Luminescent dipyrrin based metal complexes

While they may have been overshadowed by the brightness of their BODIPY analogues, dipyrrin based metal complexes have recently appeared as novel interesting luminescent species owing to the development of various synthetic strategies for the preparation of such coordination compounds with appreciable quantum yields and tuneable emission wavelength. Not only the rigidification brought by functionalization of the dipyrrin backbone either at position 5 or positions 1 and 9, but also a careful choice of the ligands present in the complex coordination sphere have been key in these developments leading to bright and stable emitters. At position 5, equivalent to the meso position of a porphyrin, introduction of peripheral groups, such as the mesityl moiety hindering the rotational freedom of this unit, has been particularly targeted, hence limiting a favourable non-radiative deactivation pathway. Regarding positions 1 and 9, their proximity to the metal center has prompted their use for the introduction of additional coordinating units, thus providing a pseudo-macrocyclic character to the ligands. In this perspective article, the different types of modification of dipyrrin as well as the resulting metal complexes incorporating these derivatives, their photophysical properties and their applications in sensing and materials science are reviewed.