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.

The use of α,β-unsubstituted dipyrrins, dpm, for the elaboration of infinite architectures in crystalline form based on coordination as well as hydrogen bonding interactions is reviewed. These ligands can be readily functionalized and derivatives bearing either a peripheral hydrogen bond donor/acceptor group or a secondary coordinating group have been developed. In the first case, the complexes incorporating these dpms self-assemble via hydrogen bonding leading to extended architectures. In the second case, the coordinating complexes, or metallatectons, can self-assemble to form homonuclear networks such as in a series of (acac)Cu(dpm) complexes. Upon association of the metallatectons with a second metal centre, heterometallic architectures are formed. These MOFs are constructed by coordination as well as Ag-π interactions depending on the nature of the peripheral coordinating group and the coordination geometry of the metallatecton.

A series of complexes based on the combination of cyclometallated palladium or platinum moieties with functionalized dipyrrin ligands bearing mesityl- or benzonitrile groups have been prepared and characterized both in the solid state and in solution; these compounds exhibit a characteristic dipyrrin-centered luminescence with an emission intensity modulated by the degree of rotational freedom of the aromatic group attached to the dipyrrin chelate.

Homo- and hetero-leptic Zn and Cu complexes of dipyrrin type ligands bearing mono- and di-cyanophenyl groups when combined with silver cations lead to the formation of Ag(I)–CC double bond interactions unprecedented in the crystalline phase.