Hopping Conductance in Molecular Wires Exhibits a Large Heavy-Atom Kinetic Isotope Effect

2021 ◽  
Vol 143 (7) ◽  
pp. 2638-2643
Author(s):  
Quyen Van Nguyen ◽  
C. Daniel Frisbie
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Heavy Atom ◽  
Molecular Wires ◽  
Kinetic Isotope ◽  
Hopping Conductance

scholarly journals Hopping Conductance in Molecular Wires Exhibits a Large HeavyAtom Kinetic Isotope Effect

2020 ◽  
Author(s):  
Quyen nguyen ◽  
C. Daniel Frisbie
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Heavy Atom ◽  
Isotopic Labeling ◽  
Molecular Wires ◽  
Conjugated Molecules ◽  
Pi Conjugated ◽  
Tunneling Mechanism ◽  
Kinetic Isotope ◽  
Hopping Conductance

We report a large kinetic isotope effect (KIE) for intramolecular charge transport through pi-conjugated oligophenylene imine (OPI) molecules > 4 nm in length connected to Au electrodes. 13C and 15N heavy-atom substitution on the imine bonds produces a normalized conductance KIE of ~2.7 per labeled atom in OPI wires, far larger than typical heavy-atom KIEs reported for chemical reactions. In contrast, isotopic labeling of the imine bonds for short OPI wires < 4 nm does not produce a conductance KIE, consistent with a direct tunneling mechanism expected for short molecules. Temperature dependent measurements on a long (> 4 nm) 15N-substituted OPI wire and its unlabeled isotopologue reveal that conductance is activated. The conductance results for long wires are thus consistent with multi-step polaron transport and we propose that the exceptionally large conductance KIEs imply a thermally-assisted, through-barrier polaron tunneling mechanism. In general, the observation of large heavy-atom conductance KIEs opens up considerable opportunities for exploring microscopic conduction mechanisms in pi-conjugated molecules. <br>

scholarly journals Hopping Conductance in Molecular Wires Exhibits a Large HeavyAtom Kinetic Isotope Effect

2020 ◽  
Author(s):  
Quyen nguyen ◽  
C. Daniel Frisbie
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Heavy Atom ◽  
Isotopic Labeling ◽  
Molecular Wires ◽  
Conjugated Molecules ◽  
Pi Conjugated ◽  
Tunneling Mechanism ◽  
Kinetic Isotope ◽  
Hopping Conductance

We report a large kinetic isotope effect (KIE) for intramolecular charge transport through pi-conjugated oligophenylene imine (OPI) molecules > 4 nm in length connected to Au electrodes. 13C and 15N heavy-atom substitution on the imine bonds produces a normalized conductance KIE of ~2.7 per labeled atom in OPI wires, far larger than typical heavy-atom KIEs reported for chemical reactions. In contrast, isotopic labeling of the imine bonds for short OPI wires < 4 nm does not produce a conductance KIE, consistent with a direct tunneling mechanism expected for short molecules. Temperature dependent measurements on a long (> 4 nm) 15N-substituted OPI wire and its unlabeled isotopologue reveal that conductance is activated. The conductance results for long wires are thus consistent with multi-step polaron transport and we propose that the exceptionally large conductance KIEs imply a thermally-assisted, through-barrier polaron tunneling mechanism. In general, the observation of large heavy-atom conductance KIEs opens up considerable opportunities for exploring microscopic conduction mechanisms in pi-conjugated molecules. <br>

Heavy Atom Secondary Kinetic Isotope Effect on H-Tunneling

2018 ◽  
Vol 122 (5) ◽  
pp. 1488-1495 ◽  
Author(s):  
André K. Eckhardt ◽  
Dennis Gerbig ◽  
Peter R. Schreiner
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Heavy Atom ◽  
Kinetic Isotope

Quantum electrocatalysts: theoretical picture, electrochemical kinetic isotope effect analysis, and conjecture to understand microscopic mechanisms

2020 ◽  
Vol 22 (20) ◽  
pp. 11219-11243 ◽  
Author(s):  
Ken Sakaushi
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Effect Analysis ◽  
Kinetic Isotope

The fundamental aspects of quantum electrocatalysts are discussed together with the newly developed electrochemical kinetic isotope effect (EC-KIE) approach.

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