Aggregation-Induced Emission-Active Fluorescent Probe for Zn2+ Based on Isolongifolanone and Its Application in Plant-Cell Imaging

Abstract

A series of hexahydroquinazolin-2-amine-based derivatives have been designed and synthesized from renewable isolongifolanone. Their solid states exhibited an enhanced emission and a dark green to bright yellow color range. In addition to good thermal stability, their solid-state fluorescence is not readily restricted by multiple conventional factors such as long term UV irradiation, increasing operated pressure and elevated heating temperature. In contrast to the derivatives which undergo serious aggregation-caused quenching (ACQ), the dimethylamino-substituted derivative 1-6,6,10,10-tetramethyl-4-(4'-(N,N-dimethylamino)phenyl)-5,7,8,9,10,10a-hexahydro-6H-6a,9-methanobenzo[h]quinazolin-2-imino)methyl)naphthalen-2-ol (3e) demonstrate obvious aggregation-induced emission (AIE) characteristics. Moreover, these fluorescent derivatives were also used for specific and sensitive sensing of Zn2+ ion in aqueous solutions. Then, their photophysical mechanisms were obtained by the density functional theory calculations. These probes were successfully applied to image Zn2+ ion in pollen grains of Althaea rosea.