Resonating Valence Bond Ground State in Oxygen-Functionalized Phenalenyl-Based Neutral Radical Molecular Conductors

摘要

We report the preparation,crystallization,and solid-state characterization of the first two members of a new family of spiro-bis(1,9-disubstituted phenalenyl)boron neutral radicals based solely on oxygen functionalization,and we show that this strategy significantly lowers the electrochemical disproportionation potentials (DELTA E),in comparison with other spiro-bis(1,9-disubstituted phenalenyl)boron salts.In the solid state,these radicals pack in a continuous array of pi-pi-stacked phenalenyl units with very short intermolecular carbon--carbon contacts.These two radicals are among the most highly conducting neutral organic solids,with room temperature conductivities reaching 0.3 S/cm.Magnetic susceptibility measurements show that the radicals do not exist as isolated free radicals,and there is significant spin-spin interaction between the molecules in the solid state as expected from the crystal structures and the calculated band structures;the solid-state properties are best rationalized in terms of the resonating valence bond model.