Electric Conductance of Single Ethylene and Acetylene Molecules Bridging between Pt Electrodes

Abstract

We have investigated the conductance and atomic structure of single ethylene and acetylene molecule junctions on the basis of the conductance measurement and vibration spectroscopy of the single molecule junction. Single molecule junctions have a conductance comparable to that of metal atomic junctions (around 0.9G 0 : G 0 = 2e 2 /h) due to effective hybridization between metal and the π molecular orbital. The ethylene molecules are bound to Pt electrodes via a di-σ bond, while the acetylene molecules are bound to Pt electrodes via di-σ and π bonds. By using the highly conductive single molecule junctions, we investigated the characteristics of vibration spectroscopy of the single molecule junction in an intermediate regime between tunneling and contact. The vibration modes that could modify the conduction orbital were excited for the ethylene and acetylene molecule junctions. The crossover between conductance enhancement and suppression was observed for the single ethylene molecule junction, whereas clear crossover was not observed for the acetylene molecule junction, reflecting the number of conduction orbitals in the single molecule junction.

Investigation on Single-Molecule Junctions Based on Current–Voltage Characteristics

“…Meanwhile, when the conductance of the junction is above 0.5 G 0 (contact regime), the conductance decreases by vibrational mode excitation. The experimental results for H 2 , H 2 O, ethylene, and benzenedithiol (BDT) junctions agree with this theoretical prediction [ 33 , 34 , 35 , 36 ].…”

High electronic couplings of single mesitylene molecular junctions

“…Recently several groups [ 17 – 20 ] including ours [ 17 , 21 – 22 ] developed a direct π-binding technique, where a π-conjugated molecule is directly bound to metal electrodes without anchoring groups. The direct π-binding technique has been applied for various systems such as benzene derivatives [ 17 , 19 – 20 ], C 60 [ 23 – 24 ], ethylene [ 25 ], and pyrazine [ 22 , 26 ]. The conductance values of these molecular junctions were close to those of metal atomic contacts.…”

Key aurophilic motif for robust quantum-tunneling-based characterization of a nucleoside analogue marker

“…The unmistakable increase in molecular conductance upon ethynyl modication in the quantum sequencer can be attributed to the unique mode of alkyne coordination to metal electrodes, as previously studied for acetylene. 36 The interaction of acetylene with metal electrodes involves multiple molecular orbitals including p and p* orbitals of the carbon-carbon triple bond engaged in electrondonating and back-donating interactions. In that case, the tunneling current is mediated by the multiple orbitals that interact with the metal electrodes, which concertedly contribute to charge transport through the metal-molecule interface.…”