Electron-Triggered Metamorphism in Porphyrin-Based Self-Assembled Coordination Polymers

Abstract

Viologen-centered electron transfer is used to trigger a complete dissociation of a porphyrin-based supramolecular architecture. In the oxidized state, self-assembly is induced by iterative association of individual porphyrin-based tectons. Dissociation of the self-assembled species is actuated upon changing the redox state of the bipyridium units involved in the tectons from their dicationic state to their radical cation state, the driving force of the disassembling process being the formation of an intramolecularly locked conformation partly stabilized by π-dimerization of both viologen cation radicals.

Dynamic supramolecular polymers built from cucurbit[n]urils and viologens

“…(b), wherein charge repulsion is lowered by the one‐electron reduction of each viologen. This homo‐valent complex involving extensive orbital overlaps between two viologen cation radicals is known as a π‐dimer . Ternary hetero‐caviplexes (1:1:1) are also frequently observed with CB[8], the latter case being illustrated in Fig.…”

Redox‐Triggered Folding of Self‐Assembled Coordination Polymers incorporating Viologen Units

“…Indeed, intramolecular π‐dimers can be readily produced when both viologens involved in the dimer are mechanically connected through suitable spacers, such as a propyl chain, whose size and flexibility is perfectly suited to promote an efficient orbital overlap between both radicals. The viologen group thus constitutes a building block of great interest and its redox‐induced dimerization can be exploited to trigger motions at the molecular level and to provide access to fascinating responsive supramolecular molecules and materials …”

Dynamic Molecular Metamorphism Involving Palladium‐Assisted Dimerization of π‐Cation Radicals

“…The structure and the synthesis of the targeted tecton 4 (PF 6 ) 2 , featuring an electro‐active viologen and an imidazole ligand as key functional elements, are shown in Figure . A conjugated butadiynyl spacer was selected to minimize steric hindrance and to provide a relative flexibility to the tecton.…”

“…One strategy that we have used over the past few years to circumvent these issues and to promote the formation of intramolecular π‐dimers between viologen cation radicals relies on tedious multistep sequences aiming at introducing suitable organic covalent linkers between both π‐units involved in the dimerization (Scheme A) . Works carried out along these lines have led to the emergence of a wide range of responsive metamorphic molecular systems, the conformation of which can be controlled by redox input …”