Periodically Twisted\nMolecular Wires Based on a Fused\nUnit for Efficient Intramolecular Hopping Transport

Realizing efficient long-distance intramolecular charge\ntransport\nbased on a hopping mechanism is a key challenge in molecular electronics.\nIn hopping transport, a smaller reorganization energy (λ) and\nenergy difference between hopping sites (Δ<i>E</i><sub>hs</sub>) should lead to a smaller activation energy and faster\ncharge transfer. However, the development of π-extended molecules\nthat meet these requirements is challenging. In this study, we successfully\nsynthesized several nanometer-scale π-extended molecules composed\nof a fused π-conjugated unit as a hopping site for reducing\nλ. Conformational twists between fused units effectively localize\nπ-conjugation in each unit, contributing to reducing Δ<i>E</i><sub>hs</sub>. The expected electronic structures of the\noligomers were confirmed using spectroscopic and electrochemical measurements.\nSingle-molecule conductance measurements exhibited higher conductance\nand lower activation energy than those of nonfused oligothiophenes.\nFirst-principles calculations indicated that smaller λ and Δ<i>E</i><sub>hs</sub> values explain the high conductance. These\nresults highlight the efficiency of the proposed molecular design\nfor effective intramolecular hopping transport.