Pyrrolo[3,4‑<i>c</i>]pyridine-Based Fluorescent Chemosensor for Fe³⁺/Fe²⁺ Sensitivity and Their Application in Living HepG2 Cells

New 2H-pyrrolo­[3,4-c]­pyridine-1,3,6­(5H)-trione-based fluorophores have been synthesized by a single-step procedure in an ambient reaction condition. By this protocol, a total of 44 new compounds were generated and the photophysical property of 23 compounds was studied in detail. These fluorophores show good fluorescence activity and illustrate high selectivity for Fe3+/Fe2+ cation in the 10–7 (M) range. Notably, this 2H-pyrrolo­[3,4-c]­pyridine-1,3,6­(5H)-trione moiety is first used as a turn-off chemosensor for the Fe3+/Fe2+ cation. In addition, this probe was further applied for imaging Fe3+ in living HepG2 cells.