A Cryptand-Type Aluminum Tris(salophen) Complex: Synthesis, Characterization, and Cell Imaging Application

Metal salen/salophen complexes have been used as fluorescent probes for cell imaging with various metal centers. Herein we synthesized cryptand-type aluminum salophen complexes LAl3 and the corresponding mononuclear compound LAl. X-ray crystal diffraction verifies the cryptand-type structure of LAl3 with C3h symmetry. Both LAl3 and LAl show moderate green fluorescence with quantum yields of 0.17 and 0.05, respectively. The hydrophilic and cationic nature of these aluminum salophen complexes renders them enhanced cellular uptake. Both complexes are internalized into cells by energy-dependent pathways and they distribute in lysosomal organelles.