Beyond BODIPY: dipyrrin complexes of P-block elements

Dipyrrin has proven to be a versatile ligand platform for metals across the periodic table. Since much of the coordination chemistry has focused on transition metals, main-group dipyrrin chemistry has been underexplored, particularly in the case of heavy p-block elements. Boron dipyrrin complexes (also known as BODIPY) were initially reported in 1968, yet the first well-characterized example of a heavy p-block dipyrrin complex was in 2006. This nascent area of research has undergone a significant surge, where nearly half of the reports in this field have been published since 2019. Given this renewed interest and rapid development, we provide a focused review on heavy p-block dipyrrin complexes, describing the synthesis, structure, and spectroscopy of these molecules. One significant aspect of these complexes is their optical properties, which access red and near-infrared wavelengths with high quantum yields. While these main-group dipyrrins have been used as catalysts, they have also been leveraged for a variety of biological applications including photodynamic therapy, tumor imaging, and cytotoxic drugs. With the advent of synthetic methods for these novel p-block complexes, dipyrrins can begin to interface with recent advances and applications of main-group chemistry, potentially offering advantages over other ligand platforms.