TY - JOUR
T1 - Control of dominant conduction orbitals by peripheral substituents in paddle-wheel diruthenium alkynyl molecular junctions
AU - Ogawa, Shiori
AU - Chattopadhyay, Swarup
AU - Tanaka, Yuya
AU - Ohto, Tatsuhiko
AU - Tada, Tomofumi
AU - Tada, Hirokazu
AU - Fujii, Shintaro
AU - Nishino, Tomoaki
AU - Akita, Munetaka
N1 - Funding Information:
This work was supported by JSPS KAKENHI Grant Numbers 18K05139 and 21K05211. YT acknowledges research grants from the ENEOS Tonengeneral Research/Development Encouragement & Scholarship Foundation and the Asahi Glass Foundation. S. C acknowledges the Matsumae International Foundation Research Fellowship. The theoretical calculations were performed by using computers in the Research Center for Computational Science, Okazaki, Japan.
Publisher Copyright:
© The Royal Society of Chemistry.
PY - 2021/8/28
Y1 - 2021/8/28
N2 - Control of charge carriers that transport through the molecular junctions is essential for thermoelectric materials. In general, the charge carrier depends on the dominant conduction orbitals and is dominantly determined by the terminal anchor groups. The present study discloses the synthesis, physical properties in solution, and single-molecule conductance of paddle-wheel diruthenium complexes 1R having diarylformamidinato supporting ligands (DArF: p-R-C6H4-NCHN-C6H4-R-p) and two axial thioanisylethynyl conducting anchor groups, revealing unique substituent effects with respect to the conduction orbitals. The complexes 1R with a few different aryl substituents (R = OMe, H, Cl, and CF3) were fully characterized by spectroscopic and crystallographic analyses. The single-molecule conductance determined by the scanning tunneling microscope break junction (STM-BJ) technique was in the 10-5 to 10-4G0 region, and the order of conductance was 1OMe > 1CF3 ≫ 1H ∼ 1Cl, which was not consistent with the Hammett substituent constants σ of R. Cyclic voltammetry revealed the narrow HOMO-LUMO gaps of 1R originating from the diruthenium motif, as further supported by the DFT study. The DFT-NEGF analysis of this unique result revealed that the dominant conductance routes changed from HOMO conductance (for 1OMe) to LUMO conductance (for 1CF3). The drastic change in the conductance properties originates from the intrinsic narrow HOMO-LUMO gaps. This journal is
AB - Control of charge carriers that transport through the molecular junctions is essential for thermoelectric materials. In general, the charge carrier depends on the dominant conduction orbitals and is dominantly determined by the terminal anchor groups. The present study discloses the synthesis, physical properties in solution, and single-molecule conductance of paddle-wheel diruthenium complexes 1R having diarylformamidinato supporting ligands (DArF: p-R-C6H4-NCHN-C6H4-R-p) and two axial thioanisylethynyl conducting anchor groups, revealing unique substituent effects with respect to the conduction orbitals. The complexes 1R with a few different aryl substituents (R = OMe, H, Cl, and CF3) were fully characterized by spectroscopic and crystallographic analyses. The single-molecule conductance determined by the scanning tunneling microscope break junction (STM-BJ) technique was in the 10-5 to 10-4G0 region, and the order of conductance was 1OMe > 1CF3 ≫ 1H ∼ 1Cl, which was not consistent with the Hammett substituent constants σ of R. Cyclic voltammetry revealed the narrow HOMO-LUMO gaps of 1R originating from the diruthenium motif, as further supported by the DFT study. The DFT-NEGF analysis of this unique result revealed that the dominant conductance routes changed from HOMO conductance (for 1OMe) to LUMO conductance (for 1CF3). The drastic change in the conductance properties originates from the intrinsic narrow HOMO-LUMO gaps. This journal is
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U2 - 10.1039/d1sc02407h
DO - 10.1039/d1sc02407h
M3 - Article
AN - SCOPUS:85113204156
VL - 12
SP - 10871
EP - 10877
JO - Chemical Science
JF - Chemical Science
SN - 2041-6520
IS - 32
ER -