Flexible Porphyrinoids.

This review underscores the conformational flexibility of porphyrinoids, a unique class of functional molecules, starting from the smallest triphyrins(1.1.1) via [18]porphyrins(1.1.1.1) and concluding with a variety of expanded porphyrinoids and heteroporphyrinoids, including the enormous [96]tetracosaphyrin(1.0.1.0.1.0.1.0.1.0.1.0.1.0.1.0.1.0.1.0.1.0.1.0). The specific flexibility of porphyrinoids has been documented as instrumental in the designing or redesigning of macrocyclic frames, particularly in the search for adjustable platforms for coordination or organometallic chemistry, anion binding, or mechanistic switches in molecular devices. A structural prearrangement to coordinate one or more metal ions has been outlined. The coverage of the topic focuses on representative examples of geometry or conformational rearrangements for each selected class of the numerous porphyrinoids accordingly categorized by the number of built-in carbo- or heterocycles.