Mechanistic Investigation and Conductance Modulation of a Metal-Molecule-Metal Junction via Extra Acid Addition.

One important prerequisite for the fabrication of molecular functional device strongly relies on the understanding the conducting behaviors of the metal-molecule-metal junction that can respond to an external stimulus. The model Lewis basic molecule 4,4'-(pyridine-3,5-diyl)dibenzonitrile (DBP), which can react with Lewis acid and protic acid, was synthesized. Then, the molecular conducting behavior of DBP, DBP-B(C6 F5 )3 , and DBP-TfOH (DBP-B(C6 F5 )3 , and DBP-TfOH were produced by Lewis acid and protonic acid treatment of DBP) was researched and compared. Given that their identical physical paths for DBP, DBP-B(C6 F5 )3 , and DBP-TfOH to sustain charge transport, our results indicate that modifying the molecular electronic structure, even not directly changing the conductive physical backbone, can tune the charge transporting ability by nearly one order of magnitude. Furthermore, the addition of another Lewis base triethylamine (of stronger alkaline than DBP), to Lewis acid-base pair reverts the electrical properties back to that of a single DBP junction, that is constructive to propose a useful but simple strategy for the design and construction of reversible and controllable molecular device based on pyridine derived molecule.

Revealing the electronic structure of organic emitting semiconductors at the single-molecule level.

Revealing the electronic structure of organic emitting molecules is instructive for tuning the electron-hole balance, one of the key factors in regulating the organic light emitting diode (OLED) performance. Herein, we introduced single molecule conductance measurement (SMCM) technology to probe the conductance of three-model emitting molecules on the Au surface, finding that their hole transporting ability across the metal-molecule interface can be suppressed after electron-withdrawing arms are connected to the center component. This observation would benefit the electron-hole balance of the film in large scale OLED devices whose holes are excessively relative to electrons. I-V modeling reveals that the conductance decrease between molecules is owing to the reduced metal-molecule coupling rather than the impaired energy level alignment. The electronic structure variation between molecules could also be revealed by photophysical measurement, electrochemical analysis, and density functional theory (DFT) simulations, which give supportive evidence of the SMCM result.

Single-molecule conductance investigation of BDT derivatives: an additional pattern found to induce through-space channels beyond π-π stacking.

The through-space conductance of individual molecules is supposed to improve the macroscopic carrier movement, but the most widely acclaimed through-space conductance channel just existed in sufficiently close π-π stacked benzene rings. As a breakthrough to this primary cognition, additional conducting channels were confirmed to exist in non-strict face-to-face aligned thiophenes or phenyl-thiophene in BDT derivatives for the first time.