Thermoelectric measurements of multinuclear ruthenium alkynyl complexes
Yuya Tanaka , 1 Sohyun Park, 2 Jiung Jang, 2 Hyo Jae Yoon 2 1 Tokyo Institute of Technology, Japan, 2 Korea University, Korea
Molecules with high Seebeck coefficients ( S ) have potential applications in thermoelectric materials. However, their S values at single-molecule and self-assembled monolayer levels are low partly due to large energy gaps ( E – E F ) between molecular frontier orbital energy and Fermi energy of the electrodes. We have recently reported highly conducting organometallic molecules with electron-rich ruthenium tetraphosphine fragments in molecular junction. 1 The theoretical study suggests that their small energy gaps ( E – E F ), which may lead to a large Seebeck coefficient. In this study, we report the Seebeck coefficient of multinuclear ruthenium complexes bridged by p -diethynylbenzene-diyl linkers and examine their thermoelectric properties. 2 Thermoelectric measurements for mono-, di- and tri-ruthenium complexes 1 R - 3 R (R = H, CF 3 , OMe) were conducted using the Au-molecule-EGaIn/Ga 2 O 3 system. 3 Upon heating the gold electrode, the S values increased with the number of metal fragments, and the trinuclear complex showed a value exceeding 70 µV/K, which is the highest S value obtained by SAM junction reported so far. Theoretical calculations and cyclic voltammograms indicate that the high Seebeck coefficient is caused by the high-lying HOMO, which destabilizes as the number of metal fragments increases. We also examined substituents effect for the dinuclear complexes ( 2 R ). References 1. M. Akita, Y. Tanaka, Coord. Chem. Rev. 2022 , 461 , 214501. 2. S. Park, J. Jang, Y. Tanaka, H. J. Yoon, Nano Lett. 2022 , 22 , 9693. 3. Nijhuis, C. A.; Reus, W. F.; Barber, J. R.; Dickey, M. D.; Whitesides, G. M. Nano Lett. 2010 , 10 , 3611.
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© The Author(s), 2023
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