π‐mers and π‐dimers: Two Radical Supramolecular Interactions – A Tutorial Review

In this review, the difference between π‐mers (pimers) and π‐dimers (pi‐dimers) will be discussed. Often interchanged or confused in the literature, these two radical interactions lead to different or even opposite physico‐chemical behaviors. This review aims at clarifying the terms π‐mers and π‐dimers and at describing their main physico‐chemical properties to address their differences. Finally, selected literature examples exhibiting the successive formation of π‐mers and π‐dimers within the same systems will be detailed to emphasize the physico‐chemical changes occurring upon conversion. π‐mers and π‐dimers are two radical interactions being easily confused on account of their similarities. This tutorial review introduces i) a clear definition of each interaction, ii) their main physico‐chemical differences observable by major analytical techniques (X‐Ray, UV/Vis/NIR, EPR, NMR and electrochemistry), iii) some of their thermodynamic features, and iii) examples showing strategies to enhance their stability (using a covalent spacer, a confined environment and mechanical bonds).