Concurrent Enhancement of Thermopower and Conductivity via Modulation of Diacetylide-Electrode Coupling in Molecular Junctions

The study of molecular thermoelectricity offers fundamental insights into charge transport via tunneling through organic and organometallic systems, with implications for nanoscale energy conversion technologies. Here, we investigate how molecule–electrode coupling strength influences thermoelectric performance in molecular junctions incorporating self-assembled monolayers of π-extended Ru(dppe)2-diacetylide complex. Surface modification of gold electrode with monatomic Pt and Pd layers via underpotential deposition enabled precise tuning of the strength of molecule–electrode contact. This tuning enhanced electronic interaction with the remotely positioned Ru core, promoted cumulene-like π-delocalization along the molecular backbone, reorganized frontier orbitals, and simultaneously enhanced the Seebeck coefficient and electrical conductivity to amplify the power factor by up to 111-fold compared to unmodified junctions. These findings highlight the broader potential of diacetylide complex to translate subtle orbital interactions into significant energy-conversion functions.