Coordination-driven assemblies based on meso-substituted porphyrins: Metal-organic cages and a new type of meso-metallaporphyrin macrocycles

Coordination-driven self-assembly of (metallo)porphyrins can produce complex metal-organic architectures bringing new functions and applications in, for example, molecular recognition, sensing, and catalysis. With the aim of constructing multiporphyrinic functional systems, this review provides an overview of the recent advances in the field of discrete metal-ligand assemblies based on meso-substituted (metallo)porphyrins with a particular focus on describing the functions that emerge from self-assembly as well as framing perspectives for future areas of research. The discussion is restricted to two supramolecular research domains related to (metallo)porphyrins whose meso-positions are directly involved in the self-organization process. First, we describe notable examples of (metallo)porphyrins functionalized with coordinating groups, which have served as building blocks to create discrete porous Coordination Cages with applications in guest-binding and as platforms to mediate chemical reactions. Secondly, we present the progress in the synthesis of meso-metallaporphyrins, a new type of porphyrin-like macrocycle that is characterized by the presence of metal ions at the meso-positions of the frame in substitution of the methine =CH-bridges; likewise, the traditional pyrrole units are replaced by triazole rings to afford coordination to metals. We thus aim to provide new methodological insights into the design of coordination porphyrinic assemblies towards the enhancement of their properties and the building of new functions. (C) 2019 Elsevier B.V. All rights reserved.