A Fully Charge‐Delocalized Two‐Dimensional Porphyrin System with Two Different Class III States. Issue 9 (7th December 2016) - Mishiba, Kentaro
Abstract: Understanding of charge‐delocalization over two‐dimensional (2D) frameworks is a further step in the path towards the development of molecular nanodevices and nanomaterials. Here, we report a porphyrin–nickel complex with four peripheral redox‐active ruthenium pendants (1 ). A cyclic voltammogram of compound1 displays reversible five‐electron, four redox waves with large potential separations, suggesting that one‐electron‐ (1 + ) and two‐electron‐oxidized species (1 2+ ) are thermodynamically stable with respect to disproportionation. The paramagnetic one‐electron‐oxidized species1 + prepared by a comproportionation reaction of compounds1 and1 2+, turns out to be a highly charge‐delocalized two‐dimensional class III compound as clearly indicated by its characteristic intervalence charge‐transfer (IVCT) band as is further supported by IR and ESR spectroscopy as well as DFT and time‐dependent (TD) DFT calculations. Furthermore, the diamagnetic dicationic species1 2+ has a spin‐paired electronic structure with a fully charge‐averaged class III character. The substantial contribution of the cumulenic structures to compound1 2+ is confirmed by 13 C NMR and IR spectroscopy as well as X‐ray structure analyses. Such unique electronic features of the 2D systems provide a clue to development of nanoscale molecular devices. Abstract : Open or closed? Both the oxidized paramagnetic monocationic and diamagnetic dicationic species of a tetraruthenium complex with a porphyrin–nickel core have been found to be fully charge‐delocalized two‐dimensional class III species (see figure).