Nanotechnologies / Materials
Nanotechnology, Molecular electronics, Organic electronics

Development of molecular wires towards efficient
intramolecular hopping transport
Department of Soft Nanomaterials, Nanoscience and Nanotechnology Center,
The Institute of Scientific and Industrial Research (SANKEN)
Professor Yutaka Ie

Researchmap https://researchmap.jp/read0105668?lang=en

Abstract
The development of several-nanometer-scale π-conjugatedmolecules for efficient intramolecular hopping charge transportremains a significant challenge. To construct localized electronicstructures at the same energy in a molecule, a series of molecularwire, with lengths up to 10 nm and periodically twisted structures,
was synthesized. Single-molecule conductance measurements ofthe twisted molecules revealed resistances lower than those of planar molecules. This study provides a rational molecular design toimprove the intramolecular hopping charge transport.

Completely insulated
several-nanometer-scale molecular wire
Planar molecular wire

▍ Significance of the research and Future perspective

In this study, we successfully designed “uniformed” intramolecular hopping sites by the modification of molecular structures andimproved the long-range intramolecular hopping charge transport.
These findings give significant new insights into the field of molecule-based electronics in terms of unveiling a general design principle for organic materials to improve their electrical conduction.

Energy leveln = 12-24

Au

Au
Hopping site

Twisted unit

Periodically twisted molecular wire

Energy level

Elucidating the nature of long-range intramolecular charge transport in π-conjugated systems is of considerable importance for awide range of scientific fields, from chemistry to materials scienceand physics. In contrast to coherent tunneling charge transport,
which governs charge transport over a short distance, the establishment of design principles for molecules with efficient hoppingtransport, which governs charge transport over a long distance,
remains elusive due to difficulties in the molecular design and synthesis of several-nanometer-scale π-conjugated systems. Under
this situation, we synthesized a series of several-nanometer-scaleoligothiophenes with periodically twisted structures and localizedconjugation. Each conjugation unit serves as a hopping site at thesame energy, which should result in more effective hopping transport than in molecules without periodically localized conjugation.
As expected, single-molecule electrical conductance measurements using the scanning tunneling microscope–break junction
technique revealed that the resistance of the newly synthesizedmolecules were lower than those of the linear oligothiophenes that
we had reported previously.

Au

Au
Hopping sitem = 2-4500,/929:-6./)3<*

Nanotechnologies / Materials▍ Background & Results

Periodically twisted molecules
Linear molecules

400
300
200
10004

10
68+74/.;4-8(4/60:1)65*

Hopping sites are alignedat the same energy.
Decrease of energy loss
Improved hopping transport

Japanese Patent Application No. 2005-065947
Japanese Unexamined Patent Publication No. 2006-248945, Japanese Patent No. 4505568
Ie, Yutaka; Tada, Hirokazu; Aso, Yoshio et al. Highly Planar and Completely Insulated Oligothiophenes: Effects of π-Conjugation on Hopping Charge
Transport J. Phys. Chem. Lett. 10 2019; 3197-3204. doi: 10.1021/acs.jpclett.9b00747
Tr e a t i s e
Ie, Yutaka; Tada, Hirokazu: Aso, Yoshio et al. Improving Intramolecular Hopping Charge Transport via Periodical Segmentation of π-Conjugation in aMolecule J. Am. Chem. Soc. 143 2021; 599-603. doi: 10.1021/jacs.0c1056
URL
K e y w o r d single-molecule electronics, hopping transport, molecular wire, π-Conjugated molecule, organic semiconductors
P a t e n t