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Single Molecule Conductance of Dipyridines with Conjugated Ethene and Nonconjugated Ethane Bridging Group

Author(s):

Xiao-Shun Zhou, Zhao-Bin Chen, Sheng-Hua Liu, Shan Jin, Ling Liu, Hai-Ming Zhang, Zhao-Xiong Xie, Yun-Bao Jiang, Bing-Wei Mao

Journal:

The Journal of Physical Chemistry C

Year:

2008

Volume:

112

Pages

3935-3940

DOI:

10.1021/jp077058l

Abstract:

We report single molecule conductance measurement of 4,4′-bipyridine (BPY), 1,2-di(pyridin-4-yl)ethene (BPY-EE), and 1,2-di(pyridin-4-yl)ethane (BPY-EA), in which the two pyridine rings sandwich the conjugated ethene group and the nonconjugated ethane group, respectively. The conductance measurements of the molecules bridged in two Au electrodes have been carried out in aqueous solutions using the scanning tunneling microscopy-based break junction (STM-BJ) technique. All three molecules show two sets of conductance values with the high conductance (HC) values about 8-10 times higher than the low conductance (LC) values. The HC values for BPY, BPY-EE, and BPY-EA are (4.7 ( 1.1) × 10-3 G , (2.3 ( 0.9) × 10-3 G , and (4.5 00 ( 2.2) × 10-4 G , respectively, in an order of BPY > BPY-EE > BPY-EA. The decrease of conductance of 0 BPY-EE can be attributed mainly to the length increase of the molecule, while the decrease of the conductance of BPY-EA reveals the degree of electron decoupling upon insertion of one CH2CH2 group between the two pyridyl rings in the molecule. The present work demonstrates that with pyridines as the end groups, it is possible to study the conductance of very short alkane chains.

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