Delocalization beyond π-conjugation

We pioneer the use of an aromatic hydrocarbon derivative to break through the limitation of molecular conductors. The constituent molecules for conductors have been practically limited to planar π-conjugated molecules. Such molecules frequently form columnar structures, when they possess unpaired electrons for electrical conduction. To extend the intra- and intercolumnar interactions, heteroatoms such as chalcogen atoms are often introduced at the periphery of the constituent molecules. Yet this strategy inevitably encounters difficulties, as such molecules would be increasingly difficult to synthesize with increasing the number of heteroatoms and the molecular weights, while they would still produce highly anisotropic conductors. They often behave insulators in the form of powder and thin films because of the anisotropy. Thus, a different strategy for developing molecular conductors has been desired for a long time. The molecule in this work features its three-dimensionally delocalized unpaired electrons extended over a planar aromatic skeleton and its surrounding upright alkyl chains. Thus, in the solid state, they spontaneously form a three-dimensional interaction network serving as conduction pathways. This approach is widely applicable to other electronic and magnetic materials to change the design of molecular functional materials.