Charge transport of F4TCNQ with different electronic states in single-molecule junctions.

The molecular conductance of 2,3,5,6-tetrafluoro-7,7,8,8,-tetracyano-quinodimethane (F4TCNQ) with different electronic states (neutral, radical anion, and dianion) was investigated by the scanning tunneling microscope break junction (STM-BJ) technique. These electronic states have distinct conductance, and the conductance decreases in the order of neutral > radical anion > dianion. Surprisingly, the molecular conductance of the neutral F4TCNQ junction reaches 10 -1.17 G 0 , attributed to its LUMO energy level being close to the Fermi level of the gold electrode. Moreover, we found that neutral F4TCNQ can be gradually reduced to radical anions under a relatively low bias voltage of 100 mV. These results will advance the development of organic optoelectronic devices and molecule electronics.