Photoluminescence behaviors of small aliphatic ketimines

Abstract

<p indent="0mm">Non-traditional organic luminescent materials have attracted more and more attention in recent years because of their unique luminescent behaviors and mechanisms. Some aromatic imines (Schiff bases) have been found to exhibit aggregation-induced emission behaviors, but there is no report on the luminescence behavior of small aliphatic ketimines yet. This work reports that aliphatic primary amines easily react with acetone at room temperature, producing products with very strong fluorescence emissions. The fluorescence intensity increases with the increasing reaction time, and the maximum excitation and emission wavelengths red-shift significantly, with the maximum emission wavelengths more than <sc>600 nm.</sc> Structural characterizations prove that the fluorescent products are aliphatic ketimines. These compounds exhibit concentration-enhanced emission behaviors. Their fluorescence intensity increases and the emission red-shifts with the increasing concentration. The aliphatic ketimines show aggregation-enhanced emissions, and the aggregate particle size increases with the increase of concentration. The fluorescence emission of the ketimines is also sensitive to solvents. Theoretical calculation results show that the HOMO–LUMO energy gap of ketimine aggregates decreases with the increase of the number of the aggregated molecules. This study expands the scope of non-traditional luminescent materials and may have potential practical applications.