Département de chimie moléculaire

Authors devised a straightforward synthetic strategy leading to a new flexible pacman-like bisporphyrin. They established from electrochem., spectroelectrochem., theor. chem., UV/Vis, and ESR spectroscopy data that this redox-switchable architecture can be efficiently and reversibly converted from an "open" charge-repelled conformation into a "closed" cofacial arrangement. This open/close mol. motion, triggered by electron-transfers centered on $π$-dimerizable bipyridinium subunits, has been shown to allow the complexation of a bidentate heterocyclic ligand pinched between both metalloporphyrins as revealed by the modulation of the porphyrin-based exciton coupling phenomena. The redn. of both bipyridiniums in the open "charge-repelled" conformer thus leads to a large reorganization triggered by the formation of an intramol. $π$-dimer, the driving force of this mol. motion being the stabilization of both org. radicals in a sandwich-like structure. [on SciFinder(R)]