzosuberenone derivatives has been efficiently prepared by inverse Diels-Alder cycloaddition reactions between tetrazines and dibenzosuberenone derivatives bearing various electron-withdrawing and electron-donating substituents. In total, 14 new fluorescent dyes were designed, synthesized, and characterized. The influence of substituents placed at the 3- and 7-positions of the dibenzosuberenone ring on photophysical properties of the compounds has been investigated in toluene. The photophysical properties of the synthesized compounds were investigated by comparing both with each other and with the unsubstituted derivate which synthesized previously via our research group. Compared with their unsubstituted analogues, the 3,7-substituted dihydropyridazine-dibenzosuberenone derivatives showed red shifts of absorption and emission maxima, which might be attributed to the large pi-conjugated skeleton that was beneficial to electron delocalization. Moreover, a very high fluorescence quantum yields (up to 0.99) and large Stokes shifts (up to 130 nm) of the dibenzosuberenone derivatives were also found, which could make them be found wide potential applications in different fields such as fluorescence sensors, biological image, and optoelectronic materials. (C) 2020 Elsevier Ltd. All rights reserved.