Synthesis and investigation of a tris-cyclometalated iridium complex bearing a single quarternary ammonium group

A novel tris-cyclometalated iridium complex (1) containing a single quarternary ammonium moiety has been synthesized, characterized, and investigated as a potential cellular imaging probe. The complex is the next generation of the aminoalkyl iridium complexes recently published by our group. The complex possesses outstanding photophysical properties. The complex is stable in solution in dark but exhibits rapid photocatalyzed transformations. Investigations of this behavior have shown that these transformations involve the formation of an electrophilic species, which can be captured by a suitable nucleophile, leading to the formation of new product. The complex has also been investigated as a potential cellular stain. It is less cytotoxic than its aminoalkyl predecessor and shows lysosomal localization as its precursor.