Green synthesis of fluorescent Schiff bases: chemo-photophysical characterization, X-ray structures, and their bioimaging

Fluorescence bioimaging technologies have become powerful tools to observe abnormalities in cells. Commercial biomarkers are available; however, there are disadvantages such as high isolation cost, low-temperature storage, photodegradation, and low yields. Therefore, some research must be carried out. The design, synthesis, and chemo-photophysical characterization of two Schiff bases derived from 4-aminobenzoic acid 4-(4-(diethylamino)benzylidene)aminobenzoic acid (1) and 4-((4-methoxybenzylidene)aminobenzoic acid (2)) are reported. The X-ray structures of both compounds showed a non-planar array with dihedral angles of 28.76° and 52.92° (4), respectively. Remarkably, both Schiff bases were isolated via eco-friendly synthetic routes such as ultrasound (US) and mechanosynthesis (MC) with reduced reaction time and energy cost compared to conventional heating. Notably, fluorescence confocal microscopy revealed that compound 1 showed good staining of the cytoplasm in hepatocytes and MCF-7 cells.