Abstract
Molecular electronics has emerged as a highly interdisciplinary field that utilizes single molecules or monolayers as functional electronic and sensing components, offering potential capabilities beyond conventional silicon-based electronics. A key mission of the field is to search for molecular candidates that can facilitate efficient charge transport over long distances. This requires overcoming the inherent poor conductivity of organic molecules and the "well-known" conductance decay with the increase in molecular length. Recent advances in molecular design and single-molecule characterizations have sparked exciting opportunities for achieving ultrahigh and length-independent transport with a near-zero or inverted conductance attenuation coefficient in single molecular wires. To highlight this progress, this review surveys the representative molecular systems, the fundamental mechanisms, and design strategies involved in creating highly conductive long molecular wires in single-molecule junction platforms. Through elucidating both the chemical and physical properties of emerging molecular systems, we will facilitate an in-depth future investigation of promising design approaches and potential applications.