Ultra-Long-Range Resonant Transport Through Open-Shell Donor-Acceptor Macromolecules*

Design and development of highly conducting molecular materials facilitating the ultra-long-range charge transport play a pivotal role in the development of emerging molecular scale technologies such as sensing, electronics, spintronics and quantum information science. The past two decades have witnessed a new generation of miniaturized electronic based on molecules whose synthetic tunability provides unparalleled functionalities absent in conventional electronic materials. Nonetheless, current design strategies lead to molecules that exhibit off-resonant charge transport, which restricts the conductance to several orders of magnitude below the conductance quantum 1 G₀ and result in an exponential decay in conductance with length. Here, we present a robust, air stable, and highly tunable molecular wire platform composed of open-shell donor-acceptor macromolecules that show remarkably high conductance close to 1G₀ over a length exceeding 20 nm under low bias, with no decay with length. Our single molecular transport measurements along with ab initio calculations demonstrate that the ultra-long range resonant charge transport is attributable to π-conjugation, narrow bandgap, and diradical character, which synergistically enables excellent alignment of frontier molecular orbitals with the electrode Fermi energy. This breakthrough in this long-sought-after transport regime within molecular materials opens new possibilities for incorporating a range of properties into advanced nanoelectronic technologies.